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Old 30th July 2014, 01:20 AM   #21
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I guess I'll give it "full power Captain" and see if "she'll no take much more of this"
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Old 3rd August 2014, 11:48 PM   #22
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Results at full power with rectifier and 5842's in place:

B+ 421VDC
B- -349VDC
Left channel coupling cap: 175VDC (variable by using trimpot)
Right channel coupling cap: 283VDC (doesn't vary when adjusting trimpot)

I checked for a faulty meter but not that.

Hmm!
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Old 20th August 2014, 12:30 AM   #23
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Swapped the 5842's and saw the right channel drop to 218VDC but again not varying with the trimpot. Left channel trimmed to 175VDC.

Will check the trimpot is functional as that isn't too far off where I need to be.
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Old 24th August 2014, 07:31 PM   #24
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Desoldered and resoldered trimpot and it resolved the issue.

Moving on to the next step in the checkout process.
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Old 6th September 2014, 08:35 PM   #25
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So I've been getting some terrific one on one support from one of the members here but I feel it unfair to keep pestering him so:

I have progressed through the checkout to where all tubes are in and I have leads across R18 and R29.

(I had previously set the output grid to its most negative (-325v more or less))

I get 424V B+

I get -365V on B-

I have both input tubes at 175V.

I get no reading at all from R18 and R29 even if I turn the trimpots (R12 & R23) all the way from one side to the other. No reading AT ALL.

I see the 300B's are glowing (one more than the other).

I have the Output Transformers hooked up and an 8ohm load attached (speakers).

All solder joints appear to be testing fine and the resistors test ok.
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Old 12th September 2014, 02:24 AM   #26
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I'm at a loss guys. Anyone else face a similar issue?
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Old 12th September 2014, 03:18 AM   #27
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BPLUS to DRV_B+ jumper installed?
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Old 13th September 2014, 03:10 AM   #28
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It is but I will check it tomorrow (too much already wine tonight). Thanks JP.
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Old 13th September 2014, 05:19 PM   #29
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Quote:
Originally Posted by moggi1964 View Post
I get no reading at all from R18 and R29 even if I turn the trimpots (R12 & R23) all the way from one side to the other. No reading AT ALL.
What is your voltmeter range set at? If it's set to read high voltage, it may not show.
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Old 13th September 2014, 09:37 PM   #30
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Even' I made that error at the beginning but changed it to a more sensitive setting and still no luck.

Swapped in a new jumper and fired it up. Started getting a reading on R18 and R29 then smelled and saw smoke from near the rectifier. Switched off quickly but before I could establish which component.

Went back to square one with no tubes.

B+ -30V (and falling towards zero)
B- -285V

Put in a known good rectifier and got

B+ 450V
B- -92V

Noticed a multimeter lead had a melted section and wondered if the smoke had come from that resting against a tube? Or maybe against an overheating resistor?

Before I start a lot of desoldering and testing, is there an obvious candidate for the B- drop? B- wasn't as high as I would expect in the first place but the drop was huge!

My son says he wants his Netbook back, the one I borrowed 6 months ago for "a month or so while I build my amplifier"! Oops!

Sometimes it really is on step forward ............
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