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31st Mar 2020, 07:52 PM #61Most Valued Member
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Now it’s getting serious. You’ve got me digging in my old boxes of transformers and “stuff” !!
Hit the jackpot though, an old multi tapped primary toroid.
Perfect:
Steve
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31st Mar 2020, 08:21 PM #62
Hi Steve,
Yep ! It works very well as long as your current (amperage) requirement is equal to or less than the transformer primary current.
I cannot find any more info on those timers, so I suspect that it triggers something else to latch within the time period. Those plastic cases come apart quite easily, you just have to take a little care that you don't snap off the latch. If it came to the pinch a 555 timer and relay would do the same job.
It would be interesting to see what the machine circuit looks like ! I'm curious to know why there are so many timers in there.Best Regards:
Baron J.
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31st Mar 2020, 08:23 PM #63Most Valued Member
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No sign of life when I apply power, so I think you might be in the right track with your comment earlier about the external capacitor.
The external contact in the diagram is interesting too. Maybe it’s a trigger.
Time to get out the wiring diagram and put all the info together.
Steve
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31st Mar 2020, 08:29 PM #64Most Valued Member
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The joy of having a TOS.... ( FNGJ32 mill )
Looks like I need to link 3 & 4
Let’s give that a try.
Steve
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31st Mar 2020, 08:30 PM #65
Hi Steve,
Pins 2 and 10 are the power feed to the timer ! it should operate when you connect it across one half of the transformer.
230 volts across the transformer.
115 across each side.
But you know thatBest Regards:
Baron J.
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31st Mar 2020, 08:34 PM #66
I think that C25 and R25 are just spike suppression components.
Interesting that pins 3 and 4 are shorted together.
I wonder if that graphic on the timer just illustrates internal components.Best Regards:
Baron J.
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31st Mar 2020, 08:41 PM #67Most Valued Member
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Moving to the electrical test lab....
With pins 3 & 4 connected it ticks like a clock. Same behavior as when fitted to the mill.
Pulled another timer of same style.
Power on, timer runs, clicks on.
No ticking.
So the original has pooped (or is repeatedly pooping) itself.
Steve
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31st Mar 2020, 08:46 PM #68
Time to examine that internal relay !
The contacts when closed should show a dead short.
Is the circuit graphic the same on that other timer ?Best Regards:
Baron J.
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31st Mar 2020, 09:47 PM #69Most Valued Member
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The joy of having a TOS.... ( FNGJ32 mill )
The other timer is actually exactly the same P/N and rating (ie 0.2-2s) - so the graphic is the same.
I'd done a quick substitution the other night, but when you pull it out of its original position there's less "I'm alive" clunks when you turn on mains power so I thought I'd disabled something by pulling it, and didn't actually proceed test the feed.
I checked the wiring diagram just now and the position it came out of is related to the spindle somehow, so nothing to do with the feed.
Did the same substitution for the dodgy timer, tested the feed - clutch engages and it works fine
Don't tell my wife I could have saved her an oil spraying if I'd gone through with the substitution test properly the other night before opening up the feed gearbox.....
So, back to the failed timer.
While I was testing the good timer on the bench, I tested what happens if you disconnect the trigger wire between 3 and 4 once the timer has run and energised the relay. Removing the trigger wire de-energises the relay.
Which I'm pretty sure means there's no internal latching in the relay - so it must be held energised by the timing circuit.
Quick sketch of the main bits:
Powered it up again on the bench.
Nice 22vdc out of the bridge rectifier, and its pulsing 22v at the relay input when it clicks.
To me that fits with my theory that the timing circuit should be doing the latching.
Steve
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31st Mar 2020, 11:49 PM #70
Hi Steve,
No I won't say anything. [snigger snigger]
Sorry for the delay, wife dragged me away for dinner, I've just got back and I know that its late where you are !
A couple of good pictures of the circuit board component side and one of the PCB will help.
Did you check the relay contacts ? Two reasons: One you said that the clutch was only weakly working when the timer was in place and linking the contacts out caused it to operate properly. Could be caused by the short pulse from the timer. Two, I would have thought the the other contacts would have been part of the latching circuit.
I'm only trying to rule out the relay contacts here, all the other components can be easily replaced.
page5.pngBest Regards:
Baron J.
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1st Apr 2020, 03:16 PM #71Most Valued Member
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The joy of having a TOS.... ( FNGJ32 mill )
No drama's John, Your input and experience is much appreciated - but absolutely not expected!
No - I hadn't actually tested the relay as I needed to dig out my benchtop power supply to have something convenient to apply the 22ish volts to it. Then I got distracted last night reverse engineering and drawing up the timer wiring diagram as I was sure I was going to need it....
BTW - the slow non-positive feed I was getting on the mill was just clutch drag.
I've tested the relay today. Contacts are toasted.
Initially tested with it still on the board, and noted that it sounded flat instead of a solid click. Energised it was still showing open circuit on the 6-7 pins.
Finally found my solder sucker after searching in the shed for about half an hour, and removed the relay from the board and opened it up.
Hopefully this photo is OK, you should be able to see the upper (NC) contact is nice and shiny, the NO contact at the bottom is burnt up.
There are 3 poles, all contacts are bridged on the board so no option to use another set.
Steve
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1st Apr 2020, 03:30 PM #72Most Valued Member
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Couldn’t resist. Tore the relay down to get a better look.
Steve
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1st Apr 2020, 04:35 PM #73Most Valued Member
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That contact damage could be caused by a crook capacitor, each time the clutch coil turns off you would get a back EMF.
That might also be a symptom of the problem of not having steady power.
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1st Apr 2020, 06:30 PM #74
Good Morning Steve,
Thankyou for your nice comments, I don't mind trying to help out at all ! In fact I quite enjoy fault finding, diagnosis and repair. You’re welcome to any help I can give.
Those pictures confirm exactly what I expected, a shot relay. Interesting how all three contacts have been wired in parallel with each other. The only reason for doing that is to increase the current handling capability. Relay technology has moved on somewhat and there are modern relays with the same footprint that have a 10 amp capability but only one set of change over contacts and 24 volt coils. These are commonly used in things like toasters that require a heating element to be switched.
Shedhappens is right, the inductive spike has almost certainly caused that failure. If there isn't a snubber across the clutch coil, there should be. Check the capacitor if there is one, it might just be easier to replace it.Best Regards:
Baron J.
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1st Apr 2020, 07:01 PM #75Most Valued Member
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Thanks guys.
According to the wiring diagram there's a diode across the clutch coil, but I haven't physically checked that its there.
No capacitor shown apart from the series capacitor/resistor combo in parallel with the timer itself on the 110v side.
EDIT: I also checked the current draw on the clutch. Only 1.2A so much lower than what I expected.
I was originally thinking I'd need to fix this timer, but seeing as it looks like I might be OK to just relocate the one from the spindle circuit, then maybe I don't have to repair it.
I'm fitting a VFD for the spindle motor, so pretty sure I won't need that timer - but I need to do a bit more digging to confirm it doesn't serve a secondary purpose.
On the issue of sourcing a replacement oil pump belt, there's good news and bad news, and more good news...
Good was that I'd found the correct part number - bad is that there's none in stock even with the manufacturer in the US. They can make to order with a MOQ of 48!!
The saving grace is that PIES Australia have the next length belt - albeit 50mm longer. I've had a look and have enough room to space the motor out from its original mount to consume the extra length. Otherwise I was looking at changing to a modern eg T5 belt style but would have meant new pulleys etc.
Steve
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