Otari MX5050BQII transport control issue...

[Goldenvoice388]

I cleaned up the budget Otari MX5050BQII I drug home, and set about to run a basic series of test. Didn't take me long to encounter a problem.

Play works - stop works - back to play - record seems to work, but...

If I push FF, it just stays running at high speed, and the only way I can figure out to stop it, is to turn the unit off.

Same thing: hit RW, and it will rewind as long as I hold that button down, but if I let it up, it drops into FF - and sticks...

My brain tells me there might be some sort of sticking relay in there somewhere?

Any ideas?? (maybe I'm doing something simple like threading the tape wrong, but it seems pretty straight forward)

Joe

 

[jpmorris]

I cleaned up the budget Otari MX5050BQII I drug home, and set about to run a basic series of test. Didn't take me long to encounter a problem.

I have to applaud your creative use of the word 'drug' there
Anyway, I haven't found full schematics yet, but from the parts manifest I could find, the BQII seems to have a tape control IC and flipflops, so I'm not sure a relay fault is going to have that kind of symptoms.
Assuming it's not something simple (does it still do this if there's no tape threaded and you defeat the switch?)
It sounds like either the IC itself has gone nuts, (IC8 on the control board apparently, don't know what it is or how obtainable) or the inputs to the IC are wrong and it is getting confused.

Now that I think about it, it sounds very much like what the TSR-8 does if the tach roller malfunctions. If you look on page 15 of this:
http://www.otari.com/support/pdf/mx5050bqii.pdf
...towards the bottom, marked #22 there is a toothed sprocket, which appears to be a direction/tach wheel. There's a photosensor next to it.

I would almost bet money that your problem is a problem with that tach wheel or the photosensors monitoring it.