Distorted/humming phono channel on vintage Kenwood amp?

[GTO69RA4]

I recently picked up a vintage Kenwood KA-5002 integrated amp. It's from about
1970, all transistor but built like a tube set (open metal chassis, few PCBs,
lots of wiring and bare parts), lots of unusual settings and inputs/outputs,
very high quality and sounds great, but...

The right channel of both phono inputs (it has two) has a strange distortion.
High frequencies sound thin and warbly. Any loud bass notes trigger what I can
only describe as a cross bewteen a less-than-60cps-hum and "farty" distortion.
It's not pure distortion like you get with something being overdriven--there's
a hum component.

It's open and easy to work so I can fix whatever the problem is, but my
knowlege of preamp theory is lacking.

Thanks

GTO(John)

 

[Jerry G.]

Take it to a service centre that can troubleshoot it for you. These take a
considerable amount of experience and knowledge to properly repair. The tech
may have to go through it with a scope and audio generator in order to find
where the exact fault is. Doing an ESR test on all the capacitors, will
allow you to find the defective ones to start with.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
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I recently picked up a vintage Kenwood KA-5002 integrated amp. It's from
about
1970, all transistor but built like a tube set (open metal chassis, few
PCBs,
lots of wiring and bare parts), lots of unusual settings and inputs/outputs,
very high quality and sounds great, but...

The right channel of both phono inputs (it has two) has a strange
distortion.
High frequencies sound thin and warbly. Any loud bass notes trigger what I
can
only describe as a cross bewteen a less-than-60cps-hum and "farty"
distortion.
It's not pure distortion like you get with something being
overdriven--there's
a hum component.

It's open and easy to work so I can fix whatever the problem is, but my
knowlege of preamp theory is lacking.

Thanks

GTO(John)