I've had this 1980's SS Peavey PA 100 for longer than I can remember.
It started to develop a lot of loud static ie pops & crackles even with all pots at zero. This static makes the PA useless for say a low volume level vocal / guitar etc. Increase in PA volume doesn't affect the static volume so it's ok for high volume performance. Not every wants the musicians blowing them away ;)
Took it to a tech who says that he'd have to start at replacing all the transistors, which would add up to many hrs and cost $400 or so.
His advice was to junk it and buy another PA.
Thought I could do the transistors myself. The problem I have is as a newbie to involved electronics [ I can do guitar electrics etc ] when I started to check out
how and which transistors to replace I realised I don't know enough. I found that Peavey has a list of replacement transistors but I found that the original and the suggested replacement have different Base wires eg existing transistor has Base as middle but replacement has Base as left side wire. See attached diagram.
A number of replacement transistors have different base wires to the original so that's got me really confused.
Any help would be great as I don't want to junk this PA. Also haven't got the money for another better one.
Your "tech" diagnostic is flawed.
"Crackling noises" are not repaired by "replacing all transistors".
The Peavey equivalence is correct (of course), you are mis interpreting your readings.
Don't "shotgun" the amp, meaning don't replace parts at random trying to repair it by chance, because it does not work that way.
Start by googling or asking Peavey for its schematic.
Write them providing exact model and if possible serial number.
x2 what JMF said.
Just like to add that I recently emailed Peavey for an old model Amp schemo and they did reply with what was asked. (took about a week)
Make sure you quote the exact model and I added the serial number for clarity as models often change mid production.
Even for the novice a close visual inspection can often reveal some clues as to what might be wrong.
At the age capacitors may have leaked, look for goo oozing out of the can or bulging ends. (not to be mistaken for glue)
And don't forget big heavy parts can stress the solder joins often I find hairline cracks in the solder joins of big Can Capacitors.
FWIW ,, I've found older Peavey gear to be very well built so yep might be worth keeping.
Phil.
Welcome!Quote from: Andy54Took it to a tech who says that he'd have to start at replacing all the transistors, which would add up to many hrs and cost $400 or so.
His advice was to junk it and buy another PA.
I've got a better idea - junk your "tech" and find somebody who actually knows what they are doing; better still, come here and have a go yourself.
"Replace all the transistors" my :grr. This makes me mad. :trouble
"Mr Mechanic, my car is going, but there is a bit of a miss in the engine"
"Oh, I will have to replace the whole engine, transmission, and back seat - $4000".
If one of the techs who worked for me came out with this sort of garbage they wouldn't be for much longer.
a) he's a total know-nothing nong :crazy2:
b) he was blowing you off because he doesn't want the job for some reason
c) he wants to sell you a new PA
...or all three.
Get the schematic/circuit, scan and post here, take crisp well lit pix of the amp internals, overview and a few section views, and post those too.
When we have that information we will suggest things to test for and try to locate the source of the problem. You report back your results, and we proceed from there. You will need a multimeter, some common sense, and possibly a soldering iron.
Have you got the schematic yet? Enzo showed you where to get it from in the other forum:
http://forums.peavey.com/viewtopic.php?f=27&t=30657
He posts here also, it is probably best to choose one forum and stick with it.
The schematic does not seem to be available, so until you can get it from Peavey and post it here, it will be hard for anyone to help you.
Thanks for the positive support guys. I really appreciate the welcome. :dbtu:
Being a newly retired high school teacher [ workshop / manual arts / materials design etc] I have time on my hands. I can solder and know some basics of using a multimeter. I've been building electric and acoustic guitars for the last ten years in my spare time.
I live in rural Australia with the closest tech a 1hr drive away. He had the PA for 2mths and charged me $110 for "servicing" ie replacing four capacitors. When I got it home it had the same problem so I rang him and that's when he told me he would have to "do a blanket replacement of the transistors".
Replaced caps are: 1 x 100v 220uF 2 x 63v 100uF 1 x 35v 68uF
Original caps seem to be in good condition from outer appearances ie no leaking or discolouration. The two big 50v 2200uF caps seem in good condition but should I resolder them in case of poor joint ?
I've attached the schematic and some general view photos of this amp.
Get yourself a freeze-spray can - in a pinch, auto refrigerant.
Spray the driver transistor and the output transistors, and the emitter resistors. Also, use a magnifying glass to check the PCB tracks, perhaps wash the whole board with alcohol.
Thanks for the info but I'm such a novice that I wouldn't know where to find those components at this stage.
Maybe you could give me a rough idea what section of the board they're on from the photos ?
What does freezing these components do ?
Freezing components does a number of things. Some problems are thermal related, ie they don;t start until the amp warms up to full operating temperature. Hiting a thermally sensitive part with freeze-it will chill it , so that identifies thermally sensitive parts.
But also the instant tempoerature change causes a mechanical shock through the part, so even if it isnlt a thermal problem, it still can sometimes reveal what parts are bad.
