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Messages - phatt

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16
Keep it Simple,, just fix what is failing FIRST,,,, then move onto other things. 8|
If you have the amp open and there are no obvious signs of corrosion or Leakey El caps then job is done.

Unless these things have sat for years in wet damp storage and full of roaches and rat poo then the rule is simple,, if it ain't broke don't fix it.
Yes visual inspection of solder joints is a good idea but don't replace parts unless they are causing failures.
No need to get too concerned about cap voltages as Most SS power supplies are likely much lower voltage that Valve amps. (if that is the worry)
If the amp runs on +40/-40 then the caps will be rated at 50VDC.
Some big SS power amps run on much higher DC rails and they can be dangerous.
ALWAYS pull Power Cord from wall when working on circuits,, don't just rely on the wall switch.

If you are concerned then just measure the caps with your meter to check they have bleed off the supply before working on the circuit.
The human body can handle up to around 80Volts but after that you have to be very aware of the danger.
Phil.

17
If the Amp has an Effects loop or Preamp out/Poweramp input then just bridge with a guitar cable.
That will bypass the internal switch in the amp.
If the amp then gives no trouble You have 2 choices,
1/replace the socket with the dodgy switch. (in some amps that can be a lot of work).
Or 2/ leave a short jumper lead inserted and forget about pulling the amp apart.
I'm sure you would rather be playing guitar than working on circuits.
The internal Sw in FX loop and like interconnects is so common that it should be the first thing you check when you have intermittent signal drop out.
If I had a dollar for every time I've answered these,, I'd be rich.
Back in the 50's these switched sockets were made to a high standard with pressed in silver contact  buttons now all you get is a strip of tin for a switch. Yes and most all big name gear now uses these crappy sub standard contacts so they don't take long to fail.
Phil.

18
Amplifier Discussion / Re: Pignose 7-100 fizz
« on: July 03, 2020, 03:25:44 AM »
I'm not in the know about that amp but I'd guess the circuit is basic and the fizz maybe just the way they come.
Being a basic unit, Crossover Distortion of the power stage is likely the issue.
If you can dig up a schematic for that amp and post it, others here might be able to help tweak the circuit for you.
Phil.

19
Schematics and Layouts / Re: Ibanez TSA30 Schematic and PCB Layout
« on: June 23, 2020, 07:14:09 AM »
OK but some stuff that might explain why not.
The Passive FX loop is for a 5E3 while the tone setup in your amp is the later TMB setup. The simple treble cut tone of a 5E3 is not as lossy as the BF type tone in your Amp.
AFAIK
Any loading of the volume control output will impact the effectiveness of your tone controls.
Yes it will pass signal but at the cost of signal strength  and tone compromised.
Some pedals will certainly load down the signal if inserted there.

You would likely need to use another HiZ stage so the tone does not suffer needless loss.
But As I mentioned the previous stage is ideal for driving an FX loop as it's a CF stage and will not suffer from any loading,, but as it's a pcb that maybe a hassle for you. I would Break signal after R72 and use the passive loop there.
The problem with the idea of FX loops inside a valve circuit is that you interrupt the magic of how the power supply drops all through the amp. Valve power supplies are not stiff like SS Amps and a lot of the mojo has to do with the interaction of supply rails as signal goes up. It's not just sag it's how it effects the whole path from input to output.

If you care to look at all those old 6V6 deluxe schematics you will notice that the first 2 drop resistors in the R/C supply are 10k & 10k in some but then the 5E3 it's 5k & 22k.
Just by changing those values makes a big difference to how the circuit responds, dynamics and feel change.

So if you want to get that stuff to happen then DON'T break into the circuit,, use pedals in front.
If you want reverb then you need to design the mixer part like later models of fender deluxe.
Hope that helps, Phil.

