Hi...
Looking for some help with an amp problem. Retired now and looking to get back into some playing. Picked up a Fender Champion 30 with a problem hoping for an easy fix for a small practice amp.
Amp has a very loud hum, unusable, when turned on. Here is what I have observed or tried so far.
1. Hum is present with all controls at 0, doesn't change with movement of any controls, did seem to be a pop, crackle (dirty pot type noise) with reverb control, after some movement now doesn't seem to cause any change/noise
2. Plug in guitar hum still present at same volume, can hear guitar in/behind hum.
3. Pulled chassis and number 1 input jack legs were loose (the 2 legs closest to front of amp) to the point the jack actually lifted slightly off of board when turned over.
4. Resoldered jack, no change in hum level
5. Looked for other cold solder joint, reflowed a couple, no change
6. Disconnected reverb tank, no change
7. Tried this speaker with a different amp, sounded fine
8. Checked DC voltage at the speaker leads... consistently 3.6v dc when turned on, bleeds off to 0 when turned off.
9. There are a few brown sticky dots on the transformer and a series of dark spots on the bottom of the aluminum pan in a pattern out about 8"but it doesn't look like "tar". Not knowing the former life of the amp, could be as simple as a spilled/splashed soft drink?, they wipe off with a wet cloth.
Suggestion for next steps?, I don't have any other test equipment, but my trusty mulitmeter. Thanks for your help.
First, welcome to the board!
Now, I have worked on a Champion 30 before. This one had no sound or low volume (I don't remember now). It turned out to be 4-5 broken solders. But while I was in there I noticed several dozen (yeah, like 48-50) cold solders that I fixed that would have probably caused issues later. So, first, I would start by reflowing all of the solder joints. I know it takes time, but it's worth it.
As far as the brown spots, I'd need to see them before I could make any suggestions. Please attach a picture of the board, or better yet, several at different angles etc.
3.4v on the output indicates that the output amplifier is faulty, possibly caused by the brown spots? There should only be a few mV on the output - TP17 on the diagram.
Are there any spots near the output amp chip U6 a TDA1514A integrated circuit. (mounted on the Heatsink) Can you read a circuit diagram? Its available from here http://support.fender.com/schematics/guitar_amplifiers/Champion_30_schematic.pdf . This should help you.
Disconnect the speaker and re-measure DCV at the Spkr out wire, I bet you´ll have even more than what you found now.
*Carefully* replace the TDA1514 with a new one, meaning pamper the board (you don't want to tear pads and tracks off).
If necessary, cut the TDA1514 legs , it´s much easiervto pull them one by pne.
Clean well each pad (solder sucker+ some solder wick), install a new TDA1514 with proper grease and mica and you *should* have it working.
2 suggestions:
1) build and use a bulb lamp limiter (search the Forum)
2) do not connect a speaker until you check you only have a few mV DC at the output.
Then you connect the speaker and play a little at low volume (1 or 2 W), still using the limiter.
Only when everything checks fine you can plug the amp straight in the wall.
Tony and Juan, I agree that it is *probably* a blown TDA1514, but I wanted him to try the easy stuff first. I still think that reflowing the solder joints is a good idea, then clean the PCB with water and thoroughly dry (making sure not to get water into transformer, potentiometers and the reverb tank etc, only on the PCB itself and cleaning the resistors, caps, ICs, diodes etc).
Odds are he'll still need a new TDA1514, but the stuff I suggested may fix it and would be free. Plus, it would make it that much better for later even if he does replace the TDA1514. Now, if time is of the essence, yeah, throw a chip in and check it. But if he's like me and money is tight, it's best to explore all options first.
Wow...
what response, I'll be away for a few days, I get the photos and upload those upon return.
I did see the light bulb limiter in a search before I posted, so I can try that as well.
I did have the speaker disconnected with the 3.4v dc read, sorry I wasn't clear, I'll try a read with the speaker connected later as well.
thanks for all the help thus far
Here are a couple of pics of transformer... looks a little worse than I thought... hmmm.
I'll get some pics of board etc, up latter.
I'll try light bulb limiter as well.
Is there anyway to check the jack that was lifting from the board intially... continuity , etc? that would tell me if it was broken as a result of only being anchored by the back "legs"
Quote from: nebraskaplayer on January 18, 2012, 07:45:03 PM
Here are a couple of pics of transformer... looks a little worse than I thought... hmmm.
I'll get some pics of board etc, up latter.
I'll try light bulb limiter as well.
