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Old 18th Aug 2011, 3:57 pm   #1
slderiron
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Default Nixie Burroughs Calculator problem

I've had this calculator a couple of years and it has always had the same problem;

when you press the 4, both the 4 and 8 light up in the nixie, and when you press the 8, again both 4 and 8 light up.

this also happens with 7, press this and the 5 also lights up, and press the 5 both 7 and 5 light up as well.

Apart from a stiff decimal point button, the calculator works in all other respects, apart from the fact that if the answer contains either 4, 8, 5 and 7, then these numbers will also display incorrectly as described above.

Is this a simple fix, or has the ic had it?

Seems such a shame, as this is a grand piece of vintage equipment.
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Old 18th Aug 2011, 5:17 pm   #2
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Default Re: Nixie Burroughs Calculator problem

To me it looks like two driver transistors are shorted making the two numbers light up at the same time. These displays are usually multiplexed which means that he same error will show up on every digit. What happens if you press the number 4 to fill the whole display, does it show the 8 on all nixies too? If so then it is probably the cathode drivers that are shorted. Try to locate a set of 10 or 11 (decimal point adds one to 0-9) transistors that drive the cathodes of the nixies and check them and the circuit around them for shorts. Sometimes diodes are used to make a voltage level change and these could be shorted too.

If you find pairs of transistors connected to each other that is likely the anode drivers. If an anode driver is shorted you migh see one digit appear on two nixies at the same time although you did not fill the display with that many number, for instance pressing just 1 will show 1 in two or more positions.

Hope this helps to find the problem.
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Old 18th Aug 2011, 5:38 pm   #3
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Default Re: Nixie Burroughs Calculator problem

I think it is more likely to be using an IC to drive the tubes rather than individual transistors. I say this because it's less likely to have the same kind of fault on different digits if it's just a mechanical issue.

I have seen exactly this kind of fault caused by failure of the high-voltage decoder chip that was designed for driving nixie tubes. They are harder to find these days because they haven't been made for a while now - but you should be able to find one eventually.
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Old 18th Aug 2011, 6:25 pm   #4
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Default Re: Nixie Burroughs Calculator problem

This appears to be the original 1969 version of the Burroughs C3300. The slightly later C3315 appeared to use at least some discrete transistors to drive the nixies, see here

http://www.vintage-technology.info/p.../burrc3300.htm

John
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Old 18th Aug 2011, 6:34 pm   #5
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Default Re: Nixie Burroughs Calculator problem

Quote:
Originally Posted by slderiron View Post
Is this a simple fix, or has the ic had it?

Seems such a shame, as this is a grand piece of vintage equipment.
There will be several ICs in this calculator! If a schematic is available, it should be fixable as long as the fault is not with some long obsolete device with no available substitute.

These calculators are likely to be quite rare in the UK and of some historical interest, so please take good care of it.

John
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Old 18th Aug 2011, 6:46 pm   #6
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Default Re: Nixie Burroughs Calculator problem

I found more info on a similar calculator here : http://www.scharfe-rechner.de/wiki/i...p?title=CS-362, where it seems that the anode drivers are transistors and the cathode drivers looks lik ICs from the picture of the display unit. If you can open it and take some photos of the display unit top and bottom it will probably be easy to discern what these IC's are and if they are in fact the cathode drivers.

You can look at the photo of the display unit and compare to yours and see if there are any similarities.

Also at the bottom of the page there is a link : http://www.cs.ubc.ca/~hilpert/eec/ics/NECmPD.html which points to the IC's used in these calculators. There are also some repair tips for calculators of this era found here: http://www.cs.ubc.ca/~hilpert/eec/index.html . I have been in contact with Brent Hilpert on other vintage electronic equipment, so if you contact him via his webpage he might have information that might help you.
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Old 18th Aug 2011, 6:51 pm   #7
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Default Re: Nixie Burroughs Calculator problem

Forgot to include this link from Brent Hilperts webpage with the schematic of a Casio AL-1000 calculator which shows the design of Anode drivers 8two transistors) and cathode drivers (transistor and diode) : http://www.cs.ubc.ca/~hilpert/eec/ca...00/display.gif
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Old 18th Aug 2011, 10:38 pm   #8
ALANS ANITAS
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Default Re: Nixie Burroughs Calculator problem

Hi

I have encountered this problem on the Anita 1011 LSI series which used the Mullard ZM1080 nixie during most of the production run. The 1211 LSI did not suffer this problem as it used "Panaplex" displays and suffered quite different display problems.

