Tascam 388 channel 4 not recording

Fetaldreamcore

New member
Hello thx for reading.

My tascam 388 doesn’t record onto track 4. Ive been troubleshooting before I posted here and I’m fairly certain it’s a malfunction in the machine. Neither line in or mic in record to tape. All other channels have meter activity and I can hear and record audio to tape. Channel 4 however has no meter activity nor audio.

Channel 4 is audible when the red L/R “assign” button is depressed in the “remix/solo-in-place” section tho the meter still shows no activity.

I’ve not pulled rec cards yet to swap and see if the problem jumps to another channel. The damn cards are really tight in there. That’s probably my next move but thought someone might have other advice on another board somewhere if this issue is common.

Thank you
 

Fetaldreamcore

New member
I swapped 3 and 4 input mixer channel pcbs and the problem remained on channel 4.

I then swapped the rec/play ass’y cards on the left of the unit (rec play pcb ch 2,4 and ch1,3 changed places). Issue didn’t move off of ch4 meter. Problem is not on those boards I guess?

Where should I look next?
 

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Fetaldreamcore

New member
I pulled and cleaned the monitor bus assembly pcb spraying out the button contact and touching up button solder on #4. No luck. Would love some guidance.
 

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flyingace

Active member
Being the holidays, I’m sure someone will get back on here that can help soon. Best of luck, I wish I knew how to help, curious to hear some ideas for the future with my 388.
 

skywaveTDR

Active member
I have not worked on the 388 since working at Teac in the 80's but the symptom you describe after changing cards is that the motheboard soldering could be the issue. In the Tascam 38 and some other models with push in cards, they are double sided and have feed through that with very anemic soldering will break over time. I pull the cards from the cage to get light in and look for possible bad solder feed throughs or joints then on the 38 I remove the RCA panel and go in resoldering the top of the motherboard which is not easy as there is limited viability so in some joints I use a dental mirror to see behind connector headers. My machines go out working with every channel.
 

skywaveTDR

Active member
All the connector pins are resoldered using Kester 44 and a magnifier head set in my case as connector with the activity they get will be the first items to crack. The solder joint will need to look shiny when it is dry otherwise it could still be bad. Other Tascam units like Tasvam 48 have had 100uFd and 220uFd Marcon caps that have shorted. I think that at some point when they changed supplier that they degraded the quality of the parts. I have had very few if any failures with Nichicon or United Chemicon but Marcon are not be trusted as they do not age well. 10V caps if you see them are also targets to be replaced with 16V Wurth or better like caps.
 

Fetaldreamcore

New member
Thanks for the info. I’ll proceed to touch up the motherboard solder and then maybe recap some things that relate to channel 4. I buttoned it back up because I exhausted my tinkering and no one responded so I appreciate the help. It’s a bear to work on being so heavy. I have already touched up the connector solder on the Mbus connector and channel 4 mother board connectors on the bottom. If it’s a two sided board I’ll pull cards and get in there to touch up stuff with rework paste.
 

skywaveTDR

Active member
That is why at Teac no one wanted to work on them so they did finally come up with a metal frame device that allowed it to be mounted and flipped over. The thing was a bad experiment and a pushing technology too far. Besides the electrical problems then you also have them from the format end and these are not easy to solve with no new parts for them.
 
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