As a teacher, if you knew some student was stealing from the class shop, you COULD just throw all the students out of the class. That would be the "replace all the transistors" approach. OR, you could take steps to determine WHICH kid was stealing, and then replace just him. That is troubleshooting, which is what we do here. ANother problem with all the transistors is, what if it is a noisy resistor? In other words we threw out ALL the students only to find it was the other shop teacher doing the stealing.
Use something like a wooden chopstick - something insulating - and push on each part on the circuit board. Do any of them respond with the crackle? And for that matter, just press down on the center of the board a little to give it a touch of flex. ANy reaction? Those indicate a cracked solder joint or a cracked copper trace.
Sure, resolder those large caps, can't hurt. Those are old and may be worn out, but crackling is not what old worn out caps do. Certainly leaking and bulging caps are bad, but 99% of bad caps look no different from good ones.
The base is NOT the middle leg of the EP430, why do you think that? The 430 is just an old Peavey house number. The TIP31 drops right into its place. That size and shape is called TO220. TO for transistor outline. As far as I know ALL TO220 bipolar transistors have the same pinout (leg arrangement), which is B C E.
Consider your troubleshooting goals: Your amp works, but makes crackling noises. SO I tend to doubt you will find some part that measures as BAD on a meter. Of course one of my Enzo-isms is to never think up reasons not to check something. SO chek them, but don;t expect to find readings WAY off the schematic unless there are parallel circuits to confuse the meter.
You isoloated the problem to the power amp by turning the master volume to zero and the noise remained. There are only four transistors in that circuit. In fact ther are only 14 transistors in the whole thing. $400?????
The small transformer is to drive the output transistors. If you removed that 430 transistor and powered up without it, you would hear ONLY any noise the two large output transistors make. The transformer isolates them. The transformer itself could have a cracked lead, but I think it would do more than crckle. Still, grasp it and give it a little wiggle, any noise? If the noise continues without the 430, the your outputs are somehow noisy or the transformer is funky. If that stops the noise, then it is coming from the 430 or the small transistor wired to it most likely.
Much as I dislike the shotgun approach, it probably would not hurt my feelings to just replace the 430 and the small guy with it.
(crossed with
Enzo, wotesaid, plus...)
Quote from: Andy54I live in rural Australia
Where? I'm at
Creswick near Ballarat Vic, but I also run Ozvalveamps, am on AGGH, and may be able to find someone to give you a hand. Your background sounds like you have a good fighting chance with this one.
In a tighter pinch some metho on a cotton bud dabbed on suspect components, followed by a gentle blow also works as poor mans freeze-it.
Quote from: Andy54Maybe you could give me a rough idea what section of the board they're on from the photos ?
We will, just have to digest the circuit a bit first.
Quote from: Andy54What does freezing these components do ?
This is based on the guess that noise such as you describe is coming from inside a failing component, most likely a transistor, and by chilling it you often get a change in its behavior.
Quote from: Andy54It started to develop a lot of loud static ie pops & crackles even with all pots at zero.
We just need you to
confirm that this is the case because if it is it means that the fault is in the "back end" of the amp, the main power amp that drives the speakers, and not in the preamps, which eliminates quite a large lump of the circuit to start with and gets us a lot closer to the fault.
Simple test; does thumping the case make
any difference to the noise? If it does it suggests that it may only be a broken solder joint or similar, if not it is more likely to be one of the components itself, and in particular a transistor, but overall this is not generally a failure mode of larger power transistors (the big ones bolted to the heatsink).
Normally I would say persist with a tech who has missed a fault, but in this "blanket transistor replacement" case, give him a
big miss. His shotgun or blunderbuss method of servicing always ends in tears (and in this case a badly depleted wallet). It is not how
real tech's repair things.
Which leads to;
first we find the fault,
then we take Berlin. Diving in and randomly doing stuff actually muddies the waters, so first we find out what is happening, then we repair that, and we know it is actually repaired and not just papered over to reappear at the worst possible moment.
Assuming that the fault is
not changed by the Master volume control, the areas we need to look at are the
driver stage which is on the end of the main PCB nearest the pilot light (that transformer is the driver transformer) and perhaps the
output stage itself which seems to be mostly on the back panel, so we need a pic of that from the inside. It also looks like the output transistors are connected via sockets, and these must also be suspect at this age, but should be cleanable if needed.
Just next to the driver transformer there are two transistors, a small pre-driver and the flat pack driver itself. What you can try at this stage is to take a cotton bud wet with (fresh, dry) metho and dab a few drops on the small transistor with the yellow top (circled in the attach), and see if that produces any change at all. If not, try the flatpack transistor next to it. This may cure the problem for a few moments, or it may suddenly make it worse, but what we are looking for is any
change, something that indicated we are close to the fault. {even if it responds it still may not actually be the transistor but an accumulation of dirt on the bottom of its case - I had one just like this that got noisy when you breathed on it, and a good clean where the leads came out cured it completely.}
You are a bit lucky in that this output stage is one of the older transformer-coupled style and should be somewhat easier to fix than a modern direct-coupled one.
- confirm it's there with the Master down
- dab the transistors and report results
- post pic of inside rear
Quote from: EnzoOf course one of my Enzo-isms is to never think up reasons not to check something.
