Two Tascam 1/2" transport issues (TSR 8 and 58)

B

bleachboy

Member
Hi everybody,

I'm looking to have a little bit of help regarding two (opposite!) transport issues on two Tascam R2Rs, if you'd be so kind !

TSR 8: I have gotten inside that machine quite a lot now, and have used it without major issues for a couple of years now. The main thing is that I can't stop the tape when it's in "fast" REWIND mode. In other words, when I want the tape to rewind to a precise previous location (whether LOC 1/2 or RTZ), it does it without problem as long as that location isn't too "far behind" the location where the tape is. It rewinds moderately fast and stops smoothly where I want it to. If I have to do a "medium" REWIND, meaning going from one point to another location a little farther back on the tape, the STOP switch works but it takes a lot of time for the reels to slow down and stop. Sometimes it even rewinds way too much, then stops and fast forwards to the intended LOC point.
However, if I'm at the end of the tape and I either want to return to zero or rewind at some location at the beginning of the tape, REWIND starts moderately fast and gradually gains speed (which is normal, I think), but when it's in fast REWIND, it can't be stopped and it's a bit frightening ! The STOP/PLAY/REW/FF switches have no effect at all. The only way I can stop the tape from rolling is by turning the TSR 8 off...
I have read somewhere that there is a R106 screw on the board that I can use to adjust the REWIND tension. Am I on the right track there ? Any advice on how to do this ? I have never ever touched anything on that board and it does frighten me a bit !

58: The issues I have with this deck are quite the opposite. REWIND is very slow. When the takeup reel is full and I hit REWIND, it starts fine (fast), but the fuller the reel on the left gets, the slower the REWIND is. It is as if the weight of the tape itself puts too much force on the motor and therefore it doesn't have enough torque, or something like that. I have however never opened that beast of a machine, I just bought it !

I will add that both of these issues occur when using a fresh SM911 tape, with both tape paths thoroughly cleaned.

Thanks a lot in advance !


Louis
 
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Adjustments in these units can not be done abstractly but must be done by the book. Slowing tape wind is a condition of sticky tape but also can be cause by adjustments by amateurs without the Tentelometer gauge.
 
Hi,

After spending some time yesterday tweaking the R106 trim pot on the main control board, I finally managed to make the TSR 8 stop when in REWIND mode. I'll start it up again today to see if it still works. The unit did stop but not immediately, it took a couple of seconds. I did check the brake tension as per the manual, but I don't think it's enough. Otherwise, I think I might be done with this one.
As per the 58, I understand that when I bought it it was loaded with the dreaded Ampex 456 tape, which was definitely shedding all over the place, it didn't even play at all. After a good cleaning, and putting on a brand new reel of SM911 tape, there were no more problems in PLAY mode, but the slowing REWIND was still there. I have never opened this beast but I'm pretty sure that it's way more intricate than the TSR 8...
 
I have had unit that other Technicians worked on and there were NOT in good shape. The wind at the end of this little machine using AC reel motors also slowed with good tape on it. Some think they know how to adjust machines but the results they get and do not even check really tell the abilities they have- they are often far over sold. Brakes can still be rubbing even when they are off. You need to know how to adjust them correctly to meet all the requirements. We at Teac never used a fish scale to measure brake torque with a rope in all the years I was there.
 
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Power supplies due to electrolytic caps decay over time. I have seen Otari MX5050 21V supplies at 17Vdc. The Tascam product was still made for profit and they may have used caps that with time do not have what is needed to get the job done. I have seen some units that the the filter caps on secondary supplies were very small and I improved the performance by a much larger caps and then also increasing the size of the diode to 3 amps. Teac does this too through bulletins as in the X1000R D44. When I saw so much ripple on a DC line for this secondary voltage, I said that can not be right and then I found a 220uFd cap filtering- I upgraded it on board to 470uFd and then on the control board there is a ghost 1500uFd cap that helps all of it very nicely. The deck worked much better after I modified it. They usually do such as my dual speed and direction capstan board mod and X-7 wind speed mod. it is possible to make some of these units work better that they were originally made. Of the 52's I have worked on they were made pretty well but age takes it toll on everything. I think I own two or three of them.
 
It is hard to give advice when people go adjusting pots away from the procedure that is written in the book. You might get it to work some of the way but the test is the specs of the fast wind in each direction per the manual. On a X1000R I worked on the wind speeds for 1800 feet are to finish inside of 100 second and they do because I check this.
Many wind, fast speed torque adjustment are done after correct tension is has at tension arms using the Tentelometer. Like I tell customers about local shops which are usually petty bad, is if they do not have a Tentelometer gauge then don't leave the deck there as they will only goof it up.
The DC motor when a lot of hours are on them can get commutators that get packed with carbon causing a shunt across the field. This needs to be cleaned out as it does not belong there. The problem is the DC reel motors have to come out to do this and then the reel position and brake adjustments can be done after this. If a unit has dynamic breaking as these two do then overshoot is caused by the opposite motor not developing enough torque to over come the inertia of the reel. The Brakes on these deck don't do breaking as I remember them. If they do like in the Tascam 38, then maybe the pad are due to be changed as the felt is flattened and worn down- it is not always an adjustment but parts do need to be changed after so many years. Power supply voltage lower due to ages filter caps might also be added to the motor issue.
 
bleachboy said:
After spending some time yesterday tweaking the R106 trim pot on the main control board, I finally managed to make the TSR 8 stop when in REWIND mode. I'll start it up again today to see if it still works. The unit did stop but not immediately, it took a couple of seconds. I did check the brake tension as per the manual, but I don't think it's enough.
Click to expand...
These are not units that you 'wing' it and hope for the best.
 
This can be the result from adjusting a pot by effect rather than the procedure they give you. Doing the effect method depending on the sensitivity of the trimmer can take a very long time if not not work at all. Hitting that sweet spot will be a task.
 
There are a lot of steps in the setting of tensions. There are opto and springs and all that is associated with the mechanical operation. Those that get into these machines and read stuff on the internet about a problem are maybe only seeing one part of the system. A person can not get these to work correctly without the use of the Tentelometer and proper procedures. Those that wing it are the machines that come to me with broken trimmers and other damage. Servo tension decks can not have winging it repairs and not without the Tentelometer. When the rewind goes past a stop point and then goes into fast to reach it that is called searching. The reason it went too far is because the tensions are off and no these do not always find the cue point exactly as the tape slips on the tachometer wheel. To get exact location positioning you need to use SMPTE code on a tape.
 
On the 58, there are DC reel motors that have brushes and a commutator. This with a lot of use fills with carbon causing a shunt across the fields of the motor. The solution is to take the motor out and apart and clean the carbon out of the commutator gaps. After that then regular motor torque will result if the adjustments are right. Bad adjustments to tension as in winging it will give these kinds of results of bad winds.
 
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