S.E.X. amp seconde hand

[Paul Birkeland]

Then the resistor at A6 would be broken or loose.

 

[mwgrient]

would like to check something before:

in de manual 2.1 - (the amp is a 2.1 S.E.X. amp) the attachment states something different than my amp. See my picture. Or is this because of the C4S module?

I will take a look at the manual for resitance checks. It looks different on the picture too.

 

[Paul Birkeland]

That's the part replaced by the C4S.

 

[mwgrient]

Thank you!

 

[mwgrient]

Messurements, resistance check.

Terminal  -  Resistance
1 - *
2 - 0
3 - 0
4 - *
5 - *

6,16 - *


7,17 - 0


8,18 - 0

9,19 - 245

10,20 - *

11,21 - *
1
2,22 - 0

13,23 - 0
14,24 - 093 / 089
15,25 - 890 / 890


A1,B1 -  245 /  245
A2, B2 - *


A3, B3 - 0 / 0
A4,B4 *

A5,B5 - 678 / 678
A6,B6 - 1 / 1
A7,B7 - 6 / 6
A8,B8 6 / 6

C
1,C2,C4,C5 *

What do you think about it?
I have to lookup the part/value and buy the resistance online (for a6), like you earlier suggested).

 

[mwgrient]

Is this the right on to replace (on A6)?
https://nl.mouser.com/ProductDetail/Yageo/MFR-25FBF52-1K27?qs=sGAEpiMZZMukHu%252BjC5l7YSmb5PYXOMoVtLr%252B5RFqJL0%3D

Many thanks! Marco.

 

[Paul Birkeland]

Those resistances look like maybe the meter isn't on a range that will adequately resolve the resistor values all that well.  You can use your meter to measure the 1.27K resistor, does it measure 1.27K?

The idea that you need to run out and buy new parts to replace all the parts in your SEX amp will create more problems than it will solve.  It's important to figure out what's actually not working, then fix that.  If you make guesses and start replacing parts at random, you will very likely make more operational problems than you had before.

 

[mwgrient]

I can not say I am knowing what I am doing.  - thanks for your guidance en tips! Much appreciated!

The resistance measure (with meter on 20k ohm) both: 1.24

 

[Paul Birkeland]

OK, so there's no need to replace a resistor that reads the proper resistance. 

You had 0V across this part, then 9V across this part.  This is indicative of loose parts or a broken wire in the amp.

 

[mwgrient]

I do get some weird measurements on terminals:

10 - 20 --> 208 - 410 (so, 20 looks OK, nut 10 is surly low on voltage).

If you would like to see all the measurements, I can post them of course.

 

[mwgrient]

Nevermind, desoldered the joint, now it's OK.
Right channel is still off.

 

[mwgrient]

Also, saw that te LEDs on the C4S, are 2x bright and 2x low or not so bright. See picture. Maybe an indication.

 

[Paul Birkeland]

Yes, it's an indication that you have a broken wire or a loose connection on that side of the amp.

 

[mwgrient]

When I touched it, one leg broke. It was on the right side. I truly hope that this was my trouble maker... So I have bought a new set and wait for delivery.

 

[Paul Birkeland]

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

 

[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?