Clarostat HV potentiometer indentification. - UK Vintage Radio Repair and Restoration Discussion Forum

factory · 30th Oct 2021, 9:43 pm

Can anyone help with identifying the Clarostat series that these HV potentiometers are from, they are the focus & intensity pots from a Tektronix 321 oscilloscope. The Tek part numbers gave no useful hits when I tried a web search.

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They have added threaded insulated sleeve to the metal front panel bushing, the plastic shafts are broken off flush with the bushing and have been lost along with the knobs by a previous owner.

David

factory · 31st Oct 2021, 12:49 pm

Well I've sort of answered my question, Tek wiki has quite a lot of info I didn't realise was there.
There is a large pdf of resistors, the the parts I have are:
311-0167-00 (311-167) 2M = Clarostat CM26544
311-0168-00 (311-168) 1M = Clarostat CM26545

These were replaced with:
311-0348-00 1M = Clarostat 381-CM30939
311-0349-00 2M = Clarostat CM30940 (NSN 5905-00-055-7942)

The bad news for me is that three of those parts are only used in the 321 scope, part 311-0349-00 is also used in the RM561A, RM564, SC502, SC503 and SC504.

The Clarostat 381 looks nothing like what I have, not made of plastic, nor has the extended section, it's looking a lot like these were custom parts.

David

knobtwiddler · 31st Oct 2021, 2:50 pm

There is a firm in the USA called 'state electronics':

https://www.state-elec.com/

They bought all of the Claro components when the firm got acquired and discontinued them (along with several other brands).

You will pay a serious premium, but there is a good chance that they will have the parts to make a replica. It will be a 3-figure sum for the single pot, though.

Just so you know!

factory · 31st Oct 2021, 9:38 pm

Thanks for the suggestion, 3-figures for each pot would be more than it would cost to buy a complete 321A scope the US.

There is a NOS 311-0349-00 in the US, oddly described as 1M despite the manuals disagreeing.
Anyway I've modified the ones I have, to make them usable with a trimmer tool.

David

Diabolical Artificer · 1st Nov 2021, 8:09 am

I think I have one or two of those,will look today David.

Andy.

woodchips · 1st Nov 2021, 10:46 am

Don't Tek use similar parts in all their old CRT based scopes? All need to be insulated for 3,000V or so.

factory · 6th Nov 2021, 10:53 pm

I don't know, the only Tek scope of similar age I have is the 502A and it might do (but maybe not same values), certainly the HP stuff I have all uses bigger pots AFAIK.

Here are some pictures showing the size for those in the Tek 321.

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This isn't from the scope, but shows the approx diameter.

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Anyway I have an idea to fix the original pots, there might just be enough space in the insulation spacer to fit a sleeve and a longer piece of plastic rod.

I have also found two knobs in the bits I got from Woodchips, they are black instead of grey, but that is all I have.

David

Diabolical Artificer · 11th Nov 2021, 2:00 pm

I finally managed to dig the pots I have out,unfortunately they're 50k and 100k, no 1M & 2M, will keep looking to see if there's any more.

Andy.

30th Oct 2021, 9:43 pm	#1
factory Octode Join Date: Jul 2009 Location: Cheshire, UK. Posts: 1,740	Clarostat HV potentiometer indentification. Can anyone help with identifying the Clarostat series that these HV potentiometers are from, they are the focus & intensity pots from a Tektronix 321 oscilloscope. The Tek part numbers gave no useful hits when I tried a web search. They have added threaded insulated sleeve to the metal front panel bushing, the plastic shafts are broken off flush with the bushing and have been lost along with the knobs by a previous owner. David

31st Oct 2021, 12:49 pm	#2
factory Octode Join Date: Jul 2009 Location: Cheshire, UK. Posts: 1,740	Re: Clarostat HV potentiometer indentification. Well I've sort of answered my question, Tek wiki has quite a lot of info I didn't realise was there. There is a large pdf of resistors, the the parts I have are: 311-0167-00 (311-167) 2M = Clarostat CM26544 311-0168-00 (311-168) 1M = Clarostat CM26545 These were replaced with: 311-0348-00 1M = Clarostat 381-CM30939 311-0349-00 2M = Clarostat CM30940 (NSN 5905-00-055-7942) The bad news for me is that three of those parts are only used in the 321 scope, part 311-0349-00 is also used in the RM561A, RM564, SC502, SC503 and SC504. The Clarostat 381 looks nothing like what I have, not made of plastic, nor has the extended section, it's looking a lot like these were custom parts. David

31st Oct 2021, 2:50 pm	#3
knobtwiddler Octode Join Date: Mar 2016 Location: London, UK. Posts: 1,051	Re: Clarostat HV potentiometer indentification. There is a firm in the USA called 'state electronics': https://www.state-elec.com/ They bought all of the Claro components when the firm got acquired and discontinued them (along with several other brands). You will pay a serious premium, but there is a good chance that they will have the parts to make a replica. It will be a 3-figure sum for the single pot, though. Just so you know!

31st Oct 2021, 9:38 pm	#4
factory Octode Join Date: Jul 2009 Location: Cheshire, UK. Posts: 1,740	Re: Clarostat HV potentiometer indentification. Thanks for the suggestion, 3-figures for each pot would be more than it would cost to buy a complete 321A scope the US. There is a NOS 311-0349-00 in the US, oddly described as 1M despite the manuals disagreeing. Anyway I've modified the ones I have, to make them usable with a trimmer tool. David

1st Nov 2021, 8:09 am	#5
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,669	Re: Clarostat HV potentiometer indentification. I think I have one or two of those,will look today David. Andy. __________________ Curiosity hasn't killed this cat...so far.

1st Nov 2021, 10:46 am	#6
woodchips Octode Join Date: May 2010 Location: Grantham, Lincolnshire, UK. Posts: 1,177	Re: Clarostat HV potentiometer indentification. Don't Tek use similar parts in all their old CRT based scopes? All need to be insulated for 3,000V or so.

6th Nov 2021, 10:53 pm	#7
factory Octode Join Date: Jul 2009 Location: Cheshire, UK. Posts: 1,740	Re: Clarostat HV potentiometer indentification. I don't know, the only Tek scope of similar age I have is the 502A and it might do (but maybe not same values), certainly the HP stuff I have all uses bigger pots AFAIK. Here are some pictures showing the size for those in the Tek 321. This isn't from the scope, but shows the approx diameter. Anyway I have an idea to fix the original pots, there might just be enough space in the insulation spacer to fit a sleeve and a longer piece of plastic rod. I have also found two knobs in the bits I got from Woodchips, they are black instead of grey, but that is all I have. David

11th Nov 2021, 2:00 pm	#8
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,669	Re: Clarostat HV potentiometer indentification. I finally managed to dig the pots I have out,unfortunately they're 50k and 100k, no 1M & 2M, will keep looking to see if there's any more. Andy. Attached Thumbnails __________________ Curiosity hasn't killed this cat...so far.