Pumpkin preamp - ordered by Steen , official making thread

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#3,021
jacco vermeulen said:
Good ones, and look brand new btw.

The odd part is that i bought up the entire stock they said they had left, the minute i saw their ad, that was before 2010.
Need a datasheet, an image of the integrated amp they came out of, or a close-up(s) of the tranny ?

(cough, me pay less than $21, mucho less :clown:)
Click to expand...


I emailed again asking to ensure availability and sure enough they dont have any now, despite saying they did a few days prior.

This may do the job

220V 50W R-core Transformer X-Former 45V-0 0-45V 0-25V | eBay
 
#3,026
Help

I have assembled my Shunty and Pumpkin boards.
Tested the Shuntys with 400 ohm resistors. Obtained +/- 36V

Hooked up Pumpkins.
One channel works as described in the setup section.

On the second board the negative rail drops to -17V.😕

Any thoughts where I should begin to troubleshoot?

Thanks in advance

Best

Bob
 
#3,034
now is tricky

it seems that you can exclude possible shortie on pcb , because you measured 10K from neg leg to gnd ;

so - reason must be that some part is conducting excessive current when power is applied .

do this : dismantle heatsink , power up and observe which of those 5 mosfets is excessively heating ; 4 of them must have similar temp , and Q10 must be (almost) cold ;

off course - for start you must be sure that you don't have some wrong resistor there

in any case - fiddle with diode meter here and there ( between pins of each transistor , same as between pins and gnd ) , comparing differences between working and non-working channel , and you'll localize what's wrong
 
#3,039
Zen Mod said:
now is tricky

it seems that you can exclude possible shortie on pcb , because you measured 10K from neg leg to gnd ;

so - reason must be that some part is conducting excessive current when power is applied .

do this : dismantle heatsink , power up and observe which of those 5 mosfets is excessively heating ; 4 of them must have similar temp , and Q10 must be (almost) cold ;

off course - for start you must be sure that you don't have some wrong resistor there

in any case - fiddle with diode meter here and there ( between pins of each transistor , same as between pins and gnd ) , comparing differences between working and non-working channel , and you'll localize what's wrong
Click to expand...

I was measuring resistance and found on the board that works
R5=R6 =16k measured across each in circuit and

on the board that doesn't R5=R6 =100k

????

Thanks
 
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