20
Schematics and Layouts / Re: Ibanez TSA30 Schematic and PCB Layout
« on: June 12, 2020, 02:51:32 AM »
The circuit already has a loop.
Inserting it in the middle will likely have little benefit.
As to your idea the problem is not an fx loop it is the design of the circuit.
i.e. a ss front end designed badly and little you can do without major mods. xP

Now note I've never been close enough to smell one of there amps but I would not be interested after seeing the schematic.
It is possible some clever chap has found a way around it but I doubt it would be simple.
There is too much happening at the front end so as you note inserting a reverb FX in the loop does not work well.
If you are hell bent that it will make a difference do it at R72.
As I have already mentioned,, I would bypass the whole front end and connect the input to V1A and change R13 to at least 470k. THEN the circuit will (Likely) be more pedal friendly.
Better mind might have more knowledge,, Phil

21
Amplifier Discussion / Re: Sunn Dymos
« on: June 07, 2020, 08:24:22 PM »
Yes the image shows the hardware mounted but that's not what I have on the bench it's an image off the web. What happens if points A and B are connected to chassis ground -i.e.  the collectors are not isolated?

I think you are missing something about how the circuit works and is confusing your question.

Point A is the supply for the collector (NOT GROUND)

Look at the bottom of Schem and find the rectifier D101
You will See that point A is the Positive supply for the collector (pointA)

The *Emitter* of the lower transistor is Point B
That is the Negative supply shown at bottom of D101.
Those 2 points DO NOT connect to ground.

To add even more confusion
This is an odd circuit and someone here with better understanding may know more.
note the speaker neg returns to neg voltage rail????
So it makes no sense to me.  :loco xP

hope it helps, Phil.


22
Guitar News / Re: DryBell releases "The Engine" - $299 preamp pedal
« on: June 05, 2020, 03:27:36 AM »
I quote the vid at 7.18

"So there you have it folks the Engine truely evokes the feel and tone of those classic Amps."

Meanwhile using a REAL JMP 50Watt Marshall. Durh???? what a load of crap :lmao: :lmao: :lmao: :lmao:

Which is much the same as promoting A Boss fender 64 reverb pedal sounding like a real 64 reverb Amp.
And demonstrating it through a,,, real 64 Fender amp.
Yeah right,,,,, And I can make a  banana flavor taste like a real banana just buy using a real banana.  :lmao: :lmao: :lmao:

This crap goes on all the time on these pedal demos,,
The REAL ACID test is how good some wizz bag pedal pulls off great tone through a small bedroom amp. 8|

Don't get me wrong the pedal sounds good but at least test it through some basic amps as well as through the obvious Big name Valve gear.
That would give punters a much more realistic impression of how well the pedal will suit their setup.
For every Big name Valve amp Owner there would be 10~100 times more basic amp owners out there.
Which equates to far greater profit if they had a even half a brain. :loco

For those that don't know, the touch response mentioned in the vid has more to do with the Valve amps used than the pedal.
The Sustain at 1.24 is simply the Valve amp feed back which has little to do with the pedal. Any basic pedal with boost up will cause a valve amp to feedback like that.
Again this has little to do with how good the pedal works. The wank factor is in a lot of these demos and it's time the young ones woke up to the hype.
Rant over,, Phil.

23
The Newcomer's Forum / Re: Tda ICs Pentawatt PCB
« on: May 29, 2020, 08:17:35 AM »
Again Electronic junk comes cheap and I'm sure it won't take long to find a heat sink in any old computer, amplifier, dead battery charger or like gear that is thrown out.
Or just go to the hardware store and purchase a 2mmx50x50mm length of angle alloy (that's 2x2 inch for those in the land that still lives in imperial :-X)
Thickness, 2mm or thicker if you can find it. Cut at least 3 inches to give the heat somewhere to go. again more is better. And don't forget to isolate the chip with a non conductive washer.
Phil.

24
The Newcomer's Forum / Re: Tda ICs Pentawatt PCB
« on: May 28, 2020, 11:15:09 PM »
What *Edvard* said :tu:
You just need to get inventive,
Scrounge some electronic landfill for small header sockets with lead wires attached and use those to interconnect to Breadboard. some will be close to the spacing,,you just need to use 2 rows,, 3 and 2.
cut the rest off.
Or (just been said) just solder lengths of wire directly to pins.
And be darn sure you mount the chip to a heat sink before you fire it up. :trouble
Re Fets,, it's a no brainer,, any BJT will work as buffer.
Many hundreds of guitar pedals use a simple BJT buffer and I've not heard of any seriously limiting issues about their use.
Yes a Fet will do the same thing and I doubt you would hear any difference,, especially when used for guitar interface.
Phil.

