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Old 14th July 2011, 07:15 AM   #741
milosz is offline milosz  United States
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Default THANKS!

Thanks to everyone who analyzed this for me and helped me see what's going on. I think it's gotta be the 9610.

I think I was a bit blinded by the "it can't be...." kind of thing.

"These are all new parts, it can't be bad MOSFETs..."

"Both channels show the same symptom, it can't be that BOTH 9610's are bad..."

And, actually, since this project sat unbuilt for a couple of years in the closet of the guy I bought it from, and the 9610's were not in conductive bags, it is entirely possible they are both open.

(I use a Hakko soldering station, it's grounded, and I did the work during humid summer months, so I don't think I blew these out- but replacements are coming and when I put them in I will be extra-careful)
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Old 17th July 2011, 02:45 AM   #742
milosz is offline milosz  United States
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Default It's working now, thanks to everyone

Replaced 9610 FET, now it works.....

Another case of the "it's a new part....how can 2 of them be bad??!?!?!" gotcha
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Old 17th July 2011, 08:38 AM   #743
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Quote:
Originally Posted by milosz View Post
Replaced 9610 FET, now it works.....

Another case of the "it's a new part....how can 2 of them be bad??!?!?!" gotcha
Glad to see the issue fixed.

The guy you got the IRFs from should have known that those parts are damaged by static spikes, hence the non-conductive bag they're originally shipped in

Oh, well, now you have a very nice regulation working.

I also would recommend to put some RC networks across the diode bridges of the PSU, like "100nF+1R2" series in parallel to each diode. If you built the two channel supply shown in the Pearl pdf, you'll need 8 x 100 nF and 8 x 1R2 1/4W resistors.

Best,

nAr
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Old 17th July 2011, 09:20 AM   #744
milosz is offline milosz  United States
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Default Snubbers

I didn't use the circuit in the Pearl article. I used HEXFREDs and I do have snubbers across them to dissipate the noise from the resonance formed by the secondary's leakage inductance and capacitance. Thanks, though. It's a useful thing to use in any audio power supply, especially power for low-level, high gain circuits like power supplies.
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Old 17th July 2011, 10:16 AM   #745
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Quote:
Originally Posted by milosz View Post
I didn't use the circuit in the Pearl article. I used HEXFREDs and I do have snubbers across them to dissipate the noise from the resonance formed by the secondary's leakage inductance and capacitance. Thanks, though. It's a useful thing to use in any audio power supply, especially power for low-level, high gain circuits like power supplies.
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Old 17th July 2011, 10:38 AM   #746
milosz is offline milosz  United States
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I meant to say,

"I didn't use the circuit in the Pearl article. I used HEXFREDs and I do have snubbers across them to dissipate the noise from the resonance formed by the secondary's leakage inductance and capacitance. Thanks, though. It's a useful thing to use in any audio power supply, especially power for low-level, high gain circuits like power supplies FOR PHONO PREAMPS"
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Old 17th July 2011, 10:46 AM   #747
MRupp is offline MRupp  Germany
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Quote:
Originally Posted by nar View Post
I also would recommend to put some RC networks across the diode bridges of the PSU, like "100nF+1R2" series in parallel to each diode. If you built the two channel supply shown in the Pearl pdf, you'll need 8 x 100 nF and 8 x 1R2 1/4W resistors.
nAr
I believe your resistor values are too small to be effective as snubbers. Here is a good article that shows how to calculate snubbers for individual circuits, depending on the transformer's leakage inductance. Btw. one snubber circuit instead of 4 would be enough: http://www.hagtech.com/pdf/snubber.pdf
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Old 17th July 2011, 10:59 AM   #748
milosz is offline milosz  United States
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Yeah you can use one snubber across the secondary.
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Old 17th July 2011, 11:05 AM   #749
milosz is offline milosz  United States
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Using high speed switching / soft recovery diodes - like HEXFREDs - reduces the amount of ringing quite a bit. Using HEXFREDs, at voltages below 100 VDC the resulting noise amplitude is just about moot.
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Old 17th July 2011, 05:15 PM   #750
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Quote:
Originally Posted by milosz View Post
Using high speed switching / soft recovery diodes - like HEXFREDs - reduces the amount of ringing quite a bit. Using HEXFREDs, at voltages below 100 VDC the resulting noise amplitude is just about moot.
Yes, I personally use MUR-160

If I recall, exact resistor value is 1R8, that's all I got ... X-formers are 10VA/24V square types. Because the pre itself consumes less power than Pearls, also 1 supply / reg per channel

nAr
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