Tacho problem

Good morning members, I'm a newbie as you can see, but before I give my reason for asking for help, in the interests og good manners, I'll give a brief resume' of myself.

I am 67 years old and retired in October after 52 years of hard graft in mechanical engineering, I left school aged 15 and went straight into a very heavy engineering apprenticeship at Robt Cort and sons in Reading, Berks and have loved my trade ever since never having been out of work.

However....to my problem...I am the owner of my 13 year old Warco 7x12 mini lathe ref No....004820RB, , the problem is with the tiny little PCB board that controls the digital tachometer, I have now tried 3 times to repar it but to no avail.

Now, after all these years, the only signal I need for the correct speed is my ears and the harmonics, so my plea for help is how do I short out the cable connection to the front control box, the cablle in question has 3 wires plus a shrouded earth wire as in a TV cable...I need to know which wires to join together so as to bypass the now useless PCB.

The wires are colouredred, grey and blue plus the earthing shroud to enable my lathe to run again, I am no electronics techie but hopefully someone out there can help me please.

Regards.

Rich from Reading.

I have no knowledge to help you but welcome along to the forum. Someone will sure to have an answer for you soon.

Hi Rich, welcome to the forum.

Can you post a photo of the lathe and board please. How to described here.

The tachometer on most lathes is just a display and can be disconnected or ignored - it shouldn't stop the motor and speed-control from working.

Except a few lathes - like my Warco Mini-lathe - use tachometer data to set and regulate the motor speed. If this fails, the motor won't run. (I sold it ages ago so can't go into detail.)

First step is to identify exactly what you have.

Worth trying if not done already is to make sure the sensor is OK. The shrouded lead probably connects to a sensor pointing at the outer end of the spindle at the banjo-end of the headstock. Mine was a red LED that bounced light off the spindle and on to an adjacent detector. My present lathe detects a small super-magnet set into spindle. Both systems need to be clean, and it's not difficult to dislodge the magnet whilst cleaning if you don't know it's there! Also important that the sensors are aimed correctly at the spindle and secure. With luck the problem is just dirt, looseness or a dislodged magnet at the sensor. Mechanical, not electronic.

If the magnet has moved, it will probably be nearby! They look like a small pill, and mine fits into a shallow recess - not obvious. Important to get magnets the right way round. If the tacho doesn't work try flipping the magnet over.

Dave

Thanks for replying dave but I just want to do away with the tacho altogether, it is a nuisance and I don't need it, all I need is guidance on how to bypass the damkn thing as I have works to get on with, anyway, thanks for you suggestion but there is no magnet involved.

PS...the PCB is toast and no longer manufactured.

Edited By Rich Kellow 1 on 04/01/2021 11:24:17

Hi Rich, from a practical point of view can't you just cut the wire[s] going to the tacho, fit a blanking plate & the job is done?

Tony

Is the lathe motor running or not? If the lathe runs, I'd leave the tacho alone. If it ain't bust don't fix it, especially if the wiring isn't understood.

On one type of mini-lathe, the tacho is just a display and can be disconnected simply by cutting the wires. Easy to do and a common arrangement. Are you sure this is what you have?

On another variant, the tacho is essential - you can't bypass it and expect the motor to work. Difficult and getting it wrong could end in tears. £££

I don't like guessing!

Dave