# Real Bull Controller box question



## sacentre (Dec 10, 2021)

I hope I'm in the right forum. Apologies if not.  

Is anyone else using a lathe with this controller box (see photo)?  I bought it to replace an older controller which didn't come with a tacho but the KBIC-240D controller board is the same. 

I have a question about the RPM display. After about half an hour, the digital display starts flashing "8888" about twice a second.  It clears if I switch off and on again. Is this some form of temp/overload signal or could it be a fault somewhere? 

TIA

Trevor


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## markba633csi (Dec 10, 2021)

Do you have the speed sensor and magnet installed?  In other words is it reading correctly and then suddenly start flashing 8888? 
-M


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## sacentre (Dec 10, 2021)

I have the opto-isolator and the slotted disk installed (I'm not aware of any magnet) and the RPM reading appears to be accurate then it suddenly starts flashing "8888" until I switch off and on again.


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## markba633csi (Dec 10, 2021)

OK you have an opto system rather than magnetic/ hall effect type.
Not sure what It could be- possibly interference from the motor getting into the sensor leads? Have you tried repositioning the wires?
Does the failure occur after a period of time even if the motor is not run?  If so then the problem would be isolated to the readout itself


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## sacentre (Dec 11, 2021)

Thanks for the help.  No, the display remains at "0" indefinitely with the motor not running. If I turn the chuck by hand, of course the reading goes up then settles back to "0" again.  As for interference from the motor, I guess I can dismount the box and move the encoder lead around and see if that helps. I'm assuming you either don't have this type of controller or you have one but don't see this problem?


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## markba633csi (Dec 11, 2021)

I don't have one but have experience with electronics.  Either the encoder is picking up EMI (electromagnetic interference) or there is motor noise coming thru the power supply to the readout.  It may require adding some filter capacitors on the readout power supply lines or the encoder.  
Experimentation is key if you don't have an oscilloscope to view the noise directly.
Be careful when working on live circuits around the motor control section
-Mark
PS is this a brush-type motor or brushless?


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## sacentre (Dec 11, 2021)

It's a brush motor. I get the EMI possibility but how might we explain the regular .5 sec timing of the "8888" display. It would have to be getting the timing via the on board crystal I imagine. Then there's the fact that the problem only occurs after I've been runing the lthe for half an hour which seems to suggest a thermal issue.  I'm a complete novice where electronics theory is concerned.  

One thing I didn't mention till now as I didn't think it was relevant, is that because this box was designed to fit the Real Bull CJ18A and its clones, the mounting holes didn't match up with my much older lathe so I discarded the original plastic box and fabricated an almost identical one out of aluminium. All the guts are in exactly the same layout as the original. I suppose it's possible that might have contributed to EMI interference. 

The only thing to do now is dismount the box from the lathe and see if the behavior changes by moving the encoder leads around a bit.  

Thanks again for the interest and helpful advice.
Trevor


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## markba633csi (Dec 11, 2021)

I discounted the thermal angle since you reported the issue doesn't occur if motor stopped- it points to a noise pickup problem
You might want to double check that- leave it on for several hours and see if it fails spontaneously. Make a hypothesis and then test it.
-M
PS by the way, it's almost certain the readout operates on a low voltage like 6 or 12 volts dc.  There may be a stepdown transformer or they derive a low voltage supply in some other way like a capacitor input supply from the 120 volt line  (the latter presents some shock hazard; no isolation)
If you can break the readout power free and run it from a battery instead it might help you zero in on the problem faster.  By all means, be careful
Post some pictures of the inside of the controller if possible so I can advise better
It just occurred to me the 8888 might be a self diagnostic if the encoder stops outputting signal or gets disconnected-? maybe


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## sacentre (Dec 12, 2021)

Thanks again, Mark.  Here are some photos and short video clips. The display started flashing after about 5 or 6 minutes when I tried it this morning (clips 1 and 2).  It usually takes much longer than that.  I got the box off and ran it again. Same thing after about the same time. I pulled the 2 white ribbon cables away from the innards somewhat (clip 5) but it made no difference.  If I disconnect the 3-way encoder cable while it's flashing and reconnect it,  the display resets and works normally until until after 5 mins or so when it starts flashing again.

As you suggest, I'll try running a separate DC supply and see if that makes any difference.  It's 5v according the silk screen printing on the PCB. That'll take me a while though.
Thanks again for your patience and invaluable help.
Trevor


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## markba633csi (Dec 12, 2021)

OK now, when it's working normally and you disconnect the encoder what happens? Does it do 8888?
I see a small transformer in there, that must be for the readout power.  The speed controller looks just like a KB electronics SCR drive or clone.
Very reliable, as long as you don't go poking around in it with power applied.
Other observations: It looks like the readout board has a large IC which might have a recognizable part number- and it's a dual in-line IC and possibly in a socket which makes for easy replacement.  
My feeling is the opto interrupter may be flaky- here's where I would break out the oscilloscope, but maybe you could monitor the output with a multimeter if you turned the spindle slowly by hand.  It should be giving a 0 to +5 volt squarewave signal to the readout board


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## sacentre (Dec 12, 2021)

With the lathe running and the display flashing 8888, if I disconnect the encoder, the display returns to 0. Once reconnected, the display shows the current RPM.

The controller is the KB-240D model from KB Electronics in the US. I was worried it might be a cheap clone when I ordered the box but was happy to find it wasn't.  The IC is indeed socketed and has a readable number if it should turn out to be suspect.  I'm still puzzled by the fact that the fault only crops up after some time. This is why I was tempted in the beginning to think it could be a thermal intermittent problem: something gets warm then fails. Off for a few seconds then it's ok again.

I don't have a scope and frankly, wouldn't know how to use one. As I indicated, my troubleshooting abilities are as good as my Swahili! That said, I do have a multimeter and a couple of spare opto-isolators I could try. Would they have to be exactly the same part number or are they mostly interchangeable?

I'm not at home right now so it'll be a while before I can get back to it. When I do, I'll post a few images.

Once again, I'm very grateful for your help.

Trevor


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## markba633csi (Dec 13, 2021)

If you want to try swapping opto interrupters you really should try to find data sheets online first,  they are similar but pinouts can vary- you can blow things up if you connect it wrong
It would be safer if you disconnect the power from the controller and tape the wires so that only the readout power supply is live when you are testing the readout
You should be able to monitor the signal from the opto either at the opto or at the connector- you might need to solder some short wires and get some alligator clip leads so that you can turn the spindle by hand while watching the meter without having to hold the test leads


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## homebrewed (Dec 13, 2021)

It might be helpful if we knew who made the tachometer board and/or integrated circuit.  There could be troubleshooting info in the product manual/IC data sheet.


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## homebrewed (Dec 13, 2021)

I belatedly noticed that the controller was sold by Amadeal.  You might contact them to see what they have to say about the problem.


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## sacentre (Dec 13, 2021)

homebrewed said:


> I belatedly noticed that the controller was sold by Amadeal.  You might contact them to see what they have to say about the problem.


That was the first thing I did but I didn't get a reply.  Busy with the Xmas rush I guess.


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## markba633csi (Dec 13, 2021)

Yep you may not find a lot of support from the company but if you can get the data sheet for the main chip that would be very helpful, usually they show an application circuit with interconnection details and power supply requirements


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## sacentre (Dec 13, 2021)

I really appreciate the time you're taking in helping me with this.

A test I plan to carry out this afternoon I'm hoping will narrow things down a bit.  I'll fix up a bit of stock bar in the chuck and turn it with a Black and Decker drill. The motor controller will be off, only the DC feed to the display board will be on. My reasoning is that if the fault appears, that will more or less conclusively point to a fault on the display PCB or encoder (as you suspect). If it does not, then it could point to some interaction between controller/motor - possibly the EMI problem you suggested originally.

I can certainly dig out the IC and try to find a data a sheet if this proves necessary.

Now, here's another wrinkle which may clarify (or confuse) things further. Shortly after the 8888 problem surfaced, I started noticing the motor "hunting" or pulsing as if the DC feed was being interrupted. This only became noticeable in the last day or so or I would have mentioned it sooner. My first thought was worn motor brushes so I will have to eliminate that as a possible cause.  Could this explain sporadic fluctuations in the load on the controller which might introduce noise into the encoder pulse train? I don't know if any of that makes sense.  Anyway, I'll post the results of the test later tonight.  Thanks again.

