JMP-1 Presets

[rtcook]

I have been working on a JMP-1 that I bought non-functioning. I have made progress with it. Tonight I fired it up and I now have power to everything (+15, -15, +5, 12V), but the HT.

While it was on I checked to see if the buttons worked and they all did. I was comparing the settings to what the manual says each should be and they do not match up. I did a factory reset and that did not help. The version on my chip is V2.01. That is the first version chip as my JMP-1 is an early 1992 Issue 1. The others I have seen have V2.02 chips. Could this be why my presets do not match up with the manual or do I have a bigger problem?

Thanks,

Roger

 

[rtcook]

Found my answer. The presets must be unlocked before you can do a factory reset. Once I unlocked them, the factory reset worked. All presets are like the manual now.

Now, I need to figure out the HT tap voltage issue.

 

[Jon Snell]

Check R86 10R fuseable resistor. ONLY fit a fuseable type or you may have a fire!
You are looking for about 160volts HT from the voltage multiplier.

 

[rtcook]

The 10R fusible resistors R85/R86 are on the 15-0-15 tap, not the HT tap.

Are you meaning 160V DC? That seems low.

 

[Jon Snell]

R86 feeds the voltage pump that produces the 160v DC, using diodes and capacitors to multiply the 15 volts AC and turn it into 160 volts DC or thereabouts. Anything north of 100 volts is fine.
A very simple crude way of getting a high DC voltage from a low AC voltage.
Example attached;

 

[rtcook]

I'm lost. Just where do you see R86 feeding the HT voltage production?