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MP-1 3TM not powering on

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jaykay73:
Hi all, been enjoying a 3TM for a long while. Hadn't powered it up for about a year and when I did all the parameters had been reset to zero. Played it a while then it became non-responsive. Powered it off and haven't been able to get it to start up again.

Have been through some of the troubleshooting guides on this site. Discovered C131 had 17 volts across it, which is also providing 17 volts to the tube heaters. Too much!!!

Wondering if there is a simple problem in the power supply I could fix myself.

Thanks,

JK

MarshallJMP:
17 volt ??? are you sure?

There is a 6 pin red connector going to the mainboard comming from the transformer. You will see 2 green and one blue wire on it. Take a meter, put it on AC volt and measure between the blue and green wire. (green and blue and then the other green and blue) and let me know.

jaykay73:
Thanks,

Between pins 5&6 I get 28.4VAC

Between pins 4&6 and between 4&5 I get 14VAC

I have a machinator transformer with 117V written on it. The voltage from my wall socket is 125.6V

JK

MarshallJMP:
Ok your line voltage is quite high which result in high secondary voltages. Did you measure the 17V with the tubes in the MP-1?

Next thing to check is the 5V rail. You can measure this on the eprom (the chip with the white sticker). Measure between pin 14 and 28.
Here you can find the pinlayout  https://www.futurlec.com/Memory/27C128-200.shtml

jaykay73:
I measured 17VDC across C131 with the three tubes OUT.

My 5V rail check gave me 4.95VDC. Both +15 and -15 rails both also are giving correct voltage.

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