Bridgeport Interact II failure

[AdeV]

If you've read the CNC failures thread over in "Ooops", you'll know I blew my Interact up last week....

The fault claims to be the DC regulator board. I've multimetered it today, and its outputting 26.4v (the spec is 24v+/-2v); Q - is that 0.4v extra enough to cause the machine to repot "Ext DC Voltage missing"?

Unfortunately, the manual doesn't give any further things to try if it should be OK on +2.4v...

I think I'll switch out the regulator anyway, I've got  shiny new packet of them... so... 1.5A or 2A regulator???

[NeoTech]

Go big or go home (maybe applies.)   

[awemawson]

AdeV I can't imagine the 400mV will be the problem. IIRC there are two 24v DC power supplies on the interact - one is the regulator board we talked about, and the other is an unregulated supply of just a bridge rectifier and capacitor. Maybe it's the other one that's u/s

The following .jpgs are the circuit diagram, and they are shown on them.

NB These are uploaded full size otherwise you couldn't read them !!!!

[AdeV]

Ta kindly, I have those diagrams, mine is subtly different (24v unregulated feed comes on wire no. 100, not 116 as shown in yours (but 100 as shown in mine)...

Having traced the 24v regulator circuit, it's extremely odd, doesn't look like any regulator circuit I've ever seen before. However, now I know its feed is already rectified, maybe that makes it more sensible.

The chip that cme off it has TIP32A as its designation - that is an NPN power transistor, not a voltage regulator... I'm wondering if I can substitute the whole rectifier board with simply a capacitor & vreg, instead of the weirdness it has now.

Oh, and since I wired the vreg in place of the TIP32, I got 41v DC for a few seconds, then 0v. So now I need to find the fuse that blew...

[AdeV]

AdeV I can't imagine the 400mV will be the problem. IIRC there are two 24v DC power supplies on the interact - one is the regulator board we talked about, and the other is an unregulated supply of just a bridge rectifier and capacitor. Maybe it's the other one that's u/s

The unreg 24v supply supplies the regulator board, so if it was u/s there'd be no volts on the regulator board either. Also, I can turn the spindle brake off, that is fed from the 24V unregulated circuit; which also suggests it's working.

I think I blew fuse CFU3 atop the transformer, I just have to locate it now & replace it with something similar...

[update: Yep, fuse CFU3 is toast. Annoyingly, I only have 500ma fuses in that size, not the 5A I need.... time to see if Maplin have any[/update]

[awemawson]

If your 24v regulated is sourced from the 24v unregulated you may not have enough voltage differential for a three terminal regulator to work - I think they need 3 or 4 volts  across them from input to output but check the spec sheet. I wouldn't mind betting that the TIP32A is being used in an emitter follower configuration withe the collector being the input, the emitter being the output, and a zener diode from it's base to common 0v, with probably a bias resistor from the top of the zener to +ve. The idea is that the emitter will follow the voltage on the base but offset by 0.6 - 0.7v which is the Vbe drop of a silicon transistor.

[John Swift]

Hi Ade ,

the TIP32A is a PNP transistor !
http://www.fairchildsemi.com/ds/TI/TIP32C.pdf

what does the 24V regulator board look like ?     a picture would help
just a very simple voltage regulator  with a resistor , 25V zenner and the TIP32 as a emitter follower ?

if it also limits the maximum current output your likely to find 3 or 4 small transistors and a power resistor to sense the current ( 0.3 to 1 ohm ?)

what voltage regulator did you use a 1A  7824 regulator IC    ?


John

[AdeV]

OK, the rectifier regulator circuit, as per Bridgeport, is below.

Below that, is my proposed replacement circuit.

Do I need to add further decoupling caps, as are often shown, near the 7824 device?

Lines 100 & 90 are from either end of the bridge rectifier. 90 is also tied to GND in several places. 100 is the direct supply. The transformer is supposed to be giving 30v, I guess that 1.4v would be lost to the bridge rectifier? (or just 0.7v?), so there should still be plenty left to run the regulator.

