Vacuum Tube Source

tta583

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I have a '73 Williams Pro Tennis with a vacuum tube based B/W TV as a display. Looks like I need some tubes for it. I have looked around and can find one tube here, one tube there, but no place that had 2 or more. Anyone here have any experience with rebuilding old tube based equipment that could turn me on to a supplier? Perhaps the Bob Roberts version of vacuum tubes???
 
I still have quite a few tubes, mostly used ones and I have tube testers too. Which tubes are you needing? Have you tested the tubes you have?
 
Well, this is definitely a case of "When I said hello to you I told you everything I know about vacuum tubes" moment. ;)

I do have a tester. From what I can tell its a pretty desirable one at that. I, however, have not dove in and tried to learn how to use it. What I have done is to stop in and see a older school TV repair man I know. Even at that he had to reach back to some stuff his dad taught him. I explained my issue and he suggested I look at the tube oscillator and damper tubes. Further discussion led me to feel it would probably be a good idea to be ready to replace the horizontal output and the high voltage tube as well. Let me grab the numbers.
 
6HB5
6BE3
6GH8A
2BU2

The rest of the tubes in the set are:
6JT8
6Z10
6GK6
6BA11

I would take them as well just to have spares.
 
Antique Electronic Supply:

http://www.tubesandmore.com/

Has lots of tubes. Their prices are traditionally a bit higher, and they're kind of a "retailer", but they're pretty good about having nearly everything.

I'm positive I have all those tubes, but at the same time, I have no idea where - I have boxes and boxes and boxes of random tubes, and as soon as I can find a round tuit, I will sort and organize them all.

I collect old television sets as well, so, I do have a lot of experience fixing them. What kinds of problems are you having with it? Believe it or not, tubes are actually quite reliable. Usually I don't have to replace them very often. But, then again, this being an arcade monitor, it probably saw all kinds of use.

The tube tester is easy to use. Look up the tube type on the scroll, and it'll tell you what socket to use, what to set the filament voltage to, and how to set the dozen or so switches on the front. Then you press the TEST button, and look at the meter, and it'll give you some indication of how strong the the emissions are. Note that not all tubes have to be super strong - in some circuits, such as a phase inverter, there isn't any gain, so a real weak tube performs the same as a strong one. And other times, you'll have a tube that tests great, but doesn't work in the circuit. Tubes are weird like that... In other words, while the tester is a great tool for a sanity check, it's not the be-all end-all. Testing the tube in the circuit is.

-Ian
 
I would say its seen some use in that it has burn in so, back in the day, I'm sure it saw the typical arcade experience.

When I first got the game going the image was rock solid but it did have a slight fold in the top inch or two. After some play its developed what I would best describe as a twitch where the entire image wobbles or jumps back and fourth at random intervals.
 
I would check the electrolytic caps in that old set first. Especially the multipart caps in the metal cans.

I bet you don't have an ESR meter... ;)
 
The foldover could be a tube, but it's more likely a passive component like a capacitor or a resistor. Usually when the vertical oscillator tube gets weak the picture just gets shorter, it doesn't fold over. These old sets use high voltage, low capacitance, non-electrolytic capacitors - really old sets would use paper caps which were horribly unreliable. This probably uses plastic caps, which are reliable, but can fail sometimes. Look closely at the ones in the vertical circuit. There are usually some high value resistors near the vertical linearity control - check those as well. Anything over about 1 meg ohm tends to drift - the old carbon composition resistors are not that stable.

Have you replaced the filter caps yet? Low or unstable B+ can cause weird things to happen.

-Ian
 
They are $21 on the 6HB5. Wow!! I may just piece them out as I have seen that one NOS, on the low end, at about $7-8 including shipping.

Eek. Yeah, I did warn you that they tend to be a bit more expensive than most, right?

That one is a bit more crazy, however.

Most television tubes aren't worth much of anything, except the random few that also found their way into a guitar amplifier or some other audio gear at some point. This one may have some other use, I'm not sure. I'm more familiar with televisions, where this is a simply horizontal amplifier. It's a beam pentode, however, so it's possible someone used it for audio or other amplification at some point.

Keep looking around, you'll find something. In the mean time, however, I doubt this tube needs to be replaced. Your problems are with the vertical.

-Ian
 
I would check the electrolytic caps in that old set first. Especially the multipart caps in the metal cans.

I bet you don't have an ESR meter... ;)

No I don't. )-:


The foldover could be a tube, but it's more likely a passive component like a capacitor or a resistor. Usually when the vertical oscillator tube gets weak the picture just gets shorter, it doesn't fold over. These old sets use high voltage, low capacitance, non-electrolytic capacitors - really old sets would use paper caps which were horribly unreliable. This probably uses plastic caps, which are reliable, but can fail sometimes. Look closely at the ones in the vertical circuit. There are usually some high value resistors near the vertical linearity control - check those as well. Anything over about 1 meg ohm tends to drift - the old carbon composition resistors are not that stable.

Have you replaced the filter caps yet? Low or unstable B+ can cause weird things to happen.

-Ian

No I have not. They are on my list to look at as well once I get into it. Those and the paper caps as I already have some exp with those (failing) in another application. Tube wise...I'm really trying to think ahead a bit to I'm not spending a lot of time hunting once I commit to tearing into it!!

Ian, if you have, can find, and are interested in selling some or all of the tubes I would be interested. If anything I will have spares down the road. I don't see the game really being sold off. Long story short is its being given back to the original owner/operator as a gift. He is a buddy of mine. It actually means a lot to him. I see it being around for a long time.

