Bottlehead Forum
Bottlehead Kits => Stereomour II => Topic started by: Stalemate on January 31, 2016, 09:39:03 AM
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Hi,
I've assembled the stereomour II kit, following the excellent instructions provided.
All my resistance tests are a-ok, but when I do the power tests, I get very low values, so low that I was wondering if my multimeter is acting up, but control tests show expected results, so I'm a bit lost here.
I've checked the transformator and gets the expected results from "secondary power check", I've checked the wiring, but the first check comes out at 2 VDC, while the expected result is 360something.
how do I troubleshoot this? I don't dare connecting it to anything, since as far as I know, there are 358 unaccounted Volts in there somewhere...
I'm a newbie, so be nice...
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Hm, so after doing a quick "RTFM" on what to look for, I turned my attention to the C4S-board. I measured the transistors, and got these measurements on the "bipolar" - 1-3 ok, 1-2 null, 2-3 ok, 3-1 ok, while the other didn't give any measurements on any combination - so is this consistent with what I describe?
oh, and the leds are dark.
any help appreciated!
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Do a complete voltage check and post any terminals that are off by more than 10%. PB or someone else at Bottlehead will help you resolve the problem. But they need the voltages that are off plus the terminal numbers to troubleshoot.
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Thanks for the advice!
I managed to break one of the mje-transistors when I was measuring its function, so I need to order some new ones :(
I'll be back!
v
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I rebuilt the C4S and measured the function of the transistors ok, I also doublechecked the solders, and everything seems fine.
I then proceeded to check my solders, and replumed where I saw it necessarry. All the resistance checks are ok, so I plug in the tubes and power, and get the following:
1: 2VDC
2: 2VDC
3-18 : 0 VDC
19: 2VDC
20: 2VDC
The rest are dead, 0 VDC
I rechecked the wiring on the OT and PT (connectivity + config) ok
The tubes light up, I'd say a bit weak, but I haven't seen an functioning amp,so I couldn't say whether it's within the norm.
please advise..
best regards
Vegar
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Perform the power transformer voltage measurement for the 160V terminals and let us know what AC voltage you get there.
-PB
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Thanks Paul,
I'm actually not able to measure any voltage over those terminals.
I've double checked my configuration, I have 236VAC in the mains, (which I'm able to measure on terminals 2-4) so I configured it by connecting terminal 1 to 6, I've checked my soldering for connectivity, and it's ok.
what more tests can I do?
br
Vegar
[edit]
When I short out the 160V (19-20), the fuse blows, which should mean there is something touching something else in there.
[/edit]
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You really don't want to test the transformer by shorting out the high voltage secondary. That can damage it. I suggest going back to the power transformer secondary voltage tests and check all of them - 19 and 20, 15 and 9, 14 and 11.
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So I did - and there is no power there. Shorting out the 19 and 20 was an accident, I was clumsy and managed to touch both poles with the multimeter.
v
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Did you test the other secondaries, 3.3V and 6.3V?
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Hi,
Yes I did, The measurements are neglible, the multimeter a very low current (~0.2 mV) on both.
So to summarize, I'm able to trace the 236 VAC from the wall, via the 46-48 mounts to pin 2 and 4.
I've connected pin 1 to pin 6 to configure the transformer for that current. I'm able to measure 0 ohms on all my connections, meaning the solder and cable is ok, but none of the secondaries gives any reading, other than flutter on the meter. What am I missing here?
thanks
V
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Post a photo of your black and red power supply jumpers that attach from the terminal strip to the set of 6 lugs.
-PB
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Hi,
Here you go
v
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Shouldn't the black wires be soldered to the earth tag at the bottom of the first picture?
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Shouldn't the black wires be soldered to the earth tag at the bottom of the first picture?
You're right, so I did, but to no avail...
br
V
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These symptoms don't make sense. You say your tubes glow, but you are reading 0.2mV on the heater windings. Are you sure you are properly switching between AC and DC as needed?
Also a lot of your solder joints look problematic. The wires on the binding posts look like they would pop off without much effort. This won't solve the power issue, but do need to be addressed at some point. The IEC inlet and terminal 6 on the transformer also don't look like strong joints. Reheating all your power input related joints might be a good first step. Some of them have a lot of solder, but not clean solder joints. Reheat them so the solder flows smooth. The joints that are barely hanging on may need some more solder while reheating.
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These symptoms don't make sense. You say your tubes glow, but you are reading 0.2mV on the heater windings. Are you sure you are properly switching between AC and DC as needed?
Also a lot of your solder joints look problematic. The wires on the binding posts look like they would pop off without much effort. This won't solve the power issue, but do need to be addressed at some point. The IEC inlet and terminal 6 on the transformer also don't look like strong joints.
Good morning, Sir. I am absolutely not. After measuring the transformer using this new _Alternating_ current measuring method, I'm happy to report that the Transformer is ok.
God that was embarassing. Apologies all around.
the terminal 6 is soldered from both sides, so it should be ok, thanks for the advice on the binding posts.
Now, I manage to trace the (_alternating_)current all the way to the tube sockets, but from there I get a bit uncertain on how to take it from there.
The measures are the same as well, when using the _Direct_ current measuring setting.
thanks.
v
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So what is the AC voltage between 19 and 20 on the power transformer?
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it's 170 V
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OK. Now do all of the voltage checks on page 65-66. Make sure to use the DC setting.