EDIT

I ran the test (see video) several times for about 5 or 6 minutes and the display behaved normally. I originally said the problem popped up after about half and hour but later said it was happening more frequently. This might mean nothing or it might simply be progressive wear of the brushes making more frequent pulses on the DC motor line and affecting the encoder signal.  Is this what is known as "parasitic EMI"?  Whatever. I'll run the test again several times tonight to see if the fault occurs. Next, run the motor on the lathe as normal and see what happens. It might turn out that the 8888 is a designed error signal to indicate square wave signal isn't being read or synched.


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## sacentre (Dec 13, 2021)

homebrewed said:


> It might be helpful if we knew who made the tachometer board and/or integrated circuit.  There could be troubleshooting info in the product manual/IC data sheet.


Thanks for the input. Finding out the OEM of all these Asian products is next to impossible. You might see "Made in China" on them somewhere if you're lucky. I received no product manual or data sheet with the box as it was supplied as a spare part. Schematics for the US made KB controller boards are readily available on the net, however. Maybe the CJ18A lathe this box is normally fitted to comes with something. This most likely would be produced by the retail seller who puts the badge on the product as it's not worth the OEM's time to write them.  I doubt it would include a schematic of the display board but it's a fairly simple circuit anyway (not that I mean to imply I find troubleshooting electonics easy. Far from it).  
Data for the IC on the tacho board should be easy to find as long as there's a readable number.   OEMs often scratch them off to make it harder for others to copy the product.


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## homebrewed (Dec 14, 2021)

sacentre said:


> Thanks for the input. Finding out the OEM of all these Asian products is next to impossible. You might see "Made in China" on them somewhere if you're lucky. I received no product manual or data sheet with the box as it was supplied as a spare part. Schematics for the US made KB controller boards are readily available on the net, however. Maybe the CJ18A lathe this box is normally fitted to comes with something. This most likely would be produced by the retail seller who puts the badge on the product as it's not worth the OEM's time to write them.  I doubt it would include a schematic of the display board but it's a fairly simple circuit anyway (not that I mean to imply I find troubleshooting electonics easy. Far from it).
> Data for the IC on the tacho board should be easy to find as long as there's a readable number.   OEMs often scratch them off to make it harder for others to copy the product.


Yeah, I've seen products where the IC ID's were removed.  Hopefully not the situation for your board.

That was a clever way to test the tach independently of the motor controller.  You might want to repeat it while heating the tach board with a hair dryer -- since the motor controller wasn't running, the box probably wasn't getting as hot as it does during normal operation.  Your comments about the readout only failing after some time immediately made me think of a thermal intermittent problem.  Those can be hard to troubleshoot.  Freeze spray can be helpful here, but is kind of a blunt instrument.  Spraying a q-tip with freeze spray and using it as a "cold probe" on components might help zero-in on the problem -- if it is a thermal intermittent.  If the "blunt instrument" approach doesn't cause the tach to recover, there isn't any reason to use the q-tip scheme.


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## markba633csi (Dec 14, 2021)

Good advice there from Homebrewed.  I salute your courage in diving into this thing- there's a certain satisfaction in fixing something with little info to go on.
Even if the IC number has been erased, you might be able to locate it online by typing in the function  "3-1/2 digit tachometer IC" or something like that.

The hunting you mentioned could be a factor or not.  I wouldn't expect the brushes to be worn unless the motor has lots of hours on it.
If you can read the part # from the opto interrupter post it here- I have some opto databooks


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## sacentre (Dec 15, 2021)

markba633csi said:


> Good advice there from Homebrewed.  I salute your courage in diving into this thing- there's a certain satisfaction in fixike you ale ling something with little info to go on.
> Even if the IC number has been erased, you might be able to locate it online by typing in the function  "3-1/2 digit tachometer IC" or something like that.
> appears, I'm less inlined to
> The hunting you mentioned could be a factor or not.  I wouldn't expect the brushes to be worn unless the motor has lots of hours on it.
> If you can read the part # from the opto interrupter post it here- I have some opto databooks


It's people like yourself and Homebrew and your willingness to help that deserve the credit.  I'm not very courageous - only desperate! After running the test with the drill over and over, I'm still not seeing the fault. I can easily try warming the board a bit with a hair dryer as Homebrew suggests.  Until and unless it appears under the test conditions, I'm less inclined to see this as a fault on the display/encoder. As for brushes, I'll be checking those later today. Fortunately, I have both a spare set as well as a new, unused motor.

