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Old 5th April 2005, 05:09 AM   #1
G4ME is offline G4ME  United States
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Default Ohhh Fire works (4780 Brian GT Kit)

Well, for the past month I have been helping my friend gather parts and assemble Brians 4780 Kit. He snagged a 500 VA +-25V torrid, binding posts. This past week we had enough time to solder her up and try it out. We tested the rectifiers to see if we were getting DC, that was a go the DC for both bridges were putting out around 36V off by a few .01V. Then connected the Chips, and powered up, upon switching on, heard loud sparks cracking sound, killed power.

We thought it was that the chip wasn't insulated, and so we pulled them away from the aluminum case, tried it again, same thing this time we blew some of the pins off. Looking at the pins looks like the V+ didn't quite agree with it.

Here are some pics

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Not really sure how we messed this up, but we double checked the voltages and what not.
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Old 5th April 2005, 05:14 AM   #2
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Default Re: Ohhh Fire works (4780 Brian GT Kit)

Quote:
Originally posted by G4ME
Well, for the past month I have been helping my friend gather parts and assemble Brians 4780 Kit. He snagged a 500 VA +-25V torrid, binding posts. This past week we had enough time to solder her up and try it out. We tested the rectifiers to see if we were getting DC, that was a go the DC for both bridges were putting out around 36V off by a few .01V. Then connected the Chips, and powered up, upon switching on, heard loud sparks cracking sound, killed power.

We thought it was that the chip wasn't insulated, and so we pulled them away from the aluminum case, tried it again, same thing this time we blew some of the pins off. Looking at the pins looks like the V+ didn't quite agree with it.

Here are some pics

.. pics ...

Not really sure how we messed this up, but we double checked the voltages and what not.
I am sorry to hear about your troubles with the amp. Drop me an e-mail if you need any replacement parts.

--
Brian
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Old 5th April 2005, 06:09 AM   #3
G4ME is offline G4ME  United States
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we have some more 4780s. hopefully we didn't damage any other parts.
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Old 5th April 2005, 10:54 PM   #4
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anyone have any ideas at what i did wrong.

The only things that i can think of is that i had a voltage off set on my 0V.

Also the RCA's arn't really shielded from the case.
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Old 5th April 2005, 11:07 PM   #5
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anyone have any ideas at what i did wrong.
Maby you connected the PSU wires wrong.
Maby you had positive voltage where there should be negative?
Can't see another reason...
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Old 6th April 2005, 03:12 AM   #6
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That's all I can think of. There are no diodes to get wrong, other than in the bridge, but you said that was cool.

Here's a pic of one I built last night. It is working fine. Compare your wiring to mine. In this pic, yellow and black twisted are V-, red and black twisted are V+.
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Old 6th April 2005, 03:15 AM   #7
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Here is another. Both Yellow/Black pairs are V- and both Red/Black pairs are V+.
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Old 6th April 2005, 03:25 AM   #8
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we Attached the CHG terminal to the star ground, I read the 3886 PDF and it said connect it to star ground.
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Old 6th April 2005, 03:47 AM   #9
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Yes, sorry. My chassis is incomplete, so I have not yet connected it. If that is the only difference you have, then it is something else. Perhaps a bad 4780? Solder bridge? Bent pin?
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Old 6th April 2005, 06:14 AM   #10
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Quote:
Also the RCA's arn't really shielded from the case.
Any chance that you forgot to shield the speakerposts?
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