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Thread: My Tascam 244 Repair Thread

  1. #1
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    My Tascam 244 Repair Thread

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    I came here with a question about something but decided I should probably post some pictures of my progress...

    I'm in the middle of doing a full-on recap of the unit. Just for some history, I got this unit probably 6 or 7 years ago (maybe more I can't remember) from a friend of mine who I believe got it in a gear trade at some point. The belts were gone, the idler tires were melted... you know, the typical fare on a unit that's probably not been taken care of. I gave him either 40 or 50 bucks for it.

    I few years back I went ahead and revived the transport with new tires (o-rings) and belts, and it basically just started working and actually working pretty well. So I recorded some stuff on it just to test it... and it sounded good. The only problem I remember at the time was there was this slight 'pumping' artifact in the tracks, which I was later told was the DBX. I hadn't really had time to play around with the 244 in a while, so when I went back to see what I could do with it, I wound up having another transport problem, related to a crack in the PC board that ran the control motor (separate thread posted). Now with that fixed, and the unit apart, I decided to do a recap of all the boards and then adjust everything and do a full calibration.

    As of right now this is my progress:

    Power supply board partially re-capped (finished this last night with the main supply filter caps)


    Meter PCB


    One channel strip done


    DBX Board


    On the subject of the DBX board, I found something interesting. There is a marking in the schematic for a capacitor that is supposed to be a non-polarized film cap, C437. However, in my unit, and based on some other photos I've found of DBX boards, they used a 1uf polarized electrolytic cap:



    And just for reference (ignore the yellow cap I circled, that was for something else..)


    So now at this point, with the DBX board done and 1 channel strip (#4) re-capped and reinstalled, I powered it up and checked my progress. I plugged in a guitar to channel 1 and the FIRST thing I notice is that it is extremely distorted with barely any gain applied. I played around with the levels and everything but I know for a fact something is wrong if I'm getting that crackle like I blew a speaker. I have recorded direct into this with a passive guitar and had plenty of headroom. Now, this isn't to say I'm over here changing out tons of capacitors and threw something off, but I'm a little concerned since I'm only monitoring the channel strip (basically it is a mixer at this point). I checked my re-capped channel strip and it's the same.

    Anyone else here do a full-on restoration, re-cap and can share any experiences? I'll post more progress as I continue along.

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    First of all, sorry for the trouble you’re having. That’s frustrating I’m sure. Been *there*.

    Regarding the differing value in that cap, it’s not uncommon the physical assembly differs from the technical documents. Maybe there’s a revision of the technical documents out in the world somewhere with an update that captures the change in type and value of that cap, but if you’re certain the cap that was there is factory, and you’ve seen other assemblies with a 1uF cap there, I’d be completely comfortable putting the same value in when recapping.

    When you were getting the “pumping” on your tracks was it on all tracks regardless of the level to tape and the source type? Or was it more prevalent on certain types of sources or at hotter levels?

    Now for your distorted signal issue...how certain are you that the issue resides on the channel strip? How are you monitoring the bass guitar? What is the signal path? And what happens if you try other source types? Is it even destroyed with like a -10dBV 1kHz test tone?

    if it was me I’d be weighing a couple pathways:

    1. Recap the next channel strip and see if it does the same thing. If it doesn’t I’d probably finish the recap and then go back and address the problem with the first one.

    2. If the problem happened with the recap of the second strip as well, I think I’d stop and start tracing back with a scope and tone from the output until the signal was clean and at the proper level. If the issue was prevalent using either channel strip I’d expect the problem to be somewhere downstream in the summing/monitor amp pathway.

    3. In the case of the second strip being A-OK then I’d use the scope and tone and trace backwards starting at the output of the channel strip.

    It *sounds* like you’re describing a blown opamp. It’s possible if an opamp was close to dying the new lower ESR caps could have kicked it over the edge. Who knows. But it can be fixed.

