viceroy 280 synchro electrical issue

[bill]

hi
I have recently purchased this 280 synchro. It has developed this issue of the contactor vibrating on and off. I have identified a small relay on the board that seems to control the main contactor in the control box, that seems to be alternating on and off. I have taken its cover off, forced it on and everything works fine but unfortunately it doesn't stay on! I have taken a picture of the label on the control box. I have had a look on the forum but I have not been able to find the right wiring diagram for my lathe so I wonder if anyone is able to provide one or help with this problem.

thanks in advance
Bill

[Andy B]

Hi Bill,

I'm sure we have those wiring diagrams somewhere, as I helped fix a similar machine which had a failed contactor coil.
I'll see if I can find them later.

Andy

[Pete.]

Has the lathe been converted to run on single phase? If it has, the voltage is not enough to hold the contactors in properly. I had to modify mine to work on 240v.

[bill]

Hi Guys thanks for geting back to me.

No, the machine is on 3 phase. I have now taken the control board out. The markings on it are : PC0469 GSM Ltd 1976

Cheers
bill

[Pete.]

Compare the pull-in coil resistances. If they are the same then check the mechanical interlock is functioning properly and go over all your electrical connections. If the suspect coil has a different resistance to the other two, you could sacrifice the coolant pump coil for the motor contactor.

[Pete.]

I just noticed you said a relay controls the contactors, Mine didn't have any relays the buttons acted directly on the contactors themselves. Here is what I had in my Synchro.

[Andy B]

Wiring diagrams are now posted here:
viewtopic.php?f=50&t=2960&p=21593#p21593

I hope they help you to isolate the problem.
Andy

[bill]

Thanks Andy that's very helpful.
The contractors you picture are not the ones I have an issue with. There is another control box under the bed which has a pcb with 4 relays on it ( one of these is the issue), two transformers and two contractors.

Cheers
Bill

[Pete.]

My machine didn't have any such PCB, and it doesn't seem to be shown in that wiring schematic Andy posted. I wonder if it is part of the optional DC-injection braking system, or perhaps something that was added on later machines, or maybe your lathe was once a combination lathe/mill variety?

The only thing that I found inside my machine was a small vacuum switch type device which was disconnected.

[Andy B]

Thanks Andy that's very helpful.
The contractors you picture are not the ones I have an issue with. There is another control box under the bed which has a pcb with 4 relays on it ( one of these is the issue), two transformers and two contractors.

I'm guessing that this extra board is one of the 2 shown on drawing A3-500016 - either the one at the top marked "Type Z 239 Rotorstop Brake Unit", or the one just below it to the right with the 5A fuse.

The troublesome relay is most likely the one marked 'DC' on the same drawing (roughly in the centre).
On A3-500014, you can see that this relay's contacts are linked to the spindle motor cables (connections 28, 29 & 30), and also to coil 3R on drawing A3-500015.
But it could also be the relay with coil 3R that is faulty.
Hopefully you can do some PCB track tracing to find out what the relay you suspect is connected to...

Pete - yes, the brake gubbins are quite separate to the spindle / direction & coolant controls.

Andy

[Pete.]

Aah yes, that would make sense. It would be worth asking if the DC braking actually ever worked. If the spindle didn't ever seem to be braked then the best thing to do would be to disconnect the braking system altogether. The lathe will work perfectly without it.

[bill]

good morning,

yes it seems to be the DC-injection braking system.

don't know about the DC braking... I will check with out it and see!

the troublesome relay is 4R on drawing a3-500015. It used to be that this was oscillating and sparking and in turn it was oscillating the LC contactor. I took the cover off the relay and forced it on and it stayed on. as long as the power supply was not interrupted it stayed on and it all worked fine. Over night though it no longer stays on. When I force it on, the contactor doesn't seem to pull all the way in as when I press the spindle button it struggles to turn. If I force the contactor close it all works fine.

I think the relay 4R is gone/contacts pitted so I will replace it. Wondering about the thyristor c106D1.. and the LC contactor coil. I also wonder about temporarily bridging over PC3 and PC4 on the PCB (35,14)...as this should make the lathe usable.

Does anyone know what is the purpose of the reset link?

Now that i have the circuit diagram I will do some voltage checks and see what's what!

thanks again
Bill