Ontari MX-5050 TAPE reel to reel player - UK Vintage Radio Repair and Restoration Discussion Forum

wazzadj · 4th Sep 2023, 6:54 pm

Hi Guys
I have a Ontari Reel to reel player in my workshop at moment for a radio station
Firstly my apologies for NO Visual imagery its a hard task as i have to take with my phone then send to my email then copy from my computer and upload too you quiet a process but doable if it will help paint the picture and clarify
i have downloaded the service manual from HIfi engine
Problem is the Servo control schematic board module i need is not included with it - MUST be a closely guarded secret as i cant find it anywhere on any service manual only a block wiring diagram
So the RR Presented with the following issues
it came in with a issue with transport not working
found oxidized and corroded micro switches i have replaced the main safety cutoff switch that was corroded terminals with high resistance
then after fixing that found a siezed Capstan motor one of the hall effects magnet had dislodged and got caught in the armature
so after freeing up and regluing and servicing the motor
i managed to get it to spin up on workbench on external supply both directions 180deg and hall effect to response
i have all so found the motor servo board had blown driver transistor and burnt resistor and some caps and heat stress across its tracks so i cleaned and reflowed new track overlays and new solder pads
so i have since replace all the electrolytic and new driver transistors

Now i have a strange fault the Servo control 24vdc fuse keeps blowing when i try to press any transport buttons the transport mechanism has no life at all i can hear the safety relay working and switching on and i cant see a short anywhere obviously i am drawing excessive current from somewhere but cant seem to find it unless i have missed a bad contact on a micro switch but when i press them all they are outputting the 24vdc with no issues
and ground reference is ok
i have all so found the motor servo board had blown driver transistor and burnt resistor and some caps
so i have since replace all the electrolytic and new driver transistors
i have all the correct voltages to the driver transistors for the motor and transport switches according to the schematic wow that's a fun diagram to decipher my brain hurts
i have a suspicion its a bad ground somewhere but i cant see it with my meter or oscilloscope
next idea was to pump a bench supply 12vdc lab supply into the micro switches and see if anything gets warm or excessive current draw i have a visual current control limiter as well as sinewave meter built into it so i can monitor when engaging the transport functions obviously with the servo board disconnected first

so i was hoping 2 big favor's please
1. does anyone have a servo board schematic diagram (not the Block diagram as it is not what i need)
2. has any one worked on one and come across this fault before and if so can you point me in a direction to find this fault please

cheers
Wayne

ms660 · 5th Sep 2023, 12:54 pm

Quote:

Originally Posted by wazzadj

does anyone have a servo board schematic diagram (not the Block diagram as it is not what i need)

Post#24 in the thread linked to below, save the thumbnail image then orientate and zoom to suit, a copy I just did is a useable repro. for troubleshooting.

https://gearspace.com/board/geekzone...int-heart.html

Lawrence.

wazzadj · 14th Sep 2023, 12:48 am

Thankyou Lawrence you're a legend.

It's got me stumped this one. I found a broken hall sensor magnet stuck in the motor cleaned and removed and installed back on but now I have no go
and when I bench test is OK. So I am guessing it's a servo control board issue. I will follow diagram see if I can fix it.

I have found numerous blown components on that servo board which I have now replaced and have drive output back but still no motor control so Iguess more fault finding on the board or motor could be a faulty tach sensor.

Cheers, Wayne.

4th Sep 2023, 6:54 pm	#1
wazzadj Diode Join Date: Jul 2023 Location: Churchill, Victoria, Australia. Posts: 4	Ontari MX-5050 TAPE reel to reel player Hi Guys I have a Ontari Reel to reel player in my workshop at moment for a radio station Firstly my apologies for NO Visual imagery its a hard task as i have to take with my phone then send to my email then copy from my computer and upload too you quiet a process but doable if it will help paint the picture and clarify i have downloaded the service manual from HIfi engine Problem is the Servo control schematic board module i need is not included with it - MUST be a closely guarded secret as i cant find it anywhere on any service manual only a block wiring diagram So the RR Presented with the following issues it came in with a issue with transport not working found oxidized and corroded micro switches i have replaced the main safety cutoff switch that was corroded terminals with high resistance then after fixing that found a siezed Capstan motor one of the hall effects magnet had dislodged and got caught in the armature so after freeing up and regluing and servicing the motor i managed to get it to spin up on workbench on external supply both directions 180deg and hall effect to response i have all so found the motor servo board had blown driver transistor and burnt resistor and some caps and heat stress across its tracks so i cleaned and reflowed new track overlays and new solder pads so i have since replace all the electrolytic and new driver transistors Now i have a strange fault the Servo control 24vdc fuse keeps blowing when i try to press any transport buttons the transport mechanism has no life at all i can hear the safety relay working and switching on and i cant see a short anywhere obviously i am drawing excessive current from somewhere but cant seem to find it unless i have missed a bad contact on a micro switch but when i press them all they are outputting the 24vdc with no issues and ground reference is ok i have all so found the motor servo board had blown driver transistor and burnt resistor and some caps so i have since replace all the electrolytic and new driver transistors i have all the correct voltages to the driver transistors for the motor and transport switches according to the schematic wow that's a fun diagram to decipher my brain hurts i have a suspicion its a bad ground somewhere but i cant see it with my meter or oscilloscope next idea was to pump a bench supply 12vdc lab supply into the micro switches and see if anything gets warm or excessive current draw i have a visual current control limiter as well as sinewave meter built into it so i can monitor when engaging the transport functions obviously with the servo board disconnected first so i was hoping 2 big favor's please 1. does anyone have a servo board schematic diagram (not the Block diagram as it is not what i need) 2. has any one worked on one and come across this fault before and if so can you point me in a direction to find this fault please cheers Wayne

14th Sep 2023, 12:48 am	#3
wazzadj Diode Join Date: Jul 2023 Location: Churchill, Victoria, Australia. Posts: 4	Re: Ontari MX-5050 TAPE reel to reel player Thankyou Lawrence you're a legend. It's got me stumped this one. I found a broken hall sensor magnet stuck in the motor cleaned and removed and installed back on but now I have no go and when I bench test is OK. So I am guessing it's a servo control board issue. I will follow diagram see if I can fix it. I have found numerous blown components on that servo board which I have now replaced and have drive output back but still no motor control so Iguess more fault finding on the board or motor could be a faulty tach sensor. Cheers, Wayne.