:lmao: :dbtu:
Thanks Enzo, Roly et al all very helpful. I'm certainly going to have to read and digest this info.
Roly, I live south of Murwillumbah Nth Coast NSW near one of those villages that consist of only a post office/ general store/ garage called Burringbar. I've gone into hiding to escape former students 8|
Over the next while I'll try some fault finding.
When the master volume is at zero the amp has static. Static starts as amp warms up
Attached are a pic of the back of the amp. Also a component [ approx 7mm x 30mm, brown with one grey & one black stripe ] I found under the two large capacitors in what I now know to be the driver stage. It looks like it's leaking a fine machine oil.
Could this be contributing to the problem ?
Hi Andy,
Man I love equipment like that,, so obvious and you can see the parts and room to work on it all. <3)
As to Enzo's thinking up reason not to not check something,, :cheesy:
And Also
"When the master volume is at zero the amp has static. Static starts as amp warms up"
The ol grey matter triggered a distant memory. Ding!
There is the very outside chance that it could be the main power switch failing.
I picked up an old Sansui HIFI unit a few years back with same symptoms, drove me nuts for ages. Amp worked,, no overheating,, just an annoying crackle as it warmed up and stayed there,, WTF?? :grr :grr
Finally had a moment of brilliance and indeed the spring loaded terminals inside the mains switch where heating up the spring causing loss of contact.
Replaced switch,,The Amp now works perfectly.
Just thought I'd mention it,,You never know?
Cheers from a fellow Aussie mate,, I'm in Nambour and I'm likely even more rural than You,, Heck apparently anything north of the NSW/Queensland border was once considered outback rural by some clown polly in Canberra. :lmao:
Phil.
Wow, we're becoming quite the Aussie hang-out here!
Welcome aboard and good luck fixing your PA.
I actually know of Burringbar - I lived at Elands near Wingham/Taree for about 15 years; same PO/general store/pub all in one. (for the benefit of our international friends, we are now about 1000 miles apart).
Quote from: Andy54Also a component [ approx 7mm x 30mm, brown with one grey & one black stripe ] I found under the two large capacitors in what I now know to be the driver stage. It looks like it's leaking a fine machine oil.
Could this be contributing to the problem ?
That will be one of four rectifier diodes, and since they don't contain oil I doubt this has anything to do with your problem (really great macro BTW).
Interesting thought
@Phil, but my money is still on the pre-driver (the little transistor with the yellow top).
A simple way to test Phil's idea would be to unplug the amp, solder a wire link across the power switch (provided it only has two connections) and switch it on at the power point. (If it has four connections please don't try that at this stage, post a pic first). Also pull the mains fuse, give the ends a good clean and restore and test.
Investigate where the wires on the driver side of the driver transformer go. (one side will go to the flat pack transistor and power rail, the other towards the output transistors on the back. If chilling the pre-driver and driver come up zip it might be helpful to lift one of the driver side transformer connections (if it's not too difficult/impossible), that way we can confirm (or not) that it's coming from the driver stage and not the output stage.
You can also try holding your soldering iron on the top of each of the driver transistors for a few seconds in turn to see if heating changes anything. My bet is that when you heat the pre-driver it will get worse, but we'll see.
Quote from: joecool85 on April 08, 2013, 09:07:35 AM
Wow, we're becoming quite the Aussie hang-out here!
Welcome aboard and good luck fixing your PA.
Rather than an Aussie thing, we might call it an Antarctic area. :duh
Argentina and Australia/NZ are *much* closer than conventionally drawn maps show. :o
Just look at our Aerolíneas Argentinas Buenos Aires-Auckland/Sydney direct flight path:
(http://4.bp.blogspot.com/-1tSxUYBPyPM/T8Go58XUUjI/AAAAAAAAK4E/l1_3zDl5Ou8/s1600/vuelo_1.jpg)
For me, shorter than flying to Europe or USA.
Yes, of course, it will be a "chilling" experience flying so close to the South Pole, and the plane should better *not* make a crash landing.
Rescue would be *very* difficult, if at all possible.
Hadn't thought of that. Better still, get off the plane in Patagonia and take the train to New York ! :tu:
Quote from: Andy54 on April 08, 2013, 07:30:14 PM
Hadn't thought of that. Better still, get off the plane in Patagonia and take the train to New York ! :tu:
Well, believe it or not, it can be done.
Not only that, this guy actually did (and wrote a book):
(http://www.penguin.com.au/covers/catalog/9780141189154.jpg)
Whose Amazon comment is:
QuoteThe Old Patagonian Express: By Train Through the Americas
Author: Theroux Paul
Beginning his journey in Boston, where he boarded the subway commuter train, and catching trains of all kinds on the way, Paul Theroux tells of his voyage from ice-bound Massachusetts and Illinois to the arid plateau of Argentina's most southerly tip.
Although, why travel in train if you can do it "our" way, on horseback?
What about riding 10000 miles, from Buenos Aires to Washington DC , in 1925, to be received by USA President Calvin Coolidge at the White House?
