Project impossible? bringing a magnet-box back from the dead? - Videokarma.org TV - Video

Yamamaya42 · #1 07-04-2021, 01:59 AM

Well I have always been a sucker for hard luck cases, and WELL, I have really found one this time!

I'm always looking on FB for vintage TVs, and found one a week ago for the fantastic price of FREE!
All I could see at the time was a CRT and a chassis that looked like it had been unceremoniously removed from the cabinet for no doubt some horrific use of a dog bed or fish tank or the like, all I could see was cut wires and it was clearly missing the tuner, but, HEY, it was free!
I got it today.

NO markings at all on the chassis, but it did not take me long to ID it...

same as in this thread.
http://www.videokarma.org/showthread.php?t=38726

A look at the CRT
https://i.imgur.com/hpVtGeS.jpg

OK,,,,
https://i.imgur.com/ELiQIcf.jpg

NOT looking good here, that first element looks VERY dark.
hooked it up to the B&K tester

https://i.imgur.com/mrWLCSS.jpg
NOPE, not looking good.

after 2 hours
https://i.imgur.com/YFSgxAo.jpg
came up a bit, but still very tired.

and finally , the murdered chassis, no tubes, and cut wires, ( i had a few tubes )
https://i.imgur.com/8ECWBpM.jpg

Sad that they do that.

I am gonna try to bring it back to life.

Starting with horizontal /HV then Vert and so on.

gonna have to work out what wires are what and where they go
but since the tuner is gone, this will most likely end up AV/input if it ever DOES work.

dtvmcdonald · #2 07-05-2021, 09:12 AM

Its not a "magnet box", the correct term is "maggot box".

When I was a little kid we had them. The pictures were incredibly sharp, and
in 1954 started showing dot crawl stupefyingly clearly.

Yamamaya42 · #3 07-05-2021, 12:53 PM

Houston, we have power!
https://i.imgur.com/54cwucJ.jpg

took a bit to work out which wires but!

https://i.imgur.com/NfzdA5Q.jpg tubes nice and glowing, no smoke

As mentioned in the other thread, the SAMs is CLOSE, with slight differences, some tubes are not the same. like it shows a different damper, so I had no idea which one to use, looked through my old tubes , found a 6DW4B, did a quick check, it matched up perfectly for the way the socket was wired, so i put it in, I see no reason why it should not work in there, a damper is a damper, the ratings for it seem good enough.

I'm now waiting for other tubes horz osc and the HV rect, to come, to see if I can get HV up.

dieseljeep · #4 07-05-2021, 05:41 PM

Quote:

Originally Posted by Yamamaya42

Houston, we have power!
https://i.imgur.com/54cwucJ.jpg

took a bit to work out which wires but!

https://i.imgur.com/NfzdA5Q.jpg tubes nice and glowing, no smoke

As mentioned in the other thread, the SAMs is CLOSE, with slight differences, some tubes are not the same. like it shows a different damper, so I had no idea which one to use, looked through my old tubes , found a 6DW4B, did a quick check, it matched up perfectly for the way the socket was wired, so i put it in, I see no reason why it should not work in there, a damper is a damper, the ratings for it seem good enough.

I'm now waiting for other tubes horz osc and the HV rect, to come, to see if I can get HV up.

The original damper tube was probably a 6AY3.
I have a newer Mag chassis that uses a 6GB5/EL500. I picked it off the street because I wanted the little stereo amp, 2 6BQ5's. That's awhile ago!

old_coot88 · #5 07-05-2021, 06:40 PM

Wasn't 6AY3 a compactron base? IIRC it was used in a lot of RCA B&W sets of the day.

Yamamaya42 · #6 07-05-2021, 06:50 PM

Quote:

Originally Posted by dieseljeep

The original damper tube was probably a 6AY3.
I have a newer Mag chassis that uses a 6GB5/EL500. I picked it off the street because I wanted the little stereo amp, 2 6BQ5's. That's awhile ago!

Well, I have been able to confirm that although THIS chassis does not use the damper as shown on the SAMS I have, ( 6DA4A) And is wired for a 6AY3/ 6DW4B type, the latter being a bit more beefy, it is wired for a 6GW6 HOT, which i had, and I THINK worked, not really sure.

Yamamaya42 · #7 07-06-2021, 11:40 AM

From what I can see, the 24AHP4 is one of the largest BW CRTs made, and a bit rare to find one at all, let alone in good working order.
It's going to be interesting to see what kind of picture the one I have can make, but first I will be trying to bring this chassis up on the 8YP4 Test CRT.

Again, it really sucks that the tuner is gone, all the missing controls, I can re-create, but the tuner, not so easy, although, I do see NOS tube tuners for sale on eBay, trying to tack on some alien tuner, and get it to work correctly and align up and be nice and happy with AGC and everything would be near impossible.

But on the upside, it looks like the input to the video output , right out of the detector is 1.5v ptp, so it would be easy to feed in composite video.

dieseljeep · #8 07-06-2021, 12:52 PM

Quote:

Originally Posted by Yamamaya42

From what I can see, the 24AHP4 is one of the largest BW CRTs made, and a bit rare to find one at all, let alone in good working order.
It's going to be interesting to see what kind of picture the one I have can make, but first I will be trying to bring this chassis up on the 8YP4 Test CRT.

