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avatar: Ken B
Ken B
9 posts
Replied to Ken B's post on May 11th, 2020

..doesn't turn on. I was able to trace back from the heater band to the power relay to the transistor array to the CMOS chip to the D6 pin on the Motorola M68000 CPU on the daughter board. The connection is all good. It's just this pin doesn't go high. (Or it could be a problem with the CMOS chip.)

I feel it's probably a problem with a temperature sensor that is preventing the logic to go high, but I don't know where to look for.

A workaround would be a jumper wire from 5V supply (or the signal for the vacuum pump) to the input pin of the transistor array so that the heater band is always on, but I am not sure if that would cause another problem.

I would appreciate any insight into this problem. Thank you.

avatar: Ken B
Ken B
9 posts
Replied to Ken B's post on May 15th, 2020

I figured that there was nothing wrong with the heater band. It's just that it doesn't turn on right away. It only kicks in after a while (like 5 minutes) into a run.

avatar: dpkleessr
dpkleessr
1126 posts
Replied to Ken B's post on June 3rd, 2020

The diffusion pump does not turn on until a minimum vacuum is achieved at which point the drive will accelerate beyond 3000 RPM.

avatar: Ken B
Ken B
9 posts
Replied to dpkleessr's post on June 3rd, 2020

Thanks, Don.

After replacing vacuum pump oil, diffusion pump oil, vacuum hose, chamber door O-ring, and diffusion pump O-ring, I'm still gettin DIAG 41. I feel the diffusion pump is not working properly.

I get about 200 V instead of 240 V for the diffusion pump. Is this normal?

I appreciate any insights into this. Thank you.

Ken

avatar: dpkleessr
dpkleessr
1126 posts
Replied to Ken B's post on June 3rd, 2020

It has been over 7 years since I retired so I'm getting a little sketchy on a lot of this but typically the heater gets turned on thru a solid state relay and they have been known to fail.  Not sure that I can even find any of my prints any more about that.  Also, unless your centrifuge is actually running on 240 volts, you are more than likely only going to see around 208 VAC so you may not really be having a problem with that 200V reading.  You may actually be having a problem with the vacuum sensor itself or its calibration which can cause this problem.  How far down does the vacuum actually go and what is the reading at around 20 minutes into the run as that is the trigger point for a slow vacuum diagnostic?  One question as to your replacing of the vacuum hose, did you apply some vacuum grease to the inside of the hose on each end where it connects to the fore pump and the diffusion pump?  Also, was the vacuum hose long enough such that it was able to go up for at least a couple of inches before the bend towards the other device?  I had issues where if you made the bend right at the top of either pump it may not seal as well as it should and a light coating of the vacuum grease inside both ends of the hose is a must.