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Thread: Tascam 388 - Multiple issues (channel 7-8 RMX is quiet)

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    Tascam 388 - Multiple issues (channel 7-8 RMX is quiet)

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    Hi yall, this is my first post here after scouring the net looking for answers but to no avail.

    I recently bought a Tascam 388 do get some analog recording going, and started running some tests on it, and found multiple issues.
    The first and most crucial issue I found is, when in RMX mode Channels 7-8 are coming in super quiet. The meter doesnt show any movement on channel 7 but channel 8's meter looks pretty healthy. Its just coming out super quiet. When I track the meters both look good, but playback is quiet.

    Aside from that, I have the tape rubbing the take up reel flange and the counter isnt functioning on playback(just FFW and RW). Is that a tension arm adjustment?

    Im just looking for some advice before I start taking the thing apart. Besides that, the rest of that channels sound great and I just wanna work on some music on it!

    Thanks!

    -Nick

    I can take videos if needed!

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    Greetings, Nick.

    And welcome!

    First of all, with your track 7 & 8 low playback level in RMX mode, what happens if you flip the tape over and play back with channels 1 & 2 in RMX mode? Do you hear your tracks 7 & 8 program material playing back at a normal level (albeit backwards and through channels 1 & 2 of the mixer), or is it still quiet? Try that and report back and then we'll go from there.

    Regarding the tape rubbing the take-up reel flange, the tension arms aren't height adjustable on the 388, but the reel tables are. Do you have the manual? There are instructions in there for adjusting the reel table height.

    As far as the counter function, without tape loaded you should be able to spin the footage roller with your fingers and have it keep going a little bit...it should spin freely. If it stops as soon as your fingers leave it, or if it feels resistant to turning, it is either missing one or both of the small black plastic thrust washers, or it needs to be cleaned and lubricated, or both. It may also need to be rebuilt if the rubber has aged. Unscrew the black top cap. There should be a small thin black plastic thrust washer sitting on the top of the roller in the center or it may be stuck to the underside of the cap. If its not there you will need to source this part. Slide the roller off the shaft. There should be another identical thrust washer sitting at the bottom of the shaft, or it may be stuck to the underside of the roller. If its not there you will need to source this part. Inspect the rubber on the roller. Is it hardened, cracked and/or slick? If so contact Terry Witt of Terry's Rubber Rollers through his website (linked there to the left for your convenience) to have the rubber rebuilt. Otherwise meticulously clean all parts, shaft, cap, washers and roller bushing faces and bore of all dirt and old lubricant, and then apply a small amount of turbine oil to the roller shaft and bushing faces using a cotton swab or similar. You only need a small amount. The copper colored bushing pressed into the center of the roller is a bronze oilite bushing that is porous and impregnated with oil, so we just want to get things cleaned up nice and get a little lubricant on the mating surfaces of the assembly. Reassemble taking care to place the thrust washers in their appropriate locations and the roller should spin freely. Report back on whether or not this resolves your issue with this. If the counter is working in fast-wind mode that means the logic works, so I do suspect it is a mechanical issue with the roller.

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    Thanks for the quick reply Sweetbeats!

    So the sound does play through channels 1-2 when i flip the tape around. And after cleaning the heads I got sound to come out of channel 7 in RMX mode as well(though it came back in once I slid the fader up and down and heard a scratching noise. Is that a dirty pot?). Channel 8 was still quiet.

    I've been looking at the PDF of the manual online, Ill have to try to adjust the reel table height when I get a chance.

    The footage roller doesn't spin for more than a half second if I spin it. The rubber seems like its in alright condition. I cleaned it with soap and water and it gets tacky but, I'm just not sure if its in bad or good condition. In my opinion it seems like good rubber though. I do see the tape slide across the rubber sometimes though. So I think it has to do with the spindle and the washers(I have both luckily). How would you go about cleaning those parts? I have some sewing machine oil too, would that be good with this?
    Sorry for all the questions, this is my first reel to reel machine.

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    You’re welcome!

    So...try this...when you are playing back your tape and monitoring tracks 7 & 8, do you have a way to monitor the TAPE OUT jacks on the back panel? Like particularly the tracks 7 & 8 out jacks? I’m wondering if the signal level is normal there.

    When you say the rubber on the footage roller gets “tacky”, do you mean it gets actually sticky? Or do you mean it becomes simply grippy? If it is at all the former you need to rebuild your roller.

    It also sounds like you need to clean the bearing assembly.

    Sewing machine oil is fine. Remember you only need minimal amounts.

    I would use a lint-free rag, pipe cleaner and 91% or greater isopropyl alcohol to clean the parts.

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    So the tape outs from 7 and 8 are coming out at normal levels.
    Just not through the monitor or master outputs.

    By tacky I meant grippy! I'll have to trying to clean that bearing assembly. But my main concern is channel 8 for now.

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    Sweetbeats, do you think it has something to do with a bad hex inverter?

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    I don’t think so. The hex inverter U104 acts as an analog switch that facilitated the dual functionality of the L-R assign switches...look on page 27 of the manual, paragraph 11...the L-R assign switch, when latched with no other assign switches latched on the given channel strip, simply assigns the signal on that strip to the L-R main buss, but if any of the PGM group 1~8 assign switches are *also* latched on that strip, then the L-R assign switch acts as a solo-in-place feature muting all other signals assigned to the L-R buss (except for any other strips that are also soloed). The point here is that this feature, which utilizes the U104 hex inverter, is not source-specific; it doesn’t care what the source of the given channel strip is (tape, line, mic...), so the problem condition would exist not only in RMX mode, but MIC or LINE mode as well. Since you can monitor mic or line source signal through channel 8 okay, and your problem is isolated to RMX mode when tape track 8 is the source, I don’t believe your issue is associated with U104. Plus, my experience is when there is a failure of U104 on the 388, the symptoms are global across all channels. Like for instance none of the channels can successfully be assigned to the L-R main buss.

    I have to look at the Block Diagram and schematic diagrams to see if they suggest anything about the cause of your problem given the information you’ve provided. I’m just a bit short on time and my clean set of schematics are well buried from my move a couple months ago. I’ll reply with more info when I can.

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    Have you tried exercising the channel 8 source select switch? Like rapidly flipping it from stop to stop a couple dozen times? Any change? How about when reproducing track 8 applying some pressure to the switch when in RMX mode like to the right or straight down? Any change in signal level or any static heard in the output?

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