Memphis 16-mcd1000

[bdgf2004]

The power supply was blown when I received this amp. I got the 3205 fets but it uses 2sa1266/2sc3198 for the emitter follower pair. I was wandering if there was a good replacement for those?

 

[Perry Babin]

There are many options. If you're trying to use something you have on hand, list ALL of the PNP transistors you have.

 

[bdgf2004]

2n4403, mpsa56, mpsw56, 2n3906, mpsw92, ksa1220a, 2n5087

 

[Perry Babin]

Of those, I'd use the KSA1220. This is to replace the 1266. They don't use NPN drivers as far as I know.

 

[bdgf2004]

thanks. i haven't even pulled the board yet to really check it out. i just saw 1 that was completely destroyed and others in the area so i read all the #'s i could see.

thank you. 1 day i will have confidence to choose my own replacements.

 

[bdgf2004]

would 91 ohm work for the gate resistors? 3205's

 

[Perry Babin]

Probably not. I'd suggest that you use 47 ohm resistors.

 

[bdgf2004]

i can make out the first line on 1 of the resistors and it appears to be red. so i figured that it was probably 2? ohm and all i had was a 20 and a 47. in the tutorial perry suggested 27-47 ohm so i am going to try the 47 ohm and see what happens.

 

[Perry Babin]

I should have looked at the photos I have. The originals are 22 ohms and would be better, in my opinion, because they were the original part. The 47s should work perfectly well.

 

[bdgf2004]

i got the power supply going but when i attempt to power it up it pulses on and off. i noticed the large caps C241 & C271 (200v 33uf non-polar) and c61 & C64 (80wv 4700uf) were buldging a bit but not vented. i removed and checked them, the 33uf caps measured 1 @ 32uf & the other @ 22uf and both the 4700uf caps were @ 4100uf. also i was checking the outputs and the 9640's all measured @ .800v (red probe on drain and the black on source) with diode check and 1.5m ohms on resistance. is that ok? i ask because i have new 1's on hand and they measure @ .500v & 2.5m ohms (that's what i usaully get).
was the 4100uf reading ok? the caps were at room temp when measured
also i was having trouble finding some of the 200v 33uf non-polar caps.

 

[joesch1999]

I am having the same problem with the same amp mine is a st1000d memphis, the problem i ended up having with it is the two I think they are zenner's right below the tl494, at least I think they are three legged smd mounted part. One of the legs is at ground the other one runs off the TL and the other one goes to the 1266 check that mine does the same thing and that is whats wrong just need to find a replacement

 

[joesch1999]

if nothing else could you give me the part number mine got to hot and burnt the P/N off

 

[bdgf2004]

in my amp the 2 sot-23 diodes are marked C3.

 

[joesch1999]

yeah same with mine hz c3?

 

[Perry Babin]

The diodes are not likely to be Zeners. They're possibly:
http://oldwww.kec.co.kr/data/databook/pdf/KDS/Eng/KDS226.pdf

Please leave a blank line after each question. It makes it a lot easier to find.

0.8 is a bit high for 9640s but not beyond what I'd expect to see.

The rail caps are probably within tolerance (typically ±20%). The 33uf is out of tolerance but not low enough to cause problems at idle if the readings are accurate.

If you pull the driver boards for the outputs, does the amp still go into protect mode?

 

[bdgf2004]

when i pull the driver boards it will flash a few times and come on. both of the driver boards have t be out for it to come on

 

[Perry Babin]

Is there any DC on the tabs of any of the output transistors when the amp is on?

It's probably pulsing because you have a current limiter in series with the B+ line.

 

[joesch1999]

well if you decide you need the sot 23 rectifiers I found them at mouser

1SS226T5LFT Toshiba Rectifiers