Just an update. My VM-1000 is still going strong after replacing the signal processing chips seven years ago.
Another VM-1000 on the field went bad after an apparent voltage spike from a failed alternator. Three new chips, along with a new battery for good measure, and it appears to be working well.
Some notes on the chips.
The ones for mine, which is a later unit with the sub-D connector uses
DG407DJ, DJZ, or DJ-E3 chips. It appears that all of these chips are obsolete with no good replacement. I did find, and order, some DG407DJ's today so that I have some spares. I found them at the following:
https://rcfreelance.com/p/ic/218094/dg407dj/
No minimum quantity required, good pricing, low shipping cost. Other places have these or newer versions such as the DJ-E3 but you have to order 50 or 100 of them.
My friends VM-1000 that went bad recently was the older style with the wire terminals. Fortunately it is the type with the pin and socket board connectors so it was easy to separate the boards. The chips for this version are also obsolete but seem to be much easier to find. We found some Harris CD4097BE chips (the same as what was in the board) for $1.80 a piece plus tax and shipping. Watch out for used chips, I see some adds for them. Especially shipping from China.
One note on this particular unit. We found many of the wire terminal solder connections fractured when we inspected the board. They were easy to re-solder but this likely would have caused problems. This box was out a about 7 years ago for chip and battery replacement. it was working fine until the alternator problem. 7 years ago there were only three cracked solder connections. Now most of them showed signed of stress. He is going to see about supporting the wiring bundles better to reduce stress on the terminals. It takes a high power magnifying glass, or better yet, a loupe or stereo microscope to see most of the cracks.
The batteries, M48T02-150PC1 or M48T02-70PC1, seem to be readily available from suppliers such as DigiKey, etc. As Reggie suggests I would replace them every 10 years. If I had my box out and open at 7 or 8 years for some reason I would replace the battery. Remember to write down the engine time before replacing the battery as you will have to reprogram the time in the VM-1000. There is a thread on how to do this somewhere on VAF.
Remember to use proper static control measures when working on these boxes/boards. Having the correct tools for removing, and especially for inserting, the chips is very important.
I hope this helps,
John
P.S. I believe Reggie is still working to get his new shop set up so he can once again support these units.