Originally Posted by SwizzyMan (Post 3142130)

Hmmm that is definitely odd that cap is there. Maybe it is indeed original out of the factory but it just isn't listed in the schematic because it may be a possible revised model. Or maybe the meter wasn't working properly so a repairman threw it in there. Either way, it is a cap that commonly goes bad. You should replace it because the meter may not function properly without it and then you couldn't rely on the unit. So yes, replace that one and all other ones that look similar to that one e.g the paper caps and the electrolytic caps if they are there. Also looks like you are missing a tube from what I see in the photo. Did you take it out for the photo? One more thing i'd replace those 10k resistors just in case they have started to drift and they can get worse just with time and with use. Better safe than sorry.

Originally Posted by Kawooa (Post 3142132)

I pulled the tube so it was out of my way when doing stuff to it. When I first opened this there were two more tubes taped together inside it! What a bonus! I will order that capacitor and after replacing everything see how it works. If the meter seems odd I could try adding the replacement in. If that seems to fix it then I guess it stays. It could have been some person "repaired" it because other more pricey parts were failing. If you can add a $1 part for 5 minutes time why replace 5 parts for an hours time? Still charge the same but make more. I think that is what someone must have been thinking.

Originally Posted by Kawooa (Post 3142126)

I have bought a b&k model 400 crt tester. . . . . ordering parts soon to get it working. Then I'll test my 17bp4(listed in TV cabinet, nothing on tube) tube. Will this tester cover it

Originally Posted by Kawooa (Post 3142126)

The schematic lists no capacitor in parallel with the meter. But on my tester there is a capacitor in parallel. It just so happens to be 250uf 6vdc..

Originally Posted by Kawooa (Post 3142126)

. Two of my three ne-48 bulbs are broken. Don't know how to test the third.

Originally Posted by Kawooa (Post 3142126)

Aside from normal cleaning which I finished like a hour ago and standard replacement of off spec parts, what else should be done to ensure safety and something in calibration?

Originally Posted by earlyfilm (Post 3142631)

This and the electrically identical B&K 350 will test any 6.3 volt filament CRT that will fit the test socket. The tester has a socket for the Small-Shell Duodecal 7-pin and the 17BP4 family has a Small-Shell Duodecal 5-pin base, so it will fit and it will test.

This base style came into use in 1946 and went out of favor in the mid-1950's.

I would not advise making adapters for more modern tubes, nor changing the wiring of the tube socket.

I also would not advise using the rejuvenate function, if the tube just tests weak until you have tried the tube in a working set. Sometimes just letting the filament run for a half hour with no load on the tube works better than rejuvenation and is almost entirely without risk to the tube. Rejuvenation is only used for extremely bad cases. I've seen more usable tubes ruined by rejuvenation than weak tubes brought back and lasting more than a few hours.

And if you are wondering where the normally blue wire from the CRT socket is supposed to be connected, it is just for looks and it goes no where. That is the difference between the 7-pin and 5-pin base, however on some CRTs this pin is sometimes connected to a grid. On tubes of this era, that pin is not critical to testing.



My guess this was added by the former owner. I suspect that since the meter has no capacitor and many meters reading DC where is a RF carrier use a small non-polarized capacitor to bypass the RF, he assumed that since this meter needs one, too. (This meter reads a poorly filtered 60 cycle DC current.)

Another theory is he added this as a shock absorber for those spikes from static electricity.

As far as I know, this was never a factory option. When working properly, one sometimes gets a meter kick when switching from switching between short test and emission test, due to a static charge on the tube elements. This will not harm the meter.

A third theory is someone in the past used a drum-tuner cleaner (common during the era of this set) that had graphite in it and this soaked into the wafers on the switch and caused a little leakage and this caused a major kick when the rejuvenate button was pushed. To clean these switches, use a small amount of non-oxy type (the residue from the oxy's collect dust) and after working the switch a few times, put a fan on it to dry it out, before it soaks into the wafer.
If this meter is stored in a damp area (like a basement floor)moisture will penetrate the wafers and that will also cause the rejuvenate function to give the meter a real kick.

If it were me, I'd leave the cap off and only reinstall if needed, and frankly if it is needed there is probably something wrong with the meter.


Oh, by the way, please check the 11 pin terminal strip. In your photo, it looks like a solder bridge between two terminals.




To test them, switch the suspected lamp with a known good one.

Those lamps are inexpensive, I'd replace all three and then you probably will have a spare.




Despite this circuit having a power transformer, there is still a connection to the AC line, so always unplug the set before testing. If the set is connected to a grounded cable, disconnect that also.

Always warm up the CRT for five minutes before the test. Test for shorts first and if none, gently thump the neck to see if any appear. Never emission test a CRT that shows shorts, or you may fry the tester.

And, the best reason I have this tester is that it is damn near idiot-proof !

Good luck !

James