Of course, it takes 2 Argentine Gauchos and a couple Argentine stallions to do it:
(http://bachlab.balbach.net/tschiffelys-ride-cover.jpg)
Maybe they were trained horses?
Not exactly:
Quote29-year-old Tschiffely ignored the legion of critics who told him his quest to ride 10,000 miles from Buenos Aires, Argentina, to Washington D.C. in 1925 was "impossible" and "absurd."
Not only did this brash neophyte propose to attempt this equestrian suttee, he said he was going to do it on two elderly horses, ages 15 and 16, owned by a Patagonian Indian, who were currently unbroken and running free on the Argentine pampas. In his own words, "they were the wildest of the wild."
Quote from: phattyou can see the parts and room to work on it all. <3)
You looked inside one of those
Aldi Fx pedals? At first I though it was a blank board, then on closer inspection I saw all that
microscopic SMD. Gak!
Indeedie
JM, many moons ago I had a project pulling down SatPix, one of which was a polar view, and I was struck for the first time that South America was "just over there". Until this route the shortest way to Buenos Aires from Melbourne was via LA!
Let's face it, if something serious goes wrong in a modern airliner you're stuffed
wherever you are.
Tschiffely's Ride - ah, they don't breed em' like that any more, not here either. "This horse has sloppy power steering and no air con!" I see farmers belting around on giant tractors that have more "mod cons" in the cab than my living room.
The Man From Snowy River - Banjo's Poem (10mins)
http://www.youtube.com/watch?v=fs_-DKUimeo (http://www.youtube.com/watch?v=fs_-DKUimeo)
Part of Aussie mythology, but on the Northern Rivers of New South Wales the country is even more forbidding and people still work cattle on horseback as the only option.
Peavey PA-100 problem seems to be fixed :dbtu:
Thanks so much for all your patience and input. I'm so glad this forum turned up in a web search and that I didn't spear off and replace all the transistors.
Through the combined effort of members help with fault finding it's been on test for 2 hours without any static. I've put a loop pedal thru all channels and they sound fine. Should I leave it on test any longer to be on the safe side ?
What I did was two things suggested 1) metho on transistors ~ no change in static 2) pushing the board down at various places gave me *heaps* of static around the driver stage transformer. Also wiggling the reverb connections where they join the board with "pins&socket" gave increased static.
Dumb luck fix ~ I re-soldered the "tabs" that connect the transformer to the board along with where the pins for reverb connection are.
So here's a photo of the board. I've marked the re-soldered points with an arrow.
Just wondering if the points I've marked as 1, 2 & 3 which are the red wire contacts from output transformer should be re-soldered as I think they may have made a noise when I was pushed on that section of board. Although they seem ok now.
Check out the date 12/76 almost vintage :lmao: BTW the *vintage* 240v to 110v converter in this thing is a monster when it comes to moving it around. They sure did make them substantial back then.
Roly, Just had a brainwave re the heavy old stepdown transformer in this PA. Couldn't I swap it for a new lighter model ? This amp is rated at 150W. What would you suggest ?
What is the power supply voltage in this? 50V? 70V? Is the existing transformer a single secondary winding? Like two red wires and that is all?
Rather than buying a smaller step down, why not find a 240v transformer that puts out the same as the existing one, and install it into the amp. That way there would be no extra transformer. A 50v transformer rectified and filtered makes about 70v.
Quote from: Enzo on April 10, 2013, 02:52:28 AM
What is the power supply voltage in this? 50V? 70V? Is the existing transformer a single secondary winding? Like two red wires and that is all?
Rather than buying a smaller step down, why not find a 240v transformer that puts out the same as the existing one, and install it into the amp. That way there would be no extra transformer. A 50v transformer rectified and filtered makes about 70v.
Gee Enzo now you're asking me hard questions :-[
The attached pic I think shows the transformer in question. It has three red wires attached to the board.
If that transformer is changed won't I have to re-wire the back of the metal cabinet to take the step down transformer out of the circuit ?
If that's the original Peavey power transformer, which it seems to be, it can be rewired for straight 240V primary, with no need for an external stepdown. :cheesy:
Quote from: J M Fahey on April 10, 2013, 04:36:51 AM
If that's the original Peavey power transformer, which it seems to be, it can be rewired for straight 240V primary, with no need for an external stepdown. :cheesy:
I wonder why Peavey used the step down transformer if they could have just rewired the power transformer to suit 240V ?
Sorry, but I'm so far behind the 8 ball on terms like "240V primary" that I don't understand what you mean. I'm really at a monkey see monkey do level ;) I wonder if you'd be able to give me a basic run down on what I would have to do rewire it ?
+1 to Enzo! :dbtu:
Quote from: Andy54Dumb luck fix
Do you mind! That's how
real technicians do stuff. ;)
Perhaps you can see why we all reacted to "replace all the transistors". He does all that transistor replacing for $400 with his blunderbuss "technique", and he's
still got the fault! You should perhaps leave sleeping dogs lie, but if it were me I'd be up his shirt for a refund.
