Bottlehead Forum
Bottlehead Kits => S.E.X. Kit => Topic started by: yay on November 24, 2017, 11:00:10 PM
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Hey, my SEX 3.0 had to endure some damage during shipping, apparently someone thought it was a good idea to throw the package on the ground or something.
The wood case was broken, but no visible damage on the electronics. I fixed the case, and tried the amp with some cheap speakers (i should've checked the resistences first, ignore me being dumb!). It worked fine, but there was an imbalance in the output. I checked all the resistences, and this is the result:
https://docs.google.com/spreadsheets/d/1OgRru82lYEGJg7s2w0KMrTQqHbm1WGzVvfh4EakMXlE/edit?usp=sharing
I also took some pictures of the interior, so maybe someone can see some damage or weirdness that i have not been able to:
https://photos.app.goo.gl/wtrG8TiyoTsVlWTu1
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Your resistance checks look good to me. Have you run your voltage checks?
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Have you swapped tubes from side to side to see if the imbalance follows?
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I have tested tube imbalance before. I would like to add that it's not a static imbalance. If i turn up the volume it almost doesn't change in one channel and get's normally louder in the other one.
It's much more obvious over speakers.
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Is it full blast on one channel and variable volume on the other? Have you checked the DC voltages?
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no, the other way around. right channel is much more silent, and reacts only very little to not at all to volume control. left channel works normally. i'm not 100% sure if right channel doesn't react at ALL to volume control or only very little, i think it's the 2nd.
i will post the DC voltages later today
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voltages are also all within 10%
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The upper and lower lugs on the volume pot on the headphone jack side of the amp need to be temporarily shorted together, then see if the issue goes away.
If the issue is still present, remove that jumper and put it between the upper and lower middle lugs on the volume pot, then recheck.
If that didn't change the issue, remove that jumper and jumper pin 10 on each 12 pin socket together, then recheck.
If that didn't change the issue, remove that jumper and jumper pin 3 on each 12 pin socket together, then recheck.
If that didn't change the issue, remove that jumper and jumper terminal 3 to terminal 17, then recheck.
If that didn't change the issue, remove that jumper and jumper the upper and middle inside headphone jack terminals together, then recheck.
If that didn't change the issue, remove that jumper and jumper the upper and middle outside headphone jack terminals together, then recheck.
Do note that if you can download a 60Hz tone onto your phone and play that through your SEX amp, you can measure AC voltages at a few spots and we can debug your amp that way.
-PB
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Well i'm retarded it seems, i misread your instructions and jumpered terminal 10 to 12 instead of pin 10!
It smelled of burning, i turned it off quickly and now there is a very weird sound in the right channel. Kind of scratching, random noises. Like random space noise or something...
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Remove the jumper, do the voltage check, report any discrepancies.
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2 82
3 19
4 0
5 0
6 420
7 422
10 398
16 87
17 20
18 0
19 0
20 404
21 422
24 398
h2,h5 3,48
h4,h7 3,29
got these voltages, seem to be the same as before
as to the checks with the jumper: when i did the check number one and two, was the sound supposed to only come out of the left channel? The left/right sound came only from left side, but with correct volume and even adjustment to the volume pot. I tested with left/right testing video on youtube.
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2 82
3 19
4 0
5 0
6 420
7 422
10 398
16 87
17 20
18 0
19 0
20 404
21 422
24 398
h2,h5 3,48
h4,h7 3,29
There are no discrepancies between these voltages and the voltages in the manual.
as to the checks with the jumper: when i did the check number one and two, was the sound supposed to only come out of the left channel? The left/right sound came only from left side, but with correct volume and even adjustment to the volume pot. I tested with left/right testing video on youtube.
We are looking to resolve the imbalance in output. That is your reported issue. If you lost the right channel, that is a new issue.
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No, not as a new issue. That was what happened when i used the jumper positions in your suggested troubleshooting. (Before i made the mistake!)
These:
The upper and lower lugs on the volume pot on the headphone jack side of the amp need to be temporarily shorted together, then see if the issue goes away.
If the issue is still present, remove that jumper and put it between the upper and lower middle lugs on the volume pot, then recheck.
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Was the pot damaged in this incident? Maybe the knob took a hit?
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I am unsure what happened exactly. When i opened the package, the wood base was split and the plate slightly bent (2mm maybe). I bent the plate back, and saw no damage on the electronics. The 100uF cap on the headphone jack side was bent, but i bent it back to it's correct position. No visible damage otherwise, no scratches on the inside or anything. They seem to have thrown the package, and the base just cracked.
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I listed out 7 quick tests to do to see where the issue may be. You've done 2 of them, could you do the next 5 and report your results?
-PB
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Yes, ofc. I just stopped with the other tests since i damaged something whil doing test 3 wrongly.
Should i open another thread for that damage caused?
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There aren't any voltage issues that I could see. Please start over with the tests and let us know. Also, if you are able to get a 60Hz tone fed into your SEX amp, we can use that to check on things as well.