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Hi,
I still get around 1-2V on 1-2 and 19-20, othervise nothing.
v
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Measure all terminals on the 41-45 strip and post those voltages.
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41 - 0V
42 - 235V
43 - 0V
44 - 471V
45 - 235V
thanks for your patience!
v
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Measure 30 and 31.
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30 - 2.4V
31 - 1.4V
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Power down the amp and resolder 44L.
Once you have a nice shiny joint that includes all the resistor leads, re-measure 31 and 32.
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31 - 2.5
32 - 0
you were right, there was a dodgy connection on one of the resistors
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Sorry, I meant 30 and 31.
You have high voltage on one end of those resistors, but not on the other. Since it was on both of them, I assumed a bad connection at 44. Resoldering should have fixed this problem, but your low voltage at 31 shows that it did not. Can you measure the resistance of each of those resistors? Pictures of the area might also be helpful.
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resistance:
44 - 30 - 2.2 mOhm
44 - 31 - 2 mOhm
Voltage
30 - 2.4
31 . 2 .5
The picture shows a right mess - The resistor from 44 to 45 was loose, so I had to desolder 44L, which didn't work out, so it was moved to 44U, after trying, hence the worn look
Are there any particular angles I need to include?
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You need to replace the resistors. You can try remeasuring them by putting one probe on either side of the resistor body just to make sure it's not a measurement error, but your amplifier will not function without the right value.
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First you should make sure that the solder joints are good on both ends of those resistors. Bad soldering could cause them to read very high. Do the resistors look overheated? The possible failure modes are resistors breaking and resistors getting fried from too much current. If they look fried from drawing too much current you will need to find out what is shorted that would cause this, or they will just fry again. If they are just broken from handling you can probably replace them and go from there.
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Is the cap on the upper right of the picture in backwards? It has a knarly burn on it and should also be replaced.
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Did you do the power transformer tests starting on page 31?
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Hi,
I've ordered replacement parts for the entire area between the 40-45 and 26 - 35 strips. When I desolder and measure the resistors directly I get some very high values, which means they're fried for some reason. I also ordered replacement capacitators while I was at it. Thanks for all the help so far, the parts will arrive next week, so I'll report back then.
br
V
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[edit] I measured the ceramic 2K, 3K and 22k 5W resistors, and got all kinds of strange values, so I gather that's the problem, but: can anyone tell me why all my resistors fry like popcorn? how is it possible?
-v
[/edit]
Hi,
I changed both the resistors and capasitator, and now the measurements are good.
However, when I plug it in, I get just clipping noises in the right channel after a few seconds, while the other seems ok. I've checked and resoldered where I saw it necesarry, tried switching the tubes and speakers to eliminate them as sources of the error.
What should I look for?
br
Vegar
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When you say measurements are good, is that both all resistance and all voltage measurements? By clipping noises do you mean distorted music, or crunching, crackling sounds?
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Hi,
Yes, I mean both tests. I can do a check and post all the results here tomorrow.
I'd describe it as the sound when you disconnect something from a powered up amp - it's like a "pop" which repeats itself. There is no music comming unless I turn the power off, when the amp powers down, I can hear it briefly.
To troubleshoot, I started comparing the measurements on the channel, and found the the wirewound "ceramic" resistors (22, 2k and 3k 5W) on the right channel was very much off, I was not able to get a good reading, but it was way up in the MOhms, while the left, working channel, gave expected results, so I went ahead and ordered replacements, which will arrive tomorrow.
Is the observation of the sound likely to be caused by the faulty resistors?
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It could be damaged resistors or a bad solder joint. Get those replacements in and then let us know how it works.
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Will do,
As I mentioned, I inspected my joints and resoldered where needed, the measurements where taken directly off the resistors, so I'm as certain as I can be that those are the culprits.
Thanks for all the help so far, people!
-v
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I changed the resistors, and suddenly it worked - for a couple of hours, before the right channel died out and started "popping". It has a signal, but it is very weak, I'd have to turn the balance all the way over and volume up to hear it.
The measurements are:
Terminal / Ohm / VDC
1. * - 380
2. * - 409
3. 0 - 0
4. 250K - 0
5. 0 - 0
6. 1.2K - 61
7. * - 178
8. 0 - 0
9. *- *
10. 7.45K - 0
11. 6.98K- 0
12. * - *
13. 0 - 0
14. * - 219
15. 1.2K - 60
16. 0 - 0
17. 249K - 0
18. 0 - 0
19. * - 405
20. * - 377
21. 1.4K - 62
22. 1.2K - 62
23. 0 - 0
24. 1.2K - 62
25. 1.2K - 62
26. 0 - 0
27. * - 406
28. 0 - 0
29. 0 - 0
30. * - 414
31. * - 414
32. 0 -
33. 0 -
34. * - 407
35. 0 - 0
36. 1.2K - 62
37. 1.2K - 62
38. 0 - 0
39. 1.2K - 62
40. 1.4K - 62
41. 0 - 0
42. * - 209
43. 0 - 0
44. * - 417
45. * - 209
I've resoldered the potensiometers, and the PT, what else should I look at?
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When you post a list of voltages and resistances, generally it helps to just mention the ones that are not consistent with what the manual lists.
In your case, the DC voltages look fine, and what you are describing is most likely bad connections and/or flaky solder joints.