Is there anyway to check the jack that was lifting from the board intially... continuity , etc? that would tell me if it was broken as a result of only being anchored by the back "legs"
You should really shrink your photos down to 1024x768 or 800x600 so they are more easily viewable.
Having issues with pics? I've been using this one,,,
http://www.irfanview.com/
Resize,, resample,, change DPI
very handy program.
oh and it's free.
Phil.
Thanks for help (again), just changed laptops no photo editing programs. Your suggestion IS very handy, (and the fact it's from CNET download), made it feel safe.
Here are downsized pics. (hopefully)
Don't think the transformer has a problem.
It looks like somebody sprinkled some Coke on it (see drops in the chassis itself) or simply it was in a *very* humid place (basement/storage room?), water drops condensed and rusted it somewhat.
But nothing beyond that.
So...
1. I tried the light bulb limiter, with a 40w bulb, get a "low" glow when turned on.
2. Again hum is REALLY loud, unusable... didn't see to change after reflowing some more joints... but I need to get some desoldering wick... some aren't too "good" (tried to add a little solder)
3. Did plug in guitar and I can still get sound, with enough volume (on amp and guitar) it equals or rises above the hum, since hum doesn't change with volume. The bulb didn't seem to change much/any with playing briefly.
4. Did seem to be a some amount of distortion (like the gain channel) almost.
That's all the farther I'm going to get for a day or so, but welcome any other suggestions/next steps.
5. I did make the mistake of wiping off the thermal grease between pan and alum. block.. so if sucessful I'll need to replace. (but it has made no difference)
You did well,, :tu: Sound like the power amp is ok.
Next one is preamp PSU,, Check C37,C38 and also C39,40.
If you have a DMM then check those voltages are close to spec
If any of these caps are blown then it will hum like mad at one fixed level ,,, much like you explain.
Phil.
So... I wasn't going to mess with this for a day or so (but I can't help myself with all the help)
Thanks to Tonyharker I have the schematic... and to answer his question, I haven't read Schematics before. I am familiar with basic A/C home wiring, and D/C simple automotive type wiring.
But I'm going to need some help, what the schematic "should" be telling me, on the test procedures now.
I did go buy a cheap Radio Shack desoldering iron/bulb combo.
Phatt..
I'm still thinking back to the number 1 guitar input jack swinging by two legs from the board when I first opened it up. Is there reason to think that either the soldering (that I did or a defect in the jack ) could still be causing my issue...
Otherwise
I"ve located C37,C38 and also C39,40 on both the board and the schematic.
Looking at the Fender load comments on the schematic:
To test C39 & C40: Test DC with no input signal?
1.power amp on (speaker unhooked, and light bulb limiter not in circuit), no guitar plugged in, all knobs to 0. ???
Then test between ( + ) leg of each to chassis ground
and C39 should be +13v dc?, and C40 should be -13v dc?
It looks like can be done from the top of board easily, if that's what I'm really looking for.
Now... C37 & C38
C37 positive leg to chassis ground = +15vdc
C38 positive leg to chassis ground= -15vdc
Again little tighter but still looks like can get probe on + leg from top of board.
Pics below.
Comments/direction?
Thanks
Wow shinny new boards,,, :)
and You are catching on fast chum. :dbtu:
Yes you have the right parts and the right voltages.
Nothing there looks odd.
My guess is that you have just lost a ground connection somewhere,,, Yes likely the input sockets as these are cheaply made and prone to solder breaks as well.
With the Amp humming,, Try gently pushing down on the PCB board especially around the input sockets as sometimes these cracked solder joins are darn hard to see by sight.
Hairline cracks,,,Even with a magnifying glass they can be hard to see.
Phil.
Thanks for everyone's help thus far...
Couple of observations.
1. Still have 3.5-3.7vdc across speaker leads (unconnected).
2. When I power down, small light pulse from gain cuircuit indicator light (maybe that's totally normal) but I thought it may mean something to someone.
3.I ran DC voltage tests on C37-40, and have one result that wasn't what I expected on C40 the (-14.2vdc showed up on negative leg not positive leg?)
attached is sketch of what I found.
(I think I have it sized ok...)
And additional question...
Taking everyone's advice and trying to be very careful of the board and traces, I did notice there was a "bridged" solder joint between these two (in photo below, not sure if I caused), used desolder iron quickly to remove most, is there a preferred method for getting the remaining that bridges between without risking damage?
