Orion HCCA 225 digital ref. blowing fuse again!

[ash4kel]

I posted early last week about my HCCA blowing fuses and Perry was great in helping me troubleshoot. Thanks again Perry for you help. Anyway, I am back to square one. After changing the FETS on one side last week, I had good sound coming out of amp and it lasted until today. When I went to turn it on today, the fuse was blown. I checked the fets and I had one 2n6488 and one 2n6491 that had .002 short between legs 1&3, and I had voltage on the corresponding resistors. I have changed those transistors out and now all fets read the same and there no voltage on the resistors (any of them). One more thing does it matter which side the rectifiers are on since they are different. While I had the amp open I took the rectifiers off because I didn't like my soldering job when I placed them back on the board from before. Well stupid me didn't pay attention to which one went on which side. I am pretty sure I have them correct but I just want you to have all info. Thanks, Scott

 

[ash4kel]

Oh, and just for clarity, the fets that were blown are on the opposite side of the fets I changed last week.

 

[Perry Babin]

See attached for rectifier location.

You had them in the correct locations if the amp powered up and produced audio.

After installing the new outputs, did you have 0.000v across all of the emitter resistors (no audio, no load)?

Are you sure that there were no defects in the insulator that is under the transistors?

Are you sure that all of the transistors were tightly clamped to the heatsink (double-sided tape intact and no stripped screw holes?

 

[Perry Babin]

One note... The 2N6488s and 2N6491s are not FETs, they're BJTs (Bipolar Junction Transistors).

 

[ash4kel]

I know the rectifiers were correct when I was producing sound, but I had taken them back off and resoldered today while I was troubleshooting the rest, and to my surprise, thanks to your picture, I transposed them today. Hopefully I have not damaged any thing else. I will switch them now.

 

[ash4kel]

There I go showing my ignorance again. Thank You for correcting me, so I know what these things are called. And it's amazing when you put the correct rectifier on the the correct corresponding side how things work. Lol. Anyway thanks again, another lessoned learned. Things are working fine........for now.