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-   -   Tube question from a rookie (http://www.videokarma.org/showthread.php?t=270310)

Wind157 04-04-2018 08:35 PM

Tube question from a rookie
 
Im testing a tube 5AQ5. Datasheet shows 3 and 4 are the filament and multimeter checks them as having continunity. It also has continunity on 1 and 7 which it shows as grid 1 for both. Is that okay?

broadcaster 04-05-2018 08:17 AM

Yes, that is correct

Wind157 04-05-2018 01:37 PM

Shoot, thought I found the problem. Now to start checking capacitors

dieseljeep 04-05-2018 09:25 PM

Quote:

Originally Posted by Wind157 (Post 3197873)
Shoot, thought I found the problem. Now to start checking capacitors

You fail to state if there's a light on the screen or noise in the speaker. If all the tubes light, there's no problem with the heater string. Outside of the tubes lighting, if there's no other indications regarding audio noise or screen illumination, the next place to go is to check for B+. It can be checked around the selenium rectifiers. It could something as simple as an open fusible resistor or a fuse in the B+ circuit. The selenium rectifiers are the units with the six metal plates. There should be two on the tube side of the chassis.
You have to determine where the original fault really lies. :scratch2:

Wind157 04-10-2018 04:03 PM

I had someone else say B+ also (not sure what that is). There is a rectangular resistor near the rectifiers that I suspect is bad. Multimeter and resistance test don't give consistent results and there is corrosion on it's lead that seems to be coming from the resistor itself and no other components have any corrosion/oxidation at all. Waiting on a new one to confirm my theory.

Electronic M 04-10-2018 07:28 PM

Quote:

Originally Posted by Wind157 (Post 3198081)
I had someone else say B+ also (not sure what that is). There is a rectangular resistor near the rectifiers that I suspect is bad. Multimeter and resistance test don't give consistent results and there is corrosion on it's lead that seems to be coming from the resistor itself and no other components have any corrosion/oxidation at all. Waiting on a new one to confirm my theory.

B+ is a/the main power supply voltage for the set. Some sets have more than one B+ rail (each will have different voltage normally) either divided off the highest voltage rail by a resistor or supplied by a separate rectifier. Typical voltage in tube sets is somewhere between 67 and 1000V (depending on the category of device).

The origin of the term dates from the first tube radios in the 1910's and 1920's...Until the late 20's there was no practical way to filter rectified AC to be clean enough to NOT swamp out RF/audio with AC powerline hum in radios, thus all radios ran on batteries...Back then the "A" battery ran the tube heaters/filaments, and "B" ran the plates...There was sometimes also "C" for the grid bias, but modern resistor dividers from the B supply eliminated the need for "C".

dieseljeep 04-10-2018 09:00 PM

Quote:

Originally Posted by Wind157 (Post 3198081)
I had someone else say B+ also (not sure what that is). There is a rectangular resistor near the rectifiers that I suspect is bad. Multimeter and resistance test don't give consistent results and there is corrosion on it's lead that seems to be coming from the resistor itself and no other components have any corrosion/oxidation at all. Waiting on a new one to confirm my theory.

That resistor runs rather hot and will corrode the lead wires.
You'd have to check the voltage on both sides of the resistor, meter set on AC range.

Wind157 04-12-2018 11:45 PM

1 Attachment(s)
That was indeed the, or at least one of the problems. No to figure out why half the screen doesn't work. Oh fun with vertical

dieseljeep 04-13-2018 11:25 AM

Quote:

Originally Posted by Wind157 (Post 3198175)
That was indeed the, or at least one of the problems. No to figure out why half the screen doesn't work. Oh fun with vertical

For some crazy reason, I like that model Zenith. They work really well when restored. It looks like the CRT has a lot of life in it. The only bad thing is it's a little hard to work on, because the way it's assembled.
In your next post, include the chassis number and maybe someone has the schematic for it. You need one to have it when doing a restoration. :thmbsp:

Wind157 04-13-2018 03:36 PM

Its a Z1819JZ chassis is a 15z31 and I have one for it. Only way I was able to find out what resistor I needed as the bad one was so worn there where no numbers on it.

Kevin Kuehn 04-13-2018 03:52 PM

Have you tried adjusting the vertical height and linearity controls? Otherwise have you replaced the paper and electrolytic capacitors in this TV?

Wind157 04-13-2018 04:23 PM

I have not. Getting it to power on was was exciting. I suspect a capitor may be an issue related to the vertical. When it did power on there was a small, barely noticeable, amount of smoke coming from a component. From seeing the smoke to getting closer to look, it wasnt happening anymore.

Wind157 04-27-2018 09:46 PM

Quote:

Originally Posted by Kevin Kuehn (Post 3198196)
Have you tried adjusting the vertical height and linearity controls? Otherwise have you replaced the paper and electrolytic capacitors in this TV?

I’ve done some adjusting, I either get a picture that takes up the whole screen but is faded and has fold over or I get a narrow picture with black section below

Robert Grant 09-19-2018 08:52 AM

It wouldn't surprise me if a foil/paper tubular cap in the vertical circuit shorted, causing overvoltage (ergo overcurrent) through the resistor.

Just a guess (Many other possibilities)

zeno 09-23-2018 10:03 AM

There is an electrolytic on the cathode of the vert output that
causes the bottom to pull up. Eventually the vert should be recapped
except for the discs. Also the 3 legged integrators changed.
Check all resistors especially high ohms ones. Do recapping
one at a time then test to be sure of no mistakes.
These will be of interest........

https://www.youtube.com/watch?v=vt7OLBCoR8o
https://www.youtube.com/watch?v=6lZIJQ-cKDs&t=141s

73 Zeno:smoke:
LFOD !


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