[John Swift]

Hi Ade ,

just a quick question

what is the off load voltage out of the transformer T1's 30 V winding ( terminals 113 & 114) ?

if the output is more than 28Vac
then 7824's maximum input voltage of 40Vdc will be a problem to workaround

http://docs-europe.electrocomponents.com/webdocs/0609/0900766b806090e4.pdf

a circuit like the simple regulator in my last post can be used as a pre regulator
to limit the DC voltage into the 7824 ic

the 0.1uF decoupling capacitors on the 78xx data sheets are needed for stable operation of the regulator


   John

[AdeV]

Off-load looks to be in the 40v range...

OK, so I've built the circuit, plugged it all in & proven 24.01vdc out, according to multimeter.

TNC151 is still complaining "Ext 24DC voltage missing"

The troubleshooting guide has nothing to say about this...

I have verified that both my E-stop buttons work as expected (i.e. they're not latched on).

I guess the next thing to find out is if the TNC is faulty...

[John Stevenson]

Ade,
Try ringing Heidenhain on Monday.
I rang them over a problem with a 151 and after telling them the error message they suggested i check the Z axis encoder, I know that's not your fault but it was ours.

Encoder was full of oil and they took a debit card number and shipped us a new out out guaranteed before 10.00am next day.
Even offered to have the old one back, repair it for about 1/2 the price as a spare.

Point being they were most helpful before they knew they had got a sale.

[AdeV]

Ade,
Try ringing Heidenhain on Monday.
I rang them over a problem with a 151 and after telling them the error message they suggested i check the Z axis encoder, I know that's not your fault but it was ours.

Encoder was full of oil and they took a debit card number and shipped us a new out out guaranteed before 10.00am next day.
Even offered to have the old one back, repair it for about 1/2 the price as a spare.

Point being they were most helpful before they knew they had got a sale.

I think you may be right John, although I suspect a new TNC151 will be beyond my means.

I've verified the operation of relay CR10 (it works), as far as I can tell everything's bob on except it can't sense the 24vdc line...

[AdeV]

Aaaarrrrghhhhh!!!!!!


It was out of lube oil!


FFS.

Need to re-assemble it properly, but it would seem to be all working again.

[philf]

Ade,

I bet you're good at cryptic crosswords.

How on earth did you get from the clue of "Ext 24DC voltage missing" to "It was out of lube oil"?

Cheers.

Phil.

[AdeV]

Ade,

I bet you're good at cryptic crosswords.

How on earth did you get from the clue of "Ext 24DC voltage missing" to "It was out of lube oil"?

Cheers.

Phil.

I was looking at the circuit diagrams & noticed the lube oil motor, which reminded me that there was also a lube oil sensor... Although there was still a good inch of oil in the bottom of the tank, I figured I'd rule it out for sure by topping up; sure enough, as soon as I did that, off it went...

It doesn't like my new 24v regulator though, I keep getting "emergency stop"; this might be because the feed voltage is high per John Switft's posts, so I'm now reverting the circuit back to its original form...

Hey ho...

I am relieved it seems to be something simple (having exhausted all the complicated options...

[John Swift]

Hi Ade

well done
you could have spent days  looking for that !
why no low oil error         
(may be they runout of inputs and wired the external 24V via the low oil switch)


I've failed to find a wiring diagram that shows the ext 24V connection thats detected

 but now you have found out about the low oil fault

I found this :- http://www.cnczone.com/forums/bridgeport_hardinge_mills/161022-anyone_got_tnc_151_155_2500_control.html

   John

 *  now I seen your last post
the 7824 regulator may not be able to supply enough current

you might need a 2 or 3A regulator IC

 the simple regulator using the TIP32 may be able to supply 3A depending on its gain and the value of the resistor connecting its base to its collector

PS    some of the manuals I looked at :-

http://content.heidenhain.de/doku/oma_controls/CD1/tnc/151_155/gb/23268625.pdf

http://content.heidenhain.de/doku/oma_controls/CD1/tnc/151_155/gb/sa151155.pdf

http://content.heidenhain.de/doku/oma_controls/CD1/tnc/151_155/gb/22504128.pdf

****  PPS note the circuit will not work with a PNP transistor like TIP32 
you must use a NPN transistor like the TIP31       *******

[AdeV]

Cheers John

I tried putting two 7824s in parallel, no joy, same issue of cutting out. 1 was a 1.5A device, the other a 2A device.

