Problem with Tascam MS-16

altruistica

altruistica

Member
Hi Guys,

In order to save the wear and tear on the MRL tape I bought for the MS-16, I decided to record the entire tape (only 4mins.....short version test tape) to the hard disk recorder (MX2424) then to record it onto some NOS Quantegy 406, using the 8" reels that JP kindly let me have :thumbs up: I'd already setup the MS-16 using the tape this week and things seemed to be overall within spec.

I used the MX2424 to edit the material to give me a test tape with 4 minute tones (1k, 10k, 16k, 100Hz) of each, making the final tape around 16 mins long. At the same time as dubbing this to the new tape, I was in and out to the other room sorting out a RAID enclosure I've bought to use for long term storage of the MX2424 material.
The signal from the MX2424 was being sent via the mixer to the MS-16 with levels at 0VU and everything seemed to be going fine.

As the tape neared the end (during a final 1K tone I'd edited on the end) something must have happened, because when i returned to the room, I noticed there was no signal on any of the MS16's meters. I stopped the tape and rewound to the beginning but on playing it back, nothing.

I dug out the manual and suspected something must have fused. I took the cover plate off and found that both of the T3.15A fuses for the 'Regulated +/-15V Rec/Rep Amp' (F3,F4) had blown.
I took replacement fuses out of my other MS-16 (as I couldn't find any T3.15 fuses in my spares......duly ordered), but these have blown as well. Hmmmm........something more serious then.

This is the first time since getting the machine (would you believe now, a year ago) that I've actually been running the system at what I guess is full whack (ie. 16 tracks recording at 0VU for 16 minutes). Would I be right in thinking I've blown something that supplies power to all the cards? I'm presuming that's what the 'Regulated +/-15V Rec/Rep Amp' (the clue being in the name of the fuse).

Have any other MS16 owners or technicians ever had this problem and more importantly what was the fix?

Thanks for any help you might offer.........time to dig into the manual methinks.

Later,
Al
 
It may be that something has shorted, or it may be something bad inside the PSU itself, e.g. there is going to be a set of components to rectify and regulate the 15v line after it comes out of the transformer.

It might be interesting if you can figure out how, to disconnect the audio system from the power supply and see if it still pops fuses when nothing is attached to it - that might help isolate the problem.
I guess pulling all the audio cards might be one way to do that.

This is all just a guess though, I don't have an MS16 or any schematics.
 
Thanks JP,

I started dismantling the MS-16 last night as the only way to find out more was to start getting my hands dirty.......and boy was it dirty inside.

Can magnetic tape shreddings conduct electricity?

The reason I ask is because there were accumulations in several places around the smaller transistors that are bolted to the PSU. I went to Maplins and got some more T3.15A fuses and as you suggested unplugged everything and started with just the transformer powered up. The fuses held although the AC voltages were different than I expected.....I don't know if I was measuring them correctly. With the meter set to 200VAC setting, I had the red probe of the meter on the fuse and the black probe on the shell of the MS16. Readings were as follows:

F1, F2 - (Regulated +/-20 V Balanced Amp) F1=22.4V, F2=15.2V
F3, F4 - (Regulated +-15 V Rec /Rep Amp) F3= 11.7V, F4=21.3V
F5 (AC 6V lamp) F5=8.1V
F6 (Regulated +24 V Relay, Capstan Motor) F6=4.0V
F7 (+24 V, Solenoid Flash V) F7=2.2V
F8 (+12V Solenoid) F8=7.5V
F9 (+22 V Reel Motor Flash V , Regulated +15V) F9=3.7V
F10 (+11 v Reel Motor, Regulated +5V) F10= 12.3V

After checking a few diagnostics videos, I started checking the diodes that are the components that are first in line following the wire down to the PSU from the 'pass side' of the fuse holder. I think these may be the problem:

https://www.youtube.com/watch?v=QwKzsq7dmLY&feature=youtu.be

Should I change these first and try it again, or should I start doing a 'Cory Special' and change the caps as well?

This machine BTW is my 'experiment' machine as it's not in as good shape as the other one, so I thought I'd try getting this one fully functioning first before tackling anything on the other one.

Thanks for any help.

Al
 
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So I replaced the diodes and put the machine back together.
I checked it in stages (recorder by itself....fuses held, then attached to audio cards...fuses held...then DBX....fuses held....finally connecting audio leads).

I'm pleased to say I've just recorded with it on all 16 tracks for over an hour and everything has been fine. I can only think the fuses originally blew because of the amount of signal being put out by the cards....maybe some of the caps are ready for changing.

Anyhow, things are coming together slowly.

I actually didn't record tonight using the DBX (units still attached but disengaged). Wow!, what a creamy punchy sound.
I think I'm going to experiment a bit with this.....sounds very different to the MSR16.

Al
 
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