Author Topic: Facit 1132 Nixie Calculator restoration  (Read 4803 times)

0 Members and 1 Guest are viewing this topic.

Offline pqass

  • Frequent Contributor
  • **
  • Posts: 705
  • Country: ca
Re: Facit 1132 Nixie Calculator restoration
« Reply #25 on: June 06, 2023, 11:16:52 pm »
...
I'll check Q1, Q6, Q7 during the course of the next days out of circuit.
...
With GREY (33R) and WHITE (60R) loaded down:
C4: 9.8 DCV (always), mystery device right leg pair: 8.6 DCV, or virtually no voltage?

minimal loads:
C4: 10.0 DCV, mystery device right leg pair: OL, 3.98 DCV, flashing bar graph?

Not sure if something is intermittent and I'm getting different results on the mystery device, but it's probably wise to exercise the pot and reflow some joints. If you think it's a good idea I could also try to scope the voltages around that area, maybe the multimeter doesn't like the output.

Btw, R1 = 1k (if it's the "dog bone" style resistor) and measures as such, R3 = 2k and is at 2k3

Before pulling off the transistors to test out-of-circuit...

If C4 is about 10V WRT GND (when both loaded and miminally loaded), then I suspect the mystery device IS NOT transmitting that through to Q6 base.  If it were, then WHITE (5) should be +8.8V (unless the mystery device was adding a Vdrop of its own).  But you also said that the right leg pair was 8.6VDC or virtually zero at times.  That sounds intermittent.  The problem could be on the right side of the mystery device but it also could be that the left legs aren't receiving a signal and therefore the right legs are open (seen as 0.4V on base of Q6).  I still suspect the mystery device is an optocoupler.

(a) Lets start with reflowing the solder on the leg pads of the mystery device and traces to all other immediate devices (Q1 collector, R1 (both sides to diode-bridge unreg. positive rail), Q6 base, and to the C4 cap and RV2 pot wiper).

(b) You could exercise the pot, although the wiper reports 10V under both load and minimal load, so it may not be necessary.  BUT IF YOU DO, mark the spot on the screw and body so you can return it to that same point. ie. output of wiper to GND should go back to 10VDC.  We don't want to lose this calibration!

(c) If the above reflow (a) doesn't produce a real voltage on WHITE(5) of +8.8V WRT GND (my prediction), then you can lift the two upper pins of the mystery device (on left and right sides, leaving the lower pins connected) and then short the RV2 pot wiper/C4 positive leg to Q6 base (tack/clip a jumper wire).  Then measure WHITE(5) and GREY (3) (loaded and minimally loaded).  If you see +8.8V WRT GND on WHITE(5) then that confirms Q6 and Q7 are okay. BUT MAKE SURE there is NOTHING CONNECTED at the other end of the WHITE (5) wire (NO logic and display BOARDS INSTALLED in the edge connectors).

(d) While you have the upper legs of the mystery device lifted, check underneath for any markings. 
(e) Also, use the diode-check on your MM to find on which pair (left or right) of the mystery device the LED is on and in which orientation (cathode on upper or lower).
(f) You can then remove the temporary jumper wire (c) and put the upper legs back into their holes and re-solder in place.


WRT using an oscilloscope, I'm not sure you'll see much since all the points to measure will be VDC. If you want, you could see if the unregulated side of the diode bridge (positive and negative) or the unregulated side of the diode-pair (positive) don't have excessive ripple (>2V) but you can do this later once we get WHITE(5) working.   DO NOT ATTACH your scope probe anywhere from the brown HV transformer winding to the RED (1) rail.  I don't want you to blowup your 'scope.  Of course, all measurements should be WRT (probe ground clip on) GND.

WRT R1 measuring 1K instead of 2K, that would just double the current through the left legs of the mystery device to ~22mA from ~11mA; that's not an unreasonable current through an LED (which I suspect is in the mystery device). 

WRT R3 being 2.3K vs 2K, thats just a 15% increase so the current through the zener goes from 4mA to 3.5mA which, for my taste, seems a bit low for a zener bias but GREY(3) is regulating properly so I wouln't worry about that.
 

