Tascam 388 Pan Pot Bad?

A

akpasta

New member
Hi Folks,

I was using the Tascam 388 at my practice space today. It belongs to my space-mate so it's not mine but I've used these before so he let me have at it. I was doing some guitar overdubbing to the left side of track 5, and suddenly the audio got all scratchy.

I figured it was a dirty head so I cleaned it, but it was still scratchy. I attempted everything I could think of to narrow down the issue. It seemes to be coming from the track itself, not the tape, not the cables, mic, or anything else.

The left side of Track 5 is almost totally dead. When I pan back to the right, the right side is perfect. I should mention, when I record or play back the VU meters on track 5 are A-OK no matter how I pan the knob.

I started comparing between other knobs on the board and sure enough, the physical pan nob on Track 5 FEELS crunchy when you turn it anywhere left of 12 o'clock. Like there's something stuck in there or something.

So I am thinking this is perhaps a dirty pot (best case) or bad pot, or worst case something even more complicated. I don't know much about these machines' internals. Any help would be great. Can I open it up somehow and have a look at the pot?

Here's a link to a video with audio of the symptom I am describing. Shows a recorded guitar track panned right (crystal clear) and panned left (fucked up). It does the same thing regardless of source (coming from recorded tape, microphone, etc).

YouTube


Thank you!
 
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If the pot physically feels “crunchy” that’s not a good sign. You can tip the unit up on its side and remove the bottom panel and maybe look up in there to see if you can see any physical damage. Did something fall in the unit and impact that pan pot?

To get a better look you will have to, after removing the bottom panel, carefully remove the buss PCB that connects across all the channel boards, and then remove all the knobs and pot nuts for that channel card to get it out of the chassis and take a closer look or to clean it, but if it feels “crunchy” I kind of doubt cleaning will resolve that problem. I suspect the element board is broken on that pot from an impact.
 
Thanks for the reply.

Nothing fell on the unit at all. It hasn't been transported in years. It sits in my practice space and I don't think it's been used in about a year. I was using the unit and this very pot for about 5 hours when the issue started. So although something may be broken inside, it could not have been sudden and dramatic as you suspect. Is there any de-soldering required to remove these items?
 
It could also be a broken wiper inside...the little metal filaments that contact the element board. No desoldering is required to get the board out IIRC...you should be able to get it out enough to look at the board and even work on it without desoldering anything. The pot itself is solder-mounted to the channel board, and there is a way to disassemble them once removed from the board but they aren’t necessarily intended to be disassembled and serviced...so...there’s that. But it can be done and I’ve worked on them before, swapping in element boards or other parts from donor pots in rare circumstances when that’s been needed. They are an ALPS part, D-shaft 5KACx2 pot IIRC. Can verify from the service manual if needed.
 
Thought you might like to know I pulled the back off my 388 and sprayed some cleaner in the pot and it cleared right up! Yay!
 
Well that is awesome. I’m glad to be wrong in my predictions. Thanks for posting the update and congrats!
 
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