Otari MX5050 problem

[nose49]

I just replaced the motor for the pinch roller, now it seems that the mic preamps quit working.  I can get an oscillator tone, but can't get any sound when I go through the the mic in or line in. I checked all the plug in connections (unplugged and plugged back in) on the boards but no luck. The motors are all working fine now just can't get a signal in. Any help? (it work before i replaced the motor. Thanks Mike

[ironbut]

Hi Mike,
Welcome to the forum.
Once thing that you didn't mention was whether the deck will playback a tape that's already recorded.
The record amp/mixer and the playback amp often occupy the same board or at least, share the same power.
My first guess is that that board may not be getting power. Check the fuses first. It could be a bad wire, a solder joint, or a component lead that got manipulated just a little too much when you replaced the motor. Probably the worst case would be a cracked circuit board.
If you go through the different functions of the machine, you might be able to isolate the problem.

BTW, are you sure that it's not passing a signal or is it just the VU's that aren't responding?

[nose49]

Good Morning Steve,
Thanks for the help.  The deck will play a recorded tape. And I have tried all the inputs (line in, mic in). I sincerely appreciate the help. I do have another board (not sure what condition it is in). Thanks Mike

[ironbut]

Hey Mike,

I think I'd start with working all the switches that route the signal to the record electronics. The record mode, monitor selector, etc. It's a little unlikely but so easy that it can't hurt.
Past that, I'd start with the input jacks (examine them to be sure they look OK)and check continuity to the circuit board. From the circuit board to the record head, try and check that visually since the voltage applied by a meter will magnetize the head (which you can demag after so it's not the end of the world if you do).
There should be a wire with a multipin connector leading from that board to the power supply. Pull that connector at the record board and check to see if there is voltage present.
While you're there, jiggle that board around a little. It could be just an iffy circuit board edge connector that's a little off center.

[nose49]

Thanks again Steve,
I have been using a shure sm57 to try to input signal.  The sure is wired pin#2 hot.  Could this be the problem? I think I seen where the Otari is pin #3 hot. Hopefully this is it. Any advice is appreciated. I noticed when I tap on the sm57 some signal is shown on the vu meters, I also tried the same with an sm58 mic and got the same results.
Respectfully,
Mike

[ironbut]

Hey Mike,
You're right about the different pin configuration but I wouldn't think that would make a drastic difference.
If I were you, I'd use something like a CD player on the line inputs to do your testing. The microphone impedance could be an issue so using something line in would keep that from skewing your results.

[nose49]

Thanks Steve,
I might be getting closer. I took the mic and ran it through a preamp and am now getting a good signal.  What's your thoughts?
Respectfully,
Mike

[nose49]

Is there a built in preamp?
Thanks
Mike

[ironbut]

The Otari does have mic preamps built in but those one size fits all preamps are alway kinda iffy.
You should have a mic attenuation switch on your machine. Try the different setting on that.
 Since you are getting a good signal in, I don't think any thing's broken. You probably just need to fool around with different settings, maybe make yourself some adapter cables (switch pins 2>3) try a different mic or use an outboard mic pre (probably preferable).

[nose49]

I just wanted to thank you for all the help. I feel like I got my problem fixed because you took the time to help. I respect you and appreciate the time.
Thanks
Mike