Looking at the copper side, if you push or flex the board there should be no signs of movement at all in any solder joint. If there is it's fractured and needs resoldering. If you have good soldering technique then do it anyway if you're doubtful. My guess is that the mass of the driver transformer on the board has led to flexing over time and fractured some nearby joints, the ones you found.
Now
JM says that these PA's were originally fitted with a power transformer, the one internally on the back panel, that has dual primaries allowing it to be connected to 120 or 240 depending on how it is wired. If that is the case (and that power tranny looks original to me), then somebody encountered a similar :duh tech back in the history of the amp and has needlessly been lugging a stepdown tranny ever since.
From your back panel pic it certainly looks like it has a bunch of wires coming out colour coded consistent with the coding on the circuit, and looking at the circuit it appears in fact to have a multi-national primary allowing operation of 110, 120, 220 and 240V. {There is a cap C26 0.022uF that we call a "death cap" that should be removed for Aussie service}, but apart from that the wires are colour coded and it should just be a matter of rearranging the primaries.
Power transformer primary (mains side) wiring.
UNPLUG from the mains.Concept:Pull up the circuit and look down in the bottom-right. The mains comes in and is shown going to two windings that are connected in
parallel for 120V. We need to reconnect these so they are in
series for 240V operation.
First check;According to the circuit there is a 0.022uF cap between the black and
ground/chassis - this should be disconnected and/or removed if not already.
As you are using a 240/110 step down then
currently the blue and black should be connected together, and the black+yellow stripe and blue+yellow stripe should be connected together to make a 120V primary.
Before you do anything you should check that this is the case.
It's hidden behind one of the white connectors in your pic, but it looks like all the transformer primary wires already go to a single tag strip, and it should be a fairly simple matter to do the required rewiring there (as I am sure Peavey intended).
If so, then;The black wire (the bottom of the primary winding) should go to one side of the mains infeed (blue, neutral).
There is a black+yellow stripe, and a blue wire. These need to be disconnected from wherever they go and connected together. These are now the middle of the primary winding or 120V point.
The top of the winding is a blue+yellow stripe. This needs to be disconnected from wherever it goes and connected to the other side of the 240V mains (brown, active) via the power switch.
The black+red and blue+red should not connect to anything (these are the 110 and 220V points).
The last step is to replace the 3 amp fuse with a 1.5 amp fuse. This is a 3AG type, standard blow (not delay).
Inspecting the central tag strip you may find that the required rewiring is actually much simpler than the description.
Check;You should end up with;
- brown infeed to mains switch,
- switch to blue+yellow,
- transformer blue to black+yellow,
- black to blue mains infeed.
And of course green+yellow mains infeed safety earth to chassis.
If for any reason any of this does not make sense, or you can't find wires with these colours - stop and ask; post another of your excellent macros of the tag strip.
I assume that the two white three-way screw terminals are where the stepdown currently wires in. These and their stubby wires will be redundant and can be clipped out.
The tag strip at the opposite end to the transformer looks like a ring-in and is now redundant. The mains neutral (blue infeed) should now go to the central tag strip, and and green+yellow mains earth can also be reterminated on the grounded tag of the central strip - keeping in mind that a solid safety ground is vital.
This stepdown mod wasn't done by Peavey, by their local agent, or indeed anybody who had any real idea of what the were doing. :loco
HTH
Three red wires, not two, right. Sorry, I had the wrong transformer in mind.
Let's get some terms straight. The existing transformer in the unit does indeed take the mains voltage and step it down to 50 volts or whatever, but we don;t usually refer to that as a "stepdown." We just call it a power transformer. WHen you say "stepdown" to me it means an external transformer that takes 240v and steps it down to 120v so a 120v amplifier can plug into it.
So when I suggested eliminating the stepdown, I was assuming you had am external stepdown unit for your 120v amp to plug into. I am still not exactly sure what you have.
I am looking at the schematic now, and I see this one has a split supply, but the transformer puts out 50vAC center tapped. The three red wires. What I was suggesting was to replace it with one with the same 50 volt secondary, but instead of 120v, get 240v.
But now looking at the schematic, it appears the stock transformer already has primary side windings so it can be used on 240v directly. WHich was just discussed above.
Quote from: Andy54 on April 10, 2013, 03:47:36 AM
The attached pic I think shows the transformer in question. It has three red wires attached to the board.
That is the power transformer. It is not "stepping down" 240 to 120V, it is transforming the 240V to the voltage the power supply uses. You plug it in to a 240V outlet, yes? So it is already wired up for 240V operation.
It is the same size/weight as a north american version of the amp would use, you can't downsize. Yes, new amplifiers deliver more power and weigh less, like modern cars do. :)
While we await @Andy54's response; the two three-way screw terminal blocks in the rear panel pic are certainly not original Peavey, and I'm reading this as as where an add-in 240-120 volt "stepdown" tranny has been installed ahead of the original power transformer. This is not that uncommon here with imported American gear that doesn't have "international" primaries as this seems to. It certainly looks to me like the 240V infeed is taken to the far side connector block, and 110 comes back in on the one near the power transformer. (or perhaps I'm misreading the situation)
I think a similar (same?) "tech" in the OP "converted" this to 240V by adding a stepdown tranny instead of re-linking the primary. :duh
Ok guys once again I *really* appreciate your eagle eyes on my amp.
