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Dr Zeus 2nd April 2011 03:33 AM

Memphis 16-ST1000D
I've worked on a few of this series already, but this one is the worst. I'm not even close to done digging through but here the starting hit-list:

All IRFZ44 fets are bad. 22 ohm gate resistors are good.

All outputs are bad IRF640/9640

IRF640s are in Q215, Q216, Q225, and Q226.

I'll be placing one of each bank of transistors at a time for evaluation and function and will report back what I find.

Dr Zeus 2nd April 2011 05:05 AM

Found Q15 and Q16 drivers on the PS driver board out of spec. A1266 transistors. Amp now holds +-60vDC at the rail with the outputs out of circuit.

I'll work on this little guy some more tomorrow. peace!

amc32 2nd April 2011 12:32 PM

I personally love working on these little amps. PS and Output Driver Cards unplug I have tons of rebuildable cards. The key is to keep a functioning amplifier on hand makes troubleshooting much easier. If you need rebuildable cards or photos let me know. Forget the IRFZ44's and go with the IRF3205's or it will be back again as soon as the customer gets drunk one night.

Dr Zeus 3rd April 2011 03:26 PM

What originally came in this amp? I could barely see the identification marking on the PS Fets and could only barely make out IRFZ44. This amp is running with 22ohm gate resistors for the PS fets.

Perry Babin 3rd April 2011 03:45 PM

As far back as the board revision PAM280-09, the 3205s were the original parts.

Dr Zeus 3rd April 2011 03:47 PM

Hmm so the IRFZ44s are likely not going to work if 3205s were original. I wonder why this amp had them in here? Or perhaps they were IRFZ48s - I cannot tell because all the fets were distroyed.

Dr Zeus 3rd April 2011 03:52 PM

In powering up this amp with several IRF640/9640s installed (And IRFZ44s), the new IRF9640s get hot within seconds. Pulled both driver boards and they stay cool. I've narrowed the drive circuit i nthe following photo where you can see the lead is attached, and the trace<s> are leading to the three drivers on the top right corner of the board.

-From Left to Right last three on the right-
Q201: C3503-D
Q202: A1027
Q203: A1023

Perry Babin 3rd April 2011 04:01 PM

Is there any DC on the tabs of the outputs with no driver boards installed?

Dr Zeus 3rd April 2011 04:10 PM

Yes as follows:

IRF9640s have +64vDC on pads 1 & 3, and 0vDC on pad 2.
IRF640s have -64vDC on pads 1 & 3, and 0vDC on pad 2.

Perry Babin 3rd April 2011 04:12 PM

Tab = top of the transistor.

It appears that you have none.

The PNP drivers, the 1 ohm resistors and the 12v zeners are all suspect.

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