Another SA-9500 Protection Issue

basil13

basil13

Active Member
I have an amp that has me scratching my head and could use some more eyes or thoughts. I will spare the long story for now. As it sits the amp won't come out of protection, there is very little dc offset (15mV) and I have checked all voltages on the power amp board and nothing stands out. I have replaced the 726 transistors.

I see that Q5 on the protection board is on (0.6V between the base and emitter). Looking at the schematic, it appears it should normally be off (20.4V on the base, 17.9V on the emitter). The thing is I have the amp apart and the outputs are removed so it can't be in overcurrent???. I have disconnected outputs in other amps in the past and never had it cause relay issues.

Does the 9500 need the outputs installed for the protection circuit to work properly or do I have something else going on?

Thanks
 
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what are the dc voltages protect board 10 and 12 ? and pin 9 ac voltage ?
also q7 base emitter and collector voltages ?
 
Looks like I received some bad parts and/or info on replacements. For Q5--2SA733. I was told that I could use a KSA733. Either I had a bad one or it don't substitute. Replaced with a KSA992 and that brought the voltages in line with the schematic. Also, either I got a bad relay or the MY4-02-24V is not a good "recommended" replacement. Swapped the old one back and I am back in business with a relay CLICK!!!!!!

Regards
 
I don't recommend ksa733's because with a one letter difference they can have an ecb or EBC lead layout, and too darn many of them were going in wrong.

The datasheet does document it, but not many people read them carefully enough.
ksa733 is ebc
ksa733c ie ecb.
 
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