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AU-D7 amp keeps blowing up outputs and drivers on left channel

SuperTech234

SuperTech234

New Member
To anyone who may have info on this model. I recently recapped and fully restored this AU-D7.
It had 2 blown output transistors,2 drivers,the bias transistor,the bias resistor, the bias and dc offset pots and a couple small transistors on the driver pc that were bad and a few .5 watt resistors as well.
After repair and restore I was able to adjust the dc offset and bias it out good.
After running it a while you turn up the volume and even though its not drawing excesive current and running clean sound it blows up the same channel again. I have repaired it 2 times and had the same result.
Is it possible that this is one of the sansui models that requires exact japanese replacement parts ?.
Thanks in advance.
 
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I'm likely not much help here but, I got one of these in the mid 90's from a customer that declined repairs. I replaced two shorted outputs on one channel and didn't even take the time to set bias or DC offset at the time.

It never failed on me but I did finally set bias and DC offset a couple years ago. Still running strong. It's one of my favorite integrated amps!

I'm not in front of my data so, going by memory, I believe I bought the outputs from MCM Electronics. Again, not much help, sorry.

I'm thinking maybe you have a capacitor issue or, possibly another smaller transistor upstream of the repair area. Compare voltages between channels and that may help you zero in.

Good luck on the fix. Likely well worth it!
 
Im not familiar with this amplifier circuit, but:

Are there VD1212 diodes in this amplifier and if so, have you replaced these?

Are there fusible resisitors in this amplifier, and, same as above?
 
1. What output transistors did you use and where did you get them?
2. Check the cap in the Zoebel network on the output of the amp, it could be leaky.
3. Put a scope on the output and check to see if it's oscillating.
 
The AU-D7 is a Sansui, not Mac.
That's a Rickenbacker 330-6. I am in a different band now and I don't play it anymore. I play acoustic in the new band, so I have the Rick down at a music store for sale. I like the Les Paul but it's too heavy.
 
moefuzz said:
Are you confident that your replacement transistors were the real thing and not cheap chinese knock offs?

There is a real problem with fake high power transistors being sold world wide.

.
Click to expand...
Yes...Turns out the output transistors 2SA1106 and 2SC2581 that I ordered were indeed chinese knockoffs.
B&D recommends 2SA1695 and 2SC4468.
 
Yep, both the Sanken 2SA1695 and 2SC4468 are good replacements for the original Sanken 2SA1106 and 2SC2581 (in most cases)...Also On-Semi NJW1302G & NJW3281G and NJW0281G & NJW0281G
 
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