Replacing spindle drive unit on green screen LB15

[WC56]

Hi, several years ago I had an issue with the SDU on my old Okuma LB15. The problem was fixed by replacing the encoder on the rear of the spindle motor. Unfortunately it seems to have failed again. I have sourced a complete spindle motor and replacement SDU from the same model of machine with the idea of swapping parts over. Both components have been in storage for several year and the seller recommended using a variac transformer to bring the voltage up slowly over a period of time. Apparently it can extent the life of the capacitors and reduce the chances of them blowing up. Has anyone heard of this before? Thanks

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[Algirdas]

Once again, please. What is relation between replacement of encoder and extension of capacitor's life? If the idea is to raise the power voltage up slower than just switching on the power breaker? Do you imagine the cost of realisation and expected effect value?
Isn't it more effective just investigate the data of capacitors ( which are exposed to the risk of blow ) and keep in storage spare set of them for replacement?
are you speaking about capacitors in the Okuma encoder ( low capacity low voltage ) or power capacitors - high voltage high volume?

[WC56]

To add a bit more...I will probably just replace the encoder, but it will need to be tuned to my SDU. Last time my electrican did that he found that one of the pots that sets the sine wave was a bit faulty...hard to get a good signal from. That is why I bought the spare SDU...I couldn't just buy the board.

The sellers comment about using a variac was only if I fitted the complete spare SDU which has been in storage for some time.

I was just wondering if other people have used a variac when fitting old boards, drives etc?

[Algirdas]

The mechanical adjustment plays the key role in order to get the good sine signal . The smaller gap between sensor and timing gear the higher initial sensor signal amplitude. Better run-out of timing gear adjustment ( 2µm is very good, 10µm good, 50µm so-so ) is very important also.
I don't comment the usage of variac without detailed knowledge of it's principle. Theoretically the idea is right. It could be not applicable in practice.