KLH Model 20: Only Record Player Works?

[tonythetech]

Hello all,

I am new to audiokarma and been a long time viewer! Finally made a account because I can't find anyone else that has had a similar problem to my KLH Model 20.

I need troubleshooting help with KLH model 20 that I recently picked up from a estate sale. Upon testing, nothing seems to turn on besides the record player amp. It will play records and sounds great! But the FM, aux 1 & 2 do not work at all. No hum, crackle or anything. The lights do not turn on either. I have already investigated the power switch and cleaned it with contact cleaner. I am seeing 90v ac at the switch (not sure if that is the correct voltage).

Any help would be great!

 

[larryderouin]

Welcome to AK.

IIRC (and it's been a decade since I worked on one) all of the P.S. voltages are Negative. POS is Ground....(kinda like a lot of older British cars although LUCAS didn't get their meathooks on KLH!). Check all the voltages coming off the Power Supply to the tuner sections 1st. The RF front end and IF sections are insulated from the chassis and are at -12V. So make sure your meter isn't connected to chassis. 90V on the power switch? AC? You should have wall voltage at the upstream side of the switch. If not check the voltage at the wall. UNPLUG the unit and check Ω's on each leg of the cord. Any higher than a couple of ohms and you have corrosion internally in the cord or a crappy plug. A 16ga 9 ft Extension cord from Home Depot will fill the bill. Either determine polarization, or grind down the neutral blade and go as stock.

If you get sound on PHONO, But none on AUX, or FM/FM Stereo, The amp is ok, most likely the selector switch (rotary) is junked up and inhibiting signal thru it. Get a can of DeOxit D-5. Regular contact cleaner won't clean off the environmental crap on the contacts. All you get is cleaned "DIRTY" contacts. DeOxit will soften up the crap and allow friction (rotate it back and forth about 40-50 times (gives your wrist a workout). Then test again. If you have some CRC 2-26 Electronics Lube, give the Rotary Switch a shot of that after cleaning.

Keep us advised.

 

[gadget73]

90vac from where to where exactly?

Sounds like a bum power switch to me. The record changer has it's own power switch that feeds power to the unit if I remember right. The one on the volume knob should be for the tuner and aux functions. I had a KLH 24 years ago and thats what I remember from it at least. I can't blow the schematic up enough to follow it. As a hacky test, you could jumper the two terminals on the back of the power switch together to see if it comes on. If it does you'll know what ails it.

 

[larryderouin]

Gadget. Hifiengine has good docs on the 20.

 

[tonythetech]

Update: I cleaned the switch as best as I can with deoxit and a small brush. A lot of black stuff came off but still nothing from FM Aux 1 & 2. I doubled checked that the record player still works and connected everything up. It sure does still work! So, could the power supply board and/or transformer be the problem? I went ahead and ordered new capacitors for the whole unit (Basically just took a tally and specs of each cap I could saw).

If I was to jumper the power and bypass the switch, how would I go about that?

 

[gadget73]

Looks like S1 is your power switch, by the schematic its marked "on / off (auto)". I'm guessing thats a slide switch on the front panel. I hit my daily quota so I can't look at the owner's manual to confirm.

Quick and painless check, leave it set to "auto" and just turn the record player on. Put the selector to FM and see if it works while the record player spins. That will bypass the power switch in the "on" position with the changer's internal switch. if that works you know it has to be a problem with the power switch. The neon power indicator would also be a clue about whether its getting power past the switch or not, assuming it works with the record player at least.

 

[larryderouin]

Turn on the Phono and leave it run. The phono switch is in parallel to the main power switch. Then move the selector switch to FM and or AUX1/AUX2. With the Turntable rotating you should be able to switch to FM or AUX1/AUX2 without it shutting off. If it runs, check the actual wiring to the switch, and check for Cold Solder Joints on the On/Off switch. Replace as necessary. The switch is a standard SPST slide switch. . https://www.parts-express.com/dpdt-slide-switch-1-2-lever--023-670 They are DPDT, (6 tabs) but you'll need only 2 tabs. 1 center and one end. If you want to split the load between sides(which is a bit of overkill), run a jumper between the two center tabs (Supply) and the remaining set of end tabs (output). Cut the other end tabs off. Power lead to center, and other lead to end tab. Mount.

 

[larryderouin]

Hey Gadget. You telepathic or something? It took me 45 minutes looking for SPST switches and best I could come up with was DPDT's.

 

[gadget73]

no, just taking some guesses at it. Once I saw the phono switch was just wired across the main power switch I had the thought. Some things loop through extra contacts on the selector, but this doesn't which makes life easier.

Original might be a 3 terminal switch, with one of them just used as a connection point.

 

[tonythetech]

You guys are the best! So, after jumping the "on / off (auto)" switch, everything came to life! So I start to wiggle the switch and it was causing the unit to turn on and off. So, it was a bad switch! I ordered a new one that you suggested. I guess I pulled the trigger on new caps too soon but I will still change them out since I have everything taken apart. I also did some reading I should change out the speaker filter caps too. Do you guys suggest re-doping the speakers while I am in full maintenance mode now?

 

[KentTeffeteller]

I think changing the caps on a KLH is good practice, they tended to need caps earlier than many did in that era. Excellent work on troubleshooting this, jolly good show, mate!!! Is it not satisfying, when you find out the cause of your problem, then repair it and it works correctly? It's joy!!!

 

[larryderouin]

As for the speakers maybe......maybe not. 1st see if you can feel, or hear air leakage from the surrounds when you push ever so lightly to almost full extension on the center of the woofer. If so it might be a good idea. They are acoustic suspension, and can over drive the voice coils if enough leakage occurs. On E-PREY Vintage-AR sells a kit that works very well for the KLH's. I've used it on KLh 20's, and 17's with very good results. A light coat is all that's needed. go to E-PREY and search
"ACOUSTIC RESEARCH SPEAKER CLOTH SURROUND WOOFER SEALANT KIT, ALSO KLH"

 

[tonythetech]

UPDATE! its been awhile...
I replaced all capacitors and the bad "off/auto" switch. No more hum! Cleaned up the unit and rebuilt the Garrard 3000c. Also, recapped and sealed the speakers (used a water/silicon mix, I know this might stir the pot a bit but the speakers sound amazing since I did that). Bought a bluetooth receiver for my phone for fun. The radio sounds great and is actuate. After all this, I have two small problems that I'm lost with trying to find remedy for.

1. Just out of my right speaker channel, I can faintly hear the radio coming through. I swapped speakers to see if the issue is in the amp or is the speaker line picking up the channel. The problem is within the amp. I have tried to separate the radio speaker wires and make shields. All this kinda helped, but did not remedy the issue.

2. For some reason, the record player (phono) channel does not respond to the volume knob adjustment very well. Ill have the volume all the way down to zero, yet the record player still comes through at a decent volume. This output channel is the only channel that has the issue. Radio, Aux 1&2 have full control of the volume, just not the phono. The volume does increase, just doesn't start at zero.

Any suggestions? Thanks again for all the help!