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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 27th Sep 2020, 6:54 pm   #1
Ted Kendall
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Default Tascam 122 Mk3 - HG 302

I'm grappling with one of these at the moment - the direct drive motor is playing up, and the routine replacement of the surface-mount electrolytics didn't fix it. When it runs, it's fine, but one time in ten or thereabouts it refuses to start unless the flywheel is poked with a stick. This doesn't seem to be a dead spot as such, as it happens in several positions of the flywheel. The cassette compartment switch is OK and has been cleaned. Next suspect is the Hall effect sensors, yclept HG 302. The only data sheet I can find for it gives little information save to state that the output is between 50 and 75 mV, which is tiny compared to other sensors, and I can find neither suppliers nor equivalents. Anybody here have either, or more information?
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Old 27th Sep 2020, 10:28 pm   #2
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Default Re: Tascam 122 Mk3 - HG 302

If all caps were replaced for the capstan motor, did you check the pitch control switch, wiring, and also the variable + - adjuster pot?

Sometimes a bad selector switch and/or speed control can cause the drive system to behave very oddly, or not function properly.

I had one of these in ages ago and obtained the circuit diagram (so I'll see if I can find it for you) but I have to say many people retrograde back to the MkII (with a simple belt drive!) as the MkIII can be such a pain when it goes wrong!

(Thankfully) I never had to get into the awful 'Hysteresis Tension Servo Control System' on these.

Ah, the possible nightmares of modern tech......
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Old 27th Sep 2020, 10:58 pm   #3
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Default Re: Tascam 122 Mk3 - HG 302

I donít play much with cassette decks, but I noticed there was a PCB inside the motor itself, on the JVC's and others I worked on, a non-electrolytic cap inside the motor was the issue, may be the same on the 122, I have 4-5 of these sitting in my loft, havenít tried to repair them yet but giving experience on others, may be an idea to pop the cover off the motor itself.

the 122 machines I have seen have motor issues, and you may have noticed, TASCAM do not list any details in the motor board, if you replaced all caps on the PCB, start by popping the cover off the motor itself and checking inside it.
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Old 27th Sep 2020, 11:07 pm   #4
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Default Re: Tascam 122 Mk3 - HG 302

I have the diagram, and the motor is a direct-drive component with the rotor and flywheel in a unit. I've seen a YouTuber butcher the thing to use a conventional motor and a belt...it deserves better.
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Old 28th Sep 2020, 1:35 pm   #5
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Default Re: Tascam 122 Mk3 - HG 302

Quote:
Originally Posted by Ewasterecycling View Post
...

I had one of these in ages ago and obtained the circuit diagram (so I'll see if I can find it for you) but I have to say many people retrograde back to the MkII (with a simple belt drive!) as the MkIII can be such a pain when it goes wrong.
. Actually the MkII has the same DD motor. You might be thinking of 112 models which were belt drive capstan.
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Old 28th Sep 2020, 1:40 pm   #6
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Default Re: Tascam 122 Mk3 - HG 302

Ted I've recapped a number over the years but not had that fault. Maybe a dry joint or hairline crack on the PCB tracks. I had one with an OC motor winding due to corrosion.
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Old 28th Sep 2020, 1:42 pm   #7
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Default Re: Tascam 122 Mk3 - HG 302

Quote:
Originally Posted by TIMTAPE View Post
Actually the MkII has the same DD motor. You might be thinking of 112 models which were belt drive capstan.
Yes absolutely, should have been the 112

....I often get confused with model numbers and Mk versions!
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Old 28th Sep 2020, 1:58 pm   #8
Ted Kendall
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Default Re: Tascam 122 Mk3 - HG 302

Quote:
Originally Posted by TIMTAPE View Post
Ted I've recapped a number over the years but not had that fault. Maybe a dry joint or hairline crack on the PCB tracks. I had one with an OC motor winding due to corrosion.
Winding continuity and the interesting corrosion on the Hall element leadouts are next...
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Old 28th Sep 2020, 4:44 pm   #9
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Default Re: Tascam 122 Mk3 - HG 302

Bang on the money, Tim! One of the coils has a break in the termination tail, which looks as if somebody has soldered it before. There is a tiny stub I might be able to use - I am loth to try unwinding a turn, as the coil seems pretty well potted and the wire is thin...

Last edited by Ted Kendall; 28th Sep 2020 at 4:51 pm.
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Old 29th Sep 2020, 10:13 am   #10
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Default Re: Tascam 122 Mk3 - HG 302

Mine was the same with very little wire left to solder to. I managed a repair but only just.
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Old 29th Sep 2020, 12:24 pm   #11
Ted Kendall
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Default Re: Tascam 122 Mk3 - HG 302

OK - the inevitable happened and the stub fell off. Close inspection of the other coils suggests that the wire end comes from the lower outer edge of the coil. If I can get to see the thing I may be able to tease it out...
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Old 30th Sep 2020, 10:58 am   #12
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Default Re: Tascam 122 Mk3 - HG 302

Quote:
Originally Posted by Ewasterecycling View Post
I had one of these in ages ago and obtained the circuit diagram (so I'll see if I can find it for you)...
The Tascam Service manual is pretty good but gives no schematic for the DD motor. If you can find the circuit that would be great, thanks.

This model is used a lot in archives for cassette transfer.

Tim.
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Old 30th Sep 2020, 11:17 am   #13
Ted Kendall
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Default Re: Tascam 122 Mk3 - HG 302

Tim, if you Google "Tascam 238 capstan motor", you will find an informative page on these little...beauties.
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Old 30th Sep 2020, 11:46 am   #14
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Default Re: Tascam 122 Mk3 - HG 302

Thanks Ted, I've been looking (obviously under the wrong name) for that schematic for many years.

Interesting he makes no mention in his repairs of corroded coil wires although he does mention PCB track corrosion possibly due to flux not properly removed in manufacture.

Apart from the normal SMD electro replacements I concur with him about the need to also replace C2.
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