Offline agent_powerTopic starter

  • Regular Contributor
  • *
  • Posts: 73
  • Country: it
Re: Facit 1132 Nixie Calculator restoration
« Reply #26 on: June 07, 2023, 08:51:51 pm »
Alright:

a) didn't solve the problem

b) didn't solve the problem

c) does make a difference, WHITE with minimal load: 8.9 DCV, with 60R load: 8.5 DCV (Q6 + Q7 confirmed working?)

d) no markings

e) no voltage drop in any direction

f) should I put it back in, or desolder it completely and test it in another circuit?

Is the mystery device or Q1 possibly faulty?
 

Offline schmitt trigger

  • Super Contributor
  • ***
  • Posts: 2205
  • Country: mx
Re: Facit 1132 Nixie Calculator restoration
« Reply #27 on: June 07, 2023, 11:04:01 pm »
Subscribing to a very interesting thread.
 

Offline pqass

  • Frequent Contributor
  • **
  • Posts: 705
  • Country: ca
Re: Facit 1132 Nixie Calculator restoration
« Reply #28 on: June 08, 2023, 03:02:36 am »
(a) bummer.

(b) bummer.

(c) YES, it looks like Q6 and Q7 are working.  The big questions are now: is this the correct output voltage given that we bypassed the mystery device? Or does it add a Vdrop to lower WHITE (5) by some amount?  And is the mystery device just a means to delay enabling WHITE (5) behind GREY (3)?

Q: While you've shorted the C4 positive to Q6 base, and WHITE (5) is +8.5VDC, is GREY (3) still outputing +13.3VDC?   
If so, then it confirms that Q1 is correctly modeled (collector to mystery device) in my last (May 31) schematic.

Nevermind, WHITE(5) won't be producing anything if GREY(3) didn't have a voltage on it since we're feeding part of that back to Q6 base. Further, if the zener D5 was disconnected then GREY(3) would be just a couple of volts below its unregulated side which would make WHITE(5) a lot higher than the predicted +8.8VDC.

(d) bummer.

(e) bummer.

(f) The dot on the left leg sure smells like it's indicating the cathode to me. 
But there is zero chance that it has an LED with large Vdrop like a modern white LED.  And your MM isn't measuring it properly.   EDIT: I just checked if my bench meter's diode-check can measure a red LED. It can't. So you'll have to do it out-of-circuit.  See "...report back the Vdrop on the left pair..." below.

Q:You said that R1 measures 1K but is it marked 2K?
If true, then that changed the current from 11mA to 22mA (based on 22V unreg. rail) but this should not be enough to kill the LED (if it exists) in the mystery device because many old optocouplers have robust LEDs that can take 40+mA continously.

I guess you can try to test Q1 out-of-circuit. 
Q: Are you using one of those component testers that shows transistor type, EBC pinout, hFE, etc?

When you do remove Q1, confirm from the underside (based on the tab) exactly which pin is going to GND, zener, and mystery device upper-left leg.  Datasheet: https://www.web-bcs.com/transistor/tc/2sc/2SC857.php

If Q1 is good, then you can remove the mystery device and test it separately by connecting:
i. upper left to 0V, lower-left to 1K to Vcc,
ii. upper right to 0V, lower-right to 10K to Vcc
iii. with your multimeter on VDC on the right pair.
iv. use 22VDC for Vcc from a lab power supply or lacking that a wall-wart/laptop power supply that can do any fixed value between 12VDC and 22VDC.
If it's a working opto coupler then connecting and disconnecting the 1K should cause the MM to go from 0V to Vcc.
Also, report back the Vdrop on the left pair when the 1K is connected.
EDIT: Also, while you have the mystery device out, confirm with your MM set to ohms, that there is very high resistance between any pin on the left side to any on the right side.

Good luck.
« Last Edit: June 08, 2023, 04:07:28 pm by pqass »
 

Offline agent_powerTopic starter

  • Regular Contributor
  • *
  • Posts: 73
  • Country: it
Re: Facit 1132 Nixie Calculator restoration
« Reply #29 on: June 09, 2023, 08:06:29 pm »
Quote
Q:You said that R1 measures 1K but is it marked 2K?
If true, then that changed the current from 11mA to 22mA (based on 22V unreg. rail) but this should not be enough to kill the LED (if it exists) in the mystery device because many old optocouplers have robust LEDs that can take 40+mA continously.


