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Where to find 6000uF 50V replacement cap cans??

Started by RG100ESROX, October 13, 2024, 09:33:56 PM

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RG100ESROX

#165
Quote from: RG100ESROX on November 22, 2024, 08:02:19 PM
Quote from: Loudthud on November 22, 2024, 07:19:47 PMWhat is the DC at the output with no signal ?

Because this thing has a pretty high output impedance, the signal amplitude at the output as well as the DC offset could change considerably when you connect a dummy load.


Voltage at the output is -0.023VDC with no signal.

Yes. No signal.

All controls at zero, and bias at FCCW.
Guitarists spend half their lives tuning their guitars, and the other half playing out of tune...

g1

Quote from: RG100ESROX on November 23, 2024, 09:42:23 PMWith reference to chassis ground on the positive side of the two far right power resistors, I get about 42.0VDC. Across the resistors there was 0.0V.

I'll check for DC on the output, and check the voltage of the two resistors again...

-42.0VDC on the far right .62R and .27R +, and  -.020mV on the far left power resistors +.

On the output I have  -.022VDC.
+42V vs -42V at the right resistors is radically different.  Triple check all your info before you post.  It's impossible to work with faulty data.

If there is no DC across any of the .68 or .27 power resistors, there should be no heat.
Do they get warm idling with no signal?

RG100ESROX

#167
Quote from: g1 on November 24, 2024, 12:42:43 PM
Quote from: RG100ESROX on November 23, 2024, 09:42:23 PMWith reference to chassis ground on the positive side of the two far right power resistors, I get about 42.0VDC. Across the resistors there was 0.0V.

I'll check for DC on the output, and check the voltage of the two resistors again...

-42.0VDC on the far right .62R and .27R +, and  -.020mV on the far left power resistors +.

On the output I have  -.022VDC.
+42V vs -42V at the right resistors is radically different.  Triple check all your info before you post.  It's impossible to work with faulty data.

If there is no DC across any of the .68 or .27 power resistors, there should be no heat.
Do they get warm idling with no signal?

Understood. Memory is not always spot on, but I'll quit misquoting.

This is after 3 minutes of initial power on with no signal and bias trim set FCCW.
Guitarists spend half their lives tuning their guitars, and the other half playing out of tune...

RG100ESROX

#168
I think this is good news...

I replaced both 2N4401's and I now get mV on both of the .62R power resistors. This is the voltage at the 8 o'clock position on the trim pot. I do not however get any voltage across the .27R power resistors.

The two .62Rs didn't get warm nearly as fast as they did before I changed the transistors.

Let me know what you think.

Thanks!!
Guitarists spend half their lives tuning their guitars, and the other half playing out of tune...

g1

Not sure why they would run cooler now since they are showing voltage, but it sounds like an improvement.
I'll post what I was writing anyway.

Some of those 5W resistors are for the power supply and will get hot when on.  As they are radiating heat, the closest 0R68 10W will get warm too.
If that is the only one of the four 10W warming up, then no worries.

Also, if you still have your jumpers in the footswitch jack, you should remove them.  You should only use LED's there, not straight jumpers.  The footswitch adds LED's in series.  Straight jumpers allow too much current which will stress the front panel LED's and make two of the 5W resistors run hotter than they should.

Do another scope shot like post #158, but turn your volume control down a bit so you only have 0.1V (100mV) Vpp at the scope.  Keep the trimmer at full CCW.

RG100ESROX

Quote from: g1 on November 24, 2024, 08:27:35 PMNot sure why they would run cooler now since they are showing voltage, but it sounds like an improvement.
I'll post what I was writing anyway.

Some of those 5W resistors are for the power supply and will get hot when on.  As they are radiating heat, the closest 0R68 10W will get warm too.
If that is the only one of the four 10W warming up, then no worries.

Also, if you still have your jumpers in the footswitch jack, you should remove them.  You should only use LED's there, not straight jumpers.  The footswitch adds LED's in series.  Straight jumpers allow too much current which will stress the front panel LED's and make two of the 5W resistors run hotter than they should.

