Bottlehead Forum
Bottlehead Kits => S.E.X. Kit => Topic started by: mwgrient on May 22, 2020, 06:46:21 AM
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Dear all,
I have a Bottlehead S.E.X. amp. Bought second hand, hence I am not feeling comfortable yet to build a complete system like the S.E.X. amp.
When I attache the power cable (220v) there is a loud sound from the headphone: It sounds "like a dolphin". I instantly shut down the amp of course.
My question is: does someone recognise my description of the sound (dolphin)? And maybe knows where to start. Could It be the tubes are dead?
Regards, hope that someone can help me a little bit further...
Marco :)
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Does it have a 240V transformer or is it wired for 240V?
If you don't know, you can flip it over and post pictures of the bottom of the power transformer.
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Hi, hope you can see the attachments for this!
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Alright, so you have a 240V SEX amp, are you in a 240V country?
This noise could easily be external interference from a wireless device like a router or a cell phone, or a badly polluted powerline.
There's maybe a 0.1% chance that it's tube related.
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The sound you describe is an oscillation. Most likely it is due to dirty tube pins or a bad connection somewhere. Try cleaning the tube pins and sockets for starters.
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oscillation: OK, I will clean the tubes! They are dirty in deed.
country: I am in a 220/230 country (Europe/The Netherlands) I have bought the amp in Norway (240). And I also will eliminate interference.
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Cleaned the tubes, no effect. After some seconds (with the volume closed) there is my loud oscillation sound.
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Is the sound only in one channel? If you wiggle the tube can you get the sound to stop?
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one side only! If I touch the
right (this must be left) tube (having the amp in front of me), and touching the tube, the sound changes a little bit. But keeps on going loud... wiggle the tube does not effect it.
I also found that if I turn up the volume a bit, It goes away?
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Now swap the tubes in the sockets and see if the noise follows the tube.
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it does not, stays left channel: so it is not the tube!
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Then it is possibly a bad solder joint. A good place to start would be to reflow the solder joints around the tube socket on the noisy side.
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Gould it be the potentiometer/volume? I have oscillation when I turn off the volume, then when I turn it on, It goes away. But on 12 a clock the oscillation is loud again. Etc.
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If you have nothing plugged into the inputs of the amplifier, then noise that varies with the position of the potentiometer isn't useful information. Your amp is just picking up ambient noise at the inputs and you're controlling how much gets into the amp by turning up the volume pot.
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OK, thanks for the information! I have nothing in the input.
I have re-soldered every joint on both tube sockets, but no effect at all. Pitty. And did a good look at all the soldering joints. Not luck either.
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How about a voltage check?
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That's my first. I do have a meter, but will come back with my measurements since I have the PDF with the build instructions.
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I would like to check something: is the cable shown in the red cirkel OK? It is soldered at the power socket (as ground), but not soldered in the power switch? See the attachment.
(I am digging into the volt meter lessons before doing a voltage check on a live system)
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Yep that’s fine.
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Ok, thanks for confirmation.
The measurements:
Terminal - Voltage
1 - 452
2 - 0
3 - 0
4 - 903
5 - 451
6,16 - 856 / 856
7,17 - 0 / 0
8,18 - 0 / 0
9,19 - 0 / 0
10,20 - 902 / 902
11,21 - 766 / 768
12,22 - 0 / 0
13,23 - 0 / 0
14/24 - 0 / 0
15,25 - 38 / 37
A1,B1 - 0 / 0
A2,B2 - 802 / 803
A3,B3 - 38 / 37
A4,B4 - 0 / 0
A5,B5 - 0 / 0
A6,B6 - 4 / 4
A7,B7 - 0 / 0
A8,B8 - 7 / 7
C1 - 0
C2 - 8
C3 - 0
C4 - 0
C5 - 7
Certainly not what it should be?
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If those voltages were correct, many of the capacitors in the amp would explode almost instantly.
Since this has not happened, I would suggest trying to measure the DC voltage of something like a 9V battery to be sure you are using the meter correctly.
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I see :-[
I have chosen the 600 V˜ since I am using a 220v amp; see pictures. A 9 volt battery measures 16 ?
What am I doing wrong?
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Try putting fresh batteries in your meter. For some reason, a lot of meters read high when the battery is low.
If new batteries don't fix the problem, I'd get a new meter.
Edit: and note that in the pic you have the meter set to read AC voltage (wavy symbol), not DC voltage (straight dashed and solid liness), which will work for taking measurements of the incoming line voltage, the power transformer terminals and AC heater voltages -- but everything else in the amp will be DC.
cheers, Derek
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You have the meter set to measure AC volts and you are trying to measure DC volts.
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The V with the squiggley line is for measuring AC volts The V with the straight line and dotted line underneath is for DC volts.
If your meter is not auto ranging select the scale that is one step larger than the voltage you expect to measure.
This will give you the most accurate reading.
