Bottlehead Forum
Bottlehead Kits => BeePre => Topic started by: Dynakitbuilder on February 17, 2021, 11:55:42 AM
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previous tests were OK: Powerline = 123 vac. Transformer secondary test: page 30. 194 vac, 6.7, 6.7, 6.7.
Page 34, high voltage test: 0.00. Checked fuse, OK. Reheated all connections from #s 7 & 8 on transformer forward.
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Check that your meter is set to read DC voltage (two parallel lines, one dashed and one solid). The previous p. 30 tests were for AC.
cheers, Derek
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meter set on V dc. reads "0.001 vdc. wish it had been that easy to correct!
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Hmm. There's not a lot that can go wrong there. I'd double check the orientation of the diodes. If that's not it, posting some detailed pics of the trafo area from different angles might be a good idea.
cheers, Derek
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I would post a photo of what you've built and be sure not to proceed with the rest of the build until this is resolved.
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HI - will send a few at a time. Thanks.
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3
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4
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6
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A few thoughts -
Test the meter's DC setting with a battery to be sure it's working OK in DC mode.
Carefully check each of the terminals from the power trans out to terminals 31 and 33 for correct wiring against the manual.
Measure resistance from terminal 31 to 33 and make sure that it is not super low, like near 0 ohms. Probably won't be, as likely you would have blown a fuse if it was.
If the wiring is all correct and nothing is shorted the .001VDC reading indicates that the high voltage is not getting all the way through the filter. Reflow all the joints from the power trans high voltage terminals to the final terminal strip of the power supply filter, where the DC voltage test terminals 31 and 33 are.
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I would reflow some of your solder joints again, especially 37L. The convex dome shape seen in one of your photos can indicate a cold solder joint in my experience.
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Found at least one problem; fuse blown, no AC volts. I checked the fuse before starting the first checks and assumed it was fine since all the other tests were OK up until the high voltage tests. Anyway, there has to be something wrong that blew the fuse, right?
Thanks for all the suggestions - at least all the soldering has been done over twice. It's my 4th kit to build in the last 12-18 months; I should be at least barely useful at that part by now...just ordered a couple fuses from the Queen.
Tom
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If 36 and 35 are shorted together with the lead of the 22R resistor, you'll blow fuses. If you have a diode backwards (you don't seem to), the fuse will blow. If terminal 8 and 9 on the power transformer are shorted out by diode leads, you'll blow a fuse (also looks unlikely from your build).
Some higher resolution photos with some more light would be helpful.
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Take that resistance measurement from terminal 31 to terminal 33.
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resistances not near zero
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#2
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If a lead from power transformer terminal 7 touches a lead from power transformer terminal 8 (on the UF4007s), then you'll short out the high voltage wiring. To avoid this, pull a little tension into all the diodes at the terminal strips so they stay away from each other.
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Separated the diodes, and did the correction @ 35 to 33. Reheated all connections from 31 to 33U.
Got 24 VDC that slowly went down to 13 VDC +/-.
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Is your fuse blown?
You absolutely need to use more solder on those 3 lug strips, especially on the lower lugs.
What is the DC voltage between 37 and 39?
What is the DC voltage between 34 and 36?
What is the DC voltage between 31 and 33?
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fuse blown - replaced
added solder to all joints, esp lowers
VDC readings on all three points: 0.00 VDC
Obviously, fuse blew again
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Heat up the solder joint on power transformer terminal 7 and pop the diodes out temporarily, then check to see if the fuse holds and let us know.
It might be a good idea to post some fresh build photos.
Stuff that causes fuses to pop instantly like this:
1. Backwards diode(s).
2. Leads from power transformer terminals 7 and 8 touching each other.
3. Backwards capacitor.
4. Solder or debris shorting terminals to the chassis that shouldn't be.
Less possible:
1. Defective diode (very rare, but we can test for this next)
2. Defective power transformer (if the fuse holds with the diodes disconnected from one end, then the PT is fine)
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fuse did NOT blow with diodes on #7 disconnected
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#3 & #4 photos
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What I would do next is to disconnect the diodes from power transformer terminal 8 as well, then use the continuity beep setting to test all your diodes to see if any are shorted. It's super rare to end up with a shorted UF4007, but not impossible. Also keep in mind that some meters may beep on every diode but only in one direction, so before declaring a diode bad be sure to swap the leads around.
If you do not find a shorted diode, that's also valuable information and there's certainly another path to take after that with more debugging.
-PB
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Sorry, but I do not know what the "continuity beep setting" is. I have a basic Fluke 101 meter.
Also, the beep means the diode is OK and should be checked in both directions on all diodes?
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Diodes: all measure 0.68 to 0.66 m ohms in one direction, 0.L in opposite direction. Never got a beep.
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Put the diodes back in place, then remove the lead of the 270 ohm resistor that goes into terminal 37L and leave it poking out sideways, then let us know if the fuse holds.
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with 270 ohm resistor detached from 37L and all diodes re-attached -- fuse held, did not blow
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OK, go ahead and reconnect that resistor.
There's another 270 ohm resistor between 34 and 31, go ahead and disconnect it at 34 and repeat the test.
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disconnected resistor @ 34L - fuse not blown
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Can you check the DC voltage between 34 and 36?
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260.5 VDC between 34 & 36
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OK, you can put the resistor back at 31. If the fuse blows for some reason after you do this, please post lots of photos of the area around terminal 31.
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Final VDC readings at 33-31: 260 VDC +/-. Passed! OK, what did you and I learn from going through the successive tests and detaching reattaching the resistors? That the problem was in my soldering? Thanks very much for your patience and perserverence. OK to continue building the kit now?
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Yes, you're good to go.