?I've got a single phase '99 BF6 which has been giving me some trouble lately. I bought the machine used and a pervious owner (now deceased) had made a few modifications inside the electrical cabinet, of course with zero documentation.?

About six weeks ago I was using the table saw and started smelling smoke after the blade had been running for a few minutes. I immediately hit the stop button, which caused the machine to begin buzzing followed by a loud pop (under a second from hitting stop to the bang). I quickly flipped the main power switch off.

Investigating inside of the electrical cabinet showed the pop came from the braking thyristor, which had exploded. When I tried to start the table saw, the motor simply buzzed. The start winding on the motor had cooked the insulation enough to cause a short, so the table saw motor was toast. I was lucky enough to link up with Philip Davidson on here who sent me a replacement motor he had on hand (thanks Philip!).

Even though the table saw motor was toast, the other two motors still started up fine. Braking doesn't work anymore (even though I replaced the thyristor; there must be further damage, though nothing obvious on the board).

I have been doing a ton of shaper work the past month. A few weeks ago I was shaping away when all of a sudden I smelled smoke again. I quickly shut off the main switch and started investigating. My control cabinet has three contractors (two mounted to the board, one on some DIN rail. Under normal operation, the DIN rail contactor controls the start winding: it closes when I press the start button and opens when I release it. In this case the contacts had welded together and the start winding never shut off, which is what was causing the smoke. Fortunately this time I was quick enough to save the motor. I replaced the contactor with a new one and it seemed like I was back in business.

On Friday I had been using the machine on-and-off for a few hours and had just changed setups. I was dialing in my cut (taking a test cut, shutting off, adjusting, testing, etc...). I hit the start button and the spindle started up for half a second and then lost all power. No pops, growls, or buzzing, just a quiet coast down. Now when I try to start the machine there's not a sound. None of the contractors attempt to close.

All of my switches seem to be fine (I can make the yellow shaper reverse light come on, and hitting the stop buttons causes it to turn off momentarily. I also tested the shaper start switch and it functions fine (plus none of the functions work, so I suspect the issue is upstream). I measure ~30VDC across the low voltage contacts of the selector switch when I push the knob in.?

OK so enough with the essay. Here are my questions:

1. I'm struggling to tell what is original and what is the handiwork of the previous owner. Can anybody else with a single-phase BF6 take a few photos of the electrical cabinet? I'm specifically interested in whether there is a third contactor, and how it's actuated (where the A1+ and A2- wires come from).

2. Does this sound like something any of you have seen before? Based on the fact that it quit during start-up I'm guessing that something in the circuitry that actuates the contractors might have failed. I took the board out of the machine and it all looks pristine.?

3. I'm in a real time crunch to get some work done using this machine. Is there a simple solution like a generic ready-built motor control with a couple of relays/contactors I can use to run the shaper motor in the interim? I don't need braking; just the ability to drop out the start winding after a few seconds.

Thanks,
Henry

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Thank you Imran - I did email Felder a few weeks ago and they provided this same system diagram. Unfortunately the schematic is similar but not identical to how my machine is built (the wire numbers are not all the same and my machine has no fuses on the low-voltage system, for example).

These older machines with the Siemens main board are a challenge - if only a detailed board schematic were available it would be way faster to troubleshoot. I asked Felder about it and they said they don’t have one - they treat the board as a black box.?

At this stage I’m seriously considering either (a) ripping out the guts and building my own motor control circuit w/o brake, using an arduino to handle the switch logic, and reusing the selector switch, or (b) buying three-phase motors and using VFDs, again plus the microcontroller for logic.

i’d really prefer not to burn the 100 hours or so I know it would take me to do this though!

?Hi Imran,

It's close but with a few notable differences, some that could be the product of half-baked repairs and others that are inherent design differences on the board. For example: the fuses on the low-voltage circuit are absent and the contactor component numbers in the silkscreen are different than the diagram.

I spent another few hours trying to build out a schematic of the contactor actuation circuit yesterday, going as far as to remove the board from the machine to do so, but I'm not having much luck decoding it. I'm a mechanical engineer and am in over my head trying to figure out how the board logic works.

I've resolved for now to get the machine running using a potential start relay and a standalone contactor to drive the existing motors. I'll leave the existing guts of the machine powered off and only re-use the function selector switch by disconnecting the power leads from the board and wiring the output of my "drive" directly into the switch. I can't see much downside to doing this besides the marginal loss of safety features (my brake is already toast, so I'm only losing the microswitches and pushbuttons conveniently located at each function's station).

If this works I'll document it here as a last resort for other folks. It shouldn't be complicated or expensive to do. Maybe if I find some time in the evenings I'll wire up a microcontroller and some simple code to re-incorporate the low-voltage functions. I think my main board has breathed its last though. A 25-year run isn't too shabby.

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