Just to make it clear in the bottom of the cabinet that this amp is housed in a *huge* transformer that I've always believed was there for two things.
1] As I was told by the guy that I bought it from in the early eighties, when I asked why it was so heavy, that he put it in there so it would run on *Australian* power because *American* power is different. :duh
2] To herniate the discs in my lower back. These days I need the help of another person to get it into the wagon.
Work carried out today....... see attached photos. Please criticize this wiring.
a) Brown mains wire to switch blue / yellow stripe to other side.
b) Remove blue .022uf cap #26 ............ ??? Of course this photo is during the stage when I was removing the stepdown transistor wiring. It was connected between the earth and black wire.
c) Following Roly's instructions on how to diffuse this thing is the 3rd photo :lmao:
Mains earth is connected to the chassis.
Mains blue is connected to black from transformer.
Black/Yellow Stripe and Blue from transformer are connected.
I 'm not sure if the fuses are wired correctly to the circuit.
The two red wires with blue masking tape connect to the pilot light. I did this as they were like that in the stepdown configuration wiring.
Please be hyper critical on this one.
Tab strip with new wiring configuration to be riveted to chassis.
Words are nice, but please make some kind of hand drawing of what you just rewired, and post it here, *before* plugging that amp into 240V mains.
Label carefully all wire colors.
Remember some are dual color (background+stripe).
*Just in case*, make a lamp bulb limiter and plug the amp there, better safe than sorry.
Had no intention of plugging it in until I got some feedback :tu:
I know I have *no* idea about electronics and not the first clue about how to draw a proper circuit.
BTW Please excuse the quality of the drawing. Can do better but just dashed this one off.
Just chimed in to post the redrawn 240V transformer wiring.
I'll check your drawing, hope the two of them match :)
EDIT: just checked your drawing.
*Almost* there.
You connected the 240V primary (2 x 120V primries in series) properly, if you plug your amp into 240V it *will* power on, :dbtu: , but you are not using the glass fuse or the thermal switch (which you labelled as fuse) which are necessary safety features.
You should remove the death cap C27 (.022x125EVL) *now*.
I'll edit the drawing to include the thermal switch, which is originally not shown.
Start getting ready for the Champagne of Victory. :lmao:
Thanks JM
Yes I had a gut feeling that the way I have the 1.5amp fuse & thermal fuse wired is unsafe :duh One reason why I wasn't going to plug the amp in. How should they be wired ?
The ominous sounding "death cap" is the second of two that were in the old "stepdown" wiring. I did remove one. The schematic shows two, #26 & #27. So am I right in saying just one should be in the "240V" circuit. If so where should it be in terms of between what combination of colour code wires ?
Oh, I missed one.
Remove both C26 and C27 .
C21, which also performs some line noise filtering, can stay because it's on the low foltage side.
As of the wiring, let me draw something, better than words.
There's also some issue with the "power on" light.
You draw it as a filament lamp, but I think (and hope) it's a neon lamp, probably direct 125V or something, please confirm.
Check here in 12 hours.
Won't say "tonight" because although somewhat close, measured in KM, we are on opposite time zones.
Quote from: g1 on April 10, 2013, 07:47:52 PM
Quote from: Andy54 on April 10, 2013, 03:47:36 AM
The attached pic I think shows the transformer in question. It has three red wires attached to the board.
That is the power transformer. It is not "stepping down" 240 to 120V, it is transforming the 240V to the voltage the power supply uses. You plug it in to a 240V outlet, yes? So it is already wired up for 240V operation.
It is the same size/weight as a north american version of the amp would use, you can't downsize. Yes, new amplifiers deliver more power and weigh less, like modern cars do. :)
Sorry about that post, the picture showed the power transformer and I did not realize there was another "step down" transformer in the cabinet.
Sounds like you are getting it sorted out, good luck.
Quote from: J M FaheyChampagne of Victory.
Which is like a Lap of Victory, except you do it sitting down. ;)
Oh duuur! :duh I've been looking at the circuit on high magnification and have only just noticed that the required connections are shown below-left of the power transformer - "primary connections for export models 240V 50/60Hz". (kicks self)
"Death cap" - while this is named with typical dry Aussie understatement, it isn't going to actually rise up and smite your firstborn; it's just something Americans have to do that we don't, and is of dubious merit.
(This arises because the American power system was "economical" and originally didn't have a third safety earth wire as we do. After innumerable deaths and places burning down Americans have decided that perhaps, after all, a third safety earth wire isn't so wasteful after all, however for various reasons the "death cap" between one side of the mains and equipment chassis lingers on. It was never needed here because of our green+yellow safety earth wire, so they get clipped out).
Now I can see them clearly they are both rated for only 125VAC so BOTH caps should be REMOVED altogether.
