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December 14, 2019, 02:08:06 PM

Author Topic: dude, where did my power go?  (Read 3265 times)

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Offline Doc B.

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Re: dude, where did my power go?
« Reply #30 on: February 04, 2016, 12:22:12 PM »
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.
Dan "Doc B." Schmalle
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Offline Alonzo

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Re: dude, where did my power go?
« Reply #31 on: February 04, 2016, 02:03:30 PM »
Is the cap on the upper right of the picture in backwards?  It has a knarly burn on it and should also be replaced.
Alonzo B
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Offline Paul Birkeland

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Re: dude, where did my power go?
« Reply #32 on: February 04, 2016, 07:18:01 PM »
Did you do the power transformer tests starting on page 31?
Paul "PB" Birkeland

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Offline Stalemate

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Re: dude, where did my power go?
« Reply #33 on: February 05, 2016, 12:15:42 AM »
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

Offline Stalemate

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Re: dude, where did my power go?
« Reply #34 on: February 09, 2016, 12:04:24 AM »
[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
« Last Edit: February 09, 2016, 01:54:27 AM by Stalemate »

Offline Doc B.

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Re: dude, where did my power go?
« Reply #35 on: February 09, 2016, 04:45:35 AM »
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?
Dan "Doc B." Schmalle
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Offline Stalemate

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Re: dude, where did my power go?
« Reply #36 on: February 09, 2016, 07:22:37 AM »
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?


Offline Doc B.

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Re: dude, where did my power go?
« Reply #37 on: February 09, 2016, 07:53:57 AM »
It could be damaged resistors or a bad solder joint. Get those replacements in and then let us know how it works.
Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline Stalemate

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Re: dude, where did my power go?
« Reply #38 on: February 09, 2016, 08:32:27 AM »
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

Offline Stalemate

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Re: dude, where did my power go?
« Reply #39 on: February 10, 2016, 05:01:28 AM »
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?

Offline Paul Birkeland

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Re: dude, where did my power go?
« Reply #40 on: February 10, 2016, 01:50:49 PM »
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.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man