Again, it really sucks that the tuner is gone, all the missing controls, I can re-create, but the tuner, not so easy, although, I do see NOS tube tuners for sale on eBay, trying to tack on some alien tuner, and get it to work correctly and align up and be nice and happy with AGC and everything would be near impossible.

But on the upside, it looks like the input to the video output , right out of the detector is 1.5v ptp, so it would be easy to feed in composite video.

I have a Magnavox combo that has a rebuilt 24AHP4, which seems to be perfect! I took it for the PPP 6V6 mono amp. If I could give the set away to a collector, I'd leave it intact.

old_coot88 · #9 07-06-2021, 04:32 PM

Quote:

Originally Posted by Yamamaya42

From what I can see, the 24AHP4 is one of the largest BW CRTs made.

Maggie also made 27 inch sets for a little while. The 24 and 27 inch CRTs were wide-deflection, small neck types that tended to go flat right away. To find a still-good unrejuvvied one would be a rarity indeed.

Electronic M · #10 07-06-2021, 05:46 PM

Quote:

Originally Posted by dieseljeep

I have a Magnavox combo that has a rebuilt 24AHP4, which seems to be perfect! I took it for the PPP 6V6 mono amp. If I could give the set away to a collector, I'd leave it intact.

If I get a house in the next couple of years I may have to take a look at it...

Yamamaya42 · #11 07-06-2021, 07:05 PM

Quote:

Originally Posted by dieseljeep

I have a Magnavox combo that has a rebuilt 24AHP4, which seems to be perfect! I took it for the PPP 6V6 mono amp. If I could give the set away to a collector, I'd leave it intact.

If you were not so far away from me T_T

because shipping is murder!

But now I have another problem to work out, I did not notice that the video going into the output tube is inverted , YES it's 1.5 ptp, but it is upside down, and gets fed into the CRT cathode at 50v
so now I gotta work out how to invert a composite video input. Because I don't think this will work to well off IF with my tuner subber as a source.

I am thinking of this a a AMP. But I do not know op-amps very well.

https://www.eleccircuit.com/simple-v...ifier-circuit/

they do not make DIP LM359 chips anymore and I don't trust the ones from china, FAKE! So all I can find are surface mount.

But I can assume, if I swap the + & - inputs, I will get inverted ( negative ) output ? And adjust R1 /R3 till I get close to 1 to 1 or slightly higher gain from it? Am I guessing right?

Electronic M · #12 07-06-2021, 08:03 PM

Quote:

Originally Posted by Yamamaya42

If you were not so far away from me T_T

because shipping is murder!

But now I have another problem to work out, I did not notice that the video going into the output tube is inverted , YES it's 1.5 ptp, but it is upside down, and gets fed into the CRT cathode at 50v
so now I gotta work out how to invert a composite video input. Because I don't think this will work to well off IF with my tuner subber as a source.

I am thinking of this a a AMP. But I do not know op-amps very well.

https://www.eleccircuit.com/simple-v...ifier-circuit/

they do not make DIP LM359 chips anymore and I don't trust the ones from china, FAKE! So all I can find are surface mount.

But I can assume, if I swap the + & - inputs, I will get inverted ( negative ) output ? And adjust R1 /R3 till I get close to 1 to 1 or slightly higher gain from it? Am I guessing right?

Google inverting op amp circuit (or read the Wikipedia page on op amps) and that will give you the schematic and maths to make a circuit.

Personally I'd try getting a tuner for it. That almost certainly uses the modern IF frequency and generally they aligned TV tuners and IFs to be interchangeable... as long as you don't try something silly like making a late 40s 21MHz tuner work with a 60's 44MHz IF TV.

dieseljeep · #13 07-06-2021, 08:05 PM

Quote:

Originally Posted by old_coot88

Maggie also made 27 inch sets for a little while. The 24 and 27 inch CRTs were wide-deflection, small neck types that tended to go flat right away. To find a still-good unrejuvvied one would be a rarity indeed.

I replaced the 27" CRT in a mid-60's Magnovox set that was probably the first solid-state set. It was a 90 deg CRT.

Yamamaya42 · #14 07-06-2021, 08:14 PM

Quote:

Originally Posted by Electronic M

Google inverting op amp circuit (or read the Wikipedia page on op amps) and that will give you the schematic and maths to make a circuit.

Personally I'd try getting a tuner for it. That almost certainly uses the modern IF frequency and generally they aligned TV tuners and IFs to be interchangeable... as long as you don't try something silly like making a late 40s 21MHz tuner work with a 60's 44MHz IF TV.

I have found stuff like this ,, no idea if it would work or not

https://www.ebay.com/itm/18459874966...wAAOSwzEpf6Su2

dieseljeep · #15 07-06-2021, 08:16 PM

Quote:

Originally Posted by Yamamaya42

From what I can see, the 24AHP4 is one of the largest BW CRTs made, and a bit rare to find one at all, let alone in good working order.
It's going to be interesting to see what kind of picture the one I have can make, but first I will be trying to bring this chassis up on the 8YP4 Test CRT.

Again, it really sucks that the tuner is gone, all the missing controls, I can re-create, but the tuner, not so easy, although, I do see NOS tube tuners for sale on eBay, trying to tack on some alien tuner, and get it to work correctly and align up and be nice and happy with AