[L98FIERO]

I have an issue with my lathe that we seem to have narrowed down to the master board, and will soon have a replacement. I have backed up the parameters, is there anything else that needs to be backed up before the boards are swapped. I know the plc parameters are not easily accessible, are they on the ROM card and can I loose them? The three daughter boards, the BMU memory, CRT/punch and ROM cards will have to be swapped, will the three large chips in the middle of the board have to swapped as well? Will I have to reload the parameters after swapping the boards on the master? Is there anything that I should watch out for in particular or is this something I should just get a service person in to swap?

[underthetire]

I don't remember having to ever re-load parameters on the early controls with the BMU board. I do believe you need to swap the chips. Later replacement boards for the BMU, yes you do.

[tc429]

we had a ton of 6_B-2 controls, mother board failures were very rare-I bet of the half dozen we changed over the years, 3 or 4 just needed a diode replaced- theres three metal cased relays (for the axis ready I think) and the blocking diodes on one of the relay coils would short out...easy check with a ohm meter...just a FYI to keep in mind for those still running Sixes.

nice thing about bubble memory, never having to reload anything bubble failures were very rare also- more failed in our robots than the sixes for sure. really the only real weak point on the six was the reed relay I/O card relays sticking... every time we'd have a problem, one of first thing to try was strumming a plastic screwdriver handle across the reeds, if the problem went away for a while you knew it was time to swap the relays...

[L98FIERO]

I assume the reed relays are the small metal 'cans' on the board, what symptoms does the sticking cause?
The problem we are having is with the CRT monitor, we get what I can only describe as 'jitter' and the screen is all but unreadable. The CRT, the CRT/puncher board and the CRT power supply have been replaced with no improvement. We even went so far as to exchange the spindle servo board as the jitter seems to correspond to the spindle speed and the spindle tends to 'hunt', particularly when doing peck drilling or grooving with G74/75. The hunting issue is nearly always the time but the CRT problem is intermittent, sometimes there won't be an issue for days and the next time it's there when the machine is started in the morning, otherwise the machine works well. The master board seems to be the only thing left to try.

[memoryman]

The BMU does fail; part of our business is the replacement of defective BMUs.
There are jumpers that have to be replaced, as well as possibly some ram chips (lower right. The large position chips don't have to be touched.