My mistake in the post with the picture, it's marked 1K and measures 1K

Quote
I guess you can try to test Q1 out-of-circuit.
Q: Are you using one of those component testers that shows transistor type, EBC pinout, hFE, etc?

When you do remove Q1, confirm from the underside (based on the tab) exactly which pin is going to GND, zener, and mystery device upper-left leg.  Datasheet: https://www.web-bcs.com/transistor/tc/2sc/2SC857.php

See pictures, looks good to me unless it's noisy or intermittent or something like that

Quote
If Q1 is good, then you can remove the mystery device and test it separately by connecting:
i. upper left to 0V, lower-left to 1K to Vcc,
ii. upper right to 0V, lower-right to 10K to Vcc
iii. with your multimeter on VDC on the right pair.
iv. use 22VDC for Vcc from a lab power supply or lacking that a wall-wart/laptop power supply that can do any fixed value between 12VDC and 22VDC.
If it's a working opto coupler then connecting and disconnecting the 1K should cause the MM to go from 0V to Vcc.
Also, report back the Vdrop on the left pair when the 1K is connected.
EDIT: Also, while you have the mystery device out, confirm with your MM set to ohms, that there is very high resistance between any pin on the left side to any on the right side.

Out of circuit, there's few dozens MOhms between the legs

See the picture.. not sure I'm doing something wrong but it's just measuring Vcc. Disconnecting the 1K doesn't make a difference

 

Offline pqass

  • Frequent Contributor
  • **
  • Posts: 705
  • Country: ca
Re: Facit 1132 Nixie Calculator restoration
« Reply #30 on: June 10, 2023, 08:16:48 pm »
Since the transistor looks to be working (and you earlier eliminated connection issues), therefore, I think the mystery device is probably dead.  Unfortunately, we can't absolutely prove that it's an optocoupler but I can't think of any other thing it could be.  It has the case style, dot mark, and high resistance between left/right leg pairs (even if one leg is broken).  And is consistent with an isolated low-current switch for the WHITE(5) darlington pair. It all fits.

But before we pronounce it truely dead, one last test...  connect a multimeter in ammeter mode to see if the left pair is drawing any current at all.   It should draw ~20mA in your breadboard setup.  See attached test setup schematic.  You had said it appeared to be intermittent in your earlier message. So try tapping on the device with your finger while watching the ammeter and voltage drop on the right pair.

If there is still no current in the left pair and no change in the right pair (always shows Vcc) then you probably can substitute the mystery device with a 4N35 or a TIL111 optocoupler (or almost any with a ~40mA LED continuous current with phototransistor output). Note the pins of cathode/emitter in the modern part (rotated CW 90°); they're opposite to dot on the mystery device.

I happen to have a TIL111 that exhibits a 100mV drop on the phototransistor when 20mA is applied to the LED.  Given that the darlington pair has a high hFE, causing only a minimal drop in RV2 wiper voltage, that should result in about a +8.3V WHITE(5) WRT GND (and about -5V WRT chassis) regulated output.  FYI: see attached schematic showing divider with RV2 wiper and opto driving the darlington pair; ie. how I believe WHITE(5) regulation is intended to work.

Also attached is the latest schematic of the PS with updated notes and measurement table.
Thanks for confirming Q1 orientation.  I can only think it is being used to delay WHITE(5) after GREY(3) is up.

Relative to GND, the outputs (1,5,3,2,6) are: +169V, +8.3V, +13.2V, +8.1V, -9.7V
But, relative to chassis, the outputs (1,5,4,2,6) are: +155V, -5V, -13.2V, -5.4V, -23.3V
The HV is sagging a bit since it's probably loaded too much (with the 2.2K). 
But it's interesting that there is a (approx) -5V and a -24V in there.
As such, we may be on the right track WRT correct output voltages.
 
