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Old 28th April 2005, 06:08 PM   #551
fcel is offline fcel  United States
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Default transformer spec / using one power supply board

I also have a question regarding sizing of transfomer for a STEREO Aleph 30 using ONE of Brian's Power Supply board.

Is this correct for minimum requirement?

Dual sec coil, 18-0-18, 650VA (1 piece) or
Single sec coil, 18-0-18, 320VA (2 piece)
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Old 28th April 2005, 06:46 PM   #552
dhole is offline dhole  United Kingdom
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Anyone noticed the possable C1 polarity problem ? Looks to be the wrong way wround.
dave
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Old 28th April 2005, 06:58 PM   #553
BrianGT is offline BrianGT  United States
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Quote:
Originally posted by dhole
Brian

I think I may have found an error on the boards. C1 (or c11 on aleph 30 or c5 on aleph 5) has the polarity marked on the board wrongly. the + leg should connect to R9.

Can you confirm this .
regards
dave
You are correct. Thank you for pointing out this error. I will put an update on the website. Here is a comparison of the schematic and the manual. I am sorry for the mistake. I will send out a mass e-mail about this soon.

The prototype amp (same amp board layout) has C1 with the polarity backwards and worked without problems:
http://www.briangt.com/gallery/miniA...Aleph_044_copy
I will talk to Mark and see if he noticed any problems. Sorry about this issue.

One more issue that I found last night, if you are using the 4 pin caps on the power supply board, you will want to remove the 2 unused pins, as the connected to the + capacitor lead, and this might cause problems. I will include this in a mass mail, and I will put an update on the webpage.

--
Brian
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Old 4th May 2005, 12:06 PM   #554
dhole is offline dhole  United Kingdom
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Hey Brian whats the led resistor value on the psu board ? I can work it out but it dosent seem to be on the parts list, so might be worth updating for others.
regards
dave
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Old 4th May 2005, 12:17 PM   #555
BrianGT is offline BrianGT  United States
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Quote:
Originally posted by dhole
Hey Brian whats the led resistor value on the psu board ? I can work it out but it dosent seem to be on the parts list, so might be worth updating for others.
regards
dave
Dave,

I have updated the parts list on the webpage:
http://www.diyamps.com/aleph/ps.shtml

The correct designation for the resistor for the LED is R20, which is a little hard to read on the pcb. It is the rectangular component closest to the LED, and the right resistor choice would be a 4.75k 0.5w resistor. I choose the compact metal film ones available from Digikey:
PPC4.75KXCT-ND
I am sorry for the confusion. I had forgotten to update the parts list to match the finalized power supply board layout.

Let me know if there is still some confusion.

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Brian
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Old 4th May 2005, 12:29 PM   #556
dhole is offline dhole  United Kingdom
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Cheers Brian

I had kinda guessed it was r5 , thanks. Still other people will benefit from the updated parts list. Thanks alot for the boards again .Oh do you have a spare psu board ? only bought 3.....
dave
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Old 4th May 2005, 12:31 PM   #557
fcel is offline fcel  United States
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Brian,

I've looked at the schematics. For minimum requirement, is this the right spec for the transformer for a stereo Aleph 30?

330VA, 18v-0-18v secondary, 120v primary (Full load amp on secondary side = __)

If I'm utilizing the resistors on the PS board for a CRC configuration, would there be some sort of voltage drop across the resistors? And thus should I order the transformer with a little higher voltage on the secondary side? Say 20v-0-20v?
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Old 4th May 2005, 12:33 PM   #558
BrianGT is offline BrianGT  United States
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Quote:
Originally posted by dhole
Cheers Brian

I had kinda guessed it was r5 , thanks. Still other people will benefit from the updated parts list. Thanks alot for the boards again .Oh do you have a spare psu board ? only bought 3.....
dave
I have about 10 power supply boards left, and 20 amp boards left (not including some boards I set aside for people who haven't paid yet). I will leave them available on the order page until I am completely sold out.
http://www.diyamps.com/aleph/orders.shtml

Best of luck with your project. I am hoping to get mine done soon, but other things keep on popping up, keeping me busy. I am going to try to put more time into this project this weekend.

--
Brian
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Old 4th May 2005, 12:39 PM   #559
fcel is offline fcel  United States
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Another question .... what are the values of those resistors located between the capacitors? Your Power Supply Parts List shows it as a short circuit jumper for R3 to R12. Is that something we should calculate on our own? Thanks.
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Old 4th May 2005, 12:40 PM   #560
BrianGT is offline BrianGT  United States
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Quote:
Originally posted by fcel
Brian,

I've looked at the schematics. For minimum requirement, is this the right spec for the transformer for a stereo Aleph 30?

330VA, 18v-0-18v secondary, 120v primary (Full load amp on secondary side = __)

If I'm utilizing the resistors on the PS board for a CRC configuration, would there be some sort of voltage drop across the resistors? And thus should I order the transformer with a little higher voltage on the secondary side? Say 20v-0-20v?
Without the CRC, 18-0-18 would be the minimum for the Aleph30. My initial plan was to try one of these per channel:
http://www.partsexpress.com/pe/showd...number=122-620
due to their quick availability.

If you are going to experiment with the CRC, 20-0-20, 500va might be a good choice to try out for a stereo amp. Victoria Magnetics should be able to wind a custom transformer for this if you are unable to find another source.

--
Brian
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