Fired up Glassware's dual/bipolar lv-reg with a variac. Did not notice any issues and at 110v input had 17.8v dc output on both sides. Sat back and was congratulating myself when the smoke started up. C5 caps on both sides domed and got hot. Did not notice any other damage. Had 3 amp fast fuses on the mains which did not blow. Any help diagnosing is much appreciated.
Doug
Doug
Polarity of all the electrolytic capacitors ok?
Sometimes a pcb can be marked wrong, so verify the correct polarity by tracing out the circuit.
Or bad/reversed diodes? Again, verify polarity by tracing out the circuit.
Sometimes a pcb can be marked wrong, so verify the correct polarity by tracing out the circuit.
Or bad/reversed diodes? Again, verify polarity by tracing out the circuit.
The secondary voltage of the Triad VPT230-110 transformer is 115 VAC, much too high!
You only need about 15 VAC to get 18 VDC from a full wave bridge and 3 pin regulator.
You only need about 15 VAC to get 18 VDC from a full wave bridge and 3 pin regulator.
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And there are certainly going to be more casualties than just those two caps. The regulators, diodes, and any other cap that was exposed to the over voltage should be checked or just replaced as a precaution, before you proceed with the correct transformer.
BTW, the transformer secondaries can be in the 15-20V AC range, or as whatever the board maker specified.
BTW, the transformer secondaries can be in the 15-20V AC range, or as whatever the board maker specified.
Best to chuck the whole thing, and start over. That would be a lot less grief.
Overstressed components, even if functional, can fail at any time.
Overstressed components, even if functional, can fail at any time.
Thanks so much for the replies. Wow! Really screwed that up!
I bought the transformer from Glassware and somehow thought I was ordering the right one but apparently not.
I thought I had already done my homework so didn't look over the transformer. If I had tested the secondaries before hooking them up I should have caught it.
Should have been 18V AC. Yeah, might just start over, slightly smarter!
I bought the transformer from Glassware and somehow thought I was ordering the right one but apparently not.
I thought I had already done my homework so didn't look over the transformer. If I had tested the secondaries before hooking them up I should have caught it.
Should have been 18V AC. Yeah, might just start over, slightly smarter!
Very cheap tuition in the school of hard knocks.
And no loans outstanding.
Someone will probably buy that transformer from you.
Only used once.
And no loans outstanding.
Someone will probably buy that transformer from you.
Only used once.