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Pioneer PL-A45D - Sourcing Microswitch(es)

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dehost00

New Member
Good morning all,

I've had a Pioneer PL-A45D for a while now and it's in *mostly* good shape. Could use some lubing up and all, but the auto return works and the sound is good. Nice!

Problem is, it suffers from that intermittent buzzing issue that many of these units exhibit. This has been documented in other forum posts, and rarely occurs during actual music playback. It's quite jarring and I'd like to fix it. I forgot just how I came to this conclusion, but I recall narrowing the source down to a microswitch (or stacked pair of microswitches); these are shown as part #22 on page 11 of the manual. Part #KSF-009-0.

A few years ago I was able to find an exact replacement for this part, although it seems it's no longer sold and the only replacements are donor parts on Ebay. Does anyone have a source for these they could share?

A little more background: I have had this turntable for several years and it's always been kind of a black sheep/problem child. I've held on to it because I really like the aesthetics of it and I'm also hopeful that I can improve its function little by little until it's basically good-as-new. If anyone knows anything about these decks and the problem I've described, please do share. I believe the microswitches I mentioned control the auto-return mechanism, timing, etc. so I'm not sure how they could possibly interfere with the audio, but I've ruled out the signal shorting switch and other than that there isn't much to investigate.

Cheers
 
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I don't know what kind of buzz you have, but wouldn't consider some sort of interference into the signal inconceivable - from the switches or the extra motor(s?). Have you tried flushing them with a contact spray? Can you cause the buzz by manipulating the switches? Does it occur consistently at specific steps in the auto cycle?

Do all motors have separate capacitors? Those should be replaced anyhow on a deck this old. But the noise due to bad caps shouldn't be a buzz, but more of a loud "pop".

I haven't been inside a PL-45 for a long time, and luckily didn't have to go too deep into the auto mechanism of it that time.
 
Here's a link to a video that describes the noise:

https://www.reddit.com/r/turntables/comments/t0p95p

Here is a pair of links to some forum posts where folks have tried to solve this in the past:

Buzzing Pioneer

I have a Pioneer pla45d, an early 70's full auto table. It has this strange problem I cant figure out. After it drops the needle, it buzzes very loudly a few times. It will usually then play the whole record cleanly with maybe an occasional buzz. It is not the cartridge or stylus. It does the...
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The OP in that AK link seems to have solved it by removing the headshell gasket - I have yet to try that, I'll give it a go tonight. I've tried dousing the microswitches with contact cleaner and I have also cleaned the signal shorting switch a few times. I have not messed with any of the caps on the circuit board - here's a screenshot of the circuit diagram:

1737390627907.png

I'm afraid I can't recall if manipulating the micro switches affected the noise, I'll have to open it up and give it some thorough testing again. The noise starts immediately after hitting "Start/Cut" in both manual and automatic modes. It's almost like the deck is grumpy that it has woken up (lol) - it spits noise at me intermittently until a maximum of ~30 seconds after the needle hits the groove, and then it's dead quiet the entire time the record is playing. Seems to be silent most of the time during the stop/auto-return sequence as well.

FWIW, I just changed the cartridge a week ago and replaced the headshell leads. This seems to have had no effect at all.

This whole thing is quite strange!
 
At least it is interesting! Looked through some of the links and then some. Somebody suggested it sounds like arching in connection to the Warren motor, which was just about my first thought. Although that removed headshell gasket would point to a grounding issue with the tonearm. Provided everybody is discussing the same problem.

If your buzz is as in the video, a bit after the needle drop, I would still suspect the vicinity of the Warren motor, which I suppose is done with its job about by that time. Does it also happen by the arm return?

There really aren't that many sources for a noise like that: the micro switch, the cap, and the motor would be the prime suspects. The caps should always be replaced by x-class parts with the same values on every deck this old, why I would start there. Next would be replacing the Warren motor switch (if it has an arch for that long time it is long past anything a spray could fix).

This could be a combination of the motor turning off, causing its current surge from the coils. The function of the cap is to neuter that post-power-off current surge, both to avoid a loud "pop" through the speakers, and to protect the surfaces in the switch from a too high current rush. So, a bad cap could have burned out the switch. If so, both must be replaced.

The caps weren't mentioned that much in the treads I browsed through.

Just a hunch.
 
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