Mazak 20/40B retrofit

Howdy everyone,
We have a 20/40B mazak 1988 model which we have used since new,over the last 2 years we have had trouble with the spindle control, it has blown the w- phase transistor [ i think ive got this correct ] 3 times now.
It has had the power supply replaced with reco one, the main board replaced,
and a couple of other electronic parts, the service guy is very experienced with mazaks and says that so many of these controls give similar trouble and that identifying the exact cause is very difficult.
He suggests that we retrofit a newer control will eventually be the go, but at a cost of at least $15000 i want to be hell sure its necessary ! albeit - its cheaper than changing machine, we are a very small business so we have to be careful what we spend.
Any ideas as to what might be causing the trouble would be appreciated, if you people think a retrofit is the only way to get reliability, then i,ll do it.
Cheers

hybrid IC is damaged, check its type, maybe I can help you

Hi Nastek,
Thanks for reply, i,m not sure what type of hybrid ic is in machine, what i can tell you is that its a freqrol se and the service guy repairs the boards using second hand ic, because mitsubishi wont sell them to anyone.Does any other company make them as aftermarket parts ? Thanks

Are you talking a control retrofit or a spindle drive retrofit?
If just the spindle drive the quote seems high.Have you asked Mits to do a rebuild of your existing drive?It`s not that bad if you can send it to the US to get done and you get a twelve month warranty.

hybrid ic is DK..., ussualy for driving mosfet transistor, there are 6 pcs.

Hi Gridley,
The quote ive got is for new mds spindle drive same as later mazaks [not full retrofit ] as the rest of machine is fine.
Price is now much better as aust dollar is highest its been for many years, $11650 with 12 months warranty. My service guy has said to send old SE drive to mitsubishi japan will cost 8k at least and he,s seen many others go down this path only to have the thing fail again after 3years ! no point repairing old drive if its design is poor, and likely to fail in the future, i think its money well spent now considering this machine is in top condition and never done hard work, plus we bought another machine to take all the electronic spares and spindle and drives etc so we should be keeping the thing running for many years at minimal cost.
Thanks for replys cheers, Mike