I am pretty sure I may need a socket or two as well so I would appreciate if you, or anyone else, has a trusted source or even an insight into different types or layouts.

Time willing I will take out the chassis this weekend. A quick glance tells me its a bit involved so I need to try to con someone into helping me at least get the tv set out of the game cabinet.
 
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While I am thinking of it...any chance if a chassis ID so I can try and hunt schematics???
 

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That's a Zenith 22DB36. It's in Sam's Photofact number 1357-3.

Sam's Photofacts are kind of the defacto go-to source of schematics for television sets and other consumer electronics. They sell them online for like $20 a folder, but many libraries have them too. My local library has subscribed to Sam's for a long time, so when I need a schematic I just go there and look it up, and photocopy the relevant page.

Photofacts are great. Not only do they have schematics, but they also have pictures of all the parts (hence the Photo), disassembly instructions, alignment instructions, etc.

-Ian
 
I'll look this weekend for tubes.

You probably don't need any sockets, just clean the ones you have. It's pretty rare for them to need replacing, especially in a Zenith.

Removing the chassis from a set like this is really easy. You usually have to take the tuner out too, which is mounted to the inside of the cabinet with a few screws. Lots of times you can remove one, and the others are shaped so you can loosen them and lift the tuner bracket up and over. Unhook the speaker. The chassis will be secured from underneath with four screws through the bottom of the cabinet. Disconnect the yoke and the tube neck connector, and the HV lead. Everything should just slide right out.

These things are usually held together with 1/4" hex cap screws, so be sure you have a nutdriver.

-Ian
 
Great info. Thanks! I will lookout for the tuner. My catch is the screws under the cabinet. I could tell from the back there were some under there. As the entire set is screwed into the game cabinet and has no back on the original case I am a little reluctant to un-screw its mounting then try and slide it out alone for fear of getting into the CRT neck.

As to the caps conversion. I want to say the papers are generally replaced with polys right? It's been a while. What are good replacements for remaking the multi value cans?
 
I read that in restoring 50s televisions, you can often get them working by replacing all of the electrolytic capacitors.. I'm sure that's sometimes and not a general rule, but definitely a must for something that old.
 
As to the caps conversion. I want to say the papers are generally replaced with polys right? It's been a while. What are good replacements for remaking the multi value cans?

Yes. You'd use modern plastic capacitors. Frankly, however, this set is too new to have paper caps in it. By the 70's they already had plastic caps, and good ceramics. Still something to watch out for though, and if you're having problems with the vertical, changing the caps in that circuit would be worthwhile. And check the resistors.

For the electrolytic cans, you won't be able to get exact replacements. They'll be multivalue cans, and chances are, there will be obsolete values in there. Just round up to the next standard value. So, to replace a 200UF capacitor, use 220UF. You can use normal radial or axial electrolytics. Come up with your own mounting solution - either terminal strips or perf board. When there are multiple caps in one can, all the negative leads are attached together (usually to the can itself).


joeycuda said:
I read that in restoring 50s televisions, you can often get them working by replacing all of the electrolytic capacitors.. I'm sure that's sometimes and not a general rule, but definitely a must for something that old.

For fifties sets, yes, you'd replace the electrolytics (of which there are only a few, in the power supply), and most importantly, the paper capacitors all over the set. They will be things like .01 at 630v, or .22 at 630v. The old wax paper and foil capacitors age very poorly. Electrolytics from that era (at least the metal can ones) are actually more reliable than the paper caps. I've got 50's era sets with their original electrolytics, since they still tested good. Paper caps all had to be changed though.

THIS set really is not that old. It's from about 1973, judging from the Photofact number. By then the capacitors were pretty good. Obviously, this one has lead a much harder life than most, since it was likely on all the time for years. Changing the power supply caps is probably a good idea. With the manual, you'll know what the B+ is supposed to be, so you can check to see if it's low or has ripple. If it is, then they definitely need to be changed.

A word of warning - be VERY careful working on a tube type television. The usual precautions of monitors apply, but the additional precautions of high plate voltage in tube type equipment also applies. There will be DC voltages in excess of four hundred volts in there. Just pay attention and be careful.

-Ian
 
Ahh.. I thought paper caps were a bit more common than that in terms of years used. There is even one used in a wells 4600. It's been a while but I think its the last on in the circuit on the main board before the jumper to the neck board to feed the focus pin.

Either way, let me see if I can get it apart this weekend and see what I have.

As to the schematic. I am kind of surprised a lot of that stuff is not online. Guess I am spoiled by the arcade community.
 
Update. Replaced the electrolytics. It was a marked improvement but not perfect. Better image, more stability. No vertical to the "jitter". It still has a slight fold in the upper portion of the image. I would say within the upper inch or less. Occasional twitch to the right.

Tube wise I tried to learn my tester this weekend only to discover none of the tubes are in the setup guide that I have. I did take the rectifier tube and the three related to horizontal control to a buddy. Unfortunately only one was in his guide. It tested bad. At this point I think I am going to shotgun the horizontal section and replace the rectifier tube. They are not necessarily expensive..but are a pain in that no place with reasonable prices seems to have all 4.

I am also going to try and round up the schematics. Library trip if a buddy of mine does not have a Sams subscription.
 
If you want, I can look through my tubes and see if I have them. Give me the four numbers you need and I'll see if I have them and if my tube testers can test them.
 
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