tascam 388 problems, repeat

T

thegunshyboy

New member
no help up in the tascam forum, so i'm copying this here,

i think i somehow fried channel 1 on my 388. neither the mic in or line in are working. i'm able to playback on channel one, and record to channel 1, if i use a different channel and route it to 1. when i use the mic/line/rmx switch on channel one it clicks, and the VU's peg, and then nothing happens. any suggestions on how to fix this? is it the physical jack, or did it blow a capacitor? i was tube rolling a pre on channel 1, and somehow me shutting the pre down and powering it back up several times caused this problem. help.
 
thegunshyboy said:
no help up in the tascam forum, so i'm copying this here,

i think i somehow fried channel 1 on my 388. neither the mic in or line in are working. i'm able to playback on channel one, and record to channel 1, if i use a different channel and route it to 1. when i use the mic/line/rmx switch on channel one it clicks, and the VU's peg, and then nothing happens. any suggestions on how to fix this? is it the physical jack, or did it blow a capacitor? i was tube rolling a pre on channel 1, and somehow me shutting the pre down and powering it back up several times caused this problem. help.
Click to expand...

If I understand you correctly you are getting the same symptoms no matter what position the switch is in… mic/line/rmx, right?

In that case you can narrow it down to see how deep into that channel card the problem goes.

Looking at the schematic, the mic, line and remix inputs are separate until they converge at the EQ stage. There are four op-amps and several peripheral caps, resistors, etc, that could have failed in the EQ block. Ignore the symptoms on the main buss for a moment and see if you can pass a signal from the line in to the AUX out. To do this set the Post/Pre button to Pre. If you can pass signal this way you know the problem is at the EQ block or later. Also see what happens to the AUX output when you change the Post/Pre button to Post.

Next plug a line level source into the RCV jack and see if you can pass signal through the rest of the circuit to a PGM output. You should be able to effect the signal with the channel fader and the Pan control. If you can you know the problem is before the channel fader. If not the problem is deeper into the circuit.

Most people would probably just want to replace the channel card anyway. But if you were so inclined you could yank the bad components out and replace them… whatever you are comfortable with.

The easiest thing if your skills allow you to get the bad channel card out is to send Herm a PM and ask if he has a spare card to sell you.

If you aren’t comfortable with hacking around inside something like the 388, you should get it to a TASCAM authorized tech in good standing.

The above exercise in narrowing down the problem circuit is valuable either way. The more you know when you take a unit in, the less likely the tech will try to take you for a ride.

:)
 
In addition to what's already been said, "tube rolling" while plugged into the input of the 388 is "definitely not recommended" . Plugging in or out a tube while the unit's switched on can cause massive voltages into the input of the following equipment. Solid state (non tube) gear is especially vulnerable to damage.

cheers Tim
 
Yeah, I second what Tim G said about tube rolling.

Also, here's a pic of the channel card (complements of Herm sometime back... if I remember right). As you can see, repopulating the entire board with new op-amps, caps and resistors is not all that difficult... there just isn't much to it (if you've done this sort of thing). It's the shotgun method, but sometimes it's the cheapest, easiest, and fastest option in the long run. Any way you slice it it’s going to take some time and/or money to remedy your situation.
 

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Tim Gillett said:
In addition to what's already been said, "tube rolling" while plugged into the input of the 388 is "definitely not recommended" . Plugging in or out a tube while the unit's switched on can cause massive voltages into the input of the following equipment. Solid state (non tube) gear is especially vulnerable to damage.

cheers Tim
Click to expand...

i powered the pre down everytime when switching tubes. i guess i should have powered everything down though.
 
Beck said:
If I understand you correctly you are getting the same symptoms no matter what position the switch is in… mic/line/rmx, right?

In that case you can narrow it down to see how deep into that channel card the problem goes.

Looking at the schematic, the mic, line and remix inputs are separate until they converge at the EQ stage. There are four op-amps and several peripheral caps, resistors, etc, that could have failed in the EQ block. Ignore the symptoms on the main buss for a moment and see if you can pass a signal from the line in to the AUX out. To do this set the Post/Pre button to Pre. If you can pass signal this way you know the problem is at the EQ block or later. Also see what happens to the AUX output when you change the Post/Pre button to Post.

Next plug a line level source into the RCV jack and see if you can pass signal through the rest of the circuit to a PGM output. You should be able to effect the signal with the channel fader and the Pan control. If you can you know the problem is before the channel fader. If not the problem is deeper into the circuit.

Most people would probably just want to replace the channel card anyway. But if you were so inclined you could yank the bad components out and replace them… whatever you are comfortable with.

The easiest thing if your skills allow you to get the bad channel card out is to send Herm a PM and ask if he has a spare card to sell you.

If you aren’t comfortable with hacking around inside something like the 388, you should get it to a TASCAM authorized tech in good standing.

The above exercise in narrowing down the problem circuit is valuable either way. The more you know when you take a unit in, the less likely the tech will try to take you for a ride.

:)
Click to expand...


i'll be sure to try these steps to narrow down the problem. i can still record to channel 1 via another channel, and i can still playback on channel 1...so i don't think it's too deep into the circuit.

i'd love to just take it in to a tech, but unfortunately i think the closest place would be a 6 hour drive to seattle. there was a tech in town who went over the 388 when i first got it, but he's gone out of business since then.

in the meantime, i've just been recording to channel one from a different channel.
 
Oh, you can still playback on channel one by switching to RMX? In that case it could be the very first stage... the op-amp and/or associated circuitry in the Trim section. But regardless we'll know more after your tests.
 
Say it ain't so, Gary... :(

Moving can lead to a form of temporary insanity.
 
Yes I am afraid so. I first had two of them set aside for just in case then I said to myself I have too much stuff and some of it has to go.
I have started getting rid of some of it cause I dont want to go through that again. The money I get from the stuff I am selling is going to buy smaller things like better mics and things like that.
One 22-4 is plenty I do not need 3 of them.
 
Herm said:
I dont even want to admit what I did with 8 of those channel cards when I moved :o
Click to expand...

oh god! i just now caught this. i finally got a chance to crack the 388 open and sure enough its the card that's bad. i hope i can find a replacement. if not where should i get parts to repopulate the board?
 
I have a similar problem on my M35 mixer. On channel one the XLR input doesn't work. I know it's in the card because you can swap channel cards on the M35. It's useable in every other way. I can assign track one to channel one from the buss in section for mixing or eq I just can't get a direct input on it. Is it the preamp? Beck, have any suggestions on how to troubleshoot that?

Also Meter 4 doesnt work. I discovered that was caused by the channel 4 submixer's card because you can swap those too. It's only the meter that's not working everything else works good.
 
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