Tascam MS-16 Sudden problem

B

bradley1023

New member
Hello Fellow members of HomeRecording
I am new to your forums but i know there are some very knowledgeable people here as i have read many helpful conversations when i first obtained my MS-16. Now to start with i would like to inform all that i don't use this machine for composition. i bought it as i just love the sound of tape and for my interest in historic machinery, i would prefer to have an older machine so if anyone in the Brisbane area Australia is interested in selling i might just have an interest. Anyway to my point of posting, i booted it up the other day to give her a run and noticed all the peak lights on all 16 meters came on and stayed on, with this no sign of sound will come out of the machine. that includes playing a tape and running an input straight through the amp. Everything else seems to operate as it should. Hoping someone here might know if the peak lights are a sign of some description telling the user a certain fault, sadly i haven't been able to obtain a manual for it, so sorry if this information is in there. thankyou for your time

Kind Regards
Bradley Fechner
 
Some things that come to mind:

-Are all cables connected properly in the back ? Make sure you didnt swap the ones labeled as 1, 2, 3. Those cables come from the heads.
-Try disconnecting the three cables that go to the heads to see if the problem persists
-Is this with the DBX units connected ? are they connected properly ? can you try with them disconnected ? does the problem persists ?

Do some troubleshooting based on those items above and report back. Then we can try some other steps.
 
Odd problem! And one that the manual doesn't cover under the scenario you described. Those OL LEDs would normally only light when the audio signal feeding them is too high or very briefly when the machine is powered up or down. So if the vu meters are not also pegged, then it's not an audio signal issue and something more akin to a short of some sort. But if you're not a technician, your next step might be to try and find one to troubleshoot the issue. One thing you might try just before that is to giggle the umbilical cords that connect the amp unit to the transport and the one which connects the meter panel to the amp unit as these cables can some times become flaky due to oxidized connections or bad solder joints. But, if after that, the trouble is still there, you'll probably have to find a local technician.

Let us know what you find from that quick test.

Cheers! :)
 
Thankyou both for your quick responses

i tried all the cables you mentioned, it does have the DBX units and i tried it with them disconnected, the heads are all in there correct sockets. i tried it with the meter panel disconnected and giggled most cables. So it doesn't look good, would one assume most likely from this problem it could be in the amp unit that has shorted? thanks for your help so far

Regards Bradley
 
Yes, the problem could be somewhere in the amp unit or perhaps even in the power supply, which is inside the transport unit. But either way, it sounds like a trip to the repair shop is required here. Sorry.

Cheers! :)
 
I think 7he Ghost of FM might’ve hit the nail on the head when he mentioned “perhaps even in the power supply.” For you see, my Tascam ms16 has the EXACT SAME PROBLEM so I took the power supply out (in the back of the transport unit remove the screws on that black fins thing and carefully lift it out being careful not to lift out ribbon cables) - but without a print I had to pray and that’s when I saw some numbers on the pc board: -15V, +15V, G, 24V. So I got my voltmeter and found no -15V. Again without a print but still having the Manuel, I traced the -15 volt supply from the fuses to the power supply pc board and found after R2 (printed on the board) the junction of R2and C6
are shorted to ground. On mine, the cap C6 is shorted.
 
…and I don’t know how that cap got shorted.
Resistor R2 reads 33K - which doesn’t seem right: resistor R1 is 33 too but in OHMS not KILO ohms. I don’t know how I missed the fact that R1 burned. Hence the high ohm reading But yeah, I cannot read all the color code on it but it looks like brown on one end and black on the other end. Maybe it’s 100 ohms.(??)
 
Suggestion #1 for you: stop guessing and download the copy of the service manual with the schematics that’s floating around the interwebs. There’s no gain in making guesses. Was the power supply isolated when you tested the outputs or connected to the rest of the system? If you have visibly failed components and power rail that is apparently down then for starters your power supply needs repaired, and then beyond that there’s still the possibility something else caused the power supply to fail. Do you have a local tech? Issues like this are becoming more common with the vintage and class of equipment and are increasingly difficult to sort out over online forums and require in-person assessment.
 
You stated “R1 burned.” Do you mean R2 burned? R1 and R2 are series input/dropping resistors. They are flameproof rated because, in this application they serve as potential protection as something of a fusible link in the event of a fault. It is not uncommon for these to get darkened and discolored because they get hot…their current rating is selected within a close margin to the normal operating load of the supply so they work hard in normal operation, get hot and discolor with age. Is R2 like scorched burned? Pictures would help. So R2 is a series dropping resistor to the M5230 regulator IC U1 pin 4, the input of the -15V power rail path through the regulator. C6 is a secondary filter cap. I’m more accustomed to electrolytic caps failing in an open state. Tantalum caps often fail in a dead short. So, bottom line is who knows how or why but if you have a short from R2 to ground through C6, that sucker is dead, and if R2 is 33K it’s dead too…the question is why and we don’t know that. Again, maybe C6 spontaneously failed causing an over-current condition for R2 and it did its job and acted as a fusible link. OR something failed further along in the system causing the over-current condition. You can start by replacing R2 and C6 (and consider recapping the entire power supply if there’s a chance C6 spontaneously failed…that may be just the beginning), make sure you use a metal film flameproof part for R2, isolate the power supply, power it back up and check the power rail outputs (all of them) for correct voltage and also for AC ripple using an oscilloscope. If all looks good, then apply load (reconnect the power supply to the rest of the system) and conduct the same checks. If all is good, all is “good”…if not, like if the voltages go out of spec or you get ripple then there is still a problem or problems to sort out either at the supply or in the system or both. If R2 and C6 or other components fail again then there are problems downstream of those components causing an over-current condition.
 