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    Quote Originally Posted by sweetbeats View Post
    It *sounds* like you’re describing a blown opamp. It’s possible if an opamp was close to dying the new lower ESR caps could have kicked it over the edge. Who knows. But it can be fixed.
    Yes.. that's actually what I was starting to think could have happened except I couldn't word it correctly. The issue with distortion is at least on channel 1 and channel 4, 4 being the one I recapped, so the issue shouldn't be in the channel strips themselves. I'll try it with a test tone and see before I conclude; I hadn't done that yet. I literally just grabbed a guitar and plugged in to make sure things were still passing signal before I got too far into the repair.

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    Yeah gotcha.

    So it does it on a non-recapped channel as well? If so, I would hypothesize it is unrelated to the recap and would proceed with the recap and iron out the issues later. Some might disagree with that, but IF there’s a blown opamp, who knows if others are going to pass away during your recap and I’d finish the recap and then start sorting out what’s toast starting with whatever narrowing down can be down just using the controls and I/O on the 244 listening to any source or program material. I can help you with that when you get to that point.

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    Yes it does it on a non-recapped channel also. I do plan to finish the re-cap regardless, as you say, and address other things after. I'm glad there is still a support community on these things!

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    Continuing on -

    Tape Cue Amp PCB:


    Control PCB A & B:


    Had to leave one BP cap in; didn't have a new replacement. Seemed to test ok on the Peak meter. Also tested the inputs with the 1k test tone; distorted and crackles immediately with barely any gain, so yes, probably borked an op amp...

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    Also... does anyone here happen to have the schematics for the 244? I have the service manual that Tabita Hub was kind enough to email me back a few years ago, but he did not have the schematics scanned at the time (and his site/email are no longer functional). I'll gladly pay for them through Teac if I have to, but if anyone has a scan of 'em...

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    Alright, so I finished up the re-capping on the 244. Last board done was the playback / record set:



    Definitely wasn't as painful to do as I was led to believe; but still, trying to manage all the wiring harnesses was a chore, and I ended up getting them in a good grouping and zip-tied them together to lessen the chance of ripping something out with all the flipping around.

    So now I'm at the point where I originally was; the input channels are all distorting on output. I haven't even played around with the transport yet. This is purely just plugging in a sound source to 1-4 and getting levels through the headphones or from the Line Outs on the rear. I'd post a video or audio clip, but in all honesty I do know for a fact that it's clipping and distorting very early. i know that I had a ton more headroom on the channels to record / monitor bass, guitar, whatever...

    So I started out probing the 3 op-amps on the power supply/output board, thinking that would be a good place to start... but I realized I really have no idea how to troubleshoot a blown op-amp! I was probing with the scope and all the pins are giving me the exact same readout, so I'm wondering if I need to use the DMM and check voltages at the pins instead? I'm still poking through the schematic. **This is where SweetBeats chimes in lol** ahem please

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    Lol!

    So I need to look at the schematics as soon as I can, but tell me which outputs exhibit the distorted sound?

    And then as a preview for how you do this, if you are using your scope, you connect test tone to one of your inputs, assign/route that tone (let’s use a 1kHz tone) so that it’s outputting with distortion, and then with your scope set to AC volts (probe your tone generator output so you can set the vertical and horizontal scale of the scope such that you can see the sine wave of the tone), just start probing at the output and keep moving upstream in the signal path one step at a time. You will *see* the distortion in signal at the output of you can hear it. The waveform of the sine wave won’t be clean and smooth...it’ll be all jagged and “dirty”. So just keep probing upstream one step at a time using the schematics to help you know which component is next in line, and you’ll reach a point where the signal is clean. That’s usually the point where the failed component resides.

    I’ll verify this with the schematic once you verify which output(s) sound distorted, but most of the opamps in this era of Tascam gear are through-hole PDIP-8 packaged dual opamps. The two outputs are usually found on pins 1 & 7.

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    Exclamation You Guys Rock!

    Quote Originally Posted by Lt. Bob
    ... subtleties of sound make a difference to those who really listen.

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