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Oh lord, thank you: I am in the learning mode now.
Will do the measurements again.
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The measurements again:
Terminal - Voltage
1 - 204
2 - 0
3 - 0
4 - 410
5 - 204
6,16 - 390 / 389
7,17 - 0 / 0
8,18 - 0 / 0
9,19 - 0 / 0
10,20 - 411 / 412
11,21 - 354 / 353
12,22 - 0 / 0
13,23 - 0 / 0
14/24 - 0 / 0
15,25 - 17 / 17
A1,B1 - 0 / 0
A2,B2 - 364 / 364
A3,B3 - 17 / 17
A4,B4 - 0 / 0
A5,B5 - 0 / 0
A6,B6 - 2 / 2
A7,B7 - 2 / 2
A8,B8 - 3 / 3
C1 - 2
C2 - 3
C3 - 0
C4 - 2
C5 - 3
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You have a lot of voltages that are the numbers we are looking for, but not listed on the terminals where we wold expect them.
What jumps out at me is that A5/B5 are 0V, but A6 and B6 are ~2V. This isn't really a likely/possible set of circumstances. I would recheck A5/B5.
-PB
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on a recheck
a5 - 71
b5 - 72
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Well, I can see enough there to say the amp is operating as expected in terms of the tubes doing their jobs.
You could try adding this modification, which will interrupt several sources of noise:
https://forum.bottlehead.com/index.php?topic=11676.0 (https://forum.bottlehead.com/index.php?topic=11676.0)
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Oh lord, thank you: I am in the learning mode now.
Will do the measurements again.
We were all new at this at one point in time or another. I still mess at least one thing up per build.
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:)
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Hi.
I buildt this amp 6 years ago and recently sold it to mwgrient. I am not an experienced amp-builder, but it worked fine all the time I had it. If anyone is interested, here is the building process documented (in Norwegian, but with many pictures) link was not allowed, but google “
hifisentralen Bottlehead Single Ended eXperimenter's kit“ and the thread should appear.
I listene to the amp for two hours (no issues) before it was double-boxed and shipped. Obviously, something must have happened during shipping, and therefore my first suspicion would be (besides damaged tubes, which was ruled out) a bad solder joint, as Doc B mentioned.
The amp is wired for 8ohm output as I mainly used it with horn speakers.
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So far there isn't any indication that there's an issue with the build. It could simply be some external interference.
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I have tried to eliminate interference. Other room, divert power cable and wall-plug. Shutting down the computer. Nothing.
I can hear music, but when the volume is turned off, de loud signal is back. I will try to install the noise eliminator.
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Here is a link to my amp, with a sample of the sound it gives true my headphone left channel.
https://www.youtube.com/watch?v=0OB8lpQ58lc
regards, Marco.
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Hi all, I have soldered the sockets lower than they where soldered. And re-soldered all the ground wires/points again and again. There is no oscillation anymore!
Only a faint hum when I connect my headphone; It is also there when the volume is turned down//closed.
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Glad it worked out!
I have soldered the sockets lower than they where soldered.
To further explain to others on this forum.
What you've done here is relocate the grid stoppers closer to the socket pins (1,4) of the tube as a preventive measure for oscillation.
Now enjoy it!
Let us know how you like the SeX 2.1!
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Oh man, that's quite a noise!
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Yeah! It is still not quiet, but doing a lot better now. Pffiew!
I would like to replace the potentiometer, jack socket and RCA terminals.
Does someone know where to get the distinctive Bottlehead knop?
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I would like to replace the potentiometer, jack socket and RCA terminals.
Why?
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The RCA sockets are fried, at least one. And do not look nice anymore. My fault!
The potentiometer gives noise at the end of the volume (almost open wide)
The big black knob is not detachable since the screw is broken that will hold him in place.
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The potentiometer gives noise at the end of the volume (almost open wide)
This is a function of the high input impedance of the amp, not the pot itself.
The big black knob is not detachable since the screw is broken that will hold him in place.
Hmm, you'll have to maybe melt it off then to get it off.
https://no.mouser.com/ProductDetail/Eagle-Plastic-Devices/45KN014-GRX?qs=EiTGd8sy9OrVz4TOJLy7AQ%3D%3D (https://no.mouser.com/ProductDetail/Eagle-Plastic-Devices/45KN014-GRX?qs=EiTGd8sy9OrVz4TOJLy7AQ%3D%3D)
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you'll have to maybe melt it off then to get it off.
A really small diameter extractor bit might work - and then you'd be able to use the knob again, provided you can find or make a replacement set screw. Failing that, I'd drill it out with regular bit made for metal.
cheers, Derek
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Ever tried to melt one? I have not, but I think maybe they are bakelite and won't melt.
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Thank you for the link to the knob!
One more thing: the S.E.X. amp is performing wonderful with speakers! But when I plug in my headphone, there is microphonic sound and a hum. When I use the same headphone on my Crack everything is OK.
