Tascam 38 tracks will not erase

WhinyLittleRunt

WhinyLittleRunt

Member
I just fired up my 38 today to record a track only to find out that nothing is erasing! I had recently fixed all the solder joints on the motherboard and got the unit to play tape signal again finally. I first noticed this with track 2; I am trying to erase at a different point in the tape (so I don't lose what's on the beginning). I ran record in sync mode with all tracks selected so it would erase them all, but upon return, track 2 still bleeds through all the recording takes on that track, and I then noticed it was doing the same on 5 and 6, which had previous recorded stuff on it that bled through.

Card issue? Relay problem? It seems more global than just one or two tracks...
 
Me too...

Hey Whiny,

I'm not sure how much help this will be, but i have the EXACT same problem with my Tascam 38...

Ever since i got it, i've had problems with random channels going in and out, working intermittently, etc. I finally decided to pull the whole thing apart, and re-soldered all the points on the motherboard PCB. While i was in there, i re-capped the power supply and main control PCBs as well. Once i was finished and everything was back together, i was excited to find, that for the first time ever, i had 8 fully functioning channels working at the same time. Everything seemed fine with recording and playback, and then i discovered the erase issue.

When i re-record over existing tracks, the old tracks don't seem to be erasing completely.

I looked through the service manual, and it has some instructions on how to test the erase ratio. Basically, it says to record a 1kHz, 0dB tone for a minute or so and then re-record a no-signal section over the 1kHz tone that you just recorded. The difference between the tone and the erased signal at the output of the deck should be 65dB or more. Then the manual says...

"If the level difference is below the specification, check erase head output voltage for 60 - 70 V using an AC volt-meter"

...Which leaves me asking a couple of questions:

1. I'm not really sure where or how to check the erase head output voltage. Where do i take the voltage measurement? On one of the leads leading to the erase head? On the head itself? I dunno.

2. If i get that measurement and find that the erase head's output voltage is off, how do i adjust it? I was expecting there to be some sort of trim pot to adjust, but the manual doesn't mention any.

Hopefully somebody with a bit more experience calibrating tape machines, can chime in and help us both out. Until then, i'll let you know if i have any luck or make any progress in getting stuff to erase. :)

-Tom.
 
Bump - this is good to know I'm not the only one. The difference is I didn't re-cap anything, and that's another good idea down the road with this thing..
 
lo.fi.love said:
Has the machine been calibrated recently?
Click to expand...

I've been studying the schematics for the 32 and as far as I can tell there is no way to calibrate the erase level. I'm still struggling to work out how it can get 70v anyway, since most of the system is 24v or less - it might be possible to calibrate it at that point...?

However, your comment has just made me wonder whether, if the voltage is correct anyway, the erase head is somehow out of alignment with the rest of it. That's a little difficult to achieve on these decks because it's only really got one adjustment screw, but I guess it's worth throwing into the pot.
 
I can take a look at my 34b manual, because it seems hard to believe they didn't add a trim pot or some other way to adjust the erase level.

The erase head may be out of alignment.... good point!
 
Been reading the manual for the 38 and came across something very important; the master oscillator. I know I've messed with the trimpot on it, on top of pulling it out and putting it back in countless times during my teardown. It's the only global thing I can think of that I actually screwed around with for no good reason other than thinking it would help fix my original issue of no signal... I will check this out first, as it explains that the master oscillator has a lot to do with the erase function (that's my moron way of explaining what I just learned...) I really need an oscilloscope down the line too, if I want to get heavy into this machine.
 
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