Discussion in 'Pioneer Audio' started by Motnick, Oct 22, 2018.
pull q36 and see if relay clicks .or might be easier to lift one end of R419 8.2K .
am wondering if pa3004 was damaged when q36 shorted
Relay does not engage with Q36 removed.
I was also wondering something along these lines, but I wasn’t sure if I had done an adequate enough job of ruling everything else out.
Does PA3004 have a substitute? Do I need to look for a good used one?
all i can suggest is try changing c418 c419 and checking resistor values
I replaced C418 and C419, but it didn’t help. The same voltages remain at PA3004.
seem to remember you changed c417 and verified its polarity .
i would check the soldering then if still no use try a new pa3004 .
You could just lift C417 and see if the voltage at PA3004 Pin 8 comes up at all.
Also, that seems to be a LOT of AC on Pin 7. Are the two resistors in the divider (R403/404) intact?
R403 and R404 both measure .5M ohm in circuit. 1M ohm - Brown, Black, Green, Gold.
Maybe I need to lift one leg to get a proper reading?
yep lift a leg to be sure
I went ahead and lifted a leg on both resistors. They both measure 1M ohm.
And did you pull C417? That will, of course, eliminate any timing delay of the protection circuit, so be sure the volume is at minimum and/or there is no signal present - Or disconnect the speakers.
I pulled C417 completely out from the board. PA3004 voltages are the same.
there is a recent thread about the pa3004 . not the same issue though .. i see yours is appearing to be barely turning the relay driver transistor on .
you may have read this already . http://audiokarma.org/forums/index.php?threads/pioneer-pa3004-ic-required.760886/
only thing i can suggest right now is removing the base connection for the relay drive transistor and measuring voltages again at pa3004 .. i expect them to be the same though .
Finally getting back around to this project. I’ve been looking for a PA3004 replacement, but so far no luck.
I went ahead and pulled Q35: PA3004 today and found this installed. Is this part equivalent to PA3004? I was expecting it to say PA3004 not HA1457. I think HA1457 is an opamp, isn’t it?
Different animal, in the same skin.
HA1457 is a high voltage low noise pre-amp.
I bought a few PA3004 on ebay to try out, I will let you know if that source is legit or not when they arrive.
Make reference to where that HA1457 part is used, assembly #,reference designator, you might have pulled the wrong part.
I have used the Hitachi HA12002, it is Hitachi's version of a speaker protector IC
HA1457 is phono amp ic .. should be 2 in there q1 q2
Yes I did find the other two that are supposed to be in the unit, but why is HA1457 also installed at Q35? Someone must have installed this by mistake during an earlier repair attempt? Am I correct in thinking that HA1457 is not going to work at Q35, and that this is what’s causing my protection issues?
yes looks like you found the issue ..i wonder how it managed to work at all .
It never did for me. I can only assume it was a failed repair attempt by someone before me.
Geez, first wrong sized emitter resistors in one of the power amp boards of my SX-980, and now this! I guess I should have verified what was installed at Q35 as a first step.
Should I try one of the eBay PA3004 ICs?
Separate names with a comma.