M-90 tape deck issues, advice needed.

[bantytfv]

I just rebelted the deck and it played for about 10 minutes, got progressively slower and stopped with the tape stuck with the heads in the up position. Re-applying power to it a few times has not worked either - the solenoid will click lightly and either the pause or record or both lights will come on. When the deck was playing it would not play while in stereo mode on the left speaker at all, but worked fine in mono mode on both speakers. Any ideas?

 

[baddboybill]

There are 4 fusible resistors on board which may have overheated and blew. Each one is for major function. 1 for each motor. 1 for solenoid and I can't remember what 4th one is for. Most likely this is cause of motor stopping.

Issue with not playing in stereo mode could be dirty function switch.


Bad Boy Bill

 

[bantytfv]

I figured someone would mention those from reading the other posts. I will have to pull it apart again and check them. This box was really dirty when I got it - I'm surprised it functions at all (only the deck is giving trouble). Is Mousers a good supplier to get the resistors from? It seems like they carry all the right values. Any ideas on why the left speaker has no output in stereo mode? There is also a noticeable hum when in cassette mode that goes away if you touch the playback head will get quieter if you turn the bass down, I have de-magnetized it already.

 

[baddboybill]

Could be bad ground from motor. Also you should clean record bar switch. As I said your function switch may need to be sprayed with deoxit or contact cleaner.


Bad Boy Bill

 

[baddboybill]

Also the resistors are gray and fusible. Not sure of value but it should be in service manual.


Bad Boy Bill

 

[bantytfv]

Function switch has been cleaned with contact cleaner - it works fine on line in and radio.

 

[baddboybill]

Function switch has been cleaned with contact cleaner - it works fine on line in and radio.

Well just because radio and line in are fine the contacts for tape may still be dirty/oxidized or bad contact...Azimuth may need adjustment !!


Bad Boy Bill

 

[=ml=]

Also the resistors are gray and fusible. Not sure of value but it should be in service manual.


Bad Boy Bill

Grab the service manual here if it you don't have it:

http://www.mediafire.com/?rk87s5e8c6ted#2x9qbu2yq322b

Go!

=ml=

 

[bantytfv]

Got it playing again, but it has other problems - the playback speed is all over the place and the capstan motor is very warm to the touch. Sometimes it won't re-engage play without a "jump" by hand to the flywheel. Weak motor?

 

[monchito]

seems like a bad motor speed control going bad ( inside motor)....mouser only has i belive 1 or 2 values of fusible resistors i belive i had to use 2 1 ohm ones to get the 2.2ohms i belive they have the 4.7 ones but that motor looks like you might need to find one soon...

 

[baddboybill]

Got it playing again, but it has other problems - the playback speed is all over the place and the capstan motor is very warm to the touch. Sometimes it won't re-engage play without a "jump" by hand to the flywheel. Weak motor?

You sure belt is not to tight? Since box was very dirty you can try taking motor apart to clean...


Bad Boy Bill

 

[bantytfv]

I don't think it is too tight, I installed a 9.2 medium flat, however it is thicker than the original. It is strange, it will play very fast and then start dragging and vice versa. The deck area wasn't that dirty Re-lubed also. It acts like it doesn't have enough torque to take off - have to jump the flywheel by hand for it to reset and play. It drags worse the farther you go into the tape from the start of it. Thanks for the help Bill.

 

[baddboybill]

Check your pinch roller to make sure it's soft enough. How is FF and Rew? Usually when the speed control is bad it's off all the time with no adjustment. I do have a 2nd deck parts unit as well but at this point it's useless without knowing actual problem. :-(


Bad Boy Bill

 

[baddboybill]

Oh and make sure belt because of being wider isn't rubbing on anything. That will cause problems too.


Bad Boy Bill

 

[bantytfv]

Pinch roller appears to be fine, not hard or glazed, the motors were actually clean outside. The belt isn't rubbing, it isn't wider: it is thicker. It may have more resistance as it is thicker and not as limber as the old belt, it's designation was FBM. FF gets slower as it advances through the tape slowing to a crawl, sometimes stopping, RR is a little better, will get way slower at times as well. Adjusting the speed makes no difference, it will still start dragging after a minute or so. Sometimes it will play 3-4 minutes at regular speed with only minute speed differences. :annoyed:

 

[baddboybill]

Well seeing this is a dual motor deck, one for play and other for FF/Rew I highly doubt both motors are bad. I would try replacing belts with proper ones and cleaning up tire under plate that rides with small pulley... If you adjusted variable resistor and motor don't change speed then that for sure is bad.


Bad Boy Bill

 

[bantytfv]

Thanks Bill, I'm going to try a little looser belt (9.4) and see what happens when I get time. The variable speed adjustment does work as it should. Thanks for all your help.