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Advice on repair Tascam 48
Old 19th March 2021
  #1
Here for the gear
 
🎧 10 years
Advice on repair Tascam 48

Hi,
I need some tips/advice on my Tascam 48!
He’s been in storage and has not been operational since 15 years!

I’ve checked some of the basic mechanical adj (tension arm/capstan pressure), cleaned the tape path and heads, installed new Athan pinch & counterwheel and bought a fresh reel of RTM SM911.
After input/VU level/peak led adjust I encountered the fact that NO channels are recording.
If I boost the input to peak then some channels (1 & 2)have an actual input. The rest is dead…Tweaking the bias level and REC did not do anything…

Next step, got my hands on a MRL ½ inch full test tape! Now I could finally allign input/reproduce level. After this I mounted the other tape and suddenly recording is back on almost all channels?? Like he woke up?! (or the OSC drive PCB suffers from bad contacts)
That is also a huge problem, lots of bad contacts when touching the audio boards, so suddenly channel 7 came to life!

So I assume that all the boards needs a checkup for bad contacts (relais?)
Swapping them to sort and rule out defective boards. (firmly pulling them out using the 2 side hole’s or is there a more gentle way to get them out?)

Then check the Bias tuning (OSC drive Amp) and bias trap on all channels at the test points?

Some tips/advice before I dive in?
Thnx!
Old 19th March 2021
  #2
Gear Head
 
Not entirely the same, but when my Tascam 58 acts weird, and pulling/reseating the boards firmly can help. I would try that first on each card.

If that doesn't help, make a note of each channel card for its corresponding slot, and try swapping around to other channels; make notes on the problem, and if it follows the card to a different slot.

Might be different for you, but I found the roll of SM911 I bought to use was a tad too wide for my 58 (different batches? I'm not sure, it was disappointing to think that my machine was junk when I first got it!)--it would push against the guide edges and not make proper contact with the heads (my hypothesis). I went back to using the 5 rolls of (non-sticky shed) Ampex 456 that came with the machine when I bought it, and it runs as good as gold!

Do you have any other type of known good tape you could try in the machine? Other than the MRL, of course.

Last edited by robbi; 19th March 2021 at 10:11 AM.. Reason: more stuff
Old 19th March 2021 | Show parent
  #3
Here for the gear
 
🎧 10 years
Hi, will surely check the tape dimensions, but as I recall it seems ok to me. And indeed, as suggested at tapehead forum, cleaning contacts is a good starting point!

No other tape, just 12 unopened AGFA PEM469 tape, but sticky as hell.
Even the MRL tape leaves traces...
Old 23rd March 2021
  #4
Here for the gear
 
🎧 10 years
Quite a challenge, these mechanical electronic devices....
After cleaning and checking all the connectors I began to swap a working card around. This did indicate that channel 4-8 had a REC repro problem.
So I concluded the main Bias Oscillator or channel Bias?
swapping the Bias drive PCB's didn't change a thing, and the main Bias oscillator works well on ch 1-3...
So then I gave up and reseated all the Rec/play cards and.... Rec Repro on all channels. There go's my test methodology!

After lots of recording and Bias tweaking channel 8 remains a problem.
After manually tweaking the tape/head contact I noticed aprovement. Tweaked the tape path, adjusting the tape tension arms height, I got channel 8 back on track.
setting the Bias is possible again.

Now further testing and recording tone's and music with succes! Channel 8 however remains the weak channel, bad HF repro, sometimes sounds better (more to middle of the tape).
Could head wear be a problem, or am I chasing ghosts?
Here a photo :
https://www.flickr.com/photos/686062...posted-public/
Old 29th March 2021
  #5
Gear Head
 
Glad to hear you're having some success with it! Sounds like you know a thing or two about getting the machine running smooth--I'm very hesitant to mess with anything involving the tape path, other than cleaning it.

It's quite hard to tell from the picture, regarding head wear. There are some recommended ways to take a photo of heads (white piece of paper in front of heads to minimise reflections). Are there any local techs you could have take a look at it?

Only once have I had a set of heads re-lapped, for a Tascam 388. This was determined necessary after some good photos of said heads, and enquiring with a few different techs in my area, and eventually being pointed to Terry at Summertone:

http://www.summertone.com/services/

Of course, once this was done, the machine required a full alignment from a competent tech!
Old 4 weeks ago
  #6
Here for the gear
 
🎧 10 years
Hi, after this little success up to the next problem.
I noticed some noise of the tape rubbing against the reel.
Look at this :
https://www.flickr.com/photos/686062...posted-public/
Seems that there is quite some deviation (wobble) on the right pick up motor.
Adjustingthe table height, switching reels, switching the reel-table, and even the shafts did not resolve the wobble. So I removed both motors, did a complete checkup/cleaning. Bearings look and feel ok! Both I don't have the right tools to measure or check in that detail...

So the only thing left to do is change the Left/right motor...
Old 4 weeks ago
  #7
Here for the gear
 
🎧 10 years
Fixed!

My mistake but apparently its a great difference how the reel table is mounted on the shaft. 3 screw, 3 positions...Due to the wear of years these 3 options have an enormous effect on the wobble.

In my methodology this was the only variable left.
Now back on track, still there is a bit of wobble but in tolerance, no scraping anymore...

Whats next?*eyepop*
Old 3 weeks ago | Show parent
  #8
Here for the gear
 
Quote:
Originally Posted by robbi ➡️
Glad to hear you're having some success with it! Sounds like you know a thing or two about getting the machine running smooth--I'm very hesitant to mess with anything involving the tape path, other than cleaning it.

It's quite hard to tell from the picture, regarding head wear. There are some recommended ways to take a photo of heads (white piece of paper in front of heads to minimise reflections). Are there any local techs you could have take a look at it?

Only once have I had a set of heads re-lapped, for a Tascam 388. This was determined necessary after some good photos of said heads, and enquiring with a few different techs in my area, and eventually being pointed to Terry at Summertone:

http://www.summertone.com/services/

Of course, once this was done, the machine required a full alignment from a competent tech!
Hi I can't figure out how to make a new post on this website I feel like an idiot. Doesn't anybody have any ideas on what is up with my tascam 388?? thanks!

https://youtu.be/nvq5r1F5bCg
Old 3 weeks ago | Show parent
  #9
Gear Head
 
Quote:
Originally Posted by studioguitarman ➡️
Hi I can't figure out how to make a new post on this website I feel like an idiot. Doesn't anybody have any ideas on what is up with my tascam 388?? thanks!

https://youtu.be/nvq5r1F5bCg
Umm, hard to say; have you cleaned the tape path well? The roller that is not spinning could need some bearing oil? I'm not sure.

Have you ever replaced capstan belt? A slew of issues were solved on mine by replacing that belt. It's pretty inexpensive and easy to do yourself. Chances are if it has been on there a long time, it will have stretched.
Old 3 weeks ago | Show parent
  #10
Here for the gear
 
Quote:
Originally Posted by robbi ➡️
Umm, hard to say; have you cleaned the tape path well? The roller that is not spinning could need some bearing oil? I'm not sure.

Have you ever replaced capstan belt? A slew of issues were solved on mine by replacing that belt. It's pretty inexpensive and easy to do yourself. Chances are if it has been on there a long time, it will have stretched.
Thank you. I'm totally down to replace the capstan belt, which I should probably do anyhow, but I'm not sure that the capstan belt is involved with the FF function. Those two rollers seem to spin quite freely by hand.
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