Tascam 388 REC/PLAY PCB ISSUE - Fixed

688

688

New member
Hello,

i bought a Tascam 388 and during the first tests it appears that track 8 wont
record.

I checked the Channel and Master Faders - ok , all XLR and 6,3mm Inputs - ok, Tape path is cleaned with Isopropanol.

The 388 has been used with Ampex and Quantegy 456 Tapes in the past, which maybe is cut more narrow then the Maxell that I use.
I tried pushing the Tape physically a little bit up and down while recording, still absolutely no signal on 8 while rmx monitoring.

I removed the Top panel, I see 6 cards there on the left side.

Does somebody has an Idea before i try reseating anything or buy a used Ampex Tape to try out?

Could the problem still be one of the Master Faders, they seem a little worn out but work ok.


Thanks
 
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do you mean dbx defeat for channel 8?
it was set to OFF during my test, but as i picked it up it was set to ON so i try it again in the ON
position, don't think thats the problem though.

can't find a sync switch.

Thanks for your Help.
 
alright i checked again with the dbx defeat in the on position and after that in off position.
nothing recorded on track 8.

any ideas besides that, i dont want to pull the cards out yeat. i see the upper 4 boards are the record/reproduce cards.
which one is for channel 6/8?

cards arranged like this from topview
rrc1______ ______rrc2
rrc3______ ______rrc4
other______ ______other

another question, which one is the 8th track on the record/reproduce head, the top or bottom one?

thanks
 
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i checked again using different input channels.
not working. so i think there is no voltage going to track number 8 on the recordhead.

input selector switch? rec function button? assign button? fader? something else?

ok the manual says it's rrc4 the lower card on the right side.
i pull it now and reseat it and report back.

update : i have not pulled the card because it sits tight in there i dont wanna go hulk on it now.
so i just wiggled it a bit, this wasnt doing anything, no recording on track 8.

i rule out the too narrow tapepath groove from ampex usage, because i eye sight checked the path under very bright light,
the maxell tape sits perfectly in the wear path. the previous original owner said he used ampex only approx 20 hours on
this machine, maxell was his standard tape since the learly 1990s.

update : i was browsing through a thread by user sweetbeats. it appears that the problem could stem
from the stereo L/R master fader, this one is worn out most, but still works without problem, its like a bumpy
road between the 0 and 3 position.

could this fader be part of the problem? has anybody a good method for refreshing those wobbly faders?
(sweetbeats?!)

thx
 
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today i tried recording a testtone on track 1 on the very end of a tape.
i flipped the tape over to see if it is reproduced on track 8 while playback.

oh sweet silence.

absolutely nothing is reproduced on track 8 and probably nothing erased and
recorded either.

and open goes it's bottom plate...:(
 
...

You might benefit more first from pulling & reseating the audio cards in the card cage, accessed from the top.

They can be in there tightly and will take a serious pull, but sometimes working it back and forth very slightly might help.

:spank::eek:;)
 
well i could give it try again, i have to swap 1 of the working rec/repro cards with the 6/8 one
anyway on some point down the failure search to rule out a defect on rec/repro card in slot 6/8 .

i think its the EVEN pgm master fader, because this one is way harder to push up and down,
like somebody spilled soda in it and it has gotten sticky and rusty, i cant help it i think i smelled
catpiss from somewhere in the 388.
 
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yes but it looks like there are 4 resp. 8 individual wipers on each of the 2 pgm master faders,
if one of these wipers is corroded then only this one doesnt make contact.
the user sweetbeats could help me out here he had a similar problem in the past

https://homerecording.com/bbs/general-discussions/analog-only/tascam-388-story-286434/8/

there is a big picture of the wipers in the middle of that page

update: at 2nd thought i can almost rule out the faders, because earlier i
flipped the tape over to see if signal recd on trk1 wil appear on trk8.
you dont need to turn up the 2 pgm masters to monitor the tape, only the
L/R Master has to be up and your indiv. monitor gains. there was nothing
to hear on 8 so no to the pgm master fds
 
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Fair enough.

It should be fairly easy to ohm out for continuity each of the 4 contacts in the Buss Master fader.

I don't see what harm it does to reseat the audio cards. It's often a quick fix for many similar problems.

:spank::eek:;)
 
ok what i did now was cleaning the heads again looking through a zoom lense,
nothing suspicious, heads look like low to middle mileage to me, no oxidation
or other feces.
next i tried to remove rrc6/8 and stopped halfway because i almost shitted
my pants while pulling and some vein on my head started pumping enormo.
but it def. moved a little and i wiggled it back down.
i wiggled all other cards except the psu one.
TRK8 still silent, no movement of the VU8 when it should get signal
from the recorder.

now i have to eat my steroids and get a big nose of sleep
so i can pull out rrc6/8 and rrc 5/7 tomorrow, and swap them to
see if the failure moves with the rec/repro cards.

next step would involve more steroids to open up this fat boy's bottom
and do a big bullshit check.

thanks for your input.
 