Your excellent macro "PA Switch.jpg" shows that the incoming mains active/brown is *frayed* where it solders to the switch. This is because the cable clamp around the mains lead stops it
pulling out, but hasn't stopped it
rotating, and over time it has flexed this joint until it is now in danger of breaking off. Unsolder this wire, clip the damaged bit off the end, then strip a few mm and resolder firmly to the switch contact. (The blue+yellow will have to come off because it has to be fed via the fuse and thermal cutout as well - see diag).
It is almost certain that the front panel pilot light is a 110V type and was intended to remain across a 110V portion of the primary winding, so that is how I have drawn it. It's the safe option and the worst that can happen is that it will light only dimly or not at all.
For your first power test you need to make up a Limiting Lamp - see;
http://www.ssguitar.com/index.php?topic=2093.0 (http://www.ssguitar.com/index.php?topic=2093.0)
This is your insurance in case you (or I) have made a mistake.
See attached diagramme.{and chill the Champagne}
QuoteI've been looking at the circuit on high magnification and have only just noticed that the required connections are shown below-left
+
QuoteNow I can see them clearly
May I humbly suggest a couple of THESE?:
(http://images.icnetwork.co.uk/upl/icwales2/nov2010/6/5/mr-magoo-68947628.jpg)
.
.
.
.
Oh, I see, you want a SS, electronic, DIY, high tech version?
.
Ok, I'll mail you the schematic of THESE:
(http://www.readingglassesetc.com/product_images/uploaded_images/rocket-glasses.jpg)
Can't attach it here because it's a 1597Mb PDF :(
Already got two pairs of those. 8)
Roly, thanks for the revised wiring diagram. I'm going to carry out the rewiring and then make a Limiting Lamp.
Re: the Lamp Limiter I read where JM feels the simplest circuit is the best but I'm having trouble sourcing a bulb. Also seeing this amp is 45W is a 75W bulb suitable ?
I can't get my hands an incandescent light bulb, only thing on the shelves at the Burringbar general store are tungsten globes are these I assuming this would work. But being a neophyte { a what ? :lmao: } I could be wrong.
As a teetotaler I won't be opening a bottle of champagne if this works, but maybe a bottle of the finest mineral water :dbtu:
Yes, 25W to 100W is fine.
Of course, the smaller one will stay brighter even with idle current, while a larger one will be all but invisible, but the basic idea is the same.
Don't know what happens in ANz but here in Argentina, after my initial worry about filament bulbs (I still treasure a small stash just for that) now I can buy anywhere the "high efficiency" version (which is actually a scam), which has a small halogen lamp floating inside a standard sized globe.
It's the same as before, as inefficient as any and with a 4X price tag, but at least it satisfies the official watchdogs.
So these are fine for amp testing.
(http://www.osram.es/media/resource/smallimagefixedwidth/318073//osram-halogen-classic-a-52w-230v-e27.jpg)
JM: thanks for the good information.
As for filament bulbs, I think they've all but disappeared from the Australian market. We've been told that the tungsten and fluro replacements are more energy efficient and with the cost of electricity, Australians have accepted that premise.
I have completed the rewiring for 240V and removed the .022uF caps. I've also removed the large convertor transistor from the cabinet. I had to rig up a block and tackle to get it out :cheesy:
Quote from: Andy54Please excuse the quality of the drawing. Can do better but just dashed this one off.
As you can now see from mine there is nothing wrong with that; more than clear enough and tells the story. :dbtu: I get some mud map tracings of amp circuits I have to decode and redraft that look like a demented spider fell in an inkwell.
Quote from: Andy54I had a gut feeling that the way I have the 1.5amp fuse & thermal fuse wired is unsafe
And your gut feeling was correct. The amp would actually
work okay like that, no smoke or anything, it's just that the overload and thermal protection are wired in a loop and would be ineffective.
Quote from: Andy54tungsten globes
This is another name for incandescent or filament globes, so I assume your store only stocks the new Compact Fluorescent Lamps - CFL's - and no, you are right, these are not suitable, however there are still a range of lamps with filaments available from hardware and lighting stores for non-standard applications, including 240V Quartz Iodine - QI - lamps as used in "Downlights", and others for ovens and fridges, and in strange shapes and bases, but anything with a *filament* is suitable.
The point here is that of there is a short in the amp all that will happen is the lamp will light to full brightness - no dramas.
Quote from: J M FaheyI still treasure a small stash just for that
Me too. And the LED's come marching in. It's clear here that LED's are already making serious inroads in lighting generally, and with QI downlights specifically, and the latter can't happen fast enough for my liking, very popular, horribly inefficient, and notorious fire starters, while LED's last 20 times longer, give better light, consume 1/20 the power, and best of all you can still touch them after they have been on an hour. A local pub just refitted their coolroom with white LED's and they've got a tonne more light at a tiny fraction of the power (and heat).
Quote from: Andy54As for filament bulbs, I think they've all but disappeared from the Australian market. We've been told that the tungsten and fluro replacements are more energy efficient and with the cost of electricity, Australians have accepted that premise.
I have completed the rewiring for 240V and removed the .022uF caps. I've also removed the large convertor transistor from the cabinet. I had to rig up a block and tackle to get it out :cheesy:
"transformer"
The tungsten QI that
JM illustrates
is a scam and are sold as "more efficient" but
aren't. The CFL's however aren't a scam ('tho they introduce another issue which is a problem for he suppliers but not an end user concern), but they also contain mercury which is a problem in the waste stream.
BOTH caps gone, good, they are only rated for 125V and could get "interesting" if subjected to 240V.
Look on the bright side, if you sell the stepdown on eBay you could end up turning a handsome profit on this repair. Note the VA/wattage rating and Google for 240/110 stepdown prices, you may be surprised what these cost.
Might be an idea to post another pic post-rewiring, just to be sure.
Note also:- that the front panel pilot light must be wired across
half the winding (as I have drawn), not all of it to 240V as you had it, or it will have a very short and exciting life.
- The unused Black+Red and Blue+Red must be
well insulated for everything including each other.
Quote from: Andy54a bottle of the finest mineral water :dbtu:
Just make sure it's a good vintage from the South side of the slope. ;)
Well fellas, with your great amount of help the Peavey PA-100 ia now working !! :dbtu:
The final push to the summit was made last night and tested with a newly constructed lamp limiter [ thanks JM ]. When the lamp glowed a dull red all those present [ myself and the dog ] gave three cheers and toasted the members of SSGAF. See photo of lamp limiter with 25W bulb.
Wiring as per diagram supplied by Roly was a success. I've attached a photo [I've been using my Canon 7.1 mega pixel camera set on macro & flash disabled ] which shows the rewiring for 240V as :
Please excuse another one of my wiring descriptions.
From mains switch ~ to fuse 1.5amp ~ to thermal cutout
: Active Brown / switch / Brown / 1.5amp fuse / black [top LH just out shot]/ thermal [ switch ] / black / blue with yellow stripe RH tab strip .
From LH to RH on Tab Strip
Tab 1 : Neutral Blue + Black from transformer + Red to "pilot light".
Tab 2 : Blue + Black from transformer + Red to "pilot light".
Tab 3 : Earth Green & yellow
Tab 4 : Blue with yellow stripe + black [ from 1.5 amp fuse ]
Third photo shows insulated red wires from transformer
Fourth photo is of the step down transformer that found it's way into the circuit. Sort of like some alien sleeper waiting all these years to be removed only to take over another unsuspecting piece of electronics.
Now let's see over the next while how amp will perform.
Quote from: Andy54the Peavey PA-100 ia now working !! :dbtu:
:dbtu:
Very professional limiting lamp.
Wiring in the pix looks good. Is there a star/lock washer under the nut holding the tagstrip?
That stepdown looks like it's about 500VA which is way overkill for this job, not that it should have been used in the first place.
Well done.
Thanks Roly, yep I put a spring washer under the tagstrip. The amp sounds the best it ever has. <3)
Maybe I should get myself an old Goldtone and start another project 8|
Quote from: Andy54Maybe I should get myself an old Goldtone and start another project 8|
That, or build yourself a
Lamington (http://www.ozvalveamps.org/ava100/ava101lamington.htm). ;)
Two weeks later.
Guess what ? Yes you probably know what I'm going to say. The same static has started again :trouble
I'm assuming I should start with the same fault finding process again ?
All very strange as the amp was "whisper" quiet after the initial fix. I should imagine that as this is
an old amp this sort of thing comes with the territory. Nothing new to you guys that have dealt with these
things for decades.
Quote from: Andy54Guess what ? Yes you probably know what I'm going to say. The same static has started again :trouble
I'm assuming I should start with the same fault finding process again ?
Well that's more than slightly annoying.
Basically yes, except hat the first place you look is where you did the repair. The fact that it went away means that you "touched" it. Now you have to have a closer look and see how it is that you touched it but didn't actually make the repair stick. You are right on it, the transformer lead, the solder joint, or the copper tracks right there; something about it got touched enough to make a difference for a couple of weeks, but it was a very near miss.
And yes, these are what we call "bouncers" in that you chuck 'em out the door, supposedly repaired, and the bounce back in again onto the service bench. Bouncers and intermittent faults are a tech's two favorite things :trouble , and they often go together.
Honestly there is not a lot that we can help you with now because it comes down to close observation - bright light, good lens, and your trusty ohm meter - but at least you now know where to start looking.
Keep us posted on your progress.
Thanks Roly, I'm sure it's just a matter of time.
Just to confirm, in your humble opinion, this problem is most probably mechanical rather than faulty components ?
BTW thanks for the link to the Lamington amp, it could be a great winter project after this bugger.
{Nothin' 'umble' 'bout my 'pinions}
Is it mechanically sensitive? Does thumping the case or poking the board produce any change at all?
I can only repeat what I said; you have been very close to it because it changed radically after you soldered up the connection to the transformer; and that made sense because it is a heavy component on a fairly flimsy board; so I would go for a good snoop around that area. But the second thing is that if this is the same/related/unrelated mechanical fault there is practically nothing we can add by staring at the circuit - a broken track or dry solder joint are not on the circuit. Very carefully and closely investigate what you repaired before, looking for what you might have missed, the cracked track, the transformer lead on the other side that didn't solder properly, whatever...