25
Amplifier Discussion / Re: Accutronics Belton Reverb Module
« on: May 23, 2020, 11:00:16 PM »
Think that I solved the problem.  I took out the 6L6 tube and replaced with a NOS GE 6V6 and it really quieted down the reverb hiss.  I'll have to check and see if the old tube is bad or not.

Thanks for the input again!

Keith

Ummh?? Generally 6L6 and 6V6 are not interchangeable. There is a good chance the 6V6 will burn out.
I'd be checking with the maker before you  swap out power valves.
Phil.

26
Amplifier Discussion / Re: Frontman 212R
« on: May 23, 2020, 10:12:13 AM »
Disconnect speaker then set meter to DCV then read voltage at the speaker output terminals/leads of amp.
It should be very close to Zero Volts.
If you have large voltage like 40Volts, pos or neg then power stage is faulty.

Terminals of the transformer are ACvolts,, you need to read the DCV after rectifier,, often easy to do at the main filtercaps.
Front panel knobs is irrelevant if the power stage has blown.
Phil.

27
Obviously the top OD input SKT has failed and ideally you need to replace that socket but as it might be hard to source the exact part then here is an option using only one input socket,, probably similar to what *Joe* mentioned.
Now as it's possible the input for Supercube 100 might be different to the cube 60 schem I'm working from I can't be sure this would work so you will have to tread careful and double check.
This requires an N/C switched Socket and a DPDT switch to work.
N/C means Normally Closed,, opens when you insert.

As to your Q re those ribbon wires, you can just gently use your fingernails to split them, might have to nic between them to get it started but they should seperate fairly easy.
If you need more length then use a piece of strip board and then add more wires.
With out a pic of how the ribbon connects to PCB it's hard to give advice.
Hope it helps, Phil.

28

Best I can make out is R101 was never installed hence the unused pads between the inputs can be seen in the pic. the amp will work without it and may even add a little more signal to pass.

I've edited the input schematic of the Cube 60 for reference.
sw1-sw4 are the internal switches.

How it works, maybe?
With no plug in either input sw1 grounds out R101 270k which mutes the normal input while sw2 grounds the output of Q1 at (point X)
with *Normal input* in use sw4 opens and signal passes through R10 with R9 running to (point X) which is still grounded via sw2.

With *OD input* in use, sw1 and sw2 open.
sw1 lifts R101 off ground which adds to the value of R10 forming a voltage divider at the input of C6.

sw2 removes the mute at point X allowing signal to pass throuh R9.
As sw4 is then closed it forms a voltage divider out of r10 and R101.

I'm not sure about the extra internal tab (the red ? mark)
I can only assume it contacts the sleve of the plug ,, which seems pointless as the sleeve is already grounded by the threaded metal socket???
unless maybe the metal thread uses a plastic isolation washer???

Hey nifty a Q, are you saying that the Od input and the Boost Switch are on that PCB? If so then my wire numbers I mentioned earlier are wrong.
 
I'm still trying to decipher Joe's idea but thought a drawing and explanation might help.
Phil.

29
I'm with Joe,, For an experienced repair shop they would know *EXactly* were to source parts,, but for the once a year home fixup guy,, well I've been caught a few times. :-\
Yep looks the same ,, oh bugga this one is slightly longer and won't fit or worse the sw is NO not NC.
At least with open frame like switchcraft you can visually see how it works.
Oh and they are easy to clean and the metal tabs are much *Thicker* and hence last for years longer that those plastic encapsulated units. I've pulled many of those type out and they just crumble.  :grr
Phil.
 

30
Probably not that simple Joe. :-\
Using the pic of back panel,
It looks like the top socket has at least 5 terminals while the bottom socket only has 2 terminals.
That tells me the top is an odd ball socket that is likely hard to replace.

Those encapsulated sockets come in many types so hard to work out how the switching works.
The internals are often quite delicate and maybe not working to spec.

Q for Nifty,

1/ Again I ask is the issue only present when you plug in?
OR
2/ Can it be evoked later by wiggling the plug After you plug in?
If it only happens at plug in then the issue could be a failing circuit.

If both 1&2 then yep failing sockets.

Here is the input setup from a Cube 60 which shows what I think you have, note the top OD input socket is drawn with the 5 terminals while the Normal  and Footsw units are 2 terminal.

Phil.

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