Conn ST-11 kinda works?

[UnluckyFett]

Got a deal on a Conn ST-11 for parts/not working. It turns on but the motor wont spin without a little help. Im not really sure with this schem but does the motor have a starting cap? I see an electrolytic cap on the motor but i really dont know. any ideas?

next is figuring out the calibration.....

Thanks

[Enzo]

Aren't there two caps on the motor? I'd replace them both.

Calibration? Nothing to figure out. Set the function switch to calibrate, turn the cents knob to get a stable pattern, you are done.


Are your neon lamps good and bright, or are they turning black inside. They blacken with age, and now is a good time to change them if so.

[UnluckyFett]

Thanks for the response. The neon lamps are blacking so I will have to do that. The problem with calibration is the cents knob doesn't effect the pattern, but the cents knob does effect the pattern on normal. I'll have to play with it more to figure it out.

[g1]

I had a Conn with the same symptom, I was sure it was a cap also. Turned out to be one of the chips, I'm not sure if it was an ST-11 or not.
I was lucky enough that someone else had the same model and allowed me to borrow it so I could do some parts swaps. The IC was obsolete or real expensive, I still have the unit somewhere in case I come across the chip sometime.

[Mark Black]

Just FYI on the chips used in that unit: The manual shows the generic part numbers for the numbers used on the schematic. 72181-1 = 74121 (TTL monostable multivibrator) and 72185-1 = 7476 (TTL dual J-K flip flop).

Looks like these guys have them both for reasonable (for obsolete) prices:
7476: MAJOR BRANDS: ICs & Semiconductors
Jameco Electronics - Electronic Components Distributor

I've got two ST-11's, and as I recall I found cracked solder joints at some heatsink-mounted transistors on one of them. Seems like both may have had a component dislodged/damaged or solder cracked on the PCB just above the power transformer from the tranny losing a mounting screw & banging around in there. Been a long time since I was inside those...

[UnluckyFett]

Thanks for all the info! I just ordered some ics from that site Thank you so much. I'm going to check all the joints and do the electrolytics. hopefully the caps solve the motor issue.