What's worrying me now is the possibility of a fault of some kind with the KB controller itself. I never asked Amadeal what warranty if any, came with the box. I will have to talk to them about returns if it turns out to be faulty. I haven't the knowledge or the tools to establish that other than by the process of elimination, though. Still, I'm not not at that stage yet.  
Thanks again for the continuing help.
Trevor


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## homebrewed (Dec 15, 2021)

If you feel up to it, pulling the tach board and looking for cold solder joints might pay off.  If nothing else, unplugging/reconnecting the connectors might clear up a contact problem.  If the IC is socketed, lift it up a bit and push it down again -- same reason.


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## sacentre (Dec 15, 2021)

homebrewed said:


> If you feel up to it, pulling the tach board and looking for cold solder joints might pay off.  If nothing else, unplugging/reconnecting the connectors might clear up a contact problem.  If the IC is socketed, lift it up a bit and push it down again -- same reason.


Yes, all good suggestions and easy to carry out. I'll do that and check that IC ID at the same time.
Thanks
Trevor


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## sacentre (Dec 15, 2021)

Just as I suspected, the cynical manufacturers have scratched off the ID.


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## sacentre (Dec 15, 2021)

Ok, I reported yesterday that I couldn't get the display to go faulty using the B&D method. Today, I have the display PCB out on the bench and ran the test again this time heating the PCB with a hair dryer.  It was too hot too touch at one point. Still nothing.

On the next go (no hair dryer) the fault appeared (see video). It's possible I didn't run it long enough.  Now, the behavior is pretty consistent and repeatable - flashing 8888 after 2 or 3 minutes without adding heat.   So, it seems fair to assume it's not a faulty controller board or motor brushes.

There's still the possibility that there's some problem with the DC feed from the filter board OR the opto-isolator itself.   I will need to figure out the routing on the PCB so I can duplicate an external DC feed.


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## markba633csi (Dec 15, 2021)

OK. It's quite possible that it could be a faulty component.  It's also possible that the way the factory put the unit together the controller was able to transfer a voltage surge into the readout board;  prone to fail by design.  This may be an endemic problem with all of these- who knows
Maybe it's time to consider either replacing the whole unit or getting a spare readout board since you don't have the means to troubleshoot down to component level
The readout chip is probably CMOS and those can be damaged by static discharge, voltage surges, lightning and even solar flares.
And the environment it's in next to the controller is definitely a noisy one, electrically speaking but the chip could have been damaged just by handling at the factory
It probably will fail even with the spindle stationary but without test equipment or spare parts to substitute it's hard to tell which part is failing
I don't think you need to bother with the external dc test, but it can't hurt to try.  A little 9 volt battery would probably work


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## sacentre (Dec 15, 2021)

markba633csi said:


> OK. It's quite possible that it could be a faulty component.
> Maybe it's time to consider either replacing the whole unit or getting a spare readout board since you don't have the means to troubleshoot down to component level
> The readout chip is probably CMOS and those can be damaged by static discharge, voltage surges and the phase of the moon, among other things.
> And the environment it's in next to the controller is definitely a noisy one, electrically speaking, but the chip could have been damaged just by handling at the factory
> It probably will fail even with the spindle stationary but without test equipment or spare parts to substitute it's hard to tell which part is failing


Yes, I was almost at the stage where I was ready to just order a replacement.

I might still try running the module on an external DC supply which should be within my capabilities. If the fault is still happening that will wrap it up as far as a faulty module is concerned. I'll report back whatever the final outcome is.  Meanwhile,  many thanks once again to you and Homebrewed for helping me out with this.


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## homebrewed (Dec 15, 2021)

sacentre said:


> Yes, I was almost at the stage where I was ready to just order a replacement.
> 
> I might still try running the module on an external DC supply which should be within my capabilities. If the fault is still happening that will wrap it up as far as a faulty module is concerned. I'll report back whatever the final outcome is.  Meanwhile,  many thanks once again to you and Homebrewed for helping me out with this.


Grizzly stocks the display board.  $60USD not counting shipping.  You may be able to do better elsewhere since you're in Singapore.   Naturally, they don't have a product manual so it's impossible to say if the flashing display is an indication of an error condition or not.

Grizzly's product page shows a photo of the part, and I was able to get the chip P/N from that.  It's a Holtek HT48R30A-1, which is a RISC microprocessor chip.  It's got a 2K program space and 96 bits of RAM so your average Arduino stomps on it.