« Last Edit: June 10, 2023, 09:16:35 pm by pqass »
 

Offline agent_powerTopic starter

  • Regular Contributor
  • *
  • Posts: 73
  • Country: it
Re: Facit 1132 Nixie Calculator restoration
« Reply #31 on: June 12, 2023, 02:39:22 pm »
Ok, I got some life out of it in the breadboard setup:

I tried your test - didn't help. The next best thing to do with intermittent devices apart from hitting them is temperature: Spraying cold spray didn't help, but heating it up with hot air turned it on pretty quickly.

The current draw was about 23mA, the voltage measured on the right pair went from 0.8V (torched) to about 0.45V (cooled down a minute), then turned off entirely (= measured voltage on right pair back to Vcc).

While conducting, I could disconnect the 1K to turn it off.

Can we pronounce it broken? I don't know of any optocouplers that need to be warmed up. Am I missing something? Some primitive delay circuit and it only works under load?
« Last Edit: June 12, 2023, 02:40:53 pm by agent_power »
 

Offline pqass

  • Frequent Contributor
  • **
  • Posts: 705
  • Country: ca
Re: Facit 1132 Nixie Calculator restoration
« Reply #32 on: June 12, 2023, 03:59:38 pm »
Good thinking with the hot/cold test!   

Yeah it's dead.  Swap-in another optocoupler and call it done. 
Then add the loads to GND: 10K*, 33R*, 33R, 22R, for RED(1), WHITE(5), GREY(3), ORANGE(6), respectively.  (*=more realistic)
Measure them WRT GND and WRT chassis and I'll update the schematic.

This part doesn't do any serious power handling.  Nor is there any constant switching; Q1 via zener turns on once at power up and keeps the LED lit.  The phototransistor shouldn't heat up since there's <1mA to Q6 base for up to 2.5A out of WHITE(5).  I guess the LED at a constant 28mW (1.2V*23mA) eventually caused a crack somewhere.

The only possible issue I see is a difference in Vce across the dead vs the new phototransistor. If the new part is less than the dead part, the new part will raise WHITE(5) output by the difference; eg. Vce=450mV vs TIL111 Vce=100mV leads to an increase of 350mV. But given that the Vce of the dead part was going down (450mV) as it was cooling off (before cutting out), even at that point it would be <5% difference in the regulated output.  So, I wouldn't worry about it.
 

Offline agent_powerTopic starter

  • Regular Contributor
  • *
  • Posts: 73
  • Country: it
Re: Facit 1132 Nixie Calculator restoration
« Reply #33 on: June 16, 2023, 09:38:44 am »
I found a 4n35 (Vce=70mV, still ok?)... quick check before I power it up:

Is it wired in correctly? Or do I need to swap the C / E around?
 

Offline pqass

  • Frequent Contributor
  • **
  • Posts: 705
  • Country: ca
Re: Facit 1132 Nixie Calculator restoration
« Reply #34 on: June 16, 2023, 03:50:08 pm »
I found a 4n35 (Vce=70mV, still ok?)... quick check before I power it up:

Is it wired in correctly? Or do I need to swap the C / E around?

The 4n35 should be fine.
And you have it the right way assuming the LED is on the left, phototransistor on the right.

But before powering up with the logic and display boards installed, let see what the output voltages are under load.
Connect to GND: 10K*, 33R*, 33R, 22R, for RED(1), WHITE(5), GREY(3), ORANGE(6), respectively.  (*=more realistic)
Measure them WRT GND (BROWN(4)) and WRT chassis (GREY(3)).
 

Offline agent_powerTopic starter

  • Regular Contributor
  • *
  • Posts: 73
  • Country: it
Re: Facit 1132 Nixie Calculator restoration
« Reply #35 on: June 17, 2023, 08:55:29 pm »

The 4n35 should be fine.
And you have it the right way assuming the LED is on the left, phototransistor on the right.


Ah, yes, I didn't have the latest schematics printed out and wasn't sure about the wiring of the phototransistor.

Quote
But before powering up with the logic and display boards installed, let see what the output voltages are under load.
Connect to GND: 10K*, 33R*, 33R, 22R, for RED(1), WHITE(5), GREY(3), ORANGE(6), respectively.  (*=more realistic)
Measure them WRT GND (BROWN(4)) and WRT chassis (GREY(3)).