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Opened the fatty up and as i thought something got dropped on the STEREO L/R Master Fader. (CH3 FDR too)
The "conductor" plate was popped out of the metal casing on some places, thats why this Fader (and
Channel Fader number 3) is so "bumpy" like a bumpy road.

All other Faders look fine and as i said earlier, all Faders were working good so there is no real
damage i just have to reassemble them properly again after little cleaning.

I can't see anything suspicious elsewhere.

Here is my question for you guys: Could my not working TRK8 problem stem from the messed up
Stereo L/R Master Fader?

Edit : I'm looking at the L/R Fader right now and i think what happened there is a "short".
I explain. The plastic board which holds "Conductortraces" and cables got popped
out because of pressure from the top towards bottom somewhere back in time.
now there are little "noses" on the metalchassis which hold this plastic board in place
after assembly. These noses have not been bend while pressure was applied from the
top, they are still in "closed" position. one of these noses makes contact now with
one of the "Conductortraces". To me this says not much because i have no clue about
electrical stuff, but it looks like a electrik "shortage" to me because the housing
of the fader makes now contact with one of the "Conductortraces".

Can someone verify this?

edit : my father told me these are "resistor" traces, pardon
 
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The STEREO fader would not effect one track/buss.

Pictures would help.

Did you swap amp cards around yet to see if the problem follows the card? That's what I'm waiting for...
 
hello, i havent swapped them because they are so tight in there that i think if it
is not absolutely neccessary to pull i wont. i will pull them if i can rule out the faders 100%.

i know this LR Fader cant directly be the cause, but like i said there is maybe a electrical shortage
between the housing of the fader and the inner traces, some little FDR housing-clamp-noses touch the "resistancetrace"
inside, maybe weird things start happen because of this...the pgm master buss faders are ok.
but i will open all faders to rule this out...pictures idk..its a mint 388 inside and outside,nothing to see.

first i rule out the faders...if necessary i swap the cards after try out and then i report back. thank you.
 
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Mint? I thought you said there were some problems with the STEREO master fader?

I asked about pictures because your written description isn't completely making sense to me as far as the problems with the STEREO master fader.

But the bottom line is that if ANYTHING is working on the left and right main busses, then there is nothing wrong with the STEREO master fader, and the advice you are getting is to swap the cards. That is the first thing I would do. So do whatever you like, but I'm waiting for the results of that test.
 
webcamphoto of the "pushed open" L/R fader attached.
nothing broken.

pardon me I ment the overall cosmetic condition of the 388 is good,
thats why i said "nothing to see there"

i report back as i progress.
 

Attachments

  • STEREO LR.jpg
    STEREO LR.jpg
    202.3 KB · Views: 50
REC/PLAYPCB1/3------ ------REC/PLAYPCB5/7
REC/PLAYPCB2/4------ ------REC/PLAYPCB6/8>card in here faulty

The symptom moves with the card.

I had a hard time pulling the suspicious REC/PLAY PCB out of the Channel 6/8 Slot.
The other card i pulled out of slot 5/7 came out without much effort.

I swapped both cards around and made a test which resulted in a non-responding
TRK7.

I try contact cleaner on the faulty card if it doesnt help i need advice on fixing.
My tools are: simple Multimeter, Simple soldering iron,simple solder sucker,
pliers, 388 schematics.

Thanks
 
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The rec/play pcb has a fault.

i cleaned the contact on the motherboard and the connectors on the card with contactcleaner.
i put the card repeatedly in and out the slot to remove possible oxide buildup on the contacts.

TRK8 not responding.

I will now look for cold solder joints, anything that looks suspicious to me and make markings there.
my first eye sight inspections reveal no leaking elements but i will take a big look now.

I need help on repairing.

Who knows what i should look for or had a fault on one of their rec/play pcb's too?
There are little IC's on these boards maybe one of these is fed up.

I am searching for a replacement card for a reasonable price.
Last week was one on ebay, gone now, someone sells a whole lot there but will
not sell me just one card.

My location is Germany.

Thanks
 
I could not find any cracks, cold solder joints or leaking, bulging or otherwise
sightly damaged parts on the PCB.

I tested a last time changing cards to see if i made any mistake while testrecording.
No, the fault moves with the card, it is defective.

I have never rebuild a PCB Board. Where would one normally start after eye sight inspection?

I heard that capacitors will go bad over time, more so if the machine is stored away and never used.
Idk if this is true. The 388 has not been used in the last 5-10 years. It was sitting unused
at the sellers homestudio, he has not the time for doing music anymore.

If it helps, the VU meter never showed any signal coming from the recorder, not even a faint movement,
so was the audio signal - absolutely nothing.

I watched the soldering tips video made by Sweetbeats.

It's helpful thank you.
 
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