The photo doesn't look exactly like yours but I'm pretty sure it is a drop-in replacement.  However, before you order a replacement I'd highly recommend measuring the power supply voltage while it's misbehaving.  It would suck if it turns out the problem is a bad controller board.

If your external supply is variable it would be interesting to lower the voltage to see if the display starts flashing.  That also would be a good indication that it's not the display board (but not good for your wallet, unless the controller is still under warranty).


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## sacentre (Dec 15, 2021)

Thanks for the info, Homebrewed.  Especially the IC P/N. I'll check check out. 

$60USD? I was hesitating to drop 18GBP plus shipping on a replacement but that price seems reasonable in comparison.  Still, if I knew for sure that's all I need to pay to get rid of this problem, I'd order one immediately.

All this stuff is knocked out by the million in factories in China probably at a couple of dollars a piece if that. By the time they're shipped to Europe or the US, marked up and re-exported to me, they're selling somewhere around the price of gold dust. Basic economics, of course.  It's a pity that being in the Far East already, I can't source them nearer. Even if I knew the OEM, they'd probably have a minimum order of 100PCS. 

I still have a way to go to establish exactly which part of the system is faulty but I think we've narrowed this down to the display module itself, the encoder or the filter board which feeds the DC to the display.  All these are available from Amadeal as spares.

 As discussed, all that remains to try now is getting the encoder and display PCB wired up to bench PSU and rigging up a makeshift rotating disk and seeing if I can see the fault.  If not, this will suggest the filter board (possibly a noisy DC line?)   I'm also inclined to think that the flashing 8888 is a designed error signal but what the error is, who knows?  

Once I can say with any certainty which part is faulty, I'll approach Amadeal to see if I can negotiate some kind of return/replacement but I may wait till after Christmas now before doing that.

Thanks again for the input.


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## homebrewed (Dec 16, 2021)

sacentre said:


> Thanks for the info, Homebrewed. $60USD?  I was hesitating to drop 18GBP plus shipping on a replacement but that price seems reasonable in comparison.
> 
> All this stuff is knocked out by the million in factories in China probably at a couple of dollars a piece if that. By the time they're shipped to Europe or the US, marked up and re-exported to me, they're selling somewhere around the price of gold dust. Basic economics, of course.  It's a pity that being in the Far East already, I can't source them nearer. Even if I knew the OEM, they'd probably have a minimum order of 100PCS.
> 
> ...


Modern-day supply chain stuff can be strange, that's for sure.  In your case, it sounds like a case of so near but so far.

If you have a signal generator you don't need to make a rotating disk setup in order to exercise the board.  It wouldn't have to be much -- even a 555 timer could emulate that interrupter/detector combo.  That's easy for me to say since I have all kinds of electronic components on hand, but it's worth mentioning.  Over here, you can buy a 555 timer for under a buck.  It also is easy to make a square wave oscillator using either CMOS inverters, NOR or NAND gates. 

BTW, looking at the display board it looks to me like the interrupter signal probably is routed through an opto isolator (it's the 4-pin IC on the board).  So you can't assume that one of the two interrupter inputs is the same ground as the board's  power Gnd input.  I don't think that means you have to have two power supplies to test the display board.  The interrupter input's negative signal line could be connected to board Gnd.


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## sacentre (Dec 16, 2021)

There are dozens of off-the-shelf panel mounted RPM displays available on line. I suppose anyone of them would do as long as there were circuit details available - like what encoder to use etc. Many of them come with magnetic (hall effect?) sensors all for around  5 or 6 dollars.

The suggestions in your second and third paras are a bit over my head, I'm afraid.  I've never owned a signal generator or a scope for that matter so it will just have to be a cardboard disk on the end of a drill - more my level.  I have assembled kits using 555 timers in the past.  As you say, one of the cheapest ICs around.

Although I've enjoyed mucking about with practical electronics since I was a kid (I'm 74 now), I never got very far with theory.  As for the maths involved. forget it! I can follow a simple circuit diagram to build a PCB but if it doesn't work afterwards, I'm lost - unless it's something obvious like a badly soldered joint or a diode the wrong way round.

