Found a Sylvania SS/Tube hybrid

[Captainclock]

Originally Posted by MRX37

Need to find out of that tube is a proper substitute for the 3CU3 that should be in there.

The 3CU3's Subs include 3AW3, 3CV3, 3CZ3, and 3DC3, but not the 3A3, so your issue might have something to do with having the wrong tube in there...

[Findm-Keepm]

Originally Posted by Captainclock

..... generally tube tester charts don't put the letter suffixes after the tube designation because they're all the same tube just different heater warmup times.

Not so - the 3A3C is an improved type with reduced X-ray protection. Heater characteristics are the same as the 3A3. The glass and plate were improved for better X-ray protection, much like the 6BK4 upgrade to the 6BK4C/6EL4

Electrically the same for tube testing, but with most testers putting only about 100V across the tube, not a conclusive test. We checked HV rectifiers with GE's suggested circuit, also used for Focus rectifiers - you can't check them accurately without a fairly high voltage.

[Captainclock]

Originally Posted by Findm-Keepm

Not so - the 3A3C is an improved type with reduced X-ray protection. Heater characteristics are the same as the 3A3. The glass and plate were improved for better X-ray protection, much like the 6BK4 upgrade to the 6BK4C/6EL4

Electrically the same for tube testing, but with most testers putting only about 100V across the tube, not a conclusive test. We checked HV rectifiers with GE's suggested circuit, also used for Focus rectifiers - you can't check them accurately without a fairly high voltage.

I see, so then the 3A3 tube test setup on the tube tester I just sent him and mine as well wouldn't be able to test the tube that he's asking about then, or would it?

[Findm-Keepm]

All the suffixed tubes will test with the settings of a non-suffixed tube.

My comments were aimed more at the incorrect statement made about the suffixed tube differences, it's X-ray protection, not heater warmuptime as you mentioned.

[Captainclock]

Originally Posted by Findm-Keepm

All the suffixed tubes will test with the settings of a non-suffixed tube.

My comments were aimed more at the incorrect statement made about the suffixed tube differences, it's X-ray protection, not heater warmuptime as you mentioned.

The "A" designation on the 12AX7s and what not do refer to warm-up time that's mainly what I was referring to, I was mainly referring to the fact that the suffixes in the tube designations referred to a revision of some sort in the tube in general, not just heater warm-up time I was using the heater warm-up time as an example of what some of the designations could mean.

[MRX37]

Guys it's kind of a moot point. Doesn't matter if that 3A3 is good or not because it's the wrong tube for that TV.

And I'm hazarding a guess that the wrong rectifier tube could further explain the dim, blurry image

[Captainclock]

Originally Posted by MRX37

Guys it's kind of a moot point. Doesn't matter if that 3A3 is good or not because it's the wrong tube for that TV.

And I'm hazarding a guess that the wrong rectifier tube could further explain the dim, blurry image

I agree, I was mainly just trying to make the point that the tube tester I sent you isn't as obsolete as you thought it was, that's all. Like I said I'll still check my tube stash out at home for the tube you need or its substitutes and get back with you about it. I had a birthday party to go to earlier and I also had to repair one of my tires because it had 3 nails in it and was low and I was checking into getting some new tires for my car as well so I won't be getting home as soon as I thought I would today. Don't worry I haven't forgotten about you!

EDIT: I just looked through my tube stash and had two boxes labeled 3AW3 (which is a proper substitute forthe tube you need) but that's all it was, just the boxes, the tubes inside them weren't even close to being 3AW3 tubes, one was a 1B3GT tube (which I'm not sure why a tv repairman would put a 1 Volt tube in a box for a 3 volt tube and is definitely NOT a suitable substitute for the 3AW3 let alone a 3CU3, and its not even the same filament voltage) and the other tube was a 3DB3, which I guess is a substitute for a 3AW3 and also a 3CU3, If you want the 3DB3 tube I have (I'll test it first to see if its any good)I can mail it off to you, for the price of shipping.

Well I tested the 3DB3 tube I have and it almost pegged out my tube tester on the good side of the meter on both the grid leakage and emissions tests. I'm kind of starting to see a pattern here, its almost like whoever owned this tube caddy before me was apparently a dishonest repairman and replaced tubes inside TVs and radios that didn't need replacing just so he could upcharge his customers for repairs that weren't needed, kind of like how auto mechanics work sometimes...

