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Old 11th May 2013, 07:31 AM   #91
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Yeah i had some left over 2.2k resistors that i bought for bleeders. They were the highest value resistor i had, so i put them between the extra 10,000 and 3300's i had ... They arent dropping the voltage much. The rails are stabilizing at 40.2 volts. A little too much.
Going to need to find stronger resistors to drop it down to something closer to 34v or so..

I lack experience, can anyone recomend values to drop around 5 or 6 volts?
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Old 11th May 2013, 05:27 PM   #92
omishra is offline omishra  India
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Quote:
Originally Posted by FormosaWest View Post
Yeah i had some left over 2.2k resistors that i bought for bleeders. They were the highest value resistor i had, so i put them between the extra 10,000 and 3300's i had ... They arent dropping the voltage much. The rails are stabilizing at 40.2 volts. A little too much.
Going to need to find stronger resistors to drop it down to something closer to 34v or so..

I lack experience, can anyone recomend values to drop around 5 or 6 volts?
Rather than resistances use 10 number of 1N4001 diodes in series for each rail. They should drop that much voltage. Resistance drop is current dependant, is your voltage reading is while current consumed by pearl boards?
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Old 19th May 2013, 06:40 PM   #93
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Originally Posted by FormosaWest View Post
Sorry i didn't post the photos, 6L6.. During the tear down process (to take the photos and show the bottom of the layout) i thought about how my dim bulb tester was glowing a bit more than id like before the fuses went. it suggested there was a short even-though i just couldn't find one in the wiring.
So i pulled the caps out and checked the resistance and wow! It was over 200k on 3 of 4! You could say, Thats a 'little' too much esr! Haha. Turns out Id cooked a couple caps with the 350deg iron. (Typical mistake for the inexperienced i hope.)

Tore down the board and rebuilt with a couple spare 10,000uf nichicon kw (m) gold tune caps i Had. Im pleased to say I'm generating 39v. Im going to throw in a 3300 and series resistor to keep the crc layout in the psu. Hopefully i can get volts down a bit with what i have here, to make for some breathing room.

Thanks for the help guys!
Hmmmmm. I usually keep my iron set a almost double that, havent fried a cap while installing yet...

Russellc
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Old 29th May 2013, 12:43 AM   #94
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Default Regulator Heatsinks?

I'm building a Pearl 2 to replace a FET 9 that I sold and had been using as a phono preamp. I am in the process of stuffing the boards and was wondering what you all are using for a heat sink on the 7824 and 7924???

As an aside, I was talking with Kent at Pass Labs when I ordered the boards and FETs. I mentioned that several years ago I'd sold my AlephOno and really missed it. He said that I will be very pleasantly surprised when I finish the Pearl 2!

6L6, Thank you so much for the BOM! That made it so easy to order the parts!!
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Old 29th May 2013, 01:19 AM   #95
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Hi

Good luck on the project. This is the heat sink I used:

513002B02500G Aavid Thermalloy | Mouser
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Old 29th May 2013, 01:39 AM   #96
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Hi bnorrish,
Thanks so much for the info!
I was also thinking about the instructions on the PCB to adjust the DC offset to zero with P1. I bought Nichicon Muse BiPolars for the output electrolytic but I wonder if a polarized audio grade electrolytic that was biased correctly wouldn't have better sound? That may be a good test after I get the unit built and burned in.

Thanks again
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Old 29th May 2013, 02:31 AM   #97
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I went with the Elna Silmic II. Not sure how other caps would sound - worth experimenting for short money. I agree - get it running and experiment after. The Pearl 2 sounds fantastic - definitely not the weak link in my setup! Once I got it running, I was more than happy with it and ready to move on to other parts of my system and buy a lot of records. It took a few months but well worth it!
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Old 29th May 2013, 03:28 AM   #98
6L6 is offline 6L6  United States
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FWIW, the Silmic output cap was chosen by Wayne specifically for it's tone. Of course, you can always play with changing it or the bypass, this is DIY after all...

I'm with Bill, however... it sounds so good it's not worth messing with.
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Old 6th June 2013, 03:24 PM   #99
6L6 is offline 6L6  United States
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hifi-hospital, FormosaWest --

How are your projects proceeding?
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Old 6th June 2013, 04:35 PM   #100
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I have my boards stuffed except for the big caps, heat sinks, and regulators. Waiting on heat sinks. I'm also working on recycling a nice 2U rack-mount chassis that once held a Crestron Control System. I also ordered a couple Panasonic Low Signal relays designed for switching uVolt signals. My main TT has two tone arms and I'd like to be able to switch between them easily. When I had an AlephOno I put a toggle switch through the power LED hole which controlled two relays mounted to the underside of the PCB where the MC/MM selection DIP switches were. (Nelson's idea) That was easy. Now I'll have to switch between two sets of input jacks and also switch between gain setting resistors on the PCB. Years ago I was spoiled by the Threshold NS-10. Remember when all of the nice preamps had multiple phono inputs? Oh it would be nice to have a Pass X-25!
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