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Pioneer VSX-D710 amplifier repair

A

Anatoly

Jan 1, 1970
0
Hi,



I am trying to fix RCA STAV 4090 amplifier that is a clone of Pioneer
VSX-D710. It is 5 channels unit that is using Pioneer's PAC011A and PAC010A
integrated amplifiers.



When I got it, it had a blown fuse in the ground rail of power supply chain
and filter capacitors in +VL and +VH rails were fried and leaked. After
replacing capacitors and fuse, amplifier has +12 V offset on the power
supply ground, amplifiers output is 0V.



When I am connecting speakers it works, but starts to overheat -- DC current
protection seems to be blown. Also there is a strong 60-120Hz noise in all
of the channels.



The question is: how split rail supply ground is controlled? It is not
connected with the signal ground as in other schemas that I saw.



There is a part of the scheme that controls some "NECK" voltage that goes to
integrated amplifiers. It was contaminated with the acid from leaky
capacitor. Does it have anything to do with that? What this "NECK" stands
for?



Thanks,

Anatoly
 
M

Mark D. Zacharias

Jan 1, 1970
0
Anatoly said:
Hi,



I am trying to fix RCA STAV 4090 amplifier that is a clone of Pioneer
VSX-D710. It is 5 channels unit that is using Pioneer's PAC011A and
PAC010A integrated amplifiers.



When I got it, it had a blown fuse in the ground rail of power supply
chain and filter capacitors in +VL and +VH rails were fried and leaked.
After replacing capacitors and fuse, amplifier has +12 V offset on the
power supply ground, amplifiers output is 0V.



When I am connecting speakers it works, but starts to overheat -- DC
current protection seems to be blown. Also there is a strong 60-120Hz
noise in all of the channels.



The question is: how split rail supply ground is controlled? It is not
connected with the signal ground as in other schemas that I saw.



There is a part of the scheme that controls some "NECK" voltage that goes
to integrated amplifiers. It was contaminated with the acid from leaky
capacitor. Does it have anything to do with that? What this "NECK" stands
for?



Thanks,

Anatoly

I'll look over the schem when I get a chance - but I have seen bad eyelets
at the power transformer boards on Pioneers, a bad eyelet at the center tap
would let the ground "float" and could cause your problem.

Mark Z.
 
A

Anatoly

Jan 1, 1970
0
I'll look over the schem when I get a chance - but I have seen bad eyelets
at the power transformer boards on Pioneers, a bad eyelet at the center
tap would let the ground "float" and could cause your problem.

Mark Z.

Mark,

Thanks for the reply. I did check the center tap wiring it is OK. The ground
is not floating relative to power supply rails -- both high and low voltage
rails stable and correct. The power stage ground is offset relative to the
amplifier signal ground. It is a kind of weird "floating" ground power stage
power supply scheme.

If you have scheme in electronic form, could you please send it to
ab_pub@[email protected] (remove at@ and dot.)?

Thanks,
Anatoly
 
M

Mark D. Zacharias

Jan 1, 1970
0
Anatoly said:
Mark,

Thanks for the reply. I did check the center tap wiring it is OK. The
ground is not floating relative to power supply rails -- both high and low
voltage rails stable and correct. The power stage ground is offset
relative to the amplifier signal ground. It is a kind of weird "floating"
ground power stage power supply scheme.

If you have scheme in electronic form, could you please send it to
ab_pub@[email protected] (remove at@ and dot.)?

Thanks,
Anatoly

The grounds dhould be the same - look closer at the eyelet of the little PC
board where it connects to the center tap pin of the power transformer. Try
resoldering the eyelets. One might curl up as soon as you heat it up and
apply solder.

Seen it more than once on Pioneers.

I'll send that PDF.

Mark Z.
 
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