The cause appeared to be swarf within the tube, which originally did not cause any problems. but became loose and short circuited some of the cathodes. This caused all the digits on all the displays to be illuminated.

The Solution ?

Take a medium sized screwdriver with a hard handle, hold it by the blade and run the handle along the row of display tubes. The amount of force required will be up to you, dont break the tubes.

We never found out why this problem occured, perhaps a bad batch, but as it was fairly common maybe the manufacturing process changed. This never reoccured on the same machine, and only on the LSI series with Mullard tubes.

Hope this helps.

ALAN
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Old 18th Aug 2011, 11:20 pm   #9
slderiron
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Default Re: Nixie Burroughs Calculator problem

Thanks Alan, this would certainly be an easy fix. Thanks for all the other responses too, the links are very helpful. It may be that in transit, Royal Mail gave the parcel some hard treatment, thereby knocking some swarf about within two of the nixies. The chap I bought it from advised that it was working perfectly before he posted it. I recall having to remove a bakelite type two pin plug and replacing with a modern plug.
I won't have time to do this before going off on holiday, but I'm hoping that when I get a closer look at the nixies I'll see that the 5 is next to the 7, and the 8 is next to the four, which would certainly support the view that swarf is shorting them.

I do feel a responsibility to look after this well, as suggested. It is a grand looking calculator and quite a feat of engineering. I'll report back hopefully with good news.

Regards, john.
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Old 28th Aug 2011, 10:22 pm   #10
slderiron
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Default Re: Nixie Burroughs Calculator problem

I had a go at this tonight. Ran the handle of the screwdriver over all the nixies. After a minute or so the 5 and 7 came through clear, and I had high hopes of sorting out the 8 and 4. However after about half hour of said method, they refused to right themselves.

I'm going to have to get the magnifying glass and search for the stubborn bit of swarf at some later date, but at least I'm halfway there.

Regards, john.
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Old 29th Aug 2011, 9:31 pm   #11
Zelandeth
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Default Re: Nixie Burroughs Calculator problem

If you do end up finding that you need a replacement nixie or two, Sphere Research are well worth a look. Has been a while but I've ordered stuff from them before and it was quite a bit cheaper than anywhere else I'd found.

Just careful how far you dig when browsing, as I imagine most of us here could end up buying half the stock listed there if we weren't careful!

No connection with the site of course other than as a satisfied customer, and it seemed a relevant link to post - especially given the crazy prices Nixies often seem to go for on well known auction sites.

Hope you get it up and running, a calculator of this sort of era is still on my wish list.

If it's just a bit of swarf in one of the tubes, would this potentially show up in a continuity test?
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Old 30th Aug 2011, 6:22 pm   #12
slderiron
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Default Re: Nixie Burroughs Calculator problem

Thanks for the tip, was unaware of this nixie site. After another half hour with this calculator I finally managed to sort out the 4 and 8. I had to remove the support panel for all the nixies, and give each individual nixie a good flick of the finger as it really wasn't playing ball. After giving the 7th nixie about 6 hard flicks it finally corrected itself.

This is probably the easiest 'repair' I've undertaken with vintage equipment.

I'm very grateful for the tips, and very pleased with the result. The only problem left with this calculator is that the decimal button is stuck and won't go down, but I'm not overly concerned with this and will have a look at that at a later date.

Regards, john.
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Old 31st Aug 2011, 2:40 am   #13
ALANS ANITAS
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Default Re: Nixie Burroughs Calculator problem

Hi

I'm glad my experiences of 40 years ago have proved useful. The fault could well occur in other types of nixies, although the only others I have come into contact with were those made by Hivac, which will be found in earlier models of Anitas.

Rereading my former post (#8) I mentioned the Anita 1211LSI. This is not the 1011LS1 with two extra digits, but a totally different machine with a single Rockwell chip ,the earlier machine had five chips made by Ellott, although the case was almost identical. Both models used the same type of key contact which despite claims elsewhere, did fracture around the 180 bend. The other major fault was the keytops were prone to disassemble themselves.

Redgards

ALAN
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Old 31st Aug 2011, 2:18 pm   #14
slderiron
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Default Re: Nixie Burroughs Calculator problem

Thanks Alan,

I forgot to add in my last post that the nixies in this calculator are Japanese Burroughs, with serial numbers 16849247 K85183, so the problem you mentioned with the Hivac nixies was not exclusive to that company. A valuable bit of advice for next time I come across this sort of problem. I have two other nixie calculators with altogether different sorts of issues, a Toshiba and a Monroe, but I'll wait 'til nearer Christmas before I have a look at them.

Thanks for your help with this, best regards, john.
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