Many years ago, I used to get a great kick out of editing single-side PCB artwork on a PC (from an existing circuit) using Protel Autotrax and then plotting the pattern out on a Roland XY pIotter _directly onto the copper clad board _(I never mastered the photo-mask method_)._ The .3mm fibre pens were etch resistant and produced very clean results.  All just .1inch stuff, of course. It was hugely satisfying watching the PCB tracks appear on the board before dropping it straight to the etching bath. After etching, I'd drill the holes by hand with a .7mm drill. I made lots of small gadgets that way.  Sadly, I had to give that method up because I couldn't get the plotter pens. If I were doing this stuff now, I'd most likely be looking for a CNC router to produce PCBs.

These days, it's just assembly and soldering I really enjoy.  Recently, I bought some kits to assemble that used SMD exclusively.  I'd only ever assembled through-hole PCBs before this. I had to buy one of these el-cheapo digital microscopes to cope with the .5mm pitch ICs. Great fun learning to solder with a soldering tip like a needle while looking at an LCD screen! 

Please excuse the ramble.


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## sacentre (Dec 16, 2021)

Well, Mark, Homebrewed, I'm more confused than ever now.

I ran the display and encoder off my bench power supply (Clip 1) for more than an hour and the fault never showed up once. "Aha!" said I. "Now we're getting somewhere!" 

Next I re-connected it to the controller box  (Clip 2) and .... nothing. No fault! I switched off and on again, left it running for many minutes. Nothing.

So, I'm back to square one having learned nothing from all this and see no evidence that anything needs replacing. There has to be some other variable I'm just not seeing.  As you can make out from the clips, I used a small hand held-drill gripped in my bench vice with the encoder fastened to a strip of steel with doube-sided tape. The disk is just a bit of thin black card with a single slot. I had the controller box connected to a length of mains wire plugged into a socket near my desk. What difference any of that makes to anything I just don't know. I'm pretty sure that once I re-install the encoder on the lathe and reconnect it back to the box, having re-connected the lathe mains cable, I'll see the mysterious flashing 8888 again. I might just have to live with it.

When things get like this , I'm reduced to suspecting that it could be the mains socket it's plugged into so I'll be running an extension to a different room to test that half-baked theory.


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## homebrewed (Dec 16, 2021)

sacentre said:


> Well, Mark, Homebrewed, I'm more confused than ever now.
> 
> I ran the display and encoder off my bench power supply (Clip 1) for more than an hour and the fault never showed up once. "Aha!" said I. "Now we're getting somewhere!"
> 
> ...


Ugh.  The symptoms look like some kind of intermittent, since messing around with the connectors/cables/boards temporarily fixed the problem.  Looking at it as a which-is-most-likely scenario, I'd look at the cable going between the display and controller board.  Problem is, it could be a broken wire inside the jacket.  So nothing visible externally.

Replacing that cable with a new one, or one you make yourself, might fix the problem -- or might not.  You won't know until you use your machine awhile.  If the problem comes back, at least you've eliminated the cable, then its time to try something else.  That's the nature of intermittent failures.


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## sacentre (Dec 17, 2021)

Your advice about possible cable trouble is of course, perfectly sound and I'll keep that in mind as I run the box on the lathe.  There's still a question mark over the controller board itself as I'm still seeing the "hunting" problem I reported earlier.  Replacing motor brushes made no difference. That might turn out to be the problem all along. As you said, it will really suck if I've got another faulty one.

On the subject of weird intermittents, you might find this interesting. I hope I'm not upsetting a Moderator with this OT stuff but I'll try to keep it brief.

When I worked as IT manager for a company in Singapore, we ran into a problem with our Dell Exchange server that suddenly refused to boot.  It was in a 19" rack along with several others all of which were working normally.  Me and a technician went through all the normal substitution routines checking connections, mains cable, re-seating and then substituting RAM modules, CPU, HD - everything. In the end we called our local Dell support tech who brought a replacement motherboard (what else was left?) which we installed. This was after he'd tried all the things we'd already done. Nothing worked. He even suspected the non-Dell monitor and keyboard that were plugged into it (I have come across a faulty PS2 keyboard that stopped a PC from booting) and then the UPS so we swapped these out.  Nothing we did made any difference. It simply wouldn't boot, no POST nothing.

Even the Dell guy said he'd never seen a problem like it before.  Everyone I've told this story to says we must have missed something. It had to be something we overlooked. I would never have believed it myself had there not been three of us there at the time.  There cannot but be a logical cause and effect, right?  It's empirical science, not magic, elves, gremlins, Feng Shui or anything else?   So we all believed and I still do. Yet, there was nothing anyone could think of that we didn't try and still the damn thing wouldn't boot.  Until ....

