388 troubleshootin'

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CAZ-PNX

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i recently picked up a 388 and am having trouble getting it working. at first i thought it was just monitoring issues, with a huge operator error component, but i'm starting to think it's not just me.

i'm peaking on each channel's OL, but having trouble getting signal to the VUs (and consequently, the tape). for channels 1, 3-8, and the stereo L-Rs, i was getting no movement at all. channel 2 responds like a hurricane, but still, nothing shows up on tape. i replaced all of the fuses the other day, and that's helped eek them a little, but nothing like it should, especially compared to channel 2's response.

anything i should be looking for?
 
Start by checking if you have clean strong uniform signal at the send jacks of inputs 1-8. Then route each input to busses 1-8 one at a time and see if clean, strong uniform signal gets to the buss out jacks (can't recall if they are called buss out or pgm out). Make sure the input faders and buss master faders are up at the normal range. Make sure all the L/R assign switches are in the up/off position.

Report back.
 
sweetbeats, first off, i've gotta say that your 388 rehab thread was a huge inspiration and my main drive for grabbing one of these guys. now that that is out of the way...

the send jacks give a very clear and strong response.

the pgm outs are very faint, except for channel 2, which is extremely loud and hot.
 
Cool...thanks!

Okay...and your 388 has always been this way (IOW the bad behavior is not a sudden recent change)?

Any visible damage to the unit?

Tip it on its side and have a buddy hold it stable or find a way to secure it such that you can still get to the control surface and also the bottom of it, because you're going to remove the bottom panel. Once the bottom panel is off look for the connector PCB that goes across all the mixer cards. Carefully make sure it is completely seated, and then gently apply pressure while running audio into an input or inputs and see if your gentle tweaking makes any difference for the output of channel 1 and channels 3-8.

In the meantime I'll look at the schematics and see what next-steps I can generate.
 
eh, nothing comes from getting touchy with that pcb and all of the channel boards look seated as snuggly as channel 2.
 
Okay.

Now raise the PGM MASTER faders up to the nominal zone and connect an input to the PGM BUSS IN jacks and see if you get signal out through the PGM OUT jacks; IN jack 1 to OUT jack 1, IN jack 2 to OUT jack 2, etc.

What we are doing is narrowing down where the problem is using the available patch points. Because you got good signal uniformly via the SEND jacks on each channel we know there isn't a problem up through the eq section of the input cards. That leaves the routing controls, fader and fader booster amp. By testing the BUSS IN to PGM OUT path we are checking the BUSS MASTER faders and the associated amps. If all checks out okay there then I have another step planned out, but I suspect your BUSS MASTER faders need servicing.

You haven't answered whether or not there is any evidence of trauma to the unit (i.e. dents, major scuffs or scratches, etc.).
 
ah, thanks. i'll give it a look later today. as far as damage, the thing looks CLEAN. no dust, dings, scratches or anything like that, all VUs still light up, and i hafta believe that if the unit was dropped or stored improperly, they'd be the first to go.
 
clean non-damaged exterior is a good sign.

Report back.

I'm able to help with the mixer section. Transport logic is too hairy for me, but audio issues on the mixer side are easier to deal, so there's a good chance we can track down the issue. No promises tho'.
 
alright, as far as today's experiment, channel 2 is the only one that returns any sound.
 
I betcha your BUSS MASTER faders need servicing.

I'll find you a link for a thread I put up awhile back about this or pm me if you are interested having me do it.
 
i had cleaned the faders up when i first picked up the machine, while i was waiting for a new capstan belt to arrive. from reading your story thread, i basically used this same method to clean the faders that was in the video, too. maybe in reassembly i did something wrong, but i would think that all of the evens would work, not just channel 2. that's where i doubt it could be in the buss masters, but i'll take it apart and check it out. any thoughts beyond that? seriously, thanks again for all your help and original inspiration!
 
Each buss has a set of wipers in that fader. The pressure between the wipers and the element decreases over time as the wipers lose some of their spring. This is furthered by pulling the faders apart and cleaning the wipers. If you didn't *gently* bend the wipers to increase their angle allowing them to apply a bit more pressure against their respective elements, signal won't pass. This is my prime suspect in your case at the moment. Did you do that step when you cleaned the faders (tweak the wipers)?

It is COMPLETELY possible to have only one buss working or two on one side and three on the other, etc., etc., etc.
 
sweetbeats... when do you want me to come over and wash your car? mow your lawn? clean your gutters? that was it. most of the faders needed a bit more contact to the element, so i went ahead and opened them all up again and adjusted the filament on the wipers. seriously, thank you.

newly uncovered issue (now that i can hear my recording)- is that channels 6-8 will record strong, 5 is a bit muted, and 1-4 don't print anything. the first test recording i did, i went though channel 1 only and bussed them all, and only 6-8 came out clear. i then went through each individual channel (channel 1 with the 1-2BUS selected, 5 with the 5-6BUS, and so on...) just to make sure, and had the same results. dbx is off for both 1-4 and 5-8. anything to check in this area?
 
congrats on tackling phase 1. ;)

Heheh...forget the gutters, lawn and car...come hang with the kids for awhile so's I can take the wife out for pint. :D

As far as your printing to tape issues, answer me this question:

How are you monitoring the tracks? Are the channels 1-8 in RMX mode, or are you using the monitor mixer?

Do you get a different result for the playback on tracks 1-5 if you monitor off the TAPE OUT jacks to an external mixer or monitor amp or whatever?

Look closely at the rec/play head...is it clean-clean-clean? The smallest bit of residue on these narrow-format heads can greatly diminish record and/or playback levels even to the point of inaudibility.

Long shot but do you have anything pre-recorded for the 388 with known good signal on all tracks to test playback? This will rule out if it is a problem with the recording process or playback. A test tape would be ideal but anything with something on all tracks will work.

in the absence of the above, try flipping the tape over off of which you are getting playback signal off of tracks 6-8. I'm wondering if you get playback off of tracks 1-3 after flipping the tape.

Let me know the results of the above and that will determine the next steps which will likely involve test-swapping some amp cards in the cardbay, but first thing's first we need to narrow down if it is mechanical or electrical, and if it is on the record side or the playback side.
 
i'm listening through the monitor mixer via the headphone jack in the front. i don't get anything different through any other playback method, and nothing shows up as being recorded on the VUs. while recording, though, they're going wild! and actually, it's just 1-4 showing up blank. i got a little hasty making that first post; channel 5 isn't as bad after playing it back a few more times.

the head has been cleaned- it was the first thing i checked when i couldn't get a signal on those tracks upon playback.

i don't have anything pre-recorded with this machine, but i tested your suggestion on flipping the tape over; 1-4 plays fine. so, something goofy is going on during the printing, not the playback.

i haven't demagged the heads since i've picked this up. it's coming; just haven't gotten my demag device yet. is that in the realm of possible factors (keeping in mind that i realize anything is possible)?
 
The symptom of gauss on the rec/play head is loss of hf response, not total loss of signal.
I'll have to do some head-scratching...i was thinking of amp card swapping, but the cards are 1-3, 2-4, 5-7 and 6-8 so that couldn't be it.
 
dbx cards swapped, still nothing picks up on 1-4. and it's a clean break: absolutely no evidence (either on tape or VU) that anything was recorded to 1-4, yet 5-8 is wild and resounding.
 
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