Vert hold/control ?

[Electronic M]

Originally Posted by Wind157

Yeah my luck is typically that I break something when fixing it though.
I suppose I should take the meter and check the various caps. It's just replacing the caps in the can, I feel like I'm flying blind without know exactly where to connect the replacement cap. Wish I could just find a replacement can instead of three separate caps.

DMMs and solid state meters only check for capacitance...Most paper caps and ~half of lytics fail by leaking DC current across their terminals. A 400V rated cap may only start to leak with 300V or more across it. SolidState meters only apply around 5V to 12V not even close to being able to smoke out the issue. I use a tube type Heathkit C3 cap tester that can check for leakage by applying up to 450V...The only true validation of a vintage cap is applying its full rated voltage to it, and even then most paper caps and vintage lytics are so unreliable that it could(and often does) test good now, then in a week short dead and burn up some unobtainium coil.

No one makes real cans like those (the last vanished in the early 80's), there is one place that makes repops by stuffing individual modern caps into a can (not how the originals were made)...They charge way more than replacing with individual parts and are not worth it. Find your self an original cap that has been removed from a set and look it over carefully...They are not that complicated. Depending on the size of the can there will be 3-4 outer (negative) lugs connected to the outer metal can and 1-4 inner (positive) lugs connected to the center insulating wafer. The can metal is always negative in tube gear as are the outer lugs. The positive lugs in cans that have more than one section are differentiated from each other with the following symbols "^", "D", "[]", "-"(or" ") those symbols will either be scratched on the insulator around the terminals, or will be cut out of the insulator as an enlargement of the hole the positive terminal protrudes from. The metal on the can will have printed on it a label showing in a table the capacitance, voltage and terminal ID symbol of the positive sections. If you or a 5-year-old were in the same room with me and one of those caps I could teach both of you to read and change can caps (assuming prior knowledge of soldering) in around 3 minutes.

The thing about tube sets is they are eventually going to die at random from original caps as long as you leave them in...Better to change them all now one at a time while it works than wait for it to die...If you kill it while working now you can find your mistake easy if you go one or two caps at a time and check after doing those 1-2. But if you wait for the original caps to kill the set and then recap a dead set you have NO way to know you made a mistake...You'll end up changing every single cap and at the end not know if there are other issues or if you screwed up.

I get that a TV can be overwhelming, I try to advise people that want to eventually restore a TV to get a couple of 5 tube AM radios to practice recap work on those first...Much simpler than a TV, forgiving, cheap, and somewhat disposable for tube gear.

[Electronic M]

BTW when we say paper caps we are referring to the dielectric inside the cap and not it's outer casing. The white tubular ceramic caps in some of the pictures and the aforementioned bumblebee caps are paper dielectric caps, and should be changed.

[Electronic M]

delete duplicate.

[Electronic M]

AC caps are almost never seen in TVs. Lytics and paper caps both new and original are and were rated for DC voltage.

Many new film/paper types are given both AC and DC voltage ratings... ignore the AC rating and choose new ones based on their DC voltage rating.

In most applications a cap would have something like 400VDC across it and maybe 5VAC of signal.... if it can handle the 400 DC then it can handle the 5 ac easily.

[Wind157]

Glad I asked then.

How far below capacitance can I go? I need to replace one that is 150 but closest is 120 and that's with being a good deal higher in voltage

[Electronic M]

Lytics typically were +100%/-50% tolerance on the capacitance so 75uF would be the lowest you can go on a 150uF. Papers typically have a 10% tolerance. Most sets don't mind some variance in the capacitance of lytics, but papers can be more critical especially in any stage of a TV other than audio or power. In some cases (usually paper caps) if I don't feel I can get a precise enough value for the circuit I'll put two capacitors in parallel to get the value I need (capacitances in parallel add).

The closer the better but 120 should be plenty close to 150...If you get excessive hum on the line it filters after the recap you can always tack a 33 or more on in parallel with the 120 after the fact.

[Wind157]

Thanks. I ended up finding one at 140 but voltage was 400 instead of 300. Fitting it will be fun.

[andy]

...

[Wind157]

Replacing the caps in a can, the negative of the new cap connects to ground?

[Electronic M]

Originally Posted by Wind157

Replacing the caps in a can, the negative of the new cap connects to ground?

The negative of the new cap(s) connects to whatever the metal housing of the original can connected to...

Many cans were soldered directly to chassis ground, but others rather than connecting the can to ground, connected it to a floating negative rail.
The original can will have 3-4 outer twist tabs coming from it's bottom...If the twist tabs contact and are soldered to the chassis metal then the can is grounded to chassis....But if the twist tabs are twisted onto a phenolic insulating wafer (the wafer is riveted to the chassis in 2 places) then the can connects to a floating negative rail (and your replacement(s) should then connect to the floating negative rail instead of the chassis). Another giveaway that a can is on a floating negative is when the metal can above chassis is wrapped in a cardboard or plastic insulator.

If that is confusing then ask me for some pictures tomorrow...Visual aid makes my point come across with at least a thousand fewer words.

[Electronic M]

IIRC you have not replaced the bumblebees and tubular ceramic caps in that set yet...Vertical troubleshooting 101 replace EVERY cap in the vertical stages first (no exceptions, total original capacitor genocide!), check for proper operation, then go after tubes and resistors.

See all the caps circled in my edit of your picture? If any of those are in the vertical stage or any vert capacitors currently installed look like them then the vertical will probably not work completely right.

Lytics can cause problems in the vertical (and sometimes are the only problem), but papers can be as bad or worse. On a set this old it is a miracle it works as well as it does now with those lousy old caps.

[Wind157]

I already have all those marked for replacing but thanks.

Guess I'll see how it appears after that. I suspect it will be the same. Which if it is then so be it, could be far worse for a free set that's 61 years old

[Wind157]

So I've replaced the caps and it actually preforms worse? The screen height issue is still an issue and now the screen flickers consistently.
I'm going back to the old caps before I stick more money into this.

[Wind157]

Unless I'm reading the can wrong. I'm assuming the prong in the upper right corner to match the cap that is stamped as square on the can. The opposite prong as the triangle and the semi circle is obvi

[EdKozk2]

Under the red wire is a triangle. Blue is connected to the half moon, as noted, and pin with no obstruction is the square. Outside perimeter tabs are ground.
Ed