restoring 1934 mod 663 Weston volt-ohmmeter - Printable Version
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+--- Thread: restoring 1934 mod 663 Weston volt-ohmmeter (/showthread.php?tid=1821)
restoring 1934 mod 663 Weston volt-ohmmeter - Texasrocker - 04-25-2009
Hello Philco Pfriends! Been busy round here lately with daily-life schedules. A couple weeks ago, I started transporting many vintage tube amps, broadcast gear, hifi stuff into my shop from a shed-find. In the mix was several pcs vintage test gear.
I am saving a orphan (circa 1933-34)highly- neglected Weston stepchild VOM. Not much info on the net about this vintage item at all, once considered a high-$ pc of vintage-test gear from the depression days. Once I ascertained the vintage meter-movement was still good, I decided to try restoring it just to try to bring it back to new life.
This item had many old orig "open" previously-fried small resistance-coils ( small ( stacked-type & centertapped together)spools of wire coated with beeswax), luckily I found ink-stamped print on the ends of the small metal round-coils orig-ohms readings after carefully removing the orig wax to use modern carbon resistor replacement parts that Weston didnt have back in 1933-34. Ive replaced all the orig coils with "closest select proper ohms matches" with precision & lots of hours of matching the orig wire resistance-coil spools (vs) new carbon 1/2 watt types resistors ( hand-matched,tested proper ohms) and all new "point-to-point" rewiring inside the unit. I have the 1934 Weston Mod 663 working again somewhat after building a new replacement battery-pack! I removed the orig batterys last installed(dated) in 7-1953, 3- 4.5v , & (1) 1.5 v Burgess D cell. Amazingly!!, those orig batteries ( last installed in 1953) never leaked, and all the battery cases still look new good as new! Ive placed the orig batteries in my "vintage-battery" collection. They look cool!!
The "ohms" readings are again ( after electronic parts resto)very precise upon initial tests with new resistors testing! Seeing that 1934 Weston meter jump-to-life again was worth all the hours Ive spent so-far indeed! However, the orig 7- position selector switch which is complex in design is intermittent at best! I sprayed it with dexoit, & cleaned it throughly, with not much improvement without completely dis-manteling the orig 7- position switch unit (yet), which will be another massive-chore!
Does anyone here know a good source for a modern-type ( low profile assembly) 7-pole rotary switch with 1/4" shaft? I can retro-fit if one still exists.
Since this vintage test-item was originally designed for DC resistance & ohms only applications, I figure the orig-coils were fried by someone previously trying AC tests with the unit. This nice little vintage pc of 1933/34 Weston "bakelite" test equip, is trying its best to "cough back to life" for me!! If you wish, you can see the only info I found on the www on this vintage item at:
http://www.stevenjohnson.com/weston/weston1934.htm
One thing I can say for vintage Weston test equip "meters",is they are "survivors" indeed!!
Any help on finding a replacement 7-position switch would be highly appreciated! This IS, a nice pc of vintage Radio repair-shop test gear indeed, in its orig 1933-34 bakelite cabinet!
Even the old orig wirewound "zero-meter" adjustment pot is still good in this vintage VOM.
This project has been much fun for me, & I hope I can get the orig switch working, or be able to replace it if necessary to get the milliamp meter section & DC current ( select from 2.5v- 1000v dc only) sections working again.
If so, another nice vintage pc of yesterdays 1933/34 era Radio repair "benchtest gear" saved! I figure 7-section, low-height mounting profile types, rotary switches may be hard to find these days?
Re: restoring 1934 mod 663 Weston volt-ohmmeter - Texasrocker - 04-27-2009
BINGO!!....I found a suitable type substitute rotary- switch to fit in the vintage vom from my junkboxes.Didnt even remember I had one in backstock!!? Early alzheimers setting in already!!?? Lordy mercy!!!, I had to modify the vintage rotary switch abit, but its working great now. This old vintage Weston mod 633 ( ca 1933-34) bakelite case VOM lives on! "Spot on" in accuracy compared with both my older Simpson 260's, and various newer mod DMMs. Glad I restored it! I figure these orig Weston mod 663's items are about as scarce a Philco mod 90 these days?!! You can bet on that! NICE vintage "updated" VOM indeed!! Definately worth updating the orig fried wire-wound resistance coils if you guys ever run across one at hamfests etc!!! Those old Weston glass-meters were built like a tank in those days!! , and very accurate too!!, ...after subbing in new modern type "hand-matched" half-watt carbon type resistors to replace orig resistance-coils, this item has new life again afterall!! Sure is a nice addition to all my fully-restored vintage test gear!! You never know whats "fully-restorable" from leaky-roof barn-finds!!! Never throw anything out!! Vintage test equip items sometimes just need the same TLC as all the vintage radios we all restore, to bring the items back to life again!! I was amazed how "accurate" this old VOM was- and now "is" again, as originally produced only for all DC type test bench test appliques, and it was "free" of charge ( except for my time & new parts added)!!! I LOVE this hobby!!
Re: restoring 1934 mod 663 Weston volt-ohmmeter - Jim Berg - 04-30-2009
Good work on the old Weston meter. I have an old Weston Checkmaster tube tester model 771 I have had it since about 1972. It was given to me and has an O1-A for the rectifier. It tests resistance, and also volts. Tube chart dated 1937.
Re: restoring 1934 mod 663 Weston volt-ohmmeter - Arran - 04-30-2009
I would have selected metal film resistors over 1/2 watt carbons, the tolerances are higher and they don't tent to drift as much, they are also reasonably cheap. Most meters used precision resistors, as yours did, they did of course have carbons at the time but they were dot code types and were off by as much as 20% the day they came off the line. More then likely someone accidentally had it switched on ohms when they tried testing high voltage, it will almost instantly take out the bottom resistor in that stack. If you just wanted to get it working for display it doesn't matter, but for a day to day work horse it could.
Best Regards
Arran
Re: restoring 1934 mod 663 Weston volt-ohmmeter - Texasrocker - 05-05-2009
Thanks Jim & Aaron! You bet, this old vintage Weston VOM test item is now working great +/- 5% accuracy as compared to my Simpson 260. As Aaron suggested, it would have been better to use metal-film type resistors from the get-go, in the restoration. I didnt have a good selection of the metal-film types here at the time, but plenty-o-new carbon types here in the workshop. Since the old weston meter was "questionable at best",.. for full restoration , I just started "hand-matching" my carbon-comp type 1/2 watters to see if it would work again, and be fairly accurate overall after resto. To my surprise, it bounced back to new life again, and is more accurate than I would have ever suspected! Definately close enough for vintage-radio-restoration work indeed, just as originally designed! Looks cool too boot!
I just wanted to save it, as it is a really neat vintage test item, and it WORKS too!!... with updated easy to find batteries.
It will go in my collection of vintage test gear, & some young whipper-snapper can swap-out all my carbon resistors someday in the future if need be to keep it working. When I saw this old neglected step-child pc of vintage test gear, I had to try restoring it!! If nothing else, a nice break from the usual restoration of vintage tube radios chassis !