bradley1023 said:
Hello Fellow members of HomeRecording
I am new to your forums but i know there are some very knowledgeable people here as i have read many helpful conversations when i first obtained my MS-16. Now to start with i would like to inform all that i don't use this machine for composition. i bought it as i just love the sound of tape and for my interest in historic machinery, i would prefer to have an older machine so if anyone in the Brisbane area Australia is interested in selling i might just have an interest. Anyway to my point of posting, i booted it up the other day to give her a run and noticed all the peak lights on all 16 meters came on and stayed on, with this no sign of sound will come out of the machine. that includes playing a tape and running an input straight through the amp. Everything else seems to operate as it should. Hoping someone here might know if the peak lights are a sign of some description telling the user a certain fault, sadly i haven't been able to obtain a manual for it, so sorry if this information is in there. thankyou for your time

Kind Regards
Bradley Fechner
Click to expand...
I think 7he Ghost of FM might’ve hit the nail on the head when he mentioned “perhaps even in the power supply.” For you see, my Tascam ms16 has the EXACT SAME PROBLEM so I took the power supply out (in the back of the transport unit remove the screws on that black fins thing and carefully lift it out being careful not to lift out ribbon cables) - but without a print I had to pray and that’s when I saw some numbers on the pc board: -15V, +15V, G, 24V. So I got my voltmeter and found no -15V. Again without a print but still having the Manuel, I traced the -15 volt supply from the fuses to the power supply pc board and found after R2 (printed on the board) the junction of R2and C6
are shorted to ground. On mine, the cap C6 is shorted.
 
sweetbeats said:
You stated “R1 burned.” Do you mean R2 burned? R1 and R2 are series input/dropping resistors. They are flameproof rated because, in this application they serve as potential protection as something of a fusible link in the event of a fault. It is not uncommon for these to get darkened and discolored because they get hot…their current rating is selected within a close margin to the normal operating load of the supply so they work hard in normal operation, get hot and discolor with age. Is R2 like scorched burned? Pictures would help. So R2 is a series dropping resistor to the M5230 regulator IC U1 pin 4, the input of the -15V power rail path through the regulator. C6 is a secondary filter cap. I’m more accustomed to electrolytic caps failing in an open state. Tantalum caps often fail in a dead short. So, bottom line is who knows how or why but if you have a short from R2 to ground through C6, that sucker is dead, and if R2 is 33K it’s dead too…the question is why and we don’t know that. Again, maybe C6 spontaneously failed causing an over-current condition for R2 and it did its job and acted as a fusible link. OR something failed further along in the system causing the over-current condition. You can start by replacing R2 and C6 (and consider recapping the entire power supply if there’s a chance C6 spontaneously failed…that may be just the beginning), make sure you use a metal film flameproof part for R2, isolate the power supply, power it back up and check the power rail outputs (all of them) for correct voltage and also for AC ripple using an oscilloscope. If all looks good, then apply load (reconnect the power supply to the rest of the system) and conduct the same checks. If all is good, all is “good”…if not, like if the voltages go out of spec or you get ripple then there is still a problem or problems to sort out either at the supply or in the system or both. If R2 and C6 or other components fail again then there are problems downstream of those components causing an over-current condition.
Click to expand...
Thank you sooooo much sweetbeats for Al the info! About R2: after it burned it became 33K. It might had been the same as R1 originally.
Btw…
I downloaded several manuals of the MS-16 all missing the print for the power supply board. There’s a picture of the board but no schematic.
 
AJ Ivan said:
Thank you sooooo much sweetbeats for Al the info! About R2: after it burned it became 33K. It might had been the same as R1 originally.
Btw…
I downloaded several manuals of the MS-16 all missing the print for the power supply board. There’s a picture of the board but no schematics
Click to expand...
I’m telling you it was the same as R1. They are both 33R flameproof resistors. They are the same part one for each side of the dual rail supply.

I think if you don’t have the full Operation-Maintenance manual you should pony up and buy a complete copy. Nobody that owns a vintage tape machine should be without a complete manual whether for yourself or your tech who may or may not have a copy either. I’ve reached out to a good resource on your behalf to check if the version they have which is available as a high-quality PDF download for $17.49USD is a complete version with schematics. Which is a good deal. I’ve used this resource a number of times, always great service, very reasonable prices and good quality. And there’s always the option of reaching out to Teac directly.
 
I don't know that machine at all but my first thought on reading the OPs fault description was "missing a supply rail" "Physic" or what!

Now, this might be heresy to peeps such as the Hon' Sweetbeats but I would not mess about trying to rebuild the discrete regulators a lot of older kit used. If it does not use '78 0r 317 devices, fit 'em! Back in the day a great deal of time and effort was put in to make voltage regulator circuits short circuit proof but unless it was something that cost $1000 and came from the labs at NASA they never were. IC regulators are not quite bombproof but are way better than old discrete circuits.

And, possible bad news? Some op amps get destroyed if they lose one or other supply rail, the NE5532/4 is one such so that might mean even more work. There are simple ways to protect against that.

Dave.
 
sweetbeats said:
I’m telling you it was the same as R1. They are both 33R flameproof resistors. They are the same part one for each side of the dual rail supply.

I think if you don’t have the full Operation-Maintenance manual you should pony up and buy a complete copy. Nobody that owns a vintage tape machine should be without a complete manual whether for yourself or your tech who may or may not have a copy either. I’ve reached out to a good resource on your behalf to check if the version they have which is available as a high-quality PDF download for $17.49USD is a complete version with schematics. Which is a good deal. I’ve used this resource a number of times, always great service, very reasonable prices and good quality. And there’s always the option of reaching out to Teac directly.
Click to expand...
Thank you. I’ll do that. Perhaps reach out directly to Teac.
 
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