No 10K available (of that wattage) for the RED supply, but with 2x22k at about 10.8K I get 207 DCV WRT GND, 193.5 DCV WRT GREY respectively.

With the 33R load, WHITE is: 8.8 DCV WRT GND, -4.9 DCV WRT GREY, but I noticed that it creeps up with temperature. Is this something to worry about? Is the 2SC830 failing or is this normal behaviour? It went from about 8.6ish to 8.8205-ish (sometimes creeping up, sometimes going back down, more or less remaining there now). If I blow on it changes a little...?

The optocoupler is slightly warm..

I think it's repaired? Time for the logic boards? Or is it better to implement the protection circuit against shorting transistors first?
 

Offline pqass

  • Frequent Contributor
  • **
  • Posts: 705
  • Country: ca
Re: Facit 1132 Nixie Calculator restoration
« Reply #36 on: June 17, 2023, 11:56:45 pm »
No 10K available (of that wattage) for the RED supply, but with 2x22k at about 10.8K I get 207 DCV WRT GND, 193.5 DCV WRT GREY respectively.


10.8K (22K||22K) is an acceptable load for the HV output. It puts the current on that output to about 20mA.  207V/193.5V (WRT GND/chassis) still seems a bit high to me but may be warranted for a 16 digit multiplexed nixie design. Later, if you wish, you can turn down the pot with the red knob if you want to lower the brightness and prolong the life of the nixies.

Quote

With the 33R load, WHITE is: 8.8 DCV WRT GND, -4.9 DCV WRT GREY, but I noticed that it creeps up with temperature. Is this something to worry about? Is the 2SC830 failing or is this normal behaviour? It went from about 8.6ish to 8.8205-ish (sometimes creeping up, sometimes going back down, more or less remaining there now). If I blow on it changes a little...?


Good to see that the WHITE(5) output is now working. Whether it's 8.8V or 8.6V (WRT GND) is not really that important. It's only about a ±1.5% difference. Transistors and diodes exhibit a -2.2mV/°C drop in Vbe as they warm up. The transistors Q6, Q7, Q3, and Q4 (last two affects the divider which serve as a reference to regulate the first two) will change due to the regulator design; that is, one without feedback to compensate for this Vbe change. The designers thought this was acceptable so don't worry about it.

Quote

The optocoupler is slightly warm..

I think it's repaired? Time for the logic boards? Or is it better to implement the protection circuit against shorting transistors first?

A slightly warm optocoupler should be fine.

Yes, I think it's repaired. 
As long as the other outputs still show these voltages (under 33R/none/22R loads WRT GND):
             GREY(3): +13.2V,    ORANGE(2): +8.14V,     ORANGE(6): -9.7V

We've reverse-engineered the PS circuit and determined that the GREY(3), ORANGE(6), and thus ORANGE(2) are solely regulated from fixed zeners. And zeners don't really change much with age, therefore, I'm confident that these outputs are correct.  RED(1), the HV output, can likely move quite a bit (via pot RV1) since there are likely only the nixie anodes connected to it (no ICs). WHITE(5) is controlled via pot RV2 but is also linked to the fixed zener D5 via divider so as long as you put back pot calibration (after exercising it), you should be fine here too.

Since we've confirmed that all the power transistors are still good and regulating properly under load, I think you can put back the logic and display boards and power it all up to see if it comes back to life.

When you do power it all up with logic and display boards installed, you're going to have to take voltage readings (WRT GND and chassis) on all outputs again to establish a base-line (under the real load).  We only tested it to a 400mA load on the LV outputs and 20mA load on the HV output.  Then we can discuss the protection circuits afterwards.

See attached for the latest schematic with updated notes.
« Last Edit: June 18, 2023, 01:41:20 am by pqass »
 

Offline agent_powerTopic starter

  • Regular Contributor
  • *
  • Posts: 73
  • Country: it
Re: Facit 1132 Nixie Calculator restoration
« Reply #37 on: June 18, 2023, 09:28:21 am »
Good and bad news:

It powers up and the nixies light up too. There was even a 0 on the rightmost nixie, but after 15 seconds it showed random numbers and went comatose.

