Author Topic: Bridgeport Interact II failure  (Read 21345 times)

Offline AdeV

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Re: Bridgeport Interact II failure
« Reply #25 on: March 24, 2013, 02:45:08 PM »
Right, scratching my head a bit now, I rebuilt the circuit according to John's diagram (minus the reversed diode behind the Zener, which isn't on my board); I get 0v & a hot resistor...

This is on my test bench, I am feeding it anything from 0-35v, 0-2A...

If I give it less than 24v, the resistor stays cool. Above 24v, it gets hot.

This _has_ to be nearly what I had before....

I have a spare N4002(ish) if adding the reverse diode will make it work...
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Occasionally: Zhengzhou, China. An even longer way from anywhere...

Offline awemawson

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Re: Bridgeport Interact II failure
« Reply #26 on: March 24, 2013, 02:51:40 PM »
The resistor should drop your input voltage minus 24.6. (=DeltaV) So using ohms law you can calculate what current it draws (DeltaV/R) And what power it dissipates (I squared x R) Is that less than or greater than the assumed 2 watt power rating? Is your TIP31 ok or is it blown up?
Andrew Mawson
East Sussex

Offline AdeV

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Re: Bridgeport Interact II failure
« Reply #27 on: March 24, 2013, 02:57:57 PM »
Is your TIP31 ok or is it blown up?

It _should_ be OK, it wasn't in the circuit when I saw 41v, and whilst the whole thing was giving out 26.4v when I removed it, that's more or less within limits...


I tried adding the reverse diode: Nada.
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Occasionally: Zhengzhou, China. An even longer way from anywhere...

Offline John Swift

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Re: Bridgeport Interact II failure
« Reply #28 on: March 24, 2013, 03:45:29 PM »
 Hi Ade

the  revised picture with the component values added

testing a transistor with a multimeter :-
http://www.allaboutcircuits.com/vol_3/chpt_4/3.html

   John

Offline AdeV

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Re: Bridgeport Interact II failure
« Reply #29 on: March 24, 2013, 04:28:43 PM »
Hrmph, looks like I've toasted the TIP31A. Time to order a new one....

Many thanks for your help John, hopefully I will have it all back up & running next week...

Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Occasionally: Zhengzhou, China. An even longer way from anywhere...

Offline John Swift

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Re: Bridgeport Interact II failure
« Reply #30 on: March 24, 2013, 07:51:01 PM »
Hi Ade ,

looking at the regulator circuit again

with 16V dropped across the 820 Ohm resistor
the current through the resistor is 16/820 = 0.0195 A  = 19.5 mA

if about half of this current  passes into the base of the TIP31A ,
( with the minimum current gain of 25 )

the maximum current that can be taken by the TNC control will be about 250 mA    (1/4 A)
before the output voltage starts to drop

with a little more current diverted from the 24V zenner and  a transistor with a current gain nearer to the maximum of 50
  you may be able to take around 700 mA  provided the heatsink is big enough

with too small a current through the zenner diode the regulation will be affected


using a 6 watt 100 ohm resistor as a load
you could test the repaired regulator  before its fitted  in the machine

  John 
« Last Edit: March 25, 2013, 01:00:21 PM by John Swift »

Offline AdeV

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Re: Bridgeport Interact II failure
« Reply #31 on: March 29, 2013, 12:09:57 PM »
 :mmr:

Woohoo! We are back in running order! Turns out the Zener was toast (probably, might have been the TIP31A as well); fortunately I bought enough parts to build a whole new regulator (er, or two) if needs be, so normality is now resumed.

Phew!

Of course, the trick next time is to not dismantle the machine before checking t'internet.... (oops).


Thanks for all your help & pointers, I would still be farting around with that circuit without your help...
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Occasionally: Zhengzhou, China. An even longer way from anywhere...

Offline awemawson

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Re: Bridgeport Interact II failure
« Reply #32 on: March 29, 2013, 02:29:11 PM »
Glad to hear that you are up and running again AdeV - I know the frustration of machines failing, and that sinking feeling in the pit of the stomach.

I do actually miss my long gone Interact - superbly made machines. (There's still a pothole outside the village school where it fell off the lorry)  :doh:
Andrew Mawson
East Sussex

Offline AdeV

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Re: Bridgeport Interact II failure
« Reply #33 on: March 29, 2013, 02:39:31 PM »
A sad end to the machine - did you keep any spare parts BTW? I have a noisy choke (or possibly autotransformer) in mine, it doesn't seem to affect the machine in any way, but it' be nice if it sat there a little quieter, when not in use...
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Occasionally: Zhengzhou, China. An even longer way from anywhere...

Offline awemawson

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Re: Bridgeport Interact II failure
« Reply #34 on: March 29, 2013, 05:12:21 PM »
S.d's law applied - it fell off because the pallet it was on collapsed, and as luck would have it the entire weight went onto the TNC151b flattening it. The sem motors both tore off their mountings and were wrecked. To be honest I literally couldn't face dealing with it for months - it choked me up. He dragged it back to his barn where I'd been storing it while I built my workshop. I did eventually manage to lever open the cabinet and extract two Bosch servo drives for a chap who's machine had failed. A good friend had offered to move it on his flat bed farm trailer and his 'man' was a bit enthusiastic with the accelerator and brakes. Needless to say no insurance covered it.
Andrew Mawson
East Sussex

Offline John Swift

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Re: Bridgeport Interact II failure
« Reply #35 on: April 05, 2013, 03:23:06 PM »

I thought I was having a bad day with the dreaded blue screen  :doh:

Ade glad to see your machine is working again  :clap:

   John