S.E.X. amp seconde hand

[mwgrient]

I would like to share the measurements again, I have a different multimeter:

Terminal - Voltage
1 - 201
2 - 0
3 - 0
4 - 403
5 - 201
6,16 - 379 / 383
7,17 - 0 / 0
8,18 - 0 / 0
9,19 - 0 / 0
10,20 - 403 / 404
11,21 - 300 / 347
12,22 - 0 / 0
13,23 - 0 / 0
14/24 - 0 / 0
15,25 - 17 / 17
A1,B1 - 0 / 0
A2,B2 - 361 / 357
A3,B3 - 17 / 17
A4,B4 - 0 / 0
A5,B5 - 295 / 66
A6,B6 - 9 / 2
A7,B7 - 2 / 2
A8,B8 - 3 / 3
C1 - 2
C2 - 3
C3 - 0
C4 - 3
C5 - 3

I can use any input since I really totally lost here. I have a focus on the right channel, special interest in A5/A6 because of te big differences.
As Paul said, loose wire or broken wire; anything? I have re-soldered all the joints on te right. I Gould replace all the wiring on the right side; but have been warned not to do more dan necessary.

I have tubes glowing; but no right channel. I spend all day thinking and wondering... but need a little push.

[Paul Birkeland]

The other thing that could make 9V across the 1.27K resistor would be if A4 isn't properly grounded.  A4 grounds through the 249K resistor, if that's not well connected or is broken, that will throw everything off.

[mwgrient]

Double checked that, reflow the solder to be sure... but the voltages stay strange.

I have to look at the manual to test the resistor.

[mwgrient]

A4 - .091 (with the volume wide open) and 000 when closed.
Left channel measures almost the same.

I am measuring Ohms, 2M on the multimeter.

[mwgrient]

That part can be 100% out of the circuit and the DC voltages will still be correct.

But will effect the sound from that channel? I have removed them all (2); now there's no sound at all. Right or Left. I understand that these resistors are responsible for eliminating noise?

[Paul Birkeland]

Those are capacitors you removed.  The amp will not pass signal without them.  You should never listen to an amp that doesn't pass its voltage checks.

[mwgrient]

I see, I have learned enough for one day.  Will never listen to a amp that do not pass the checks! Sorry for that.

Will come back if I have installed the capacitors again. Also thinking about the repair service BH is offering.

[mwgrient]

there was a very tiny but effective shortcut between the legs of Q2 on the C4S module. This was giving the weird values in measurements.
I do pass the resistance check; and the voltage check now.

Woud like to check first this before I can listen to the amp:
Because I have broken the leg of "0.1uF 630V capacitor" during my inspection I have ordered new ones but those will come in next week. I have come in these ones today:

https://www.tonefactory.nl/tubular-film-capacitor-0-1uf-630v

My question is: can I safely use them until to right ones will arrive?
Have a nice day! Marco.

[Deke609]

can I safely use them until to right ones will arrive?

Yes. Since the new caps have the same value and rating (0.1uF and 630V), and are non-polarized, they are interchangeable withe the stock cap.

But note that the caps you linked to are metalized polyester caps. The stock caps are likely metalized polypropylene.  A lot of people believe that polypropylene caps sound better. Assuming you've also ordered a polypropylene cap that is similar or identical to the stock cap, you'll be able to test this for yourself.

cheers, Derek

[mwgrient]

Thank you Derek! My soldering station is getting hot already :-)
And thanks for the info behind the polyester/polypropylene cap!