I think it's between the legs of C48 and C49 (labled >IJ63 part number?)
thanks
Are you sure those two points aren't on the same trace? Is that the ground end of the cap??
Ah...
Younger more knowledgeable eyes, Yes I do see now looking at pic, it is on same trace, so I'll just solder back up.
The pic below show what the legs come from , white block "things", they are labeled C48 and C48 so that means they are capacitors even though they don't have the traditional canister shape?
Still don't understand what the reading on (-and +) legs of C40 in post above means?
and why I have 3.5+ v at speaker leads... unless the TDA151 is "partially bad"?,
Also if there is any way to check number 1 input jack since that was the only visible issue when I started or remove or jumper it somehow to eliminate that possibility. I'll try to look at schematic , (or if I can pick up a jack local might be easier to replace then troubleshoot)
thanks ALL...
As I read the schematic, you should have 0 zero volts on the positive side of C40 cap and minus 13V on the negative side of the cap, which it sounds like what you reported, so no problem in that case. Zero is more positive than minus 13, so that works.
Some of the caps are in rectangular white "blocks". Look at the top and see if it doesn't say something like ".1u" on top.
The 3 volts DC on the speaker is still a problem. Somehow you have DC on the speaker and that shouldn't be. The likely path is through your output device. Maybe C46? Gurus help here.
I missed the part about your input jack. A bad ground there can cause hum. If you fixed it, check that the ground lug is really continuous to ground and that the "switch" lug is grounding the input lug when no plug is inserted.
Thanks...
Does that make the reading on C38 in the earlier post suspect then?, as I got a (-15.8vdc) on the POSITIVE leg? When looking at the schematic it looks like it should test like the C40, you are referencing, meaning it should be testing (-15vdc) on the NEGATIVE leg ? , or is it dependent on how it's used in the circuit? ( I'll double check readings today).
Can you provide a brief description of the DVM testing for the jack you suggest?, here is a pic of the jack I believe is in question.
Thanks
Dave
C38 per schematic, should be like c40, with zero VDC on the positive end of the cap and minus 15 VDC on the negative end of the cap. Double check this - if the cap is original its not likely to be inserted backwards.
Regarding the jack, viewed from the top, the back-left lug is the tip of the guitar cable. If you look closely, it is a spring and it grounds itself on the righthand side of the jack. Sometimes the spring gets weak and doesn't make contact, which can hum. With no plug inserted, that back left lug should be continuous to ground. With a (good) cable inserted, it should isolated from ground and continuous with the tip of the cable. The schematic shows this relationship with the little "arrow" connections that go to ground on the two jacks. If you experiment with your multimeter on continuity (amp off), one end to ground, one end to probe with you should be able to see if the switch/spring isn't making contact.
One afterthought, the schematic gives "TP" locations, i.e., test points, presumably marked on the board, for you to measure VDC to ground. Those are meant to give you convenient locations to test DC. iF you get a the appropriate reading there, you don't have to really worry, you can assume the cap is in correct place. Personally, I always write these measurements on a copy of the schematic as I work (in pencil). IF they (TP 3,4,5,6) are good, you can continue on in your fact-finding. Also, later if something changes, you have a baseline to work from.
I'll recheck c38, and I do (now) see the test points and values, I'll take a look and see what I find.
My wife seems to think putting a new blower motor in her car before snow flurries tonight should take priority over this IMPORTANT project...
I also see that the TDA1514A may be tough to find?, (and a little expensive?) if I end up needing that.
Quote from: nebraskaplayer on January 22, 2012, 03:21:47 PM
I'll recheck c38, and I do (now) see the test points and values, I'll take a look and see what I find.
My wife seems to think putting a new blower motor in her car before snow flurries tonight should take priority over this IMPORTANT project...
I also see that the TDA1514A may be tough to find?, (and a little expensive?) if I end up needing that.
I hadn't realized how hard they are to find now (not the case a few years ago). Anyway, you can still get them for $10 or so on ebay. If you can't find a TDA1514A, the NTE7118 is apparently the substitute although it appears it is even harder to find and also $43 from mouser.com...ouch! Another option would be to scrap the poweramp section of your current amp and feed the preamp into an LM3886 or similar board. This would require you to get a "kit" from somewhere like chipamp.com. I think you should be able to power the LM3886 board off your current PSU which would make this a cheap option. $3 for the LM3886 board from chipamp.com, then just buy the components. Should be able to do that for less than $15 or so I'd imagine.
So heat in the wife's car...