When I use a headphone adapter for the speaker-outputs, and plug in my headphone to the adapter it is wonderful!
So my question is: what is happening? Why microphonic sounds (tapping n the chassis is really noisy) and a hum when I plugin the headphone?
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https://www.youtube.com/watch?v=0OB8lpQ58lc
Could someone explain what this sound could be? What could cause it? Is this how an oscillating tube could sound?
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When I use a headphone adapter for the speaker-outputs, and plug in my headphone to the adapter it is wonderful!
Is the adapter straight wire, or does it have a pad?
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... not sure what you mean. I have a picture of the cabin. It's Chinese made and I think with resistors in it. Its working great :-)
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Hi mwgrient,
Regarding the noise on one channel when you turn the volume down, you suggested that perhaps it could be the pot and I think it possibly can be. A long time ago I built an amp and the wiper on one channel did not make good contact to ground when turned to zero volume, it was used pot and I sprayed contact cleaner inside and worked it in. that worked but I replaced the pot with a new one as I did no trust the used pot.
The problem you showed on your video can be indicative of a tube grid with no ground reference.
Maybe try turning the volume all the way down and measure the resistance from the center connection (wiper) and the outer connection that goes to ground, this should be 0 Ohms or close to 0
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A resistive divider will pad down any noise at the outputs. You'll probably want to use it in general with IEMs or super sensitive headphones.
We have done some tweaks over the years to bring the noise floor down, and one that you could do would be to change the output transformer wiring from 8 to 4 ohms.
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Oh sorry, I see that you fixed the oscillation problem, disregard last transmission.
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Hi all, thanks for thinking! I will take a look at the manual about the 4/8 ohms.
Regards, Marco.
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I have done the 8 to 4 ohms thing on the pc-3's, according to the manual that came with the amp. To reduce the buss/humming.
Now my right channel has stopt working. There is a c4s board in there. Do not know if this is good to now. And not all the leds are burning.
Am I in deep trouble now?
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You likely have a loose connection or a broken wire.
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I have done some precise inspection, with a nylon stick... gould not find anything. Reflowed some soldering points. But nothing. I switched to the 8 ohms again, and still no right channel.
I am wondering: when is it advisable to rebuild the amp; from scratch? I totally lost here because I have no insight information from building it. I bought it build.
Another wondering: can I eliminate de C4S Upgrade easily? Just the plane amp t keep it simple...
What would you do?
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I am wondering: when is it advisable to rebuild the amp; from scratch?
No. How about a check of the DC voltages?
Another wondering: can I eliminate de C4S Upgrade easily? Just the plane amp t keep it simple...
You could, but at this point your amp already isn't working, so making more changes that aren't aimed at repairing the problem may just cause new problems.
What would you do?
Check the DC voltages on the channel that isn't working and report any that aren't what they are supposed to be.
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I have some measurements
Terminal - Voltage
1 - 205
2 - 0
3 - 0
4 - 410
5 - 204
6,16 - 385 / 390
7,17 - 0 / 0
8,18 - 0 / 0
9,19 - 0 / 0
10,20 - 409 / 410
11,21 - 303 / 352
12,22 - 0 / 0
13,23 - 0 / 0
14/24 - 0 / 0
15,25 - 17 / 17
A1,B1 - 0 / 0
A2,B2 - 362 / 365
A3,B3 - 17 / 17
A4,B4 - 0 / 0
A5,B5 - 298 / 70
A6,B6 - 0 / 2
A7,B7 - 0 / 2
A8,B8 - 3 / 3
C1 - 2
C2 - 3
C3 - 0
C4 - 2
C5 - 3
A5 is certainly to normal.
11 too...
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A5,B5 - 298 / 70
A6,B6 - 0 / 2
A7,B7 - 0 / 2
I suspect you have a broken wire, likely one of the ones connecting the C4S to the A side of the circuit.
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A5,B5 - 295 / 72
A6,B6 - 9 / 2
A7,B7 - 2/ 2
I checked and replaced the A side of the circuit with new wires. To be sure.
Still got that weird A5 high value?
But the values of A6 is also weird.
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Then the resistor at A6 would be broken or loose.
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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.
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That's the part replaced by the C4S.
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:-) Thank you!
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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).
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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.
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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.
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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
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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.
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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.
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Nevermind, desoldered the joint, now it's OK.
Right channel is still off.
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Also, saw that te LEDs on the C4S, are 2x bright and 2x low or not so bright. See picture. Maybe an indication.
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Yes, it's an indication that you have a broken wire or a loose connection on that side of the amp.
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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.
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That part can be 100% out of the circuit and the DC voltages will still be correct.
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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.
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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.
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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.
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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.
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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?
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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.
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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.
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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.
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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
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Thank you Derek! My soldering station is getting hot already :-)
And thanks for the info behind the polyester/polypropylene cap!