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Old 20th November 2013, 10:54 AM   #1
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Default replacement readout meter Jackson 648

Greetings to all, The first thing I want to say it's been awile since I have posted anything and I want to let you all that the replies and comments I recieved were extemely helpful. I am not trained or educated in electronics and am learning as I go. This made your help even more important to me and I want to say thanks.

I have a new problem. I have a Jackson 648 tube tester. I took the faceplate off to clean contacts, pots, switches ETC and in doing so broke the readout meter. I have spent allot of time trying to find a tester for the use of parts but no luck. The meter movement is 1 mA, 100 ohms. I am sure that besides the size more info is needed to determine if an off the shelf meter will work. I have been unable to find a direct replacement and while I have reasearched information on analog meters I am not confident of my abilty to know if a the meter is available even if I see one. The tester can be replaced for not much money but for me it is about keeping it alive. I would appreciate any assitence and direction with findng a meter or a way to modify a meter that is available inot one that will work. Thanks in advance,Paul
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Old 20th November 2013, 08:16 PM   #2
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I looked at a few online photos of that tester and it doesn't look like the meter is anything special. Since you know the electrical specs (the full-scale current is probably more significant than the movement's resistance), use it as the main criteria and look for something that fits the physical space. You'll have to figure out some way to calibrate the unit after replacing the meter - and this would be required even if you somehow got an exact replacement meter from the original manufacturer.
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Old 20th November 2013, 09:10 PM   #3
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If you post pictures and dimensions I'll look in my junk box.
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Old 21st November 2013, 03:22 AM   #4
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Default Jackson 648 test meter

Thank you greatly for your reply. I am relieved to hear the meter isn't an unusual one off design which prevent replacement. Your input helps me in narrowing down what will work. There is limited info available on specific parts for tjhis tester even though I have complete wiring diagram. It was built in the 1950's and the manufacturer no longer exist. I am going submit a request to Simpson Meter Company ( who's product line seems endless) for a meter that will meet the specs. I have learned how to callibrate the tester. They are truly an amazing tester in the design, versitility, accuracy and testing range. I know that with the your help and from others on DIY that I will find a meter. It gets diificult to stay with something when you don't have the training required but that is the nature of DIY'rs. I will keep you posted on progress. Cheers Paul
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Old 21st November 2013, 06:50 AM   #5
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A new meter movement will probably be MUCH more expensive than you expect! Better to check with the surplus dealers, hamfests, flea markets, etc. You may end up salvaging a meter from, say, an old battery charger, cast-off industrial equipment, etc.

The industry roughly standardized meter movements based on size. I'll WAG that yours is called either a 2-1/2" or 3" meter. When you find a meter of the proper electrical spec and same nominal mechanical size you may need to re-locate the screw holes attaching it to the panel.

Unless you get a meter from the same make & model tube tester, it will not have the same scale markings but from the photos I saw that isn't a major problem. Depending on your artistic ability and resources on hand you can create a new scale for the replacement meter that replicates the original scale down to the slightest detail - or just tape a post-it note on the tester saying something like "Readings below mid scale indicate faulty tube - readings above 90% indicate likely short or gassy condition.".

Dale
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