Thanks again to all who have responded so far>
1. Tested Jack Inputs with these results:
Tested with meter for continuity.
Both Input 1 & 2: W/O cord inserted both of the top "tabs" were to ground.
Both Input 1 & 2: W/ cord inserted, front (closest to threads) "tab" was still to ground but back "tab" was open on each.
2. With the chassis out checked the solder joints on the "legs" of each jack to ground.
Interesting results, I'll look at schematic and see if I can figure out if this is right... (if I need to upload sketch to make clear let me know)
JACK 1 (bottom view) JACK 2 (bottom view)
Leg 1 leg 2 Leg 5 leg 6
Leg 3 leg 4 Leg 7 leg 8
• With NO cord in any Jack
Legs (2,3,4)&(5,6,7) are to ground
• With Cord in Jack 1
Legs (2,3) & (6) are to ground
• With Cord in Jack 2
Legs (2,3,4) & (6,7) are to ground
3. Here are the DC test points
S/B ACTUAL
TP 3 +25.9 +26.4 vdc
TP 4 -25.9 +26.4 vdc
TP 5 +15.1 +15.0 vdc
TP 6 -14.8 -15.3 vdc
I rechecked the earlier test on :
+ lead - lead
C39 +14.2 0
C40 0 -14.2
4. I tried a couple of A/C test points:
S/B ACTUAL
TP1 20.3 20.2VAC
TP2 20.3 20.2VAC
Still have the 3.5 vdc on speaker leads (speaker unconnected).
I did borrow a "better" meter a UEI dm383b ... Didn't seem to make me "better"... it does have capability of mvolts... but I think it needs an input load?, and load on speaker leads to test>
Regarding the TDA1514A, I did notice the EBAY sellers before, but ALL are Hong Kong, and most are still "branding" as a Phillips part, I did see on some other places there is some complaints regarding Fakes blowing up. I also saw there was a bunch of late 80's Phillips and Marantz CD players (of all things that used this,that foks are canabilizing).
Next steps?...
From the above it sounds like the jacks are fine and C39 and C40 are correct. The voltages are pretty close to the schematic, except for the 3+ volts DC on the speaker. I'm think we keep coming back to the chip.
Duh... might be easier if you all could hear what it sounds like.
http://www.youtube.com/watch?v=vOjYjR-2WQ4&feature=youtu.be
hopefully it's ok to post links, otherwise go to youtube and search for
troubleshooting fender 30
I did find a US repair shop that has a single td1514a available, but the $20 to buy and ship will equal the cost of the amp... so I'd like to see if we can narrow it down to that before I pull the trigger.
thanks
Jhow... I posted before I read last post regarding your chip comment.
I'll let a couple of folks listen to youtube recording and see if you all agree with the testing that I/we have done, resoldering the loose jack, still having the 3.5vdc on the speaker leads, that I need to get the chip and replace it next..
Does only having 3.5 vdc on the speaker leads (vs. the much higher that was suggested there would be if the chip was "blown" ) mean it's "somewhat" failing?, also the fact that there is some input from the guitar that still passes through to the speaker through the chip (as shown in the youtube clip as well, although it was very weak and had to be turned all the way up).
Only other thing I noticed the guitar volume as well as the ambient noise level was higher when the gain circuit was engaged with both gain and volume vs. the standard channel?
tks
I'd say 99% chance at this point that it is a blown TDA1514A.
As a last check before you order your TDA1514, please read and post the Dc voltage on its pins: 1/9/6/4/5. Thanks.
PD: If you can´t find it, or it´s a "Hong Kong fake", I can suggest a way to replace it with an LM3886 , but it involves some brain surgery. :duh
To see that it´s possible, i´ll need a couple sharp. well illuminated closeups of the TDA1514 mounted to its heatsink and PCB, to check available space.
Well Mr Fahey,,you beat me to it :)
The thought crossed my mind also but wondered if the supply was big enough?
27-0-27 VDC should be good enough for the LM3886 but you need a bigger chunk of Alloy to cool it.
IME,, I've noticed Fender have always skimped on heat sinks. :trouble
He has a reasonable picture at the top of this page.
Looks like plenty of room to move inside.
I'd be mounting the NEW power chip on a separate board and just tap off the main board.
Phil.
Thanks
Which raises a couple of (more) questions.
To test :
1. unit powered on
2. NO input? nothing plugged in
3. speaker leads disconnected
4. Each lead (numbered left to right looking at chip mounted to heat sink) from the top of the board is numbered 1-9.)
5. Each will be tested individually for pins 1,4,5,6,9 (tested from the solder points to chassis ground)6. I "tried" looking at what I would exect to see for results on schematic (since my meter isn't autoranging...