[MRX37]

Take your time. I'm in no major rush.

[Jeffhs]

That Sylvania TV has a very nice cabinet. I have two end tables and a coffee table in my apartment with the same type of legs as your TV has. That design must have been popular in the '60s-'70s, and made a comeback in the late 1990s when I bought my furniture (I was moving to an apartment, the one I live in today, at the time, and wanted to make a fresh start).

That your TV's cabinet has absolutely no scratches whatsoever on top is wonderful. Your set's former owner(s) must have taken extremely good care of it, which is good. I've seen console TVs with all manner of dust, dirt, scratches, etc. on them (I've owned a few, mostly trash finds; they stayed in the basement of my former home, of course), and again, your Sylvania console, as scratch-free as it is, is a sight for sore eyes.

Back on topic: I'm not sure what tube substitutes for a 3A3, as it has been years since I worked on TVs of any kind (my apartment is very small, so I limit the little restoration work I do to small radios). However, the list of subs for the 3A3 I saw in another post seems quite comprehensive, so one of them should work.

I'd be extremely careful with a tube such as a 3A3, as the filament of this tube carries extremely high voltage (especially in color TVs), on the order of kilovolts, not just three volts as the type designation would have one believe. These tubes get their filament voltage from a single turn of exceedingly well insulated wire wrapped around the laminations at the base of the flyback transformer.

[Findm-Keepm]

Originally Posted by Captainclock

Well I tested the 3DB3 tube I have and it almost pegged out my tube tester on the good side of the meter on both the grid leakage and emissions tests. :

No grid leakage in a 3DB3? Amazing, considering it doesn't have a grid...

[Captainclock]

Originally Posted by Findm-Keepm

No grid leakage in a 3DB3? Amazing, considering it doesn't have a grid...

Well Then I'm guessing that the Emissions test would be the only test that would apply in this case then, which in that case it still nearly pegged out my tube tester on the good side of the emissions test, which means it's a perfectly good tube yet, which means that what I said about the previous owner of my tube caddy being a greedy/shoddy repairman that replaced perfectly good tubes in radios and tvs just to upcharge his clients still would apply here because most of the tubes I found in my tube caddy were previously used tubes that still tested like new on my tube tester with quite a few NOS tubes thrown in for good measure.

[MRX37]

No worries Captainclock. 3CU3's are available on ebay for a few bucks including shipping.

[zeno]

Dont trust a tube checker. It does not test the tube under
normal use. The are not run at say 200 mhz as an RF amp
or 1000 V spikes like a horz output. Some tubes will
check bad & work fine & some check good & not work at all.
Use it as a helper but never the last word.

BTW We had a very nice B&K checker but never used it.
It was for the customers. Biggest cash cow in the shop.
What we did have was a filament tester. Did 7&9 pin minis
& compactrons. Useful to find an open filament in a series
string set without easy access to the bottom. Great for AA 5
radios too ! Cost abt $10 back then.

73 Zeno

[MRX37]

Update: I have a new 3CU3, but I don't know if it solves my problem because I have a new problem now.

I think I fucked over the shunt regulator tube.

When I got my tube tester, I decided I was going to test every tube in the chassis. You might recall I tried to remove the shunt regulator tube before and couldn't. I eventually found out why.

After pulling on it, probably harder then I should have been, I found that it was being held in with a retainer clip.

So I removed it and put it in my tube tester. The tube is a 6BK4C and my tester has settings for a 6BK4, so I used those settings. Emission almost immediately jumped to max, then the needle started jerking quickly. Then a purple glow appeared near the bottom of the tube so I cut power. Not having another 6BK4 I put this one back in the TV.

So I put in the new 3CU3 and power on the set. As soon as HV comes up I hear rapid arcing, then the sound goes weird. I immediately cut the power.

I suspect I messed up the 6BK4. Can I run the TV without the HV regulator tube in it, or would that be a really bad idea?

[Electronic M]

Don't run it without the reg unless you are metering the HV. The HV can easily go above it's ratings without that tube, and if HV goes above ratings stuff like the fly can be damaged.