Tascam 58-OB - advice on replacement power mute reed relays

Discussion in 'TASCAM DIY Repairs and Mods' started by Mega-Ohm, Jun 26, 2022.

  1. Mega-Ohm

    Mega-Ohm New Member

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    Gear:
    M-600, 58-OB, 52-B.
    Hi all,

    After a number of years of reading this forum without needing to post anything, I finally have the need to ask a question. Hopefully someone out there can help me.

    I bought a TASCAM 58-OB over a decade ago for a very cheap price, even though I knew wasn't fully working. The majority of the functions actually work fine, and the heads seem good. The main problem is intermittent audio in and out, which I traced to major problems with the motherboard. I've thoroughly analysed this by swapping cards, etc, and the performance of record and playback is completely random. Playback is interrupted by pressing on the RCA inputs on the back, which is a sure sign of bad solder or cracks in the MB. I decided to pull it down and get the motherboard out, and saw someone has already attempted repairs by jumping bad sections with wire. I re-flowed solder and reinstated it, but no improvement. I concluded that it was unrepairable, and after keeping an eye out for several years, irreplaceable as well. So I plucked up the courage and have drawn a replacement in Kikad, which I'll be sending off to a fabrication house as soon as I can get the damn Solder Paste layer to show something. It's so cheap to get things done now, I'll probably do half a dozen or ten. If that seems like a lot of trouble to go to, it was a fun project to learn Kikad, and I hate the idea that a beautifully made and mostly functioning machine should just be scrapped for parts because of one circuit board.

    I haven't even got to my question yet. Here it is:

    The power mutes K1-4 (OMRON LAB2L 12v) were all working before I pulled it apart, but I want to do this job once and do it properly, and not have to pull the MB out for another 10 years at least. So I want to replace them. I read in another thread that the member Skywave suggested COTO part 8L02-24-00 (although that was for a 40 series machine I think). It's an awkward form factor, but I suppose with some extra wiring I could make it work. I can't find any information about the Omron original part, but I believe it is a DPST, Normally Open, 12v coil.

    * Should I be buying the COTO 8L02-12-00 for the 58 instead? (12v coil)
    * There's stacks of n.o.s. OMRON LAB2 24v on feebay, which just seems to be a 24 v version. Could I use that? Maybe I'd need to remove R-R4 (1k2) to get the coil voltage up.
    * On feebay I've also found a FUJITSU FRL764D12/2AS-02 12Vdc which is DPST and appears to have the right form factor (6 pins, 3 at each end). But I can't find a datasheet. Worth a punt? Don't know if it's NO or NC.

    Looking forward to some responses.

    PS - any recommendation on PCB fab houses in the US that cater to hobbyists? A friend suggested OSH Park.
  2. Mega-Ohm

    Mega-Ohm New Member

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    Gear:
    M-600, 58-OB, 52-B.
    Update: I had 3 motherboards made by OSH Park (minumum quantity) and it worked. I decided to re-use the reed relays since I couldn't find any info on replacements, and I re-used all the 90 degree pin connectors. I used new pin headers for the 12 and 13 pin card connectors (had to cut up some 15 pin ones). . Good audio in and out of all card slots now. There's a few other problems, Card 5 has playback on REPRO but no SYNC and no RECORD. Relay I suppose. Tape tension is crap, so channel 8 record level is down (applying some back-pressure to the supply reel brought rec level back up). I don't have access to a tentelometer so I don't think I'll try it. RCA ins and out are all fine, but not all XLR ins and out are working. I might have to try reflowing the solder on that board, which is a shitfight to get out. While I was waiting for the boards to be made, I pulled the reel motors and cleaned them, that seems to have done the trick, they were previously sluggish but are running nicely now. So I'm getting there.

    I'll add some photos when I figure out how that works.
  3. Mega-Ohm

    Mega-Ohm New Member

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    Gear:
    M-600, 58-OB, 52-B.
    Ok... can't figure out how to upload photos. Sorry.
  4. Arjan P

    Arjan P Veteran

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    @Mega-Ohm Noone can upload photos to the forum, they have to be hosted somewhere else and then linked here.