-noticed they don't specify dc volts...
Pin 1= ?
Pin 4= -27v
Pin 5= 0?
Pin 6= +27v
Pin 9= ?
If you gentlemen could fill in the ?? above before I test.
Regarding the replacement chip, it is a US "fender" repair shop, I need to call and discuss the glut of fake chips before if I order.
I'll have a few more questions regarding front vs. back identification, mica insulator, white thermal paste,and thermal grease, assuming I get that far...
It's not a repair... it's a quest...
Went to check on testing method for TDA1514A... pins 1,9,6,4,5 per J.M.Farey, per my post above,
I assumed that I would test each pin to chassis ground, but looking at the spec sheet below, now I'm not so sure.
It does look like pin 4 is ground?, so assuming chip is isolated , it would be the same as going to chassis ground?
I'll hold on until I get advice and don't kill the chip (or something else).
From Phillips spec sheet
http://www.next.gr/components-datasheets/TDA1514A.pdf
Opps sorry for the spelling: J. Fahey,
So... Some Sucess!!, as a result of inspecting pins closely for testing and replacement on TDA1514A... I found a cold solder joint on pin/leg 1.
After all of the joints I reflowed and looked at I never saw these smaller pins as a problem even with the magnifying glass I was using.
So I have virtually all of all humm gone and 0 dvc at the speaker leads, thanks everyone.
There are still some issues I need to figure out.
1. There is no reverb.
2. Trying briefly input jack 1 and 2 and the gain/volume impact seems off or wrong ... but the clean (on channel 1) I think seems OK with enough volume for a small amp..
I need to look at those and do some basic trouble shooting on those before I bother all of you on those items.
Should I continue on this thread, or start a new one (if needed for each of the other problems I discover?>?)
thanks again, great help...
Dave
Cool. I love an inexpensive solution.
GOOD !!!!!! :dbtu: :dbtu:
Joecool was right after all !!
I asked you to measure those voltages (measured relative to ground if nothing else specified) because I was not happy with the voltage results.
With a blown TDA1514 I expected to fin a higher voltage, even +/- 27V (the full rail voltage) or thereabouts at the output pin.
Or less than 100mV on a healthy chip.
3.5V were strange, that's why I asked for those measurements.
Why?
Because most SS power amps (specially chip amps) are nothing more than a "big" Op Amp.
And they faithfully amplify whatever you feed them on the input pin (in this case pin 1).
So if for some external malfunction you have 3.5V on pin 1 ... you´ll have 3.5V on the otput pin ..... which is exactly what happened. :)
You had 3.5V on pin 1.instead of 0 or just a couple millivolts because of a cold/bad solder which did not let it be referenced to ground.
Also causing hum problems and such.
Funny thing is, if you had mounted a new TDA1514 there, it would have worked perfectly ... because it would be hand soldered :lmao:
Great news,
Re the cold solder join.
I wonder if this is due to the RoHS solder that has been forced upon us? :grr
I've seen quite a few boards that show shrinking issues, especially on warm to hot running components. Some reading reveals that some military folk are fully aware of the high failure rate on this inferior product. Refusing outright to use it.
At the moment I'm still able to purchase Lead Solder where I live but that may change in the future. :(
Phil.
Quote from: nebraskaplayer on January 25, 2012, 10:51:24 PM
So... Some Sucess!!, as a result of inspecting pins closely for testing and replacement on TDA1514A... I found a cold solder joint on pin/leg 1.
Ah, I thought you had already reflowed ALL joints as I mentioned quite a while ago. :trouble
On amps like this it is best to just reflow them all then to try and do "just the ones that look bad." Trust me, none of them are that good. Honestly, it might take you 30 minutes to reflow every single joint, but it will most likely save you hours or days of troubleshooting.
Glad you got it mostly working though :tu:
As for the reverb not working and other issues, go ahead and leave them in this thread as it is a generic troubleshooting thread anyway. Plus it's easier if it all stays together in one area.
Now, go reflow EVERY solder joint carefully, then let us know if you still have issues and we'll go from there.
Quote from: J M Fahey on January 26, 2012, 03:42:02 AM
Joecool was right after all !!
Don't act so surprised!
Quote from: phatt on January 26, 2012, 05:01:43 AM
Great news,
Re the cold solder join.
