Kyocera rcvr VCC high?

[Michael]

I have a Kyocera R451 rcvr I'm looking at and the VCC on all the chips (not
the power amp but all the "low level stuff")....seems awfully high.

Like 17 volts (?!)

This is an early 80's rcvr...hard to find any data but I did see one of the
chips datasheet (LA1245) that shows an absolute maximum of 17 with a typical
VCC of 12v.

How many times have you repair guys seen chips sitting at
higher voltages like this?

The things working alright but it has some "issues".

 

[Mark D. Zacharias]

I have a Kyocera R451 rcvr I'm looking at and the VCC on all the chips (not
the power amp but all the "low level stuff")....seems awfully high.

Like 17 volts (?!)

This is an early 80's rcvr...hard to find any data but I did see one of
the chips datasheet (LA1245) that shows an absolute maximum of 17 with a
typical VCC of 12v.

How many times have you repair guys seen chips sitting at
higher voltages like this?

The things working alright but it has some "issues".

It's possible that a regulator transistor or fixed voltage regulator has
"shorted through". Not really a common failure - but it does happen. A
service manual would be most helpful here.

Mark Z.

 

[Michael]

Yeah, I see about 27 volts on the input at the regulator...same as the raw
dc output from the supply.

So, the regulator seems ok as it shows 17 on the output.

I just can't believe they would operate these chips so high.

Every chip has a VCC of 17.

I may just replace the regulator and the resistor on it and
see what happens.

 

[Mark D. Zacharias]

Yeah, I see about 27 volts on the input at the regulator...same as the raw
dc output from the supply.

So, the regulator seems ok as it shows 17 on the output.

I just can't believe they would operate these chips so high.

Every chip has a VCC of 17.

I may just replace the regulator and the resistor on it and
see what happens.

Yeah - 14 to 15 volts would be more normal, I would think, although I did
have a Tandberg tape deck which used a single-ended 17 or so volt rail for
the logic IC's. Never did find out which family those weird chips fell in
to.


Mark Z.