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Bridgeport 6f powerfeed repair

sawjam

Plastic
Joined
Oct 23, 2012
Location
New Zealand
Hi

I've been lurking for a while, so thought I'd reach out and ask for some advice, I've a Bridgeport Mill with 6f power feeds which have never worked since I bought the machine. I've decided to investigate why, It's a hobby shop not production so dont care about time just want to investigate. The electronics are Erskine (UK Bridgeport) cant find any reliable circuit diagram so I'm tracing out the circuit to see if I can understand it.

This is my investigation to date, not to productive!

Misadventure bridgeport powerfeed - YouTube

The 5 amp fuse wasn't such a great idea! I guess it's reaction time was too slow compared to a thermal switch.

I've since stripped the motor appart and apart from general bushes dust and a bit of grime looks resonable. I've checked the field resistance and its about 280Ohms each side, dont know if this is good or bad but have assumed as both sides are the same it's probably good?

I seem to have come to the conclusion I can't test the motor armature unless I can power the motor would this be correct?

If any body can suggest a path of investigation I would appreciate it, or a possible cause to the problem.

Thanks
 
Hi Sawjam,

I was in a similar situation. A few weeks ago I purchased a Bridgeport with a ERSKINE power feed controller that was dead. It turns out two of the small gold FRAKO electrolytic caps had failed. One had 5 ohms across it and another had 150 ohms. Replaced them both and has been working well since.

In the process I managed to weld the microswitches closed in the handle which needed to be replaced.
Might be worth looking at these too. Apparently it is not uncommon for these to fail.

My thermal switch was working. I do like the way you let the smoke out though. ;)

Paul.
 
Hi Sawjam,

It turns out two of the small gold FRAKO electrolytic caps had failed. One had 5 ohms across it and another had 150 ohms.

Paul.


Hi Paul

thanks for the response, just one question how did you measure the resistance of the capacitors? Were they in circuit?

A little smoke always makes things more interesting!
 
I don't know how close the UK versions of the 6F are to the US units, but I have some saved info about converting them over to an off the shelf DC power supply. The cost is about $75 US.

Also, the BP manual that I have for my mill has the circuit diagram for the US 6F feed board.

If any of this will help, I'll send it to you.

Mike
 
Yeah, Measured them in circuit. They didn't show any signs of physical damage or distortion but they were the problem. One was dragging the analog signal from the pot down to ground thus stopping the unit. Yours may have the opposite going on somewhere.

I couldn't figure this out initially, but one of the avionics engineers at work sorted it for me. It all made perfect sense when he pointed it out.

He said he would be very sus about any electrolytic that measures less than 5K in circuit.
 
I don't know how close the UK versions of the 6F are to the US units, but I have some saved info about converting them over to an off the shelf DC power supply. The cost is about $75 US.

Also, the BP manual that I have for my mill has the circuit diagram for the US 6F feed board.

If any of this will help, I'll send it to you.

Mike

Hi Mike

Thanks for the offer, I've managed to source the manuals and US wiring, it's different to the unit in my machine, If I can't get it working I might ask for the conversion docs:D
For the moment I'll keep persevering, mainly because I can :nutter:
Regards

Paul
 
Could I get a copy of the circuit diagram of the feed board? [email protected]




I don't know how close the UK versions of the 6F are to the US units, but I have some saved info about converting them over to an off the shelf DC power supply. The cost is about $75 US.

Also, the BP manual that I have for my mill has the circuit diagram for the US 6F feed board.

If any of this will help, I'll send it to you.

Mike
 
Could I get a copy of the circuit for the feed board US? Thanks [email protected]


Hi Mike

Thanks for the offer, I've managed to source the manuals and US wiring, it's different to the unit in my machine, If I can't get it working I might ask for the conversion docs:D
For the moment I'll keep persevering, mainly because I can :nutter:
Regards

Paul
 
So current update.

Started desoldering capacitors as in circuit tests were very inconclusive, main problem with an old circuit board was delamination of traces when desoldering and crushing of ceramic capacitors!! Long and short no capacitor issues except the ones I created!

I then reverse engineered the wiring and found the issue lay on the AC to DC power side to the armiture of the motor, 1 of the thyristors was open circuit when tested, original was CR8-401C, I've sourced the closet thyristor I can from RS TIC126D which is on its way so I'll keep you posted if it works!
 
sawjam,

There are numerous very good threads here on power feed rebuilds. If you search you should hit paydirt. I need to follow in your footsteps so I will be rootin' for ya...

I remember reading a very intriguing thread in which a guy disassembled the boards then sprayed them down with simple green, rinsed them off with clean clear (possibly distilled - I cannot remember) water, let them air dry, re-installed 'em, and like magic was operational again. So you might even try the search terms "bridgeport power feed simple green".

Vernon
 








 
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