Otari MTR-12 channel not arming
« on: July 31, 2019, 08:23:53 PM »
Hi folks!

I'm having a problem with my Otari. The record arm switch on channel 3 does not activate the ch3 "armed" LED or the "record ready" light on the transport. I checked the switch and it looks to be okay. Does anyone have any familiarity with these units? I fear the problem might be in the control logic, which I feel unprepared to fix! I have the full schematics for reference. Thanks all.


radardoug

Re: Otari MTR-12 channel not arming
« Reply #1 on: August 01, 2019, 04:49:59 AM »
Count the number of parts in the logic circuit. Any one of them could be faulty. To find the fault you have to diagnose it by measurement. None of us here are capable of remotely diagnosing your device. We are not psychic.

gyraf

Re: Otari MTR-12 channel not arming
« Reply #2 on: August 01, 2019, 06:48:58 AM »
I'm psychic, and still I can't... 

Isn't MTR12 supposed to be a stereo (two channel) unit? Mine was..

Make sure that it's not simply the LED not working.

Jakob E.
..note to self: don't let Harman run your company..

Re: Otari MTR-12 channel not arming
« Reply #3 on: August 01, 2019, 07:29:49 AM »
Count the number of parts in the logic circuit. Any one of them could be faulty. To find the fault you have to diagnose it by measurement. None of us here are capable of remotely diagnosing your device. We are not psychic.

Yes, that's what I'm afraid of. I know I'll have to dig in there to figure it out, just wondered if anyone had a deep knowledge of these machines that would have familiarity with what might've caused this failure. I'll report back after some probing.


I'm psychic, and still I can't... 

Isn't MTR12 supposed to be a stereo (two channel) unit? Mine was..

Make sure that it's not simply the LED not working.

Jakob E.

It's a 4-track 1/2" machine, I love it!
I'll check the LED, but based on the circuit the "record ready" light should be flashing even if that LED failed. But I will investigate, I'd be thrilled if that was the only problem! Thank you all.

squarewave

Re: Otari MTR-12 channel not arming
« Reply #4 on: August 01, 2019, 09:51:32 AM »
Find the spot in the schem that matches those switches / leds and post a graphic with references noting any differences between your specific unit and the schem. If you get that far, people can comment a lot better. It might look like a morass but it's quite possible to trace with a meter and some patience.

Just be careful about poking around logic ICs. They are sensitive to static electricity.

Re: Otari MTR-12 channel not arming
« Reply #5 on: August 02, 2019, 07:43:14 AM »
I did some poking around last night and think I've narrowed down the connection between the switch and the logic board to be the problem. I jumpered the channel 3 switch input on the logic board to another good switch's input, and successfully controlled both channels with the "good" channel switch.

I then jumpered the "bad" switch to activate the channel, and that had no effect. So I think it must be the ribbon that connects the meter bridge to the logic board, or a solder connection on either side.


 

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