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-   -   RF punch 800a2 channel repair question (https://www.diyaudio.com/forums/car-audio/235485-rf-punch-800a2-channel-repair-question.html)

chipper 6th May 2013 03:38 AM

RF punch 800a2 channel repair question
 
1 Attachment(s)
Hi forum, I recently bought a punch 800a2 not sure of the board rev # still waiting for it to come. Anyway I wanted to know is it hard to repair the channels on these? This one has one blown channel (according to the seller) I've never repaired one of the larger RF amps before.

What components in the shorted channel would need to replaced in order to get it working?

chipper 6th May 2013 03:40 AM

1 Attachment(s)
Picture he sent me of the channel, you can see discoloration on the source resistors.

seankane 6th May 2013 03:53 AM

When you get it re-post and I will help you. No sense in writing up long post about what "could" be wrong.

Likely it has shorted outputs, as well as some defective source resistors.

You will need to replace all the outputs and source resistors in the channel.

You will also need to check/replace any gate resistors for the output FETS.

If any of the source resistors are open you will likely have protection circuit issues to deal with.

You will have to check the various 1A and 2A transistors, and the 5D and A7 diodes for leaks or shorts.

There is also some 20 ohm resistors that usually need replaced in the channel as well.

Call Rockford get the schematic and re-post when you get it.

chipper 9th May 2013 09:24 PM

Ok got it. Is Q8, Q7, Q6, Q5 suppose to run a little above warm?? The other side remains cool when just idling. And for the blown channel all of the source resistors where shot out and both 5 IRF640 & IRF9640 also shorted.

chipper 10th May 2013 01:56 AM

Quote:

Originally Posted by seankane (https://www.diyaudio.com/forums/car-audio/235485-rf-punch-800a2-channel-repair-question-post3480314.html#post3480314)
When you get it re-post and I will help you. No sense in writing up long post about what "could" be wrong.

Likely it has shorted outputs, as well as some defective source resistors.

You will need to replace all the outputs and source resistors in the channel.

You will also need to check/replace any gate resistors for the output FETS.

If any of the source resistors are open you will likely have protection circuit issues to deal with.

You will have to check the various 1A and 2A transistors, and the 5D and A7 diodes for leaks or shorts.

There is also some 20 ohm resistors that usually need replaced in the channel as well.

Call Rockford get the schematic and re-post when you get it.


I need some help. Q8, Q7, Q6, Q5 run a little above warm when idling while the other side stays cool. What's causing this? Thanks

S Merlington 10th May 2013 04:20 AM

Have you turned the bias pots fully counter-clockwise??

seankane 10th May 2013 04:41 AM

Quote:

Originally Posted by chipper (https://www.diyaudio.com/forums/car-audio/235485-rf-punch-800a2-channel-repair-question-post3485174.html#post3485174)
I need some help. Q8, Q7, Q6, Q5 run a little above warm when idling while the other side stays cool. What's causing this? Thanks

Well if one whole channel was shorted then obviously you clipped the legs of the FETS to enable the amp to power and idle.

The side of the power supply that is still driving the enabled FETS will get warmer more quickly than the side that has the FETS clipped, especially if the board is not mounted in the sink.

It should take a little bit for them to get warm though. They should not be getting warm very quickly if the amp is just idling.

chipper 10th May 2013 01:46 PM

Quote:

Originally Posted by seankane (https://www.diyaudio.com/forums/car-audio/235485-rf-punch-800a2-channel-repair-question-post3485283.html#post3485283)
Well if one whole channel was shorted then obviously you clipped the legs of the FETS to enable the amp to power and idle.

The side of the power supply that is still driving the enabled FETS will get warmer more quickly than the side that has the FETS clipped, especially if the board is not mounted in the sink.

It should take a little bit for them to get warm though. They should not be getting warm very quickly if the amp is just idling.

Yes I desoldered them from the board and all of the open source resistors (all of them were no good) didn't take out anything else. I also wiggled the transformer around didn't seem to do anything. One bank of fets get really warm when mounted tightly to the sink while the other side just chills. It's not making any sense to me. Both bias pots are turned down.

Weirdest thing is they start to heat up after a minute of being powered up. Could it possibly be the channel that failed? I also noticed a group of smd components get very hot on the failed channel.

seankane 10th May 2013 05:53 PM

Which side is running hot, the side you removed the fets on or the remaining channel?

chipper 10th May 2013 05:55 PM

Quote:

Originally Posted by seankane (https://www.diyaudio.com/forums/car-audio/235485-rf-punch-800a2-channel-repair-question-post3485908.html#post3485908)
Which side is running hot, the side you removed the fets on or the remaining channel?

The side with the removed outputs. The other bank of fets of the power supply (right channel) runs cool.


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