MYJG-100W Pot trimming question

I’ve got a MYJG-100W PSU together with the external ammeter that can control the PSU’s output and is connected to the PSU via an ethernet cable.
According to the RECI website my W2 has a maximum recommended current of 28mA and a recommended current of 24mA. At the moment I’m controlling that using the external ammeter but the control knob doesn’t need to be turned fully to reach 24mA. I’m concerned that it might get knocked accidently and ramp up the output without me knowing so it is presently held in position by the high tech solution of BluTack.
What I would like to know, and maybe someone else has done this… Can the internal POT on the side of the PSU itself be used to set a maximum output, or would adjusting the knob on the external ammeter still alter the output?
What I’d ideally like is for the maximum output to be 24mA when the control knob on this ammeter is turned to it’s full extent. I can test this myself of course but my PSU is located at the back of the machine and currently inaccessible. Before dragging it out and seeing if I can get this idea to work I just wanted to see if anyone else had had the same sort of idea. Cheers

What control knob? My China Blue has no such ‘knob’ and it’s controlled via the layer power setting.

I have a 50watt tube (advertised) and a 60 watt supply. My tubes maximum current rating is 21mA. When I run my machine at 50% power I get 14mA on the mA meter.

This indicates the supply is giving my tube 28mA when it fires. I used the internal lps adjustment to lower the maximum output at 50% to 10.5mA.

I don’t know how the mA meter you use works, but they all pretty much have to be rms type readings. My digital meter on the lps ‘samples’ and jumps all over the place. It has never read any higher than the mechanical meter I have.

Does this help?


This is what I am referring to… It connects to my PSU and I am able to control the output via that little knob.
I just want to know if the knob overrides the POT in the PSU itself or not. Cheers

I would assume the internal control would dictate the allowed output current.

Again, I don’t know how those actually work. I looked up the lps and I see no place to put or ‘wire’ that meter to the device. A link to that site with the meter might help me answer the question…

How is it wired up?

You should be controlling the ‘power’ via the layer setting, not an external pot.

Using the Ruida console, I’d suggest setting the ‘pot’ at maximum, and do a continuous pulse at 50% power and see what kind of current it’s supplying. 50% should be well within the ‘safe’ operating range of the tube.


Ok, sorry for the delay in replying, have been a little busy.
In the end I decided the best course of action was to pull the machine out and get access to the MYJG-100.
So here’s what I found… The POT on the side overrides the external meter/pot. The MYJG100 has a ammeter built into it so I was able to adjust the output to be capped at 24mA, which is the recommended maximum working amperage for my RECI W2 if you want to prolong the tune life. In doing so I found that the external POT was under reading the output by 1 mA. Not a huge discrepancy but still. I know this because both the built-in ammeter and my analogue needle one where showing 24mA but the external one was showing 23mA.
So now I can still control the mA externally (if needed) but know that it can never be set above the safe power level for my tube.

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