Ohhh Fire works (4780 Brian GT Kit)

G4ME · 5th April 2005, 05:09 AM

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

Not really sure how we messed this up, but we double checked the voltages and what not.

BrianGT · 5th April 2005, 05:14 AM

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

G4ME · 5th April 2005, 06:09 AM

we have some more 4780s. hopefully we didn't damage any other parts.

G4ME · 5th April 2005, 10:54 PM

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.

carlosfm · 5th April 2005, 11:07 PM

Quote:

Originally posted by G4ME
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...

BrianDonegan · 6th April 2005, 03:12 AM

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+.

BrianDonegan · 6th April 2005, 03:15 AM

Here is another. Both Yellow/Black pairs are V- and both Red/Black pairs are V+.

G4ME · 6th April 2005, 03:25 AM

we Attached the CHG terminal to the star ground, I read the 3886 PDF and it said connect it to star ground.

BrianDonegan · 6th April 2005, 03:47 AM

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?

kmj · 6th April 2005, 06:14 AM

Quote:

Also the RCA's arn't really shielded from the case.

Any chance that you forgot to shield the speakerposts?

5th April 2005, 05:09 AM	#1
G4ME diyAudio Member Join Date: Jun 2003 Location: Location: Location	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 Not really sure how we messed this up, but we double checked the voltages and what not. __________________ Two little mice fell in a bucket of cream. The first mouse quickly gave up and drowned. The second mouse, wouldn't quit. He struggled so hard that eventually he churned that cream into butter and crawled out.

5th April 2005, 06:09 AM	#3
G4ME diyAudio Member Join Date: Jun 2003 Location: Location: Location	we have some more 4780s. hopefully we didn't damage any other parts. __________________ Two little mice fell in a bucket of cream. The first mouse quickly gave up and drowned. The second mouse, wouldn't quit. He struggled so hard that eventually he churned that cream into butter and crawled out.

5th April 2005, 10:54 PM	#4
G4ME diyAudio Member Join Date: Jun 2003 Location: Location: Location	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. __________________ Two little mice fell in a bucket of cream. The first mouse quickly gave up and drowned. The second mouse, wouldn't quit. He struggled so hard that eventually he churned that cream into butter and crawled out.

6th April 2005, 03:25 AM	#8
G4ME diyAudio Member Join Date: Jun 2003 Location: Location: Location	we Attached the CHG terminal to the star ground, I read the 3886 PDF and it said connect it to star ground. __________________ Two little mice fell in a bucket of cream. The first mouse quickly gave up and drowned. The second mouse, wouldn't quit. He struggled so hard that eventually he churned that cream into butter and crawled out.

6th April 2005, 03:47 AM	#9
BrianDonegan diyAudio Member Join Date: Dec 2004 Location: Rock Ridge	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? __________________ Twisted Pear Audio


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