Tascam 388 low recording signal on channel 1

[LUNE]

Hi everyone,

recording with the 388 today I notice now that signal on channel 1 is extremely low - so much so that at first I thought there was nothing at all - but it is possible to hear the recording if its pumped all the way (adding eq etc.).
so for perspective, when I get a level into the +3 range while tracking, it does not move the VU on playback. I can play some older recordings that have signal, so I guess its a problem on its way to the tape. I switched out the chanel strip for 1/3 and the problem remains on channel 1, so I don't see how the problem could be on the channel card.

I'll be pouring over the schematics ect. later but would really appreciate if anyone that knew these tascam decks had an idea which board is the likely problem or any other testing ideas. my guess is that it would have to be close to where the signal goes to the tape.

any ideas appreciated.

 

[LUNE]

update...

Tried switching DBX cards, channel one is still the odd one out...

 

[LUNE]

Update #2

Tried swapping Bias PCB cards - no change. I think i've run out of things to swap. - and as best I can read the schematics, the head connect pcb just goes to the motherboard which forwards to the channel cards - so there's not much to go off there that would still be giving me the low signal that i do have. logically, i'm thinking perhaps there's something wrong with the actual head somehow, but i'm loath to think that could be the case.

incidentally, i did mess with the recording level on the channel card (R143), wondering how much i could make up for the low level - and i can a little in fact, but turned up too much it records a high pitched sound along with signal. I tried recording absurdly hot as well, hovering around where the VU red lights up - and i can get some signal, but its slightly muffled and bears marks of distortion if i try to make up for this with eq on the way in...

 

[LUNE]

getting closer...

ok, i tried some experiments pushing the tape to the head with my finger intermittently and got a slight change in signal... so this all might come back to my tentelometer fiasco that was never resolved. or could likely be mechanical issues anyway - I've had the habit of starting on tracks 3&4 for main tracks so i wasn't noticing much by the time i'd record on 1 with the extra shaker or whatever (i can get a little sloppy & inattentive when inspiration hits...).

crazy though that so much signal can be lost on one channel without change to the others with just tension differences - makes me worry that my head might be a little malformed or that something in the tape path is. i realize track 1 is outside, but there's been no change to track 8.

in any case i have a slightly more workable track 1 now with more tension set on the servo board. I really need to calibrate the whole machine, but I'd need of course first to calibrate my calibration tools... and i've got a busy poor man's month (including finishing up the recordings on the 388!), then i'll be out of town for 2 months so it would have to be a summer project....

I'm going to have to try and finish up what i've got with the 7 1/2 tracks that I'm left with...
still liking the sounds i'm getting on 2-8 though.

 

[sweetbeats]

Is your record/repro head grooved at all?

I have the same issue with mine and I think it is because there is a groove in the head and possibly the tape that was used earlier in its life was slitted at an ever so slightly thinner dimensiion (or the LPR-35 I'm using now was slitted ever so slightly wider) so one edge is lifted at track 1 or track 8 and with the narrow track width it takes very little change in tape to head contact to effect input or output...and realize that when you are reproducing anything recorded on that unit (if the issue I'm taking about is the problem) you are going to double the effect of the issue because the record level will be diminished as well as the reproduce level. You could run a test and track 1kHz tone across all tracks, note the reproduce level on track 1, then flip the tape over and reproduce...betcha it reproduces higher because after flipping the tape you are reproducing tone that was tracked on track 8 which is working pretty normal right?

I was able, like you, to apply slight upward pressure on the bottom edge of the tape (the edge closest to the transport face) and get track one to come up in level but then track 8 would drop because now THAT edge of the tape was riding out of the groove.

Solution?

Relap.

 

[LUNE]

Is your record/repro head grooved at all?.

hmmmm. i'd thought of this, because of course 457 must've been used on it and now i'm using lpr35, but funny that i wasn't having the problem originally and when it was low it was very low... (i've always been using the lpr35 - until just yesterday when i tried out some quantegy 457 someone gave me - haven't noticed any difference between them yet).

fiddling with the tension helped a little immediately, but only to about half strength, then somehow at some point track one started working full strength again. a little strange and i guess i could imagine it being something to do with the shape of the head, or the grooves or something very subtle in the tape path - or something that happened when i had the tension too high then too low (maybe i 'grooved' it bad somehow, but now it smoothed out??). i guess for the moment i'm going to use it while its working, but of course i'll pay attention once in a while to how track one is reacting (and likely save it for last...) and if it looses strength again perhaps i'll run those reverse-the-tape tests. (i was actually thinking to try something like that at some point, just didn't get around to it)

most of my tracks now 'playback' a little hotter than they 'record' - but they are each a little different from another it seems - this may have changed a little with the tension settings as well - (need to calibrate...) when i get back in town for the summer a priority will be getting the tentelomter working or getting a new one, then the rest of the calibration gear i suppose. one thing i noticed that surprised me a little in testing out is just how hot you can record on the thing without extreme artifacts. but maybe this is also because its not properly calibrated so perhaps i'm not anywhere near the threshold when i'm looking at 0 to +3 on the VU. nice to think the headroom is there though... i'm not having any issues with tape hiss at all, i boost a little bit of high freq on the way in on just about everything and only end up using any post tape high freq boost on 1 or 2 tracks at most.

do you think you might dare to relap your head yourself?

 

[sweetbeats]

I believe I will do it myself when I get around to it.

 

[TheRealRoach]

I just got a 388 and it appears to have the same issue. The guy I got it from gave me a reel of Scotch tape just to get me started and I noticed that Channel 1 hardly had any volume on playback (unfortunately I didn't notice this before buying it). I cleaned the heads and tape guides and bought some new LPR35 reels and loaded them up. This time there was only about a -3db difference on channel 1, but the tone was about -5db in the top end and lacking in some resolution.

Did you guys ever reach any definitive conclusion with your issue?

Mike Rocha

 

[sweetbeats]

Look at my post 4 posts back...that was the definitive conclusion...

 

[TheRealRoach]

So after accepting that channel one's low output and poor fidelity could only be fixed with a head relapping I decided to take a closer look at the tape guides and whether I could rotate them.

Anyway long story short after removing and replacing the second tape guide channel one is as good as new (the "second" referring to the second guide from the left that the tape travels over in play mode). I removed the tape guide all together at first to clean and inspect it since its the last tape guide that the tape travel over before passing over the erase and rec/repro head. I printed test tones on to all eight tracks and upon playback everything was great. I then replaced the guide and it still worked.

 

[GCalo]

Along the lines of tape guides causing low audio output, I have attached a document from where it came I do not remember but it is certainly an interesting read which ties to this issue as well as to excessive tape shedding.

One of the first things I did upon receipt of my 42 was to thoroughly clean the heads etc, cleaned the guides, and then rotated them based primarily upon this article.

 

[miltonalcon]

I have the same problem my channel one is distorted/quiet. i can't get anything out of it even when i am just trying to set up the instrument/mic. I dont think its a misalingment on the machine. I think i might have blown something but what?