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December 08, 2024, 01:15:30 PM

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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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g1

Those readings are good.  Yet it was giving you an impossible voltage reading in circuit (for a good PNP).
It's possible it is breaking down under voltages higher than your meter can provide on 'diode check' function.
Might be easiest to just replace it if you have one.

RG100ESROX

Quote from: g1 on November 12, 2024, 08:44:32 PMThose readings are good.  Yet it was giving you an impossible voltage reading in circuit (for a good PNP).
It's possible it is breaking down under voltages higher than your meter can provide on 'diode check' function.
Might be easiest to just replace it if you have one.

Already replaced it.👍🏻
Guitarists spend half their lives tuning their guitars, and the other half playing out of tune...

g1

Then re-do the voltage readings on it (and see post #79).

RG100ESROX

#93
Quote from: g1 on November 13, 2024, 12:20:00 PMThen re-do the voltage readings on it (and see post #79).

The only change in voltage is boxed in blue...on Q12 (far right) This is the one I changed.

I've included a photo of the current limiting light bulb at 110VAC.
Guitarists spend half their lives tuning their guitars, and the other half playing out of tune...

g1

#94
That's better, but as far as I know it is Q10.  Did you mean to say that, or is there a reason you called it Q12?

Are Q8 and Q9 replacements or the original parts?

RG100ESROX

#95
Quote from: g1 on November 13, 2024, 01:52:11 PMThat's better, but as far as I know it is Q10.  Did you mean to say that, or is there a reason you called it Q12?

Are Q8 and Q9 replacements or the original parts?

I have replaced all of the transistors from Q8 thru Q16. So, they're all new.

I believe Q8 and Q9 are the 2N5484s near the bias trim pot??? I was then calling the first TIP32C Q10, and the TIP31C Q11, and the last TIP32C with the heatsink Q12. Then the power transistors Q13 thru Q16.

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

RG100ESROX

Are we still at a point where we do not want to fully test the amp yet?

In other words, no speaker or guitar connected?

Or can we test the amp for audio output?
Guitarists spend half their lives tuning their guitars, and the other half playing out of tune...

g1

The DC voltages are way off, so no point in testing audio.  There is -18V at the output.
I can only go by the schematic.  It is up to you to find the parts that correspond to it, by following what the transistors are connected to according to the schematic.  From the connections and circuit components, you should be able to locate which transistor is which.
If you are unable to read schematics, there is not much more I can do.  Not meaning to be rude, but this is not a repair that can be accomplished just by random parts replacement.

RG100ESROX

Quote from: g1 on November 13, 2024, 08:56:49 PMThe DC voltages are way off, so no point in testing audio.  There is -18V at the output.
I can only go by the schematic.  It is up to you to find the parts that correspond to it, by following what the transistors are connected to according to the schematic.  From the connections and circuit components, you should be able to locate which transistor is which.
If you are unable to read schematics, there is not much more I can do.  Not meaning to be rude, but this is not a repair that can be accomplished just by random parts replacement.


I can read schematics.

So, I should follow the signal path and check for continuity??
Guitarists spend half their lives tuning their guitars, and the other half playing out of tune...

g1

You need to get the DC voltages right.
Something in the bias string is not working.  Q10 is not turning on.  Possibly because Q8 is not on.  You had given voltages for one of the small transistors, but not sure if it was Q8 or Q9.  Q8 connects to R41 and base of Q10. 
Measure e,b,c voltages for Q8.
Measure voltages through the bias string (the bias string consists of:  R47, Q10, D7, D8, trim pot, R48, R49).

RG100ESROX

Quote from: g1 on November 13, 2024, 09:07:16 PMYou need to get the DC voltages right.
Something in the bias string is not working.  Q10 is not turning on.  Possibly because Q8 is not on.  You had given voltages for one of the small transistors, but not sure if it was Q8 or Q9.  Q8 connects to R41 and base of Q10. 
Measure e,b,c voltages for Q8.
Measure voltages through the bias string (the bias string consists of:  R47, Q10, D7, D8, trim pot, R48, R49).

Okay. I'll post the voltages within the hour.

Thank you very much for your help.
Guitarists spend half their lives tuning their guitars, and the other half playing out of tune...

RG100ESROX

Here are all of the voltages in the bias pot area...

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

g1

I need the voltages from the points I listed in post #99, according to the schematic.
I don't have a board layout so the picture doesn't get me anywhere. 

RG100ESROX

Quote from: g1 on November 13, 2024, 10:49:08 PMI need the voltages from the points I listed in post #99, according to the schematic.
I don't have a board layout so the picture doesn't get me anywhere. 

Okay. Sorry. I thought that would be helpful in some way.

I'll get those for you.

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

g1

Quote from: RG100ESROX on November 13, 2024, 02:30:13 PMI have replaced all of the transistors from Q8 thru Q16. So, they're all new.

I believe Q8 and Q9 are the 2N5484s near the bias trim pot???
I just caught this.  Q8 and Q9 should be TIS98, not TIS58 or 2N5484.  They should be bi-polar transistors, not Fets.  What were the originals and what is in there now?