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Old 20th Mar 2021, 7:01 pm   #1
ChristianFletcher
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Default Compucorp Sumlock 320G Scientist Calculator

Before we all locked down I was enjoying browsing my favourite antique warehouse when I found this calculator. I have to admit I don’t have any interest in calculating machine but at £8.00 I just couldn’t walk away. I know these were built in the USA around 1972 and were distributed under the Sumlock name in the U.K. but wondered if anyone knows anymore. It goes without saying service information would be handy.

Thanks regards Chris
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Old 20th Mar 2021, 10:14 pm   #2
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Default Re: Compucorp Sumlock 320G Scientists Calculator

For some reason pictures didn’t upload
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Old 21st Mar 2021, 12:30 am   #3
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Default Re: Compucorp Sumlock 320G Scientists Calculator

There was in the 1970s at work (Muirhead-Vactric), a Sumlock 322G, the programmable version of the 320G. By the time I got to use it, the programming feature was made pretty useless by key bounce, which forced you start over again from the beginning of the program if you were entering a key sequence. There was no way to edit the program, which made it a real pain to use.

I recall it had a big handful of rechargeable 'D' cell size Ni-Cad batteries to power it.

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Old 21st Mar 2021, 7:06 am   #4
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Default Re: Compucorp Sumlock 320G Scientists Calculator

I've got the Compucorp 324, which is a similar machine, but 'programmable'. I think it had twice as much program memory as the 322.

Anyway, I've attached the circuit diagram that I reverse-engineered of the 324. It may be some help, things like the power converter are likely to be similar.
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Old 21st Mar 2021, 2:35 pm   #5
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Default Re: Compucorp Sumlock 320G Scientists Calculator

Thanks for the information I think the schematic probably will be quite close as I understand that these were somewhat modular in nature. I assume the higher voltages rails were for the gas display but what was things like -30 and 15 used for ?

Just looking at the information Tony provided that’s an amazing body of work. I hope you will consider passing that on to some of those calculators museums etc as there is very little information or reverse engineering around that I can find. Great job Tony


Thanks regards Chris
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Old 21st Mar 2021, 3:45 pm   #6
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Default Re: Compucorp Sumlock 320G Scientists Calculator

I believe the -30V will be one of the specific voltages required by the VF display.
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Old 21st Mar 2021, 3:48 pm   #7
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Default Re: Compucorp Sumlock 320G Scientists Calculator

Quote:
I hope you will consider passing that on to some of those calculators museums
Tony IS a computer museum, to all intents and purposes. One of these days we'll have to try to persuade him to have an open day.
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Old 21st Mar 2021, 3:48 pm   #8
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Default Re: Compucorp Sumlock 320G Scientists Calculator

It's not a VF display, it's a Panaplex which is a neon discharge device. That's what needs the highest voltages. The 15V and 30V rails are used by the PMOS logic chips.

As for the reverse-engineering, most if not all of the HP ones are available from the HPCC site. I will happily share others as appropriate.

And I have had the odd 'open day' in my house when friends can visit, see some odd machines, read some even odder manuals, etc. If we ever get out of lockdown I'll consider doing it again.
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Old 21st Mar 2021, 3:49 pm   #9
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Default Re: Compucorp Sumlock 320G Scientists Calculator

Quote:
It's not a VF display
I stand corrected.
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Old 21st Mar 2021, 5:58 pm   #10
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Default Re: Compucorp Sumlock 320G Scientists Calculator

Well again Tony a mind of information and fascinating. I have just been reading up on Pmos technology.
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Old 21st Mar 2021, 6:09 pm   #11
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Default Re: Compucorp Sumlock 320G Scientists Calculator

I have powered this and it does show signs of life but it going into a error mode as it displays an E. it does respond to reset and some keyboard inputs. As I said earlier I don’t have any experience with calculators but I do have experience designing and equipment with microcontroller so I can work on this. A few people have mentioned this is quite rare piece of early computing history on my Twitter stream so I’m asking can this be worked on or is it significant enough as a museum piece etc.

I thought I would start by cleaning the edge connectors and checking the power supply rails etc. I didn’t think I was interested in computers as it’s too close to my day job but I was wrong again it’s actually fascinating
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Old 21st Mar 2021, 8:01 pm   #12
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Default Re: Compucorp Sumlock 320G Scientists Calculator

Taking a quick look at the inside I can see the ribbon cable looks to have taken damage. It doesn’t show up well in the picture but it looks like someone has in the past tried to glue the flexible PCB back together and some of the traces look green. I’m wonder if it’s detecting multiple buttons presses and going into error.

Just managed to get a little tingle off it picked up the circuit board whilst powered. I forgot about the high voltage display. Ouch Lesson learned!
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Old 21st Mar 2021, 10:25 pm   #13
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Default Re: Compucorp Sumlock 320G Scientists Calculator

Well at least you know that the HV PSU is running!

Is that just a flexi-cable, that's soldered to both the main and the keypad? PCB? - or does it form part of the keypad?

If it's just soldered at each end, then it could have got cracked at a few solder joints, if flexed too much. So may be able to buzz-out to check and cut down a bit to remove any breaks at the ends
Green residue sounds a bit like liquid leak into it, causing corrosion of copper etc. Hot-melt etc. glue may have also been used on the ends of the flexi-cable, to provide some extra mechanical fixing and guard against it breaking.
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Old 22nd Mar 2021, 3:06 pm   #14
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Default Re: Compucorp Sumlock 320G Scientists Calculator

It’s just a thin flex cable. It could probably be replaced with a hand solder ribbon cable but that would loose the originality of it. I think a could possibly buy a new manufacturer flexible PCB via China. I am going try and look at the ribbon for problems but it looks in a poor state. I think it uses real mechanical switches but they feel spongy and nasty

Oh yes the HV works - silly me!
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Old 22nd Mar 2021, 4:38 pm   #15
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Default Re: Compucorp Sumlock 320G Scientists Calculator

There's some information on this series of calculators here.

John
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Old 22nd Mar 2021, 6:35 pm   #16
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Default Re: Compucorp Sumlock 320G Scientists Calculator

Quote:
or is it significant enough as a museum piece
Play away, most (99.999%) of museum pieces are static, unpowered, lumps* just keep the outsides looking good.

*There are exceptions, The National Museum Of Computing (Bletchley) has an Enigma machine you can (under supervision) press the keys on along with other stuff to play with. Milton Keynes museum is very hands on too.
 
Old 22nd Mar 2021, 6:44 pm   #17
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Default Re: Compucorp Sumlock 320G Scientists Calculator

The Centre for Computing History (Cambridge) is even more like that.
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Old 22nd Mar 2021, 7:43 pm   #18
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Default Re: Compucorp Sumlock 320G Scientists Calculator

I guess I will dig in and have ago I do like the idea of using this calculator on a daily basis but the keyboard does feel nasty.
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Old 22nd Mar 2021, 7:52 pm   #19
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Default Re: Compucorp Sumlock 320G Scientists Calculator

Just a daft thought, is there room to hard wire the dodgy connections? Maybe with a bit of enamelled copper wire, probably doesn’t need to be particularly thick, just run it along the back of the ribbon and stick it down with a bit of Kapton tape.

Regards
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Old 22nd Mar 2021, 8:02 pm   #20
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Default Re: Compucorp Sumlock 320G Scientists Calculator

Fascinating... "Sumlock" was a brand that had loads of tentacles - their UK operation was "Sumlock Bondain" and they were big in the 'sixties with their "ANITA" range of electronic calculators - full of Thyratrons!

See: http://www.vintagecalculators.com/ht...ock_anita.html
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