Chirping noise from cassette deck in Panasonic RA-6500

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ChopperCharles

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So I've just repaired the amplifier part of this RA-6500 integrated amp, and now I'm moving on to the tape deck. The transport is fine, but I've got something electrical amiss. I get a loud chirping from both channels -- although sometimes the right channel seems like an echo of the left channel - it's a lower volume and feels like a bleed over from the left channel. But sometimes it's full volume too. This happens when pressing play without a tape loaded in the mechanism. When a tape is loaded I can hear music but the chirping is still there and much louder. If I press stop, I can still faintly hear the chirping.

Unplugging the heads from the main board stops the chirping cold. Does this mean my heads are bad? Or could I have some other issue at hand here? I'd think if it was downstream of the heads the problem would persist without the heads attached. Thoughts?

Here's a video of the problem: https://www.youtube.com/watch?v=7Ltn0meAWhU

Here's the service manual:
View attachment panasonic_ra-6500.pdf

The deck records fine, but playback does this every time. I suppose it could be the playback preamp transistors gone bad, but it seems unlikely it would do this with both channels and it would seem to me that it should chirp when the heads are unplugged if it was those transistors. Thoughts?

Charles.
 
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ChopperCharles

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There is some wear to it, there's a visible ledge where the tape has worn a path, big enough to catch a fingernail on, but it doesn't look worn out to me.

Charles.
 
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ChopperCharles

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I'm wondering if I can just replace the tape head. For the inexpensive two-head decks, is there a universal replacement head I can use? Or must I match it exactly? This head is 11mm (1.1cm) wide, has the mount on the right and the adjuster on the left. It has the following markings:

43?AS
7H26N

The third character has only the bottom visible, the top is missing because there's an indention in the head. It could be a 0, a 6, or an 8.

Can I just swap any old head into this, so long as the dimensions match? Or should it match electrically?

Charles.
 
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Can you get a good picture of the head assembly, with indirect lighting and flash off?

In other words, like a small light not aimed at the head to diminish reflections. can you crossreference the part no in the manual or on the head with a search engine or parts website?

PS if you have the noise in your audio without a moving tape, you probably need to look elsewhere...how often does it chirp, more or less than 1 per second? Is a motor running when the deck is stopped? Do you have other devices such as test equipment, DVD players or other such things nearby that can be shut off to check for inducted noise/EMI?

Do you have a servo in the all in one and can you isolate the circuits more specifically?

Have you cleaned the record/play switch?
 
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orange

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One last idea.

It the tuner bleeding though? Switch to Phono with nothing plugged in...

record nothing. See if you record the noise. I haven't looked past the cover yet but does this set have a grounding terminal?

Is that is a PLL tuning circuit?

Did you blow it out good? Our motto here is a good blow never hurts.
 
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ChopperCharles

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Recordings come out perfectly, without the chirping noise. Recording nothing or recording music, recordings sound just fine. I've recorded from aux input and from the radio and had no issues. Even the Dolby seems to work fine.

Haven't cleaned that switch. I suppose I can try that next.

The part numbers yield no search results, so I can't cross-reference it.

Please watch the video, it shows what's happening.

Chirping is still heard (albeit quietly) when the tape is not playing, and the motor for the cassette deck is not turning.

Charles.
 
orange

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That is feedback oscillation, just from looking at the meters. It's in the left channel alright.

Clean the R/P switch, blow it out and work it before spraying it, work it again and blow it and work it again. It sounds to me like it's partially on.
 
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Hmm. Okay. What exactly is feedback oscillation? I did a quick google search and didn't come up with anything -- anything related to cassette decks at least. I'm out of deoxit so I'll have to wait to fix this until Amazon can deliver to my door :)

Charles
 
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Found an almost-empty can of deoxit, and low and behold I fixed it! There was so much goop in there the switch couldn't return fully to resting (playback) position. Deoxit and about 60 actuations and it works now! No more chirping! I think it needs a little more to be perfect, the recordings drop out here and there ever so slightly, especially if I wiggle stuff. But playback is now rock solid. I won't be using this deck for recording at all, but I still want it to be right. Now the only thing I'm needing is a new stereo indicator lamp!

Charles.
 
orange

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EXCELLENT! I thought so!

I hope you'll really enjoy your Panasonic, they were very nice and well built and with Dolby B, no joke to any audiophile...a nice set!

PS I will finish our trade on Monday.
 
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By the way, is the indicator actually out or is it not going into FM stereo? Give a careful listen.
 
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Well, the bulb is definitely black looking and I think I can see the filament is broken. I can definitely hear a difference between the FM mono and FM stereo modes too. Ugh, the cassette deck runs fast... and requires some significant disassembly to get clearance to get the screwdriver in the back of the motor. Heh, it's pretty close now though, so I'm happy!

Charles.
 
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orange

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I'm not a wild haired genius but after 35 years fussing with them beasties I'm lucky I still have hair, and the original color.
 
orange

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And Charles, make sure there isn't a control board that regulates the speed and/or blank search before you go in to poke in the motor, there might be components out of spec.

I have the manual downloaded but I haven't looked at it much, I'm working on my experiences. I had an MCS cassette deck that had and IC or two that were NLA.
 
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There are no electronics to control the speed. The manual says to adjust the screw in the back of the motor with a plastic screwdriver. I didn't have a plastic one so I adjusted it with a metal one with the power turned off. That worked fine. Got a recorded tape to sound close to CD, and that was good enough for me. One day I'll get an actual test tape and equipment to adjust the speed on the cheaper decks.

Charles.
 
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