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Old 28th November 2011, 08:59 PM   #21
jrobson is offline jrobson  South Africa
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Hmmm let's take another stab, found some problems oops...
Fixed them unless something blew, right now I get 465v over R30, -260-270v over R7 and -80v on the grid with GZ34 plugged in.
No voltage over pin 4 on the output sockets.
Plugged in the 5842's and R27 blew spectacularly...
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Old 28th November 2011, 09:26 PM   #22
jrobson is offline jrobson  South Africa
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Dang nobody with any advice?
I'm assuming Q2 blew....
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Old 2nd December 2011, 06:59 AM   #23
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Doesn't it get too hot inside ?

D.
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Old 2nd December 2011, 07:08 AM   #24
jrobson is offline jrobson  South Africa
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At this point it's upside down so certainly not a factor right now, when it's done I'll monitor and see, it should be okay.
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Old 7th December 2011, 07:05 PM   #25
jrobson is offline jrobson  South Africa
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Here we go again... Okay replaced the Q's or mosfets, and the resistor that blew, from the tubelab checkout page:

"Put a meter from the grid of the output tubes to ground. One meter for each tube. Power up the board. Each meter should read a negative voltage. With ONE HAND BEHIND YOUR BACK carefully adjust one of the bias pots (R12 or R23). The negative voltage for the corresponding output tube should change. Set it to the most negative voltage, and then adjust the bias pot for the other channel."

From what I read on there I adjusted them to the most negative they would go, they went all the way to -140 and -152, is this OK?
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Old 7th December 2011, 07:11 PM   #26
jrobson is offline jrobson  South Africa
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Initially they were at -78 and -80.
Before I plugged the 5842's in I measured the plate, I am getting B+ on one of the plates... any idea why this would happen?
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Old 7th December 2011, 07:45 PM   #27
jrobson is offline jrobson  South Africa
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Okay I must have a short, I took the board out, measured resistors R27 and R28, both 540, measured R16 and R17, one 330, the other 1000 as it should be, R27 blew before so this most likely the cause.
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Old 7th December 2011, 08:28 PM   #28
jrobson is offline jrobson  South Africa
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Scratch that, R27 260, R28 320, R16 and R17 is ok.
C11 gives a resistance when on the board, when removed it's fine... C9 is fine in the board... I don't know where else to look...

Any help?
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Old 15th December 2011, 03:12 PM   #29
jrobson is offline jrobson  South Africa
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Got new CSS's, previous problem solved but no voltage at the 5842 plate, I'm using these: eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices

wrong tubes?
Everything else checks out fine.
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Old 15th December 2011, 03:59 PM   #30
jrobson is offline jrobson  South Africa
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Never mind I see some of you guys use these tubes, any ideas why there is no voltage, there is around -110v to -125v on the other side of the caps. On startup the plate reads negative then as B+ starts to turn positive the plate just goes to 0.
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