Do another scope shot like post #158, but turn your volume control down a bit so you only have 0.1V (100mV) Vpp at the scope.  Keep the trimmer at full CCW.

Will do.

Thanks for the explanations.

I'll remove the jumpers and plug the foot switch in.

Back in 30.
Guitarists spend half their lives tuning their guitars, and the other half playing out of tune...

RG100ESROX

#171
Here's the latest sine waves.

I tried to keep the voltage as low as possible.

Q: Why does it look like every other sine wave is clipped??
Guitarists spend half their lives tuning their guitars, and the other half playing out of tune...

g1

That is just power supply ripple again.  You can see on the scope readout that it is approx. 120Hz.
The first pic says 1Vpp at 0 Hz, so not sure what is going on there.
Get your 3Khz back up to a level where the scope says 3Khz.  Reduce the amp volume while increasing the scope sensitivity, so it shows a larger waveform from top to bottom.  Try to get around .1Vpp at 3Khz.

RG100ESROX

#173
Quote from: g1 on November 24, 2024, 10:22:10 PMThat is just power supply ripple again.  You can see on the scope readout that it is approx. 120Hz.
The first pic says 1Vpp at 0 Hz, so not sure what is going on there.
Get your 3Khz back up to a level where the scope says 3Khz.  Reduce the amp volume while increasing the scope sensitivity, so it shows a larger waveform from top to bottom.  Try to get around .1Vpp at 3Khz.

I cannot get a sine wave for some reason.

I guess I'll keep messing with it until I can get a sine wave out of it. I'm not sure what's different today than yesterday.
______________________________________________
Well, it's tomorrow, and I was not able to get a sine wave. For the life of me, I have no idea why. All test voltages remain unchanged.

I am pretty sure the SG is working properly. I've checked as many wire connections as possible, and it turned up nothing. All connections look good.

Would you have any suggestions at this point? Aside from throwing in the towel. (-;

I really appreciate all of your help and input
Guitarists spend half their lives tuning their guitars, and the other half playing out of tune...

g1

Hook the scope up to the signal generator.  Make sure you have signal there.
If so, connect gen. to amp and scope at the FX send.  Do you get signal?

RG100ESROX

Quote from: g1 on November 25, 2024, 10:33:02 AMHook the scope up to the signal generator.  Make sure you have signal there.
If so, connect gen. to amp and scope at the FX send.  Do you get signal?

Here ya go!!

Looks like the signal Generator is working just fine.

Connect gen. to amp and scope at the FX send.  Do you get a signal? Answer: No.
Guitarists spend half their lives tuning their guitars, and the other half playing out of tune...

g1

It says .02V on that scope shot.  Is that what it is set to put out, or is that the most it can do?

RG100ESROX

#177
Quote from: g1 on November 25, 2024, 01:24:03 PMIt says .02V on that scope shot.  Is that what it is set to put out, or is that the most it can do?

It's set there because I thought you wanted it as low as possible. Plus, I had it set to a Vmax instead of Vpp. I have set it now for Vpp.

Do you want it higher?

Also, I'm noticing some lower than spec'd preamp voltages. They're about .6VDC when they should be 1.0VDC.
Guitarists spend half their lives tuning their guitars, and the other half playing out of tune...

g1

That's fine if you had the gen. set for low level output.
Check the amps power supply (DC)voltages, shown as  A,B,C,D,E on the schematic.

RG100ESROX

#179
Quote from: g1 on November 25, 2024, 03:37:05 PMThat's fine if you had the gen. set for low level output.
Check the amps power supply (DC)voltages, shown as  A,B,C,D,E on the schematic.

VOLTAGES REQUESTED:

A =   41.90VDC
B = -41.60VDC
C =  12.61VDC
D = -12.60VDC
E =   25.38VDC

Guitarists spend half their lives tuning their guitars, and the other half playing out of tune...