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F6 Illustrated Build Guide
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Old 9th October 2017, 12:00 AM   #951
Zen Mod is online now Zen Mod  Serbia
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well , you reprted that you have problem

try to be systematic , and use bulb tester

is diode bridge functional ?

is cap bank functional ( no shorts - check with buzzer on your DMM) ?

is everything oriented as prescribed ?

something is wrong ...... and as long pcbs are at your bench , only you can find where is the culprit
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Old 9th October 2017, 10:15 AM   #952
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Which problem may be if after diode bridge i get only 17VDC (must be AC*1.414=25.45V) and on transformer secondary 18VAC. Also i try diode bridges from Vishay and remove thermistor, but voltage after diode bridge still remains 17VDC

Last edited by ilikeit; 9th October 2017 at 10:23 AM.
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Old 9th October 2017, 10:33 AM   #953
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there will not be 1.41 without caps

voltage is pulsating in a way which DVM can't measure properly

check diodes with diode test , check caps for shorts

connect them together , power up via bulb tester

report here
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Old 9th October 2017, 10:46 AM   #954
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Click the image to open in full size.
After powering off, light bulb can glow for 3 seconds...
Full size: https://i.imgur.com/CV0Mjug.jpg
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Old 9th October 2017, 11:05 AM   #955
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clarify

where you put bulb tester ?

it's usually connected in series with xformer mains
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Old 9th October 2017, 11:19 PM   #956
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I make an research, i make following decision - short in one or more caps.
Caps probably arrive damaged, because diode bridge functioning normally and everything is soldered correctly.
Also one of wire from diode bridge (600V 35A Vishay) moves when i turn on amplifer, that's because MUCH use of current - short.
Time to order new PSU PCB because i absolutely hate to desolder
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Old 11th October 2017, 08:29 PM   #957
silasmellor is offline silasmellor  Denmark
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Quote:
Originally Posted by 2 picoDumbs View Post
From the results Euvl posted keratherm performed even better than mica and goop.
I haven't personally done that comparison (mica vs keratherm) but I wouldn't doubt it. Keratherm really is that good.
Quote:
Originally Posted by Zen Mod View Post
Keratherm will deliver
Indeed, the package from DA store arrived today and switched them immediately - mosfet temperatures are now 25-30 degrees lower, so quite a difference. Temperature differential with heatsinks 2-5 degrees at the moment (depending on how much you trust my cheapo laser thermometer).

Interesting observation, after switching and letting the amp warm up, bias now reached just 0.38 V (it was biased to 0.5 V before). I guess that's all down to the mosfets operating at different temperatures (they were around 75-80 degrees before).

Edit: attribution

Last edited by silasmellor; 11th October 2017 at 08:41 PM.
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Old 11th October 2017, 08:39 PM   #958
2 picoDumbs is offline 2 picoDumbs  Australia
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I've been sounding off like a broken record about keratherm, even tested them to prove the point.

Zen Mod says three words, and he gets all the credit.
You bastards. It's not like I'm getting paid here.
That's it the friendhip is over.
Hahaha
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Old 11th October 2017, 09:40 PM   #959
grimberg is offline grimberg  United States
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Quote:
Originally Posted by silasmellor View Post
...mosfet temperatures are now 25-30 degrees lower...
Is that just from switching insulator types? Without getting into the merit of which one is best, switching between silpad, keratherm and mica + goop never results in such a big difference. I would believe differences measured in single digits only. I know because I have tested several of them, including different types of thermal compounds when using mica.
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Old 11th October 2017, 09:48 PM   #960
silasmellor is offline silasmellor  Denmark
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yeah. The previous ones were some that a guy from the local electronics shop sold me, so i have no idea what kind they were (there's a photo a few pages back but that doesnt help much), but they were clearly not doing their job very well...
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