I wonder if this is due to the RoHS solder that has been forced upon us? :grr
I don't think it is a direct correlation. I think it's more that the RoHS stuff is a little more picky on how you solder with it. When done by hand it appears to me that it is just as good as a lead solder, just more difficult to do. It may be true that when done by robot they just aren't as good. It doesn't flow as readily and takes more heat, set times take longer too so everything has to stay very still. I think this has to do with the higher silver content.
Excellent forum, you folks really go the extra mile in helping the newcomer,
joecool... RE-Looking at your post you did say ALL and that you had seen instances where a few WERE bad but... 40-50 COULD cause problems latter... AHHH...makes so much more sense now, I should have paid a little closer attention.
Plus I was really scared of damaging the chip ...
JM Fahey... Thanks for staying on the low DC voltage at the chip... that finally got me back to it, and the actual problem. (and the picture resizing program)
Tonyharker... early on for link to schematic
Phatt and Jhow... your specific directions for test points and values kept getting us back to the root cause... I did try the plastic "chop stick" pressure on the board to find any changes,... but with the heatsink bolted to the chip obviously didn't get any movement. I also appreciate the resizing and mod program for pics you provided.
A little board protocol, since I've asked so many questions, I have enough posts (although they are all questions, not help) I can "award" chips... should I do so for above the help received?, or is that something reserved for "regulars"?
I'm not going to spend a lot of time of the Input 2 volume, as I did research and discover it's a darker channel for active pickups and I'm testing with a cheap Fender Tele.
I am going to look at reverb, as I like a touch when playing, It has spring reverb in a "cardboard" pan (see pic below). (I do think I had some reverb day 1, with the pot very noisy, but it was hard to tell as lound as the hum was previously. Physically it seems that is the only control pot that turns with no physical resistance, which I understand is very subjective).
I did a quick resistance test of reverb pan input and output wires, R/B was 202ohms, and G/G was 27, I tested another Fender SS with a physically similar size, and it tested virtually identical at 202/28.
I tried to test millivolts at TP13 and TP14 on a 4 vdac scale and got .095 at TP13 and .004 at TP14. converting that gives me 95 millivolts (s/b878m, off by a factor of 10?) and 4 millivolts (s/b >5m, close). That was with amp on, no input, reverb at midpoint on control.
I also need to put thermal grease back on between chassis and heatsink and spacer?, any recommendations or cautions?, It was a clear almost like vaseline with just a tiny amount between each.
I haven't pulled the board again (or reflowed anything...yet), I want to play it a day or two to see if it holds up.
Dave
nebraska player: Footnote #5 at the bottom of the schematic has instructions for measuring AC voltages. You need 1khz signal, 8ohm load, various settings...otherwise the readings aren't going to match TP. you can probably fix this too with out worrying about the AC. If you have no verb at all I would start looking if U4 and U5 have necessary voltages. I'm guessing you re-soldered those guys too?
Hi nebraskaplayer,
Re Reverb, Simple test no teck required; 8)
Turn the rev knob up full ,,Now bang on the cardboard.
Do you hear any boyoying?
If you do then you know the Pickup side of the reverb works fine.
If nothing,, or very low sound then the PU side of the circuit has issues. :'(
Not much point playing with the driver end until you know the PU side works.
Re points,,,, feel free to click a few for those that help.
Frankly I don't worry much about it as I prefer to thank on a more personal level.
Just for the record,,, There are some incredibly talented folks who frequent this site and I'd like to thank Them for their input into helping those of us with lesser experience.
(Which of course includes Me,,, LOL.)
Phil.
I would get some thermal paste between the chips and heatsinks before playing too much or you could fry them in short order. No more than a minute or two of play time at low volume I would say if you don't do the thermal paste. As you've found, sometimes these chips can be expensive to replace, no point in possibly wrecking them.
I won't get back too it until later this weekend.
1. Thought you all may find another SS amp I have interesting... hopefully from what I've read I never have to ask for help on this one, as I understand they can be a bear.
http://entertainment.webshots.com/album/573733998UhWDVL
2. I may be mixing terms up here, I didn't demount the chip so the white thermal "paste" is still between chip and heatsink. When I first took apart there was a block of aluminum between, L shaped aluminum that chip is mounted to (with the white thermal "paste"), but between the block and the L shaped aluminum, and the block and the metal pan, there was the "Vaseline" style grease. I have seen some other reverences to late 90's Fender solid state amps having it but not what it is or replacement options..., Almost seems more like a dielectric grease to just prevent corrosion on aluminum to aluminum and aluminum to steel?.
