It has one dead amp channel. You guys have come through for me before--please help me get this going so I have a decent workshop stereo!

Thanks in advance...

Isn't there a schematic on the bottom cover? A frequent offender on these KLH stereos is the 1000 mfd output capacitor. At least, from memory, I think that is the cap value.

Yeah, the schematic's glued to the inside bottom cover.
But for replacing the output coupling cap it's easy to trace down without one.

No schematic for me, says the Schematic Nazi. The inside board is pristine--no dried glue, etc. I guess the record changer comes out first in order to get at the rest of the stuff?

It reminds me of a Philco Seventeener with the guts wrapped around the CRT.

Thanks for the tip on the output caps--they were 1000 mfd but replacement did not help. I'm lousy working on solid state stuff; suggestions are welcome.

On the Twenty-Four, the first thing you should always to is treat the switches and controls with a good-quality contact "cleaner". As my repair shop, we use Caig DeoxIT D5.

I'm not at the shop yet, but as I recall the output transistors are transformer driven. In other words, the driver transformer has two secondaries wound out of phase so that the amplifier operates push-pull. I have identified a few failures of the class-A driver transistor in the primary of this driver transformer.

Also, the interconnects between the boards are done using pins. Although the heads of the pins are soldered to the boards, the tails are crimped onto the wires, and over the years the crimps can oxidize, leading to loss of signal. When this is the problem, the symptom is usually intermittent.

The preamp section (with the volume and tone controls) is located on a separate board. Check the electrolytic caps on this board. Over the years, a few of them have turned up open.

* * * * *

Also -- and unrelated to your complaint -- check the large electrolytics on the power-supply pcb. These have a long history of opening up.

* * * * *

As for the Garrard . . . the dominant failure modes on these are that the grease gets extremely gummy, the idler wheel gets hard, and the motor dies. In the last several years, we've encountered about half a dozen Garrard motors from this era that were bad. The common precursor is that the motor was allowed to run in a sticky condition, and so the coils got extremely hot. After a standard clean-and-lube, the motor will often display an intermittent symptom of runs slow and has poor torque. "Ringing" the coils won't turn up a bad coil; neither will ohming them out. Our guess is that the stator coils are mounted around the core using plastic frames. Perhaps these frames deform with the heat, so that the coupling of coils-to-cores is compromised. In any case, watch out!

Best,

Fred
Owner
Classic Audio Repair

Thanks, Fred--controls and switches were already cleaned with Deoxit. I suppose it wouldn't hurt to recrimp all those pin/tail connections. I'm pretty sure I have both channels out of the preamp board, but it's hard for me to follow the channels thru the cables from board to board.

When I first opened the KLH up, I noticed that one of those push-on connectors was off--but sitting in mid-air about 1/8 inch from a pin. So that's where I replaced it. Today when tightening all those connectors, I saw a second pin, not used, maybe 1/2 inch from the original one. Looking at the wire mess, it appeared the original detached wire might be an output from the preamp board. So I turned the thing on and touched the blank pin with a screwdriver and got a roar from the "bad" channel. Moving the originally detached wire to the correct pin solved the problem.

Thanks to all that replied.

Great! Glad to hear it...

My unit, this model, has a schematic somewhat obscured by mold, if you would still like it I will try to get around to photographing it. Please tell me, I will check back for that.

PM sent to Plutopete.

Thanks!