Author Topic: QRV-08 hum  (Read 26997 times)

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Offline CapRock

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Re: QRV-08 hum
« Reply #30 on: March 07, 2011, 01:58:53 PM »
Electrolytic caps are turned the right way.  They look exactly the same as the ones in the picture on the QRV-08 page.  I Have not noticed anything hot.  Like I said before I mounted the snap in electrolytic caps on the top of the pcb and the though hole electrolytic caps on the bottom.  What is your email maybe I can send you a few pictures and see if anything stands out to you as a problem.  What could be causing the lack of voltage at the secondary of the transformer?  Is it even possible that parts that come after it in the chain effect its voltage?

Offline peranders

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Re: QRV-08 hum
« Reply #31 on: March 07, 2011, 08:06:26 PM »
What is your voltage after the regulators? Is it zero volts?
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Offline CapRock

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Re: QRV-08 hum
« Reply #32 on: March 07, 2011, 11:58:59 PM »
The voltage after the regulators is as follows: (I measured at the output tab of each regulator)

ic10: -2.94
ic7: .63
ic18: -2.92
ic14: .63

whats next?

Offline CapRock

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Re: QRV-08 hum
« Reply #33 on: March 11, 2011, 02:26:09 PM »
So what do you think I should check next regulator voltages posted in last post

Offline peranders

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Re: QRV-08 hum
« Reply #34 on: March 11, 2011, 05:32:07 PM »
I'm not sure you have damaged something or not with your high supply voltage but you must remove the short circuit.

Remove R3/E3 by this the amp will be disabled. What happens? More supply voltage? Still short circuit?
/Per-Anders Sjöström, owner of this forum

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Offline CapRock

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Re: QRV-08 hum
« Reply #35 on: March 15, 2011, 03:28:17 AM »
I removed E3/R3 and it did not change the voltages at all.  I also tried removing the electrolytic caps that I had mounted to the bottom of the circuit board and that also did not change the voltages.  Do you want me to take a closeup picture of the power section of the circuit and see if you notice anything visibly wrong?

Offline peranders

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Re: QRV-08 hum
« Reply #36 on: March 15, 2011, 06:17:55 AM »
It might be a good idea before you cut any traces. I think we can agree on that you have the same error in both channels. You can send big pictures to peranders at sjostromaudio dot com
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Offline CapRock

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Re: QRV-08 hum
« Reply #37 on: March 16, 2011, 12:45:52 AM »
Yes I agree.  Clearly I have the same problem with both channels.  I will send pictures to your email right now.  It may take 2 emails because of the size of the photos, thanks.

Offline peranders

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Re: QRV-08 hum
« Reply #38 on: March 16, 2011, 06:24:39 AM »
I can't see much and certainly nothing wrong. Could please a take pictures in daylight and more towards the parts? Can you take so I can see the text in the semiconductors?
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Offline CapRock

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Re: QRV-08 hum
« Reply #39 on: March 16, 2011, 01:47:26 PM »
Yes is there a certain section of the board you want me to focus on or do you need detailed pics of the whole thing

Offline peranders

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Re: QRV-08 hum
« Reply #40 on: March 16, 2011, 05:54:11 PM »
Details of the whole board with special attention to the semiconductors.
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Offline CapRock

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Re: QRV-08 hum
« Reply #41 on: March 28, 2011, 07:57:21 PM »
I am having trouble getting pictures with enough detail of the semiconductors to read the values/markings.  At this point I will do whatever it takes to get this thing working.  Is there any chance of me shipping it back to you to look over and paying you through paypal for your time.

Offline peranders

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Re: QRV-08 hum
« Reply #42 on: March 28, 2011, 09:07:36 PM »
I'm afraid I have no possibility to repair this board but you must take a guess and assume that the regulators might be defect therefor you must cut the traces with +- 12V to the amps. If you still have more or less zero volts raw voltage, then you have to concentrate on the regulators.
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Offline CapRock

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Re: QRV-08 hum
« Reply #43 on: March 28, 2011, 10:26:41 PM »
ok, can I separate the amp from the regulators by simply removing the tin jumpers on the bottom of the board, it looks as if on the schematic these connect the regulators to the amp?  Or do I actually need to cut traces,  How many traces will I need to cut if so?  which regulators do you think may be causing the problem? thanks per

Offline peranders

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Re: QRV-08 hum
« Reply #44 on: April 01, 2011, 09:38:34 AM »
Do you have tin on all tin jumpers? In case if this is true you will have a massive short circuit.
/Per-Anders Sjöström, owner of this forum

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