3. I wasn't getting any of the traditional "bong" from anything I was trying, but it was only for a couple of minutes,... and I haven't reflowed everything, so I don't want to get to carried away until I get that done. ... (also I need to move everything from the kitchen island... )
Quote from: nebraskaplayer on January 27, 2012, 01:38:02 PM
2. I may be mixing terms up here, I didn't demount the chip so the white thermal "paste" is still between chip and heatsink. When I first took apart there was a block of aluminum between, L shaped aluminum that chip is mounted to (with the white thermal "paste"), but between the block and the L shaped aluminum, and the block and the metal pan, there was the "Vaseline" style grease. I have seen some other reverences to late 90's Fender solid state amps having it but not what it is or replacement options..., Almost seems more like a dielectric grease to just prevent corrosion on aluminum to aluminum and aluminum to steel?.
As long as you didn't remove the chip from the heatsink, you are good. If there is a bracket that attaches the heatsink to chassis, I wouldn't worry about putting any "goop" on it. As you have guessed, most likely it is just dielectric grease.
Done !!! (I think).
Thanks for clarification on grease...
So , the reverb was a little more work than I thought,
1. Went to reflowing everything...
2. Noticed with the right light, that the pot for reverb was cracked down the back, see pic below, (by the way, that was one of the two knobs that was missing when I received it, looks like it must have taken a good impact).
Still need to locate a couple cheap push on D shaft knobs.
Pulled pot from board, it tested open. Ordered new pot... PITA, mini, snap in, Fender proprietiery..., Got new pot today, stuck in board , and expected instant successs, Nope...
3. If you look at the pic of the cardboard "reverb tank" I posted back on 1/27, I now see the fine wire was broken always, at the time I didn't know it was a wire.
4. Pic below is a closeup of tank fine wire, after I pulled tank (read, cut the double sided tape it was mounted with.)
5. Tried to stretch wire with tweasers to reach the other post to solder ,too short, unsucessfully I broke it from the post it was anchored too. Just to see what it would solder like I "pretinned a post and tried to solder and it appeared that the heat from 30w iron actually melted the wire more before the solder could attach to wire.
QUESTION... anyone have an idea it there is a wire type, substitute that I could play with to try to fix this one? I know a reverb tank is only $20-30, but so far only spending the $5 on the reverb pot thanks to all of your help, has been very rewarding.
6. I did have a matching dimension and input/output tank from a small Fender 15R that this amp will replace, that I pulled and installed, although not very "rich", it does the job.
So fixing the old reverb tank would be to stick in the little 15R.
Thank again to all that helped
Reverb tanks come in different impedances, shown by some codes stamped on them.
For best results, you must match codes or at least have a very close one.
Google the Belton page where they explain it.
If you use a non matching tamk, it *may* work (poorly) or be unreliable.
I'd check the code and order a matching one.
Anyway, congratulations on your troubleshooting skills.
Good to hear it is almost there. I'm with Juan though and would replace the tank with a proper one.
Gentlemen...
Perhaps I overstated the "weak"; I believe it's relative to a nice rich reverb that I remember from the classic Fender amps of my youth... the 60's.
I think I have reached what this amp is capable of (or at least how it was initially sold), I might look for a better tank, (read, better specs), if I can come up with one cheap. With the understanding that it would only help "some".
I have read many of the posts on this site regarding reverb and if I could use a quote from Phatt...
"... but my answer was based on the high likelihood that the owner is chasing a ***MUCH MUCH MUCH better Reverb*** and unknowingly assumes that the *TANK itself* is where the mojo (Killer tank slapping) reverb comes from."
I had tested the tanks in both amps and got virtually identical resistance readings on both input and output leads. Coincidentally both of these relatively inexpensive starter Fender starter amps were made in 1999.
I used the table I found here, http://www.tubesandmore.com/ to estimate what that would mean for Impedance. My tests for both tanks were 26 ohms input and 200 output static, equating to the 150, and 2250 respectively at 1khz.
Below is a pic of the "bad" tank removed from the cardboard tube, with the Fender part number and the codes show the BB in positions 2 & 3, which according to the tables in the above website I believe confirms those values.
Not sure if I understand why the absence of the "fine" wire between the two posts terminating each spring at the Green (output) end affects the output sound so dramatically, but doesn't affect the resistance measurement of the input or output leads?, I need to do some more reading to understand the magnetics in play?