-PB
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I finally have some time to take care of this once and for all now.
I did the jumper tests, and this is my result:
The upper and lower lugs on the volume pot on the headphone jack side of the amp need to be temporarily shorted together, then see if the issue goes away.
-> Left and Right channel coming from only the left speaker, both the same volume and also the correct volume.
If the issue is still present, remove that jumper and put it between the upper and lower middle lugs on the volume pot, then recheck.
-> Left Channel coming from the Left Speaker, correct volume. Right Channel and Right Speaker no sound.
If that didn't change the issue, remove that jumper and jumper pin 10 on each 12 pin socket together, then recheck.
-> Left and Right channel coming from only the left speaker, both the same volume and also the correct volume.
If that didn't change the issue, remove that jumper and jumper pin 3 on each 12 pin socket together, then recheck.
-> Left and Right channel coming from only the left speaker, both the same volume and also the correct volume.
If that didn't change the issue, remove that jumper and jumper terminal 3 to terminal 17, then recheck.
-> Left and Right channel coming from only the left speaker, both the same volume and also the correct volume.
If that didn't change the issue, remove that jumper and jumper the upper and middle inside headphone jack terminals together, then recheck.
-> Left Channel coming from the Left Speaker, correct volume. Right Channel and Right Speaker no sound.
If that didn't change the issue, remove that jumper and jumper the upper and middle outside headphone jack terminals together, then recheck.
-> Left Channel coming from the Left Speaker, correct volume. Right Channel and Right Speaker no sound.
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I strongly suspect you have a broken wire between the binding posts and the headphone jack.
-PB
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Should i just replace the whole CAT5 cable there and see if the issue persists?
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Each length of wire should measure about 0 ohms from one end to the other. I would measure them and see where you might have a break. These tend to happen near the ends of the wire, so it may be fixable without doing much modification.
The reason I believe you have a broken wire is that you shorted together the outputs of both channels at the headphone jack, and this goes from the headphone jack to your speaker jacks. One channel works in this scenario and one does not, so the only plausible conclusion is that the wired connection from the headphone jack to speaker jacks isn't working.
Another way to test this would be to plug in headphones and check that output. It may provide another useful data point.
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I believe the break is somewhere in the middle of the CAT cable, under the shield. After unpacking and looking at the damage, it looked like at that spot it might've gotten some damage.
What are the specifications of the CAT cable? I only have one without the shielding and in 26AWG around.
Would this cable work well? It's AWG 24, and looks like this: (see attachment)
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We use plenum rated (better with heat) shielded cat5 with solid core conductors. If you can find some with shielding and solid core conductors, it should work just as well as what we provide.
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So i removed the CAT5 cable, and then tested each strand for resistence, and it measured 0ohm on all of them. Seems like this isn't actually the reason?
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If that didn't change the issue, remove that jumper and jumper the upper and middle outside headphone jack terminals together, then recheck.
-> Left Channel coming from the Left Speaker, correct volume. Right Channel and Right Speaker no sound.
That would still tend to suggest an interruption in that wire. The other possibility is that the CAT5 on the output transformer on the offending channel has shorted itself out. There isn't a good way to measure this, you'll just have to inspect the wiring. Look for two wires that may have been crushed together by shipping damage.
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Alright, so i switched out the CAT5 cable for the input/output incl. the ones coming from the transformer.
Resistence checks all check out, Voltage tests fail for terminal 2.
I measured only 1V there, all other tests worked out.
No sound coming from the right channel, i checked out if it was coming from a RCA input with too much solder, but they are not shorted together.
Doesn't even seem like an issue with the new cables at all?
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You now have a voltage issue, so that's something to go for. If you have 1V at terminal 2, your voltage at terminal 6 should be off as well.
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Full measurements:
Terminal 2: -1.16V
Terminal 3: 18.8V
Terminal 4: 0.02V
Terminal 5: 0.00V
Terminal 6: 411V
Terminal 7: 413V
Terminal 10: 390V
Terminal 16: 85.3V
Terminal 17: 19.2V
Terminal 18: 0.02V
Terminal 19: 0.00V
Terminal 20: 395V
Terminal 21: 412V
Terminal 24: 388V
H2: 3.38V
H5: 3.38V
H4: -3.18V
H7: -3.18V
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The 150K 2W resistor may not be adequately connected.
Having 0V at terminal 2 could be caused by an internal tube short, but you don't have enough voltage difference between 6 and 7, so that's not the case.
A dead triode would leave you with about 400V at terminal 2.
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It seems to be the resistor, it is measuring inf. resistence.
I will resolder and check again.
If i have to switch out the resistor for another one, any resistor with 2W and 150k ohm would work?
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Yup, i removed the resistor, checked if it still worked (it did), resoldered it and now everything seems good. Will check it out for a few hours if everything is fixed for good now.
Thanks alot for the super fast help, even if i can be an annoying customer with alot of problems! :-X