Here are the voltages, with the RED pot all the way down (one dot on the nixies still lights up, I guess that's good enough voltages)

WRT GND, chassis in VDC:

RED: 190, 176.8
WHITE: 5.6, -7.7
BROWN: 0, -13.4
GREY: 13.4, 0
ORANGE(2): 2.9, -10.5
ORANGE(6): -9.8, 23.3

WHITE and ORANGE(2) deviate from the prediction.. close, but no cigar

EDIT: Attached are some scope pictures.. not sure what to make of it, WHITE still looks weird compared to the others
« Last Edit: June 18, 2023, 11:49:35 am by agent_power »
 

Offline agent_powerTopic starter

  • Regular Contributor
  • *
  • Posts: 73
  • Country: it
Re: Facit 1132 Nixie Calculator restoration
« Reply #38 on: June 18, 2023, 02:42:36 pm »
I swapped some boards out while trying to figure out if one drags down voltages due to a shorted component. Voltages were all over the place with some boards missing, so I'm not sure if there's additional regulation or referencing happening in the whole circuit.  :-//

The last try was having all boards in but the keyboard disconnected, and it seems to work now.

Almost every key was completely stuck and tried to get it going with some contact lubricant (it usually dissolves the old grease well enough).... in this case I might have addition faults in there
 

Offline pqass

  • Frequent Contributor
  • **
  • Posts: 705
  • Country: ca
Re: Facit 1132 Nixie Calculator restoration
« Reply #39 on: June 18, 2023, 02:51:26 pm »
Good and bad news:

It powers up and the nixies light up too. There was even a 0 on the rightmost nixie, but after 15 seconds it showed random numbers and went comatose.

Here are the voltages, with the RED pot all the way down (one dot on the nixies still lights up, I guess that's good enough voltages)

WRT GND, chassis in VDC:

RED: 190, 176.8
WHITE: 5.6, -7.7
BROWN: 0, -13.4
GREY: 13.4, 0
ORANGE(2): 2.9, -10.5
ORANGE(6): -9.8, 23.3

WHITE and ORANGE(2) deviate from the prediction.. close, but no cigar

EDIT: Attached are some scope pictures.. not sure what to make of it, WHITE still looks weird compared to the others

WRT GND
WRT chassis
My Comments
RED(1):
+190V
+176.8V
Good. Within acceptable limits. Nixies light-up (typ. >165V) nor excessively bright.
WHITE(5):
+5.6V
-7.7V
Bad. Likely a consequence of ORANGE(2) droop.
BROWN(4): a.k.a GND
0V
-13.4V
Good. No drooping.
GREY(3): a.k.a chassis
+13.4V
0V
Good. Confirms reverse of BROWN(4).
ORANGE(2):
+2.9V
-10.5V
Bad. See below.
ORANGE(6):
-9.8V
+23.3V
Good. No drooping.

WHITE(5) is 2 volts below what it should be but this is very likely because of ORANGE(2) is drooping. And the +5.6V WRT GND is consistent with a +2.9V ORANGE(2).  Normally, for RV2 wiper to output +10V (with GREY(3) at +13.4V) RV2 needs to be split 160R/340R.  But, given  that ORANGE(2) is now +2.9V, therefore, 13.4-2.9=10.5×(330+160)÷(330+500+500)+2.9=6.77 at the wiper, and therefore, 6.77-1.2=5.6V at WHITE(5).

ORANGE(2) should be close to +8.1V WRT GND or -5.4V WRT chassis.  Because it is derived from a resistor divider, that implies that whatever it feeds must be high impedence otherwise it will cause it to droop.  Which is what is happening.  Unfortunately, you are going to have to trace where the ORANGE (2) wire goes; which board(s), which component(s) it immediately touches. It is probably used as a reference (my guess) so it shouldn't be used in lots of places; probably leads to a [bad] buffer amp that's loading it down.

Q1: Immediately upon power-up, is ORANGE (2), WHITE(5) normally at +8.1V, +8.6V, respectively, and then they droop?
Q2: Immediately upon power-up, can you type on the keyboard and does the machine respond normally before it goes comatose?

The 'scope shots show high-frequency noise (the most on WHITE(5)) and the periodic ripple/spikes are below 20mV and likely due to transistor/IC switching.  That doesn't look that bad. There should be local cap decoupling next to the ICs to get rid if it.

