General Radio 1454-A

[jonpaul]

Hello all: 

  Unearthed   GenRad 1454-A 10,000 ohm voltage divider. Serial 1973.

Use will be to calibrate meters with a 10.0000 V standard reference, use as a potentiometer or voltage divider up to 100V.


 Does  SN 1973 come  before or after the accuracy improvements implemented per the Gen Rad experimenter article of Volume 33 No. 7, July, 1959. ?


Can you say the date /year of mfg?

The articles   mention selection of certain resistors to provide the improved specs?


 It works OK but several switch taps are slightly flaky, and not stable.


How to open the chassis and clean the switch contact?



Many thanks


Jon

[chekhov]

Hi,

Maybe some photo will help people to answer certain questions ?
Doesn't it have screws under knobs ?

[jonpaul]

Hello all:

I succeeded to open the unit, the foot screws are in long standoffs from front panel. very easy.

Spec
https://www.ietlabs.com/pdf/Manuals/GR/1454-A,%20-AH%20Decade%20Voltage%20Dividers.pdf

 app notes  see page 13 and up
https://www.ietlabs.com/pdf/GR_Experimenters/1959/GenRad_Experimenter_July_1959.pdf



Inside its pristine, and the contacts seem bright and still have the original lube.

I used Miller Stephenson MS-230 contact cleaner, then exercised ever decade.


Now it works 100%, Testing on a Fluke 8842A DVM and with HP 4115A precision Power supply set a 10.0000V all decades seem to be well within spec.


As the app note was 1959, and this unit seems much later (by the knob style and case condition) I think its the revised version.

Any other Metrology Mavens or GR 1454 owners advise on lube or serial numbers vs mfg year is appreciated.

 Many thanks Jon

[jonpaul]

Here are A few photos, need recommendations on contact lube and cleaner for gray crinkle case and front panel, case has paint on it front has stickers residue.

Many thanks again

Jon

[Conrad Hoffman]

Can't tell you much about accuracy, but it will degrade if you load it down. I clean the contacts and use Superlube grease or Vaseline. Remember the center contact! Properly cleaning these up can be a bit of a project. These are a nice general purpose divider but remember, they're no Fluke or Julie or ESR.

[jonpaul]

Conrad many thanks the GR spec is fine for my use.

In 1965..1967 I worked for Loebe JULIE in NYC, as a work-study tech while at college.

I managed to save a few of their handwound resistors, but alas not the real standards.

Jon

[bob91343]

I would avoid lubrication unless there is a problem.

[Conrad Hoffman]

I would avoid lubrication unless there is a problem.

Really? There's a lot of pressure on those contacts and the factory certainly lubed 'em.

[Kosmic]

Personally I had to clean and lubricate all the old decade resistors and KVD I bought. Probably the reason they were sold in the first place.

Anyway, I clean with IPA, then apply Deoxit G5 on the contacts (don't spray all over the place. Use something like a syringe). Finally I lubricate the contacts and switchs with Deoxit S5.

They all came out of that little process good as new.

[Stray Electron]

I would avoid lubrication unless there is a problem.

Really? There's a lot of pressure on those contacts and the factory certainly lubed 'em.

  I would take what Conrad says as gospel!

   IMO not putting lubricant on any sliding metal surfaces is just asking for problems.

[srb1954]

Here are A few photos, need recommendations on contact lube and cleaner for gray crinkle case and front panel, case has paint on it front has stickers residue.

Many thanks again

Jon

Nice clean condition. I have S/No 1987 so it may have come out of the same production batch as yours.

However mine is not as original looking as yours: someone had removed the original GR binding posts and replaced them with non-standard binding posts although they did use some nice gold-plated ones.

[jonpaul]

Rebonjour a tous!

Many thanks for the notes, it was from a ham radio flea (SV ARRL) or a silent key friend's estate. Very little use.

1/ After contact cleaning and exercise, Divider is working 100%, in all switch pos.

2/ I used MS-230 contact cleaner, original lube is still present on all switches.

3/ The ratios are within or better than spec, tested with  Fluke 8842A.

4/ The crinkle finish is quite pleasing,  Used IPA, then paint thinner and finally acetone of the paint of the case,

 impossible to  remove the huge paint stencils without affecting the finish. Any other things to try?

 Many thanks again.

Jon

[Conrad Hoffman]

GR black and grey crackle  finishes are quite fragile and almost anything will dull or damage them, even Windex! I've had some luck with the yellow markings using brief and repeated applications of naphtha or xylene, operative word being brief. Sometimes I just live with the yellow markings because they can just be too tough to get off. A good polishing with Armor-All will bring back the shine.

Caution- I'm wrong only slightly less than I'm right, and that's on a good day!

[SilverSolder]

Personally I had to clean and lubricate all the old decade resistors and KVD I bought. Probably the reason they were sold in the first place.

Anyway, I clean with IPA, then apply Deoxit G5 on the contacts (don't spray all over the place. Use something like a syringe). Finally I lubricate the contacts and switchs with Deoxit S5.

They all came out of that little process good as new.

That's exactly what I do, and the results appear to be good and durable.

[SilverSolder]

I have an example of the  1454-AH model, which is the same as yours except 100K Ohm resistance instead of 10K.

I measured mine with a ratio transformer (<1ppm accuracy) and found it to be well within spec (most positions/setting are 10x better than spec!).

But the real winner is:  it is extremely stable, so once you know what each setting actually is, that is what you will get - every time.   That fact makes it usable for a lot of things.  The sheer physical size of everything inside means self heating at modern voltages (10V or less) is not a big concern.

[jonpaul]

Conrad, many thanks re the gray crinkly finish, thought so!

I  will test with xylene later.

Still the front panel cleaned up well, just traces of stickers.

Jon

[Kosmic]

Personally I had to clean and lubricate all the old decade resistors and KVD I bought. Probably the reason they were sold in the first place.

Anyway, I clean with IPA, then apply Deoxit G5 on the contacts (don't spray all over the place. Use something like a syringe). Finally I lubricate the contacts and switchs with Deoxit S5.

They all came out of that little process good as new.

That's exactly what I do, and the results appear to be good and durable.

Yep, Deoxit for the win! 

[Conrad Hoffman]

Conrad, many thanks re the gray crinkly finish, thought so!

I  will test with xylene later.

Still the front panel cleaned up well, just traces of stickers.

Jon

Be very careful as xylene will definitely attack the paint.

[guenthert]

[..]
   IMO not putting lubricant on any sliding metal surfaces is just asking for problems.

      I know next to nothing about materials, but afaik, if at least one of those metals were brass (which I don't know whether it is), then additional lubrication wouldn't be necessary (and probably not advisable).  Isn't brass advertised as "self-lubricating"?

[Kosmic]

 impossible to  remove the huge paint stencils without affecting the finish. Any other things to try?

you could try magic erasers. They don't last but they work really well.

https://www.mrclean.com/en-us/shop-products/magic-erasers

[bob91343]

I recently acquired two GR decade resistors of similar type.  Apparently they have had so little use that the contacts were a bit unstable.  But after some use, they have come back well within spec, even after most of a century since manufacture.

As far as I know, the contacts have never been lubricated since first sold.  Perhaps if they get used a lot there will be some contact wear but these are beefy contacts and won't wear out within my lifetime.  But then, I am old.

Lubricants vary in their activity.  They can cause poor contact because they don't conduct current.  It's not wear we are worried about; it's accuracy.  And some may cause long term damage due to chemical reaction.

[stevebyan]

I clean the contacts and use Superlube grease or Vaseline. Remember the center contact!

How do you get in to clean and lube the center (wiper) contact? On the General Radio switches that I’ve seen, it’s swaged together. I don’t see how to clean it or get fresh grease into it.

[Conrad Hoffman]

There's usually some wavy contact washer in there. Usually you can squirt it with contact cleaner, then jam a bit of grease in after it's dry. Deoxit Faderlube might also be a good choice for the center, but it's light oil, not a grease. The big pots in the bridges are another place where the center contact can give trouble. You'd think grease could lift contacts and cause poor connections, but it turns out to be really hard to do. If you have some time to burn, go to the Nye site and look at their info on electrical contact lubes. I have it from someone that used to work at L&N that Vasoline was the recommended lube for the big lug type switches. I don't know what General Radio used, but it tended to turn green (if it didn't start that way) and by now is ready for removal and replacement with something better.

[stevebyan]

It's been a while since I opened it up, but I couldn't see any opening big enough to force lubrication into the wiper bearing on the switches from my G-R 602-J resistance decade box.




The zero resistance is a little above spec. I suspect the rotating contacts in these wipers are the problem.

[Conrad Hoffman]

Well, hypo needle and lots of pressure at the interface, plus a certain amount of faith that something probably got in there.