Polytone Mini Teeny Brute Distorted Output

[g1]

If it now reads 1R it's leads may be corroded or oxidized. I would clean them up with sandpaper and see if you can get it to measure the same as R18.
If not, replace it.

[glebert]

R19 is showing 4K in circuit, compare to R18 showing 0.28 R

Removed R19 and out of circuit it reads 1R

Paraphrasing Enzo, there is no way that a resistor should read higher in a circuit than out. There had to be some bad contact there, either in probing or the circuit itself.

[misterc57]

Good news.

Cleaning up R19 out of circuit I could not get it to read below 1R. So I installed a 0.33R into that slot (closets value I had on hand).

Amp is now sounding fine. I am reading 0.40R at R19 and 0.28R at R18 in circuit. Is it okay to leave them this way or should I order a new pair of 0.15R for those positions?

Thank you!

[g1]

Your meter is reading a little high, which is fine as most meters are not designed for such low resistances and the probes & leads add some. But it would be best for them both to be the same so I would suggest using the proper rated value for R19, or add another 0.33 in parallel.

[g1]

Paraphrasing Enzo, there is no way that a resistor should read higher in a circuit than out.

Theoretically this is true, but demands there be no DC present to the meter. So caps in circuit can create issues, as they may not be fully discharged, or may be charging/discharging due to the voltage put out by the meter itself (in resistance or diode check ranges).
All that said, usually this situation will not give a stable 'high' reading, but rather a reading that will not settle.

[misterc57]

Your meter is reading a little high, which is fine as most meters are not designed for such low resistances and the probes & leads add some. But it would be best for them both to be the same so I would suggest using the proper rated value for R19, or add another 0.33 in parallel.

My probes do add about 0.12. I have another 0.33 so I will try that.

[misterc57]

Installed a 0.33 at R18. Still have a difference of about 0.15 between R18 and R19.

Anyway, now things are bad again. A similar distortion as previous heard when playing a guitar.

Schematic Q4 layout is backwards, should be top to bottom C, B, E.

Q3 MJ4502 E: 32.9V
Q3 MJ4502 B: 32.17V
Q3 MJ4502 C: 2.4mV, not stable, keeps falling

CR3 C, A: 33V, 2.5mV

Q4 MJ802 C: 2.5mV
Q4 MJ802 B: -34.1V
Q4 MJ802 E: -34.1V

CR4 C, A: -34V, 2.6mV

Q2 NSDU57 E: 2.5mV
Q2 NSDU57 B: -0.5V
Q2 NSDU57 C: -34V

And this is strange, C1+ is 8.2V, (in prior tests it was 33V). And down the line at C3+ I read 33V

I see no continuity from C1+ to C3+

[misterc57]

Turns out there are bad connections on the trace side of the board where C1 and C2 connect. I had to hard wire C1+ to the BR. I also see that C1- had prev been hard wired to the chassis.

Now I have a hum and an over current. This just keeps morphing into different issues.

I noticed that CR4 cathode and CR3 anode are 8 ohms to ground, as well as R21 and R22. Is this right?

[Jazz P Bass]

"I noticed that CR4 cathode and CR3 anode are 8 ohms to ground, as well as R21 and R22. Is this right?"
Yes, IF you have an 8 ohm load connected.

[misterc57]

Amp is fine now.

I fluxed and reflowed the large holes where C1 and C2 meet the board. Removed two jumper wires I had added, leaving only the original jumper on the top side to ground.

Thank you all for the help on this.

Mark