 

Offline agent_powerTopic starter

  • Regular Contributor
  • *
  • Posts: 73
  • Country: it
Re: Facit 1132 Nixie Calculator restoration
« Reply #40 on: June 18, 2023, 04:17:46 pm »
ORANGE(2) should be close to +8.1V WRT GND or -5.4V WRT chassis.  Because it is derived from a resistor divider, that implies that whatever it feeds must be high impedence otherwise it will cause it to droop.  Which is what is happening.  Unfortunately, you are going to have to trace where the ORANGE (2) wire goes; which board(s), which component(s) it immediately touches. It is probably used as a reference (my guess) so it shouldn't be used in lots of places; probably leads to a [bad] buffer amp that's loading it down.

Q1: Immediately upon power-up, is ORANGE (2), WHITE(5) normally at +8.1V, +8.6V, respectively, and then they droop?


It looks like it stabilises at 5.6 V immediately.

I traced it to yet another alien looking thing (see attachment). The second legs seems to go to a ground plane as the trace then stretches across the board connecting many other components...I haven't found out if it's one of the established grounds (BROWN or GREY). I guess to know what the voltage should be we need to figure out this component too.

Quote

Q2: Immediately upon power-up, can you type on the keyboard and does the machine respond normally before it goes comatose?


See my second post after the scope pictures. It seems to power up correctly without keyboard and there is possibly a fault there.
 

Offline pqass

  • Frequent Contributor
  • **
  • Posts: 705
  • Country: ca
Re: Facit 1132 Nixie Calculator restoration
« Reply #41 on: June 18, 2023, 06:05:03 pm »

Q1: Immediately upon power-up, is ORANGE (2), WHITE(5) normally at +8.1V, +8.6V, respectively, and then they droop?


It looks like it stabilises at 5.6 V immediately.

I traced it to yet another alien looking thing (see attachment). The second legs seems to go to a ground plane as the trace then stretches across the board connecting many other components...I haven't found out if it's one of the established grounds (BROWN or GREY). I guess to know what the voltage should be we need to figure out this component too.


That half-dissolved pill thing looks like a cap.  The '70s had some weird packages.

I looked around and just see carbon resistors, green polyester film caps, glass diodes, transistors, ICs, and some kind of hybrid(?) packages (those marked "Sharp" "DP4" "DN3" etc.). I only see one blue axial electrolytic cap and no tantalum caps; the latter can go short.  The carbon resistors might increase in resistance as they get old but the semiconducters should be fine if not abused.

Yeah, figuring-out which is the common is hard given we don't have any datasheet on any of the ICs.

I suppose it is possible that ORANGE(2) is intentionally being pulled down.

Quote
Quote

Q2: Immediately upon power-up, can you type on the keyboard and does the machine respond normally before it goes comatose?


See my second post after the scope pictures. It seems to power up correctly without keyboard and there is possibly a fault there.

So, without the keyboard (all other boards installed), the voltages are still those below?
   WHITE(5):  +5.6V    -7.7V     WRT GND/chassis
   ORANGE(2):   +2.9,    -10.5    WRT GND/chassis

And, also without keyboard, does it still go comatose after 15 seconds?
If it DOES NOT go comatose without the keyboard then I'd give the keyboard a good cleaning and test each of the switches for continuity (high-resistance when not pressed, low-resistance when pressed).  Then reboot with keyboard installed and see if it still goes comatose.  A key may be loading down a power rail.

The comatose issue or low ORANGE(2) may not be related.
 

Offline agent_powerTopic starter

  • Regular Contributor
  • *
  • Posts: 73
  • Country: it
Re: Facit 1132 Nixie Calculator restoration
« Reply #42 on: June 19, 2023, 09:05:50 pm »

So, without the keyboard (all other boards installed), the voltages are still those below?
   WHITE(5):  +5.6V    -7.7V     WRT GND/chassis
   ORANGE(2):   +2.9,    -10.5    WRT GND/chassis

And, also without keyboard, does it still go comatose after 15 seconds?
If it DOES NOT go comatose without the keyboard then I'd give the keyboard a good cleaning and test each of the switches for continuity (high-resistance when not pressed, low-resistance when pressed).  Then reboot with keyboard installed and see if it still goes comatose.  A key may be loading down a power rail.

