Hi Cheeto333,
Well done.
We all went through that stage and later on we developed a search and repair strategy.
"Rome is not build in one day ..."
The connectors that I mentioned are these with, probably, a flat cable connected to it.
White in color? probably as I can't see the amp right now.
But these voltages will all be present as the test result from 1 to 3 prove that they must be, other wise we found a problem already.
Now we know the pre amp sections are working.
We did not test the reverb section yet but I assume this will work as well.
But a test will confirm that later.
Section 4.
You checked for output on the Chorus and Dry outputs.
I actually meant the Speaker outputs.
Then we know if there if there is a problem with a power amp.
Can you run that test again? (4.a. and 4.b.)
Well done.
We all went through that stage and later on we developed a search and repair strategy.
"Rome is not build in one day ..."
The connectors that I mentioned are these with, probably, a flat cable connected to it.
White in color? probably as I can't see the amp right now.
But these voltages will all be present as the test result from 1 to 3 prove that they must be, other wise we found a problem already.
Now we know the pre amp sections are working.
We did not test the reverb section yet but I assume this will work as well.
But a test will confirm that later.
Section 4.
You checked for output on the Chorus and Dry outputs.
I actually meant the Speaker outputs.
Then we know if there if there is a problem with a power amp.
Can you run that test again? (4.a. and 4.b.)
Ojee, I'm maybe not clear. English is not my first language so what I mean and what I write can be different due to the translation in my head.
And as that one isn't young any more, errors are very likely to hapen now and then.
So back to business:
I like to know if both power amps are working as intended.
Before testing switch the amp of.
1. Connect a loudspeaker to the speaker A output jack.
Switch the amp on.
Insert a signal into the line input jack.
Do you hear anything?
Is it loud and clear?
Switch of the amplifier.
3. Connect a loudspeaker to the Speaker B output jack.
Switch the amp on.
Do you hear anything?
Is it loud and clear?
Now let's see what the outcome is for point 2 and 3.
Cheers
And as that one isn't young any more, errors are very likely to hapen now and then.
So back to business:
I like to know if both power amps are working as intended.
Before testing switch the amp of.
1. Connect a loudspeaker to the speaker A output jack.
Switch the amp on.
Insert a signal into the line input jack.
Do you hear anything?
Is it loud and clear?
Switch of the amplifier.
3. Connect a loudspeaker to the Speaker B output jack.
Switch the amp on.
Do you hear anything?
Is it loud and clear?
Now let's see what the outcome is for point 2 and 3.
Cheers
I have done the above test:
1. Connect speaker cabinet to speaker A (Chorus) output jack. A 500 HZ tone into the Effects return (line input) jack can be heard through the speaker. It is not very loud, but it is there.
2. Change speaker cabinet from speaker output A (Chorus) to speaker output B (dry) output jack. A 500 HZ tone into the Effects return (line input) jack can be heard through the speaker. It is not very loud, but it is there.
1. Connect speaker cabinet to speaker A (Chorus) output jack. A 500 HZ tone into the Effects return (line input) jack can be heard through the speaker. It is not very loud, but it is there.
2. Change speaker cabinet from speaker output A (Chorus) to speaker output B (dry) output jack. A 500 HZ tone into the Effects return (line input) jack can be heard through the speaker. It is not very loud, but it is there.
OK, as said My interpretation of your writing created a misunderstanding.
So both the amps are working.
Good thing.
The low level at the lsp jacks is due to the signal level from your generator.
If you connect your signal to the guitar input at the front of the amp, your level would be much higher.
Can you do that test again?
Thanks
So both the amps are working.
Good thing.
The low level at the lsp jacks is due to the signal level from your generator.
If you connect your signal to the guitar input at the front of the amp, your level would be much higher.
Can you do that test again?
Thanks
I would not have guessed English was not your first language, you are communicating very well 
I ran the above test again using the guitar input. The tone is present at both speaker outputs, and can be manipulated with the preamp controls. As usual, it is very quiet until I crank the gain and level controls above ~6.
I ran the above test again using the guitar input. The tone is present at both speaker outputs, and can be manipulated with the preamp controls. As usual, it is very quiet until I crank the gain and level controls above ~6.
Ok All circuits are running wel.
Only levels are not as they should be.
In post nr 20 you said that the controls were responsive.
If you connect another power amp in the Line out of your amp and insert a signal in the front input jack;
1. Do they react smootly and as they should?
2. Or do you have suddenly a louder volume past 6?
What happens if you connect the other amp to the dry and wet line outputs (not the speaker out!!!)
3. Do they react smootly and as they should?
4. Or do you have suddenly a louder volume past 6?
I try to guide you one step at the time...
Only levels are not as they should be.
In post nr 20 you said that the controls were responsive.
