RF punch 800a2 channel repair question

[chipper]

If the Amp has IRF3205's in it right now what ohm gate resistors does it have in it??

68 ohm

 

[S Merlington]

That may explain why they are warming up With the 3205's the gate resistors should be 47 ohm

 

[chipper]

I agree with Sean, the power supply FETs need to match & need to go through the power supply thoroughly for reliability. You need to do that now anyway, check the drivers & gate resistors thoroughly, as maybe that was overlooked during a previous repair causing the uneven heating of one bank.

If you have to order parts, make sure you order gate resistors & driver transistors as there cheap, if you don't already have extra.

Main reason for me posting here is to say be careful when you got the back off testing stuff, FETs can blow apart & throw pieces of themselves violently, could really mess up an eye. I had some close calls over the years & highly recommend wearing safety glasses when the backs off & the amp has problems.

It could have been a factory repair back then? They looked factory soldered to the mehsa board or I could be wrong. I blew a fet in the power supply a piece just blew off when the prob shorted the legs and I jumped! Strange the amp was still on would have figured it would have caused a massive melt down! I took out all 8 fets and checked gate voltage all 8 sit at a steady 4.51 vdc but still going to rebuild the whole power supply.

I'm piecing up a parts list right now
8x 3205's
8x 47 ohm resistors (smd)

And I already have a ton of new smd driver transistors ready.

 

[chipper]

That may explain why they are warming up With the 3205's the gate resistors should be 47 ohm

I think so too when I looked at them. Thought about changing them but would make no sense bc the other bank is totally different. Ordering new everything soon I really hope this gets rid of that problem so I can fix the other channel.

 

[seankane]

I personally have used 68 ohm gate resistors with IRF3205's.

I have opened amps (warranty seals in tact) and seen 68 ohm gate resistors with the IRF3205's straight from Rockford.

The only reason I switched to 47 ohm was because Perry told me it was a better choice and he explained why but I cant remember now. Now I recommend it to everyone. It has proven to me to be a reliable combo.

The fact that the power supply FETS do not have matching date codes, nor do they even have matching part numbers is a problem. This will cause problems and could be causing what you are experiencing.

 

[chipper]

Does this explain my heat problem?

 

[seankane]

I think you have found your power supply problem.

How did you not see this before as the they are not covered with a buss bar?

 

[chipper]

I think you have found your power supply problem.

How did you not see this before as the they are not covered with a buss bar?

Do you have any new 3205's for sale?

 

[seankane]

No sorry I have to order some. I just repaired 2 1500bd's and I am out.