The comatose issue or low ORANGE(2) may not be related.


The voltages remain the same with the keyboard disconnected, the only difference is the 0 doesn't show up (it only appears comatose with the keyboard connected).

Working assumption: the boards regulate ORANGE(2) and WHITE somehow and there are no faulty components that influence it.

Any idea how to disassemble those type of keyboards? I've never handled one like that... the wires are soldered to phenolic boards sandwiched between metal plates. Is it possible to bend those metal pieces back..? I guess that's how you un-sandwich it...

I would like to throw this in an ultrasonic cleaner but I don't own one and the keyboard can't be disconnected from the backplane. Alternatively, I'll try to map out the keyboard. My hope is that maybe just one or two keys are stuck close and hinder the calculator from operating correctly.

PS: There's a really bizarre connector on the back.. what could be the purpose? Remote control... factory testing?



 

Offline pqass

  • Frequent Contributor
  • **
  • Posts: 705
  • Country: ca
Re: Facit 1132 Nixie Calculator restoration
« Reply #43 on: June 19, 2023, 10:22:49 pm »

The voltages remain the same with the keyboard disconnected, the only difference is the 0 doesn't show up (it only appears comatose with the keyboard connected).

Working assumption: the boards regulate ORANGE(2) and WHITE somehow and there are no faulty components that influence it.


That's a reasonable assumption.

Quote

Any idea how to disassemble those type of keyboards? I've never handled one like that... the wires are soldered to phenolic boards sandwiched between metal plates. Is it possible to bend those metal pieces back..? I guess that's how you un-sandwich it...


Maybe you can first separate all key groups from the top of the enclosure. It looks like it can come off as one unit.  I think that row of brass phillips screws above & below the blue wires (from your first message) secures them.  That should give you access side-on to spray contact cleaner and exercise the keys.  I don't think you should separate those plates as they are punched along the left and right edges (4 times) of each key group.  It'll probably cause you grief to put back together with multiple springs and alignment points. And never be flat again.

Quote

I would like to throw this in an ultrasonic cleaner but I don't own one and the keyboard can't be disconnected from the backplane. Alternatively, I'll try to map out the keyboard. My hope is that maybe just one or two keys are stuck close and hinder the calculator from operating correctly.

PS: There's a really bizarre connector on the back.. what could be the purpose? Remote control... factory testing?

I don't have an ultrasonic cleaner so I can't say whether it will work or be non-destructive.
Printer maybe?
 

Offline Haenk

  • Super Contributor
  • ***
  • Posts: 1076
  • Country: de
Re: Facit 1132 Nixie Calculator restoration
« Reply #44 on: June 20, 2023, 08:50:12 am »
PS: There's a really bizarre connector on the back.. what could be the purpose? Remote control... factory testing?

In that era, some calculators had "options" - for example a "secondary operator", a detached display and keyboard connected to the main machine. (I have no idea how this did work out, maybe one operator could lock out the other operator?) Also some had an external display option or even a line printer port.
 

Offline agent_powerTopic starter

  • Regular Contributor
  • *
  • Posts: 73
  • Country: it
Re: Facit 1132 Nixie Calculator restoration
« Reply #45 on: July 02, 2023, 09:49:47 pm »

Maybe you can first separate all key groups from the top of the enclosure. It looks like it can come off as one unit.  I think that row of brass phillips screws above & below the blue wires (from your first message) secures them.  That should give you access side-on to spray contact cleaner and exercise the keys.  I don't think you should separate those plates as they are punched along the left and right edges (4 times) of each key group.  It'll probably cause you grief to put back together with multiple springs and alignment points. And never be flat again.


I beeped out all the keys. All of them appear to work with exception of the division key, where the readings are erratic - between .5 MOhm and few hundred Ohms when pressed down. No amount of cleaner and exercising seems to help  :--

Unless there is an issue on a component inside the keyboard (I can see some in the sandwich) or the sliding switches, I'm not really sure how the keyboard is causing a problem.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf