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-   -   Probs w/ Pearl (http://www.diyaudio.com/forums/pass-labs/37461-probs-w-pearl.html)

hatfield 8th July 2004 08:47 PM

Probs w/ Pearl
 
After a month or two of off and on work on a Pearl and some great information/insight from the fine folks on this board, I finally completed the project... at least I though I did.

Everything seems to test OK... PSU is up and running. DC is making its way to the Pearl boards. The solder joints are all solid. The resistors/diodes/caps/etc. are all testing fine. All the grounds seem to be doing their job. And I have not strayed from Wayne's plans or part list... everything is - for lack of a better term - stock.

Here's the problem... when I test the voltage points on the boards, I only get trace levels. I even hooked it up to my system and heard nothing. No hum, no crackle, definitely no music... nothing.

Wha'happened?!?

Is it possible to have too much current being sent to the boards? I'm assuming it is. They're rated for 38-45v, and my PSU is sending 48v. If the overage is the culprit, than my solution seems relatively simple. But I didn't really think 3v would have an impact.

If anyone has any suggestions what the problem may be, it would be greatly appreciated.


Danke,
Hat
:confused:

Panelhead 9th July 2004 01:24 AM

Re: Probs w/ Pearl
 
Quote:

Originally posted by hatfield
After a month or two of off and on work on a Pearl and some great information/insight from the fine folks on this board, I finally completed the project... at least I though I did.

Everything seems to test OK... PSU is up and running. DC is making its way to the Pearl boards. The solder joints are all solid. The resistors/diodes/caps/etc. are all testing fine. All the grounds seem to be doing their job. And I have not strayed from Wayne's plans or part list... everything is - for lack of a better term - stock.

Here's the problem... when I test the voltage points on the boards, I only get trace levels. I even hooked it up to my system and heard nothing. No hum, no crackle, definitely no music... nothing.

Wha'happened?!?

Is it possible to have too much current being sent to the boards? I'm assuming it is. They're rated for 38-45v, and my PSU is sending 48v. If the overage is the culprit, than my solution seems relatively simple. But I didn't really think 3v would have an impact.

If anyone has any suggestions what the problem may be, it would be greatly appreciated.


Danke,
Hat
:confused:


Start at the place where the dc comes in. Measure the voltage all the way to the 9610. If you have no voltage before the 9610, recheck connections.
If there is no voltage after the 9610, replace it,
It should be fairly simple to trace the voltage from your power supply through the boards. Several voltage points are listed.
Do not worry if the measured voltage is way off from the listed values. The current draw through the transistors is not very consistant, and this is a fairly high impedance circuit. A small change in current level will shift the operating points a lot.
Good luck!

George

hatfield 9th July 2004 06:46 PM

seems like the 9610's are the problems. they show a voltage of about 8 and change... after that, nothing (well, trace amounts).

i'm actually kind of surprised that they are so delicate. i don't think they were man-handled when soldering them to the board, and i used a heatsink. oh well, lesson learned.

thanks for the help george! i'll report back when i get new diodes installed.

best,
hat

Panelhead 9th July 2004 11:44 PM

Recheck your voltages
 
Quote:

Originally posted by hatfield
seems like the 9610's are the problems. they show a voltage of about 8 and change... after that, nothing (well, trace amounts).

i'm actually kind of surprised that they are so delicate. i don't think they were man-handled when soldering them to the board, and i used a heatsink. oh well, lesson learned.

thanks for the help george! i'll report back when i get new diodes installed.

best,
hat

Measure the voltage coming from your raw power supply with the Pearl connected and not connected. If the connected raw supply voltage is close to what is with the Pearl connected there is nothing loading it down.
Reading your post it says that you are only getting 8 volts at the 9610. Use should be seeing close to the 48 volts from the supply.
Try measuring the voltage at the dropping resistors to ground. Also check the voltage from one end of these resistors to the other. This will alllow you to check the current draw. It should be around 50 ma or so per channel. With a 4.7 ohm resistor you should see 200 mv or so from one end to the other of those resistors.
I suspect one of the filter caps is either hooked up backwards, the polarity of the raw supply is reversed, or lastly the 9610's are shorted. Whatever it it, it should be an easy fix.

George

kilowattski 10th July 2004 03:16 AM

Hatfield,

Maybe excess heat was not the problem. The MOSFETS are very static sensitive. Whenever I handle them I use a grounded wriststrap. It doesn't take much to pop one. Simply walking across a carpeted floor, can build up enough charge to do it if the humidity is low.


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