Hi all,

If anyone has the schematic for a Pioneer SX-680 and could scan and email it
I would be very greatful.

The unit has no output and I'm pretty sure it's going to be the STK-0039
modules. It has some other problems. It's not recieving am/fm so there's
also some small signal stuff that's going to have to be looked at.

Kind Regards,
Jamie

Hello,

Before you condemn the STK's, take a look at the soldering of the
voltage regulator pass transistors (T0-220 packages) on the power supply
board. These commonly run hot enough to bake the connections over time
and could be your only problem. I suggest removing the old solder
(solder wick or a solder vac, which ever you prefer) and then apply a
fresh pool of solder to the connections.

Sorry, I don't have a schematic that I can scan.

Regards,
Tim Schwartz
Bristol Electronics


unix-freak wrote:

Hi all,

If anyone has the schematic for a Pioneer SX-680 and could scan and email it
I would be very greatful.

The unit has no output and I'm pretty sure it's going to be the STK-0039
modules. It has some other problems. It's not recieving am/fm so there's
also some small signal stuff that's going to have to be looked at.

Kind Regards,
Jamie

Tim Schwartz wrote in message ...
Hello,

Before you condemn the STK's, take a look at the soldering of the
voltage regulator pass transistors (T0-220 packages) on the power supply
board. These commonly run hot enough to bake the connections over time
and could be your only problem. I suggest removing the old solder
(solder wick or a solder vac, which ever you prefer) and then apply a
fresh pool of solder to the connections.

Sorry, I don't have a schematic that I can scan.

Regards,
Tim Schwartz
Bristol Electronics

Actually, power is good to the output modules - +/- 35Vdc. After
scoping things out, there is no audio inputting those modules...so I'm
guessing that it's a transistor. I know there's a few FETs in there as
well as plenty of bipolars.


unix-freak wrote:

Hi all,

If anyone has the schematic for a Pioneer SX-680 and could scan and email it
I would be very greatful.

The unit has no output and I'm pretty sure it's going to be the STK-0039
modules. It has some other problems. It's not recieving am/fm so there's
also some small signal stuff that's going to have to be looked at.

Kind Regards,
Jamie

Yeah..one of the STKs is good. Turns out that the audio muting circuit
was not getting the + voltage from the power supply. That voltage is
what allows conduction of the FET's source to drain. The audio signal
inputs the source. It was an open TO92 NPN series pass transistor.

I still have one channel that has clipping audio. It's biased wrong at
the output stage and could be the STK on that channel, but I haven't
gotten back to it.

Tim Schwartz wrote in message ...
Hello,

Before you condemn the STK's, take a look at the soldering of the
voltage regulator pass transistors (T0-220 packages) on the power supply
board. These commonly run hot enough to bake the connections over time
and could be your only problem. I suggest removing the old solder
(solder wick or a solder vac, which ever you prefer) and then apply a
fresh pool of solder to the connections.

Sorry, I don't have a schematic that I can scan.

Regards,
Tim Schwartz
Bristol Electronics


unix-freak wrote:

Hi all,

If anyone has the schematic for a Pioneer SX-680 and could scan and email it
I would be very greatful.

The unit has no output and I'm pretty sure it's going to be the STK-0039
modules. It has some other problems. It's not recieving am/fm so there's
also some small signal stuff that's going to have to be looked at.

Kind Regards,
Jamie