R/E/P > Bruno Putzeys (Designer) - Dave Hecht (Master Tech)

Studer A80 Mark IV Slowing down

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Mikeyod:
Hi guys,
I've got an A80 2 inch 24 track Mark IV and it has begun randomly slowing down.
After about a half hour the problem is gone and it runs fine.
What I have done/checked.
Stabilizer voltages all check out fine.
All motor caps have been replaced.
All motors have been rebuilt by Athan corp. in Jan. 2017
Replaced timer IC on capstan control board
While viewing the 1600 Hz signal on a scope with frequency counter the frequency drops to around
1300-1375 Hz the second I hit the stop button the frequency comes right back up to 1600Hz.
When the freq. drops the tape tensions on both sides remain normal 300 on left 450 on right.
However if I turn the left tape tension sensor manually and lower the tension down to 100 the frequency comes back up to 1600Hz but falls off again as soon as I release it. All voltages on the stabilizer card hold steady when the machine slows down. Like I said after about half hour I can go about my business as usual and it will not slow down.
Any thoughts ? Thanks in advance.

Mike O'Donnell

radardoug:
Have you replaced the Frako caps on the cards in the card frame? They will probably start smoking soon if you haven't! I had an A80 with speed problems, this cured it. But I still have a problem with 30 ips I haven't sorted.

Mikeyod:
Yes, all of those caps have been replaced.
I tried running the machine from cold with the auto-locator unplugged to see if this could help narrow it down but the same result. After half hour it cleared up. I'm assuming something is warming up then functioning properly ?
   Could the LY4 contactor be a cause of this ? Looking at Mouser to see if it is still available.

Mike

radardoug:
Are you running high speed or low speed?  If high speed, check it on low speed.

Mikeyod:
This is a 15/30 i.p.s. machine that I run mainly at 15 but I will try it at 30.
I took the contactor apart, the contacts were very fried. I am cleaning them up to see if it helps.
Meanwhile I ordered a new one if it does help.

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