If you connect another power amp in the Line out of your amp and insert a signal in the front input jack;
1. Do they react smootly and as they should?
2. Or do you have suddenly a louder volume past 6?
What happens if you connect the other amp to the dry and wet line outputs (not the speaker out!!!)
3. Do they react smootly and as they should?
4. Or do you have suddenly a louder volume past 6?
I try to guide you one step at the time...
Ran 500 Hz signal into low guitar input jack on front of Ampeg. Ran “line out” from front of Ampeg into effects return of amp 2.
1. Preamp controls on both channels react smoothly and as they should, no clear volume jumps, volume on both channels the same. Chorus controls do nothing when engaged (may be by design?)
2. Reran test using mono line output, dry line output, and wet line output (not speaker output!) from rear of Ampeg into effects return of amp 2.
a. Mono line output: Volume very low (much lower than in test 1!). Preamp controls still technically work, but no volume below 6 on gain/level on each channel. Volume on Channel A much higher than Channel B.
b. Dry line output: Volume very low (much lower than in test 1!). Preamp controls still technically work, but no volume below 6 on gain/level on each channel. Volume on Channel A much higher than Channel B.
c. Wet line output: Volume very low (much lower than in test 1!). Preamp controls still technically work, but no volume below 6 on gain/level on each channel. Volume on Channel A much higher than Channel B. Chorus controls work as expected on both channels.
Thanks very much for bearing with me, Tarzan.
1. Preamp controls on both channels react smoothly and as they should, no clear volume jumps, volume on both channels the same. Chorus controls do nothing when engaged (may be by design?)
2. Reran test using mono line output, dry line output, and wet line output (not speaker output!) from rear of Ampeg into effects return of amp 2.
a. Mono line output: Volume very low (much lower than in test 1!). Preamp controls still technically work, but no volume below 6 on gain/level on each channel. Volume on Channel A much higher than Channel B.
b. Dry line output: Volume very low (much lower than in test 1!). Preamp controls still technically work, but no volume below 6 on gain/level on each channel. Volume on Channel A much higher than Channel B.
c. Wet line output: Volume very low (much lower than in test 1!). Preamp controls still technically work, but no volume below 6 on gain/level on each channel. Volume on Channel A much higher than Channel B. Chorus controls work as expected on both channels.
Thanks very much for bearing with me, Tarzan.
It's getting late here but still a few ideas.
The chorus has no effect because the line out is before the chorus and reverb circuitry.
Between the Line out from the front and the outher outputs (dry, wet, mono) at the back we have:
An opamp (IC6B) that send the signal to the reverb and the Chorus circuitry.
Did you constructed the probe you suggested and Enzo confirmed in #7-10?
If yes, then feed a signal into the gutar input and "probe" at pin 7 of IC6B.
Is the signal level OK or do you have to go up to 6 to hear something?
If so; then the chip is probably dead.
But maybe the Line input jack at the front is corroded but you allready mentioned that you used a jumper on the effects loop. But are we talking about the same jacks?
Any way, jump these and check the signal level.
If all is well here, we have to move further forwards. this time into the chorus circuitry.
But I have to leave that to tomorrow.
It's almost 22:00 hours here and my bed is calling me.
Cheers
The chorus has no effect because the line out is before the chorus and reverb circuitry.
Between the Line out from the front and the outher outputs (dry, wet, mono) at the back we have:
An opamp (IC6B) that send the signal to the reverb and the Chorus circuitry.
Did you constructed the probe you suggested and Enzo confirmed in #7-10?
If yes, then feed a signal into the gutar input and "probe" at pin 7 of IC6B.
Is the signal level OK or do you have to go up to 6 to hear something?
If so; then the chip is probably dead.
But maybe the Line input jack at the front is corroded but you allready mentioned that you used a jumper on the effects loop. But are we talking about the same jacks?
Any way, jump these and check the signal level.
If all is well here, we have to move further forwards. this time into the chorus circuitry.
But I have to leave that to tomorrow.
It's almost 22:00 hours here and my bed is calling me.
Cheers
Ran 500 Hz signal into low guitar input jack on front of Ampeg. Used chassis-grounded signal trace probe to gather the following data at pin 7 of IC6B:
Without or without front effects loop jumped, 500 Hz tone is present and responsive to preamp controls on both channels. Signal is present even on low gain/level settings on both channels. Progress!
Without or without front effects loop jumped, 500 Hz tone is present and responsive to preamp controls on both channels. Signal is present even on low gain/level settings on both channels. Progress!
Tarzan's advice is right on the nose. I traced the signal chain from pin 7 of IC6B, and found that the positive side of C43 on the preamp board is deformed (see photo here, C43 is black electrolytic next to keps nut). 500Hz signal is present on the negative side of C43, but not on positive side. Next step is to replace C43. Even more progress! The parts list denotes C43 as a 2.2/50 cap. This means 2.2uf 50V capacitor, correct? Will these work?
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