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 Post subject: Jackson 634 schematic
PostPosted: Jun Wed 19, 2019 3:16 pm 
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Joined: Nov Thu 22, 2007 11:31 pm
Posts: 894
Location: Johnston, Iowa
All, I'm finally getting around to restoring a Jackson 634 tube tester I picked up at auction. This tester has only three carbon type resistors and I can't read the value on one of them. The resistor in question is either red-green-orange (body-cap-dot) or brown-green orange and goes between the switches Q and R. I found a schematic for the related 637 but it's unclear if the resistor is a 15K or a 25K. In fact on the copy I found it looks like the 2 was overwritten with a 1 or vise versa. Does anyone have a schematic for the 634? The body is a reddish brown and my eyes can't make a determination. Either way it will work better since the old one tested and 34K.
Thanks in advance.
Keith


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 Post subject: Re: Jackson 634 schematic
PostPosted: Jun Wed 19, 2019 4:27 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Cape Breton Island Canada
Don't have the 634 but did you compare with this blueprint one of the 637 in the link below...There is 15000 (15K) listed connected to the R switch.

https://www.antiqueradios.com/forums/vi ... 8&t=246346

Ken


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 Post subject: Re: Jackson 634 schematic
PostPosted: Jun Wed 19, 2019 5:34 pm 
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Joined: Nov Thu 22, 2007 11:31 pm
Posts: 894
Location: Johnston, Iowa
Thanks Ken, there is one that listed 15,000 ohms but what about the one to the right? Is that one labeled 15M or 25M? I believe they used M for K and Meg for Meg.
Keith


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 Post subject: Re: Jackson 634 schematic
PostPosted: Jun Wed 19, 2019 6:37 pm 
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Location: Cape Breton Island Canada
I see how that's connected to R and Q...Can't say I'm a big fan of that schematic and the way they used M and thousands (1000) right next to each other and meg elsewhere on the schematic..M was used years ago for 1000. Pretty muddled schematic for values. The other versions aren't much better as this one from radiomuseum..

https://app.box.com/s/rq58ghjs09zg1x0v47zhj5qddrptrpz6

I'd like to say it's a 2 but is it a 2.5 or 25.?...Just guessing on my part...Perhaps you might contact Uptown through a PM and see if he still has his 634 ..I know he's still around.

https://www.antiqueradios.com/forums/vi ... 8&t=247303

Ken


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 Post subject: Re: Jackson 634 schematic
PostPosted: Jun Wed 19, 2019 8:25 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
Keith, try just measuring that resistor. It may be off value, but should not be so far off that you can't figure out what it should be. Certainly within better accuracy than the difference between Megohms and Kilohms.

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 Post subject: Re: Jackson 634 schematic
PostPosted: Jun Wed 19, 2019 8:36 pm 
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Joined: Nov Thu 22, 2007 11:31 pm
Posts: 894
Location: Johnston, Iowa
Barry the old one reads 34K, from the markings I know it's either a 15K or a 25K but the body color isn't clear if it's red or a reddish brown. I'm pretty sure they're using M for K but from the schematic it's not clear. I'm guessing it a 25K.
Keith


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 Post subject: Re: Jackson 634 schematic
PostPosted: Jun Thu 20, 2019 1:10 am 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 5359
Location: Sunbury, Ohio 43074
I'd concur on the 25K based on what's been posted so far. Might be able to find a better schematic eventually perhaps

good luck

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Preserving the hist. of electronics, one boat anchor at a time! :)
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 Post subject: Re: Jackson 634 schematic
PostPosted: Jun Thu 20, 2019 3:46 pm 
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Joined: Nov Thu 22, 2007 11:31 pm
Posts: 894
Location: Johnston, Iowa
All, I never knew there was a Jackson 636 model. Radiomuseum has a very high resolution schematic and the resistor in question is indeed a 25K. From what I can tell the only differences between the two are the addition of noise jacks, a separate on/off switch and a switch to test Noval tubes with a pin3 grid. I took a high resolution close up photo of the questionable resistor using a flash that I was going to post but surprisingly the body color came out red. Perhaps the flash brings out the true color.
Keith


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 Post subject: Re: Jackson 634 schematic
PostPosted: Jun Thu 20, 2019 3:52 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 5359
Location: Sunbury, Ohio 43074
Yup, the color temperature of light on a subject can dramatically change the colors you see, or don't see ;-) Your flash is probably closer to daylight temperature (approx 5000 K)

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https://www.bbtvtestequipment.com


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