I must have mis-drawn that circuit diagram as well, 'cos I rewired it as drawn & now it only outputs 1v & the resistor gets toasty hot.... (damn)


Edit to add: MY mistake, the chip is a TIP31A, that might change things?

[John Swift]

Hi Ade

yes

the TIP31A is a NPN transistor

http://www.st.com/web/en/resource/technical/document/datasheet/CD00104631.pdf

the polarity of the circuit will be reversed

    John

***** update circuit using TIP31A added  *****

[Bluechip]

Ade
 
Oh dearie, dearie me ... don't directly parallel regulators. One will do all the work and shortly go phtttttt 
I put a 0R22 resistor on the o/p pins and connect the outer ends, Take the o/p from there.
As per the Application notes ... 
 
Dave BC
 

[John Swift]

Hi Ade,

I've had a quick web search for the bridgeport 24V regulator

the only result was a picture of some components mounted on some tag board

using your first circuit and the tag board picture to come up with the picture below

( note -  the wiring between the tags is my guess )

John

not sure why I could not upload 2nd picture as jpeg - see pdf

[awemawson]

In fact rather like my description of your circuit in words a few posts ago! thus :

"I wouldn't mind betting that the TIP32A is being used in an emitter follower configuration withe the collector being the input, the emitter being the output, and a zener diode from it's base to common 0v, with probably a bias resistor from the top of the zener to +ve. The idea is that the emitter will follow the voltage on the base but offset by 0.6 - 0.7v which is the Vbe drop of a silicon transistor."

I have a vague recollection that the regulator on my late lamented Interact was mounted on tag strip.

[John Swift]

we have come full circle !

If Ade can let us know the value of the resistor , capacitor and part numbers for the diodes

I'll amend the circuit and if Ade wants to get parts in a hurry ,
possible alternatives from Maplins limited range

( just looked and they sell the TIP31C and BZV85 1.3 Watt zenners both 12V &24V versions
depending on the resistor you may need  two BZV85C12V in series will give you a 24V 2.6W zenner )

RS components sell the 78S24   24V 2A   IC regulator but the maximum input of 40V
could be exceeded without a preregulator!



as an  example the circuit below is  for a   commercial 1A 24V supply
the simplest solution is to rebuild the original 24V regulator


John

[awemawson]

I agree - build the original simple regulator circuit - I just hope that the 41v Adev briefly unleashed into the TNC151 didn't blow anything up. I do seem to remember that there are current limiting resistors on each input but cannot remember whether there is a voltage clamp on the far side of the input resistor.

[AdeV]

Andrew - yep, the 24v regulator is on a piece of tag board. I notice there are a few circuits on this size/style board dotted around the machine...

John,

The components are as follows, connected top-bottom or as described:

Capacitor: 470uF, 63v electrolytic, negative to top strip.
Empty tag pair
Mystery diode (signal diode I think), looks like "4002" printed on it. -ve end down.
TIP31A base (bottom tag only)
TIP31A collector (bottom tag only)
TIP31A emitter (bottom tag only)
Empty & unused tag pair
Zener diode BZX61C24, -ve end faces down
Resistor, 820 ohm (confirmed with multimeter)



The top left 3 tags have GND, +24V, and INPUT from bridge rectifier (pins 2,3,1 on the schematic Andrew posted).


Andrew: I've had the unit functioning, but it kept cutting out (stating "Emergency Stop"), which I hope is due simply to the 7824's not delivering sufficient current.  I was obviously overvolting them as well, as the output voltage was beginning to drift downwards away from 24v...


Edit: Please note the wire link between the -ve end of the Zener & the resistor... that is original

[awemawson]

That'll be a 1N4002 which is a 70v piv 1 amp diode. The output (emitter) is tied to the base less 0.6v Vbe drop, so they are putting another diode in series with the 24v diode to make (effectively) a 24.6v zener to give 24v output!