TRK-8600E cassette deck repair - lost cause?

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Touchstone64

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Sep 12, 2021
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Hi folks, thanks to the excellent advice in the forums I'm starting a repair of a TRK-8600E cassette deck, but having removed what was left of the belts and looking closely at the motor spindle (which has a partly broken band stopper) I'm wondering if it's a non-starter. I've also noticed what looks like a lot of manual soldering on the bottom PCB, perhaps it's been repaired in a previous life?

I'm attaching some pics, if you have the time to take a look and comment it would really help me determine whether to start buying replacement bands etc. Thank you!
 

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Radio raheem

Radio raheem

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a simple way to test the motor, connect a 9v battery to it if it works it's probably a fusible resistor that has blown
 
Bloodhound

Bloodhound

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Id find a donor motor with a plastic or brass spindle/pulley of similar size and replace it. You should be able to cut that broken spindle off using a dremel or by heating it up with a heat gun.
 
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Touchstone64

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So ... belts replaced and contacts cleaned, the deck is turning but no clean sound as yet. It sounds like a grounding issue to me, sound from the FM tuner is clean so the amp circuits and mains supply appear OK. Also, if I touch any earthed surface while a tape is 'playing' you can hear a hum drop in volume.

For now I have two main worries, the pinch roller is in the way of the cassette when I try to insert a new tape, and the spring doesn't look like it's in the 'right place'. Also the transport microswitch looks a bit worn.

Does anyone have a clear picture of how the pinch roller spring should look? For those with this unit, does anything look obviously wrong in these pics?

Thanks again for your time folks, you've been a great help :bow:

IMG_9306.JPGIMG_9307.JPGIMG_9308.JPGIMG_9310.JPGIMG_9311.JPG
 
hopey

hopey

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Dec 28, 2014
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You may have a ground loop on the audio cable from the tape head to the PCB. Try separating the cores at the termination to reduce the hum.
 
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Touchstone64

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Sep 12, 2021
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hopey said:
You may have a ground loop on the audio cable from the tape head to the PCB. Try separating the cores at the termination to reduce the hum.
Click to expand...
Hi @hopey, thanks for that :) I’d actually read your post and disconnected that cable from the PCB, the noise was still there :( But I think you’re right about the ground loop, I just don’t know where yet.

The only time it happens is when the transport is powered up. If the deck is paused or not running, there’s no hum. If it’s playing, fast-forwarding or rewinding, there’s hum. That should help me narrow down the cause, but inspiration hasn’t struck yet…
 
Wes125

Wes125

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it amazes me how these things get broken. ive got loads of motor pullies and motors..i wont sell the motors. ive collected those over many years..il have a look in me spares box
 
Wes125

Wes125

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i thought i had one. got a nip out of the small belt drive sideDSCF9579.JPG but that wont effect it
 
Bloodhound

Bloodhound

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If the pinch roller is in the way of inserting a cassette then I would think the transport isn't lowering all the way. Could be dried up grease, a lax spring etc. Try pushing the transport and working it up and down by hand a few times. Be careful not to force it. I've had dried up grease/lubricant cause the transport to hang up a few times.

As for the hum have you cleaned all the pots and switches? I've been able to resolve a lot of sound and feedback issues by spraying and working the switches about 100 times each.
 
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Touchstone64

Member (SA)
Sep 12, 2021
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Thanks @Bloodhound ! That's an excellent collection @Wes125; pro or hobbyist repair by the way?

The pulley seems to be holding up well, even with that big chunk out of the large belt side. I could manage with just Bluetooth/AirPlay on this unit but I'm a bugger for leaving something broken when I think I might be able to repair it :-D

I've cleaned all the pots and switches I could find, which is what resurrected the unit's sound. Tuner and Line In/Phono are working fine now, it's just the tape deck that's left. I need to have a closer look at the mechanics of the transport and see what else I can clean/lubricate. To be honest it *looks* like the transport is reaching the lower limit of its movement but I could be wrong.

The spring pushing the pinch roller up appears to be at its maximum travel so that even lowering the mechanism wouldn't affect its position, but I should get a chance to look closer this weekend. I also want to remove the big electrolytic cap from the deck PCB so I can test it with a multimeter :hmmm:
 
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hopey

hopey

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Dec 28, 2014
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Some of these old motors have a capacitor inside;

boomboxery.com

How to service small DC Motors (running slow)

The motor on your tape drive can develop internal friction on the brass bushing. This can be observed by the tape transport speed sounding slow. While these motors are small they are very reliable and can be serviced. The object of the task is to ensure the shaft rotates with minimum friction...
boomboxery.com boomboxery.com
 
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Touchstone64

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Sep 12, 2021
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Oh well, so much for that project. I powered the unit up, a little smoke started coming from the case and there was a distinctly electrical burning smell. I disconnected the mains, left it for a while then tried again.

Now there's no more smoke or burning smell but now the audio from all sources is somehow 'limited' - when the volume of the audio increases sharply the sound kind of cuts out. Also, if I turn on 'Dolby NR' when using either the TUNER or PHONO sources (so it shouldn't have any effect), the sound cuts out altogether. I think something's fried on the DOLBY NR/PHONO/AMP circuit board.

Might be time for a post-mortem.
 
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