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Old 29th November 2012, 04:17 AM   #1321
Mr. dB is offline Mr. dB  United States
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Quote:
Originally Posted by craigtone View Post
19 years of PCB design here. I'd love to help and ironically enough I was planning to build an Aleph J this winter ...

I have the Aleph J schematic if someone can educate me on "Universal Mounting Spec", I can start tomorrow.

http://www.diyaudio.com/forums/image...ation-v2.1.pdf
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Old 29th November 2012, 04:48 AM   #1322
6L6 is offline 6L6  United States
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Thanks for the link, you beat me to it.

As for the board, I was envisioning the same basic layout as the F4, F5c, etc... The longer board with the outputs all on the lower edge.

Also, I would love to see R7 replaced with a trimmer pot, as that's where you will be able to dial out any DC offset on the outputs... Maybe put pads for a parallel resistor there as well...

J109's are basically impossible to get anymore, so most people will be using a matched pair of J74's... it would be handy if they were face to face so their cases can be zip-tied together for better thermal tracking.

Thanks a bazillion for the offer!
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Old 29th November 2012, 08:14 AM   #1323
kroyin is offline kroyin  India
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Ok i fell flat with the second channel

Offset is (-)23.6Vdc
R7 - 36V
Q3 Vce-36V
Q2 Vce - 0V
Q4 Vce ~ 4 V
Z1 - 9.9V
R8 - 9.1V
All source resistors are around ~.56xV

Q5 & Q6 gets pretty hot (case temp of 70C after 5 mins)

So before i unmount the setup, anything that comes to anybodys minds pls.

I have used 2Sj74 & BC550/560 (have been careful with the pinouts )

Last edited by kroyin; 29th November 2012 at 08:20 AM.
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Old 29th November 2012, 11:40 AM   #1324
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Can I jump in and suggest right now, please fellers, that a new thread is opened for discussion of a new UMS Aleph J board design rather than doing it in here?

I'm interested in following if not contributing to the process and I think it would be a mistake to bury something that important in the 13?th page of an existing thread.

Much respect to craigtone for bravely volunteering ;P and all due respect to 6L6, and Mr dB.
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Old 29th November 2012, 12:09 PM   #1325
kroyin is offline kroyin  India
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Quote:
Originally Posted by kroyin View Post
Ok i fell flat with the second channel

Offset is (-)23.6Vdc
R7 - 36V
Q3 Vce-36V
Q2 Vce - 0V
Q4 Vce ~ 4 V
Z1 - 9.9V
R8 - 9.1V
All source resistors are around ~.56xV

Q5 & Q6 gets pretty hot (case temp of 70C after 5 mins)

So before i unmount the setup, anything that comes to anybodys minds pls.

I have used 2Sj74 & BC550/560 (have been careful with the pinouts )
I dug up a old post from Zen it says

'so - voltage across R7 is completely dependent on input LTP's CCS (Z1, Q2,R8)'

So as of now Q2 seems to be the culprit as R8 & Z1 reads more or less ok
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Old 29th November 2012, 01:25 PM   #1326
Jay is offline Jay  Indonesia
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Default What is your power supply Zen Mod?

I use your bablefish variation. 24V-25V seems optimum. So 28Vdc transformer with the standard Zen mosfet pre-regulator to lower the voltage to optimum value. What PS do you guys use? What is best?
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Old 29th November 2012, 03:37 PM   #1327
Zen Mod is offline Zen Mod  Serbia
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whatever you have , between +/-18 and +/-28Vdc

be sure that steady dissipation of each IRFP150 is no more than 50W , with proper heatsinking

Pa sez that input Jfets (in that configuration) are pretty safe up to ....... +/-35Vdc PSU , if I remember correctly
whatever - I don't like regs in power amp supply , for my taste better solution will be to un-wind some turns of xformer secondary , if possible
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Old 29th November 2012, 10:41 PM   #1328
Jay is offline Jay  Indonesia
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Okay thanks ZM. I will use 18Vdc EI transformer then. The 28Vdc toroid for another amp.
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Old 2nd December 2012, 05:42 AM   #1329
kroyin is offline kroyin  India
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Default pls help

Quote:
Originally Posted by kroyin View Post
I dug up a old post from Zen it says

'so - voltage across R7 is completely dependent on input LTP's CCS (Z1, Q2,R8)'

So as of now Q2 seems to be the culprit as R8 & Z1 reads more or less ok
Change q2,q3,q4 but things are not right

ZD1-9.36V
R8-8.75V
Q2 Vce-13.8V
Q2 Vbe- 0.6V
R7-8.7V ?????
R16,17,18,19- 0.59xV
Q5,Q6 Vgs - 4.2V
Q7,Q8 Vgs- 8.1V ???
Q4 Vce-4.68V

One other thing the good channel has 0v across 5pF, while the bad one has 2.8v

I am confused
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Old 2nd December 2012, 07:36 AM   #1330
kroyin is offline kroyin  India
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I don't think the input JFets are blown since Q2 readings are same across both the channels...but I think the problem starts with R4 (bad channel 27v good channel 0V) which again point to JFET
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