Denford Software & Machines

I have a VMC 1300 with a melted tachogenerator on the SEM motor. (MT30U4-36)
Is it an easy job to run it in AVF mode?
I am a bit disappointed the thing only lasted 2 years light duty before blowing up. The machine was new in 2009 but not used until i bought it 2013.

Hi Jim,

Switch 4 on the Sprint 1200 spindle drive swaps between Tacho & AVF but you would need to adjust the MAX SPEED pot to suit. This would involve using a tachometer to read the actual spindle speed. It would also be worth turning the IR COMP on a quarter of a turn.

hi Martin,
Thanks for the advise, finally got to tackle the job today.

on spindle motor- disconnected tacho wires & parts.

changed 10A fuse feeding sprint board.

on sprint 1200 board;
Switch 4 to on.
turned IR comp 1/4 turn clockwise.

called for spindle start, & it runs
But slow.
so on sprint board turned max speed pot up & up eventually to max.
now actual speed is about half called for speed. ( ask for 4000 , get 1600 rpm)
spindle over ride knob works & is set at normal.

is there another pot to tweak somewhere to match theoretical & actual speed ?

Yes. You will need to change switch 1 & 2 also. With the TAC fitted switch 1 should be on & 2 off(24-50 volts). Change them to 1 off & 2 on(45-100volts) You may want to turn the max speed down then set the spindle to run at 4000rpm & wind it up.

hello,
Thanks, switches 1 & 2 now set for 50 - 100v, to get 2000 rpm at spindle requires indicted 2800. almost there!
tomorrow i will select the 100- 200v setting.

Today I put switch 1 & 2 to on & set max speed pot to low.
on manual controls; start spindle at 2000 rpm, adjusted pot till spindle reached 2000 rpm, pot about half way.
GREAT! all working again.
Thanks very much for your help.
cheers,
jim