We decided to take the server to another room down the corridor along with monitor and KB, where we had a big table and more space to work so we could strip it down and progressively re-establish it. Naturally, the first thing we did was plug it into the wall and .... You guessed it!  It booted normally!  Back again to the server rack. Nothing. Remember that the rack housed 3 other servers all working OK from the same mains socket strip and the same UPS.  Back once more to the other room and it booted fine.

We never got to the bottom of it having worked the problem to exhaustion well into the small hours. What was it about that one server that prevented it booting in that particular room? In the end, we took it to my office on another floor,  plugged it into the wall and connected the LAN where it worked without fail until it was replaced under our Dell replacement programme.  There are more things in heaven and earth etc, etc..

Thanks for reading and apologies again for a not so brief ramble.
Trevor


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## markba633csi (Dec 17, 2021)

Weird story!  Thankfully those don't happen that often.
The 4-pin IC that Homebrewed mentioned on the power board is, I think, the bridge rectifier for the readout power supply
so it seems likely the opto interrupter feeds directly to the readout chip.

You could use an LED and approx. 2K resistor to make a signal probe, see if the opto is going dead when fault occurs

Japan has a section of town called "Akihabara" a market place for all things electronic- maybe there is a place in your city like that?

Remember that these products spend a long time on ships in salty air before delivery- your problem may simply be some slight corrosion on a connector or IC socket- by moving things around you "fixed" it.  A poor solder joint could also be the culprit


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## markba633csi (Dec 17, 2021)

Simple logic probe:
By the way, you never told us what happens if the unit is working properly and you disconnect the opto cable.  Do you get 8888?


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## sacentre (Dec 18, 2021)

markba633csi said:


> Weird story!  Thankfully those don't happen that often.
> The 4-pin IC that Homebrewed mentioned on the power board is, I think, the bridge rectifier for the readout power supply
> so it seems likely the opto interrupter feeds directly to the readout chip.
> 
> ...


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## sacentre (Dec 18, 2021)

And not the first time I've see totally inexplicable problems with PCs. I'm not thinking this controller display issue is anything like that though.  

Thanks for the logic probe suggestion. We have a place here called Sim Lim Tower which has 3 floors of wall-to-wall electronics parts shops.

I've now run the lathe several times without the fault occurring and I'll continue to test it each day while the box is off the lathe. You mentioned corrosion and I've seen plenty of problems caused by the humidity here which is 70-90% all year round. It's just possible one of the headers might not have been making a good connection but there's certainly nothing obvious.  Anyway, I'll continue to monitor.


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## sacentre (Dec 23, 2021)

Mark, Homebrewed
I'm sure you must be pretty bored with this thread by now but I thought I'd let you know the state of play.  As I expected, the problem reappeared after I'd screwed the box back on the lathe and started using it.  Exactly the same behavior.  This suggests now the trouble lies with the filter board and the 5v DC supply to the display/encoder combo. I'll take the box off again and have a look a that regulator IC or perhaps just replace it and see what happens.  I'll wait till after Christmas and then make a trip down to the electronics shops to see if I can find one. Assuming the maker hasn't scratched the ID of it (I never bothered to look when I had it on the bench).  Of course, this wouldn't explain why the problem never appeared when I had it running on the bench but then again, that was with no motor connected.

Thanks again for all your help and I wish you both an enjoyable and relaxing Christmas.
Trevor


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## sacentre (Jan 15, 2022)

Mark, Homebrewed

*Problem with RPM Display fixed.*
I felt I owed it to you to let you know the outcome of this issue after you both contributed so much of your time helping me with it.

Following your suggestion, I replaced the BD107 bridge rectifier and the 78L05 voltage regulator and there was no further problem with the display during several hours of use today.  After running the module on batteries without trouble prior to this, it seemed this was the only thing left to try. It seems likely that it was after all, a thermal intermittent fault with one or both of those components. I would have replaced one at a time and re-tested but I got lazy. Anyway, all's well now.

Thank you both once again for all your help.

Trevor


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## homebrewed (Jan 15, 2022)

sacentre said:


> Mark, Homebrewed
> 
> *Problem with RPM Display fixed.*
> I felt I owed it to you to let you know the outcome of this issue after you both contributed so much of your time helping me with it.
> ...


Excellent!  Intermittent failures can be the very devil to track down, so your patience has been rewarded.  Good Work!


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