The amplifier I took the tank from would have a dollar value less than a new tank, but the enjoyment of the learning experience continues, so I think I'll continue to research the above, as well as if there is a method to find a wire with "solderability" that would have similar resistance characteristics of the missing "fine wire" attempting to repair the "bad" tank. I don't see much support for that effort across the web, (even for more valuable, classic tanks) much less the cheap cardboard one, but... that's what makes it interesting.
Thanks again.
Dave
Are the numbers on the good tank similar to those on the "bad" one? Also, if the resistance tests similar on both you're probably fine anyway.
Yep... identical tanks , So I'm done with this one.
I would still like to play around with the "bad tank" and see if I can find a suitable "Fine wire" to repair as stated in the earlier post, so if anyone knows of a product that may work I'd be interested in trying, like maybe a winding from a resistor or a magnetic bobbin or something?...
I know it's not worth the time or effort, but the education I have received from all here has made the repairs so far enjoyable.
I'll check back to this post occasionally to see if there are any ideas, and continue to view the forum on a regular basis, and I may have some excellent photos to share of what CAN go wrong on a solid state amp....
Dave
Dave, try using wire from an electric guitar's pickup.
Hello nebraskaplayer,
Let me know if I'm off the track with this answer
But Something you said there leads me to think you might be not fully understanding the workings?
**The electrical wires go to the coil,,,not the spring ends.**
The springs are purely a mechanical function, they are NOT directly connected to the electrical circuit.
The spring movement is created by the magnetic effect induced by the electric coil.
(From what I can see) It is the coil wires that have broken away from the green and black lead block terminal.
Oh yeah those wires have a coating and no you can't solder them as is ,,, you need to scrape the varnish from the end you wish to solder,,, then it can be soldered as normal.
You mention wanting the golden reverbs from 60's era Amps. Sorry mate not much chance of that with the pathetic circuits used in those Amps.
Far better to buy a digi reverb pedal.
Anyway a pic might help,
Phil.
Just found another picky,, close up Reverb transducer setup.
Phil.
Thanks for replies,
looks like I won't be looking for fine wire to repair original tank.
Phil..
I've read all your posts regarding reverb; don't think you could be off track with an answer, but thanks for being polite.
Your comment about not fully understanding the workings, was right on the money as I stated in my previous post...
"Not sure if I understand why the absence of the "fine" wire between the two posts terminating each spring at the Green (output) end affects the output sound so dramatically, but doesn't affect the resistance measurement of the input or output leads?, I need to do some more reading to understand the magnetics in play?"
My confusion came from the fact that the "wire" that I was looking at was either something left over from production that got stuck on the end of the spring post(s).. or perhaps a fabric thread that had somehow (in this poor little amps previously hard life, based on all the damage I've found thus far), got wound around the two spring posts, and under normal magnifying glass looked like a fine wire. I'll repost that pic below and if you save it and blow it up you can see that it is actually thread not wire. (that also explains why when I tried to "tin" it with soldering iron it burned to half it's length immediately).
I could see the other remnant of it on the other post, that is why I couldn't understand why there would be a fine wire between both the spring posts. (that appeared broken)
Now that I have completely disassembled the tank, read your posts, and looked at these diagrams (the two below) from Tubes and Mores website.. I do now understand the electromagnets and the wiring...
I looked at the wires from the windings on the magnets to the connectors and they are actually OK, I did find one of connectors wasn't fully engaged... connected but not "tight"...
I am posting pics of windings to connectors (where we thought the problem might have been), thought might be of value to someone else in the future... if they have these tiny "tanks".
Cleaned it up, checked all the push connections, stuck in in amp... and now REVERB ...., So now I need to get some double faced foam tape to mount back in cardboard tank, and then more tape to anchor to cabinet.
SO both amps will have working tanks in them... I might play around and make a metal tank cover, and rivet tank to it (I have some light gauge aluminum sheet stock), and see if it makes any difference.
Regarding wanting the golden reverbs from 60's era Amps...
I guess I'm getting a little greedy for a $20 1999 SS amp... and with all the free help here, only $4.50 in parts, It is a nice little practice amp.
Now to find the two D shaft knobs and I'll be set...
I do have a SuperChamp XD that can produce a fairly nice reverb blackface sound ...the amp, not me...lol.
I have "looked" at this pedal, Boss FRV-1 '63 Fender Reverb, excellent review, but I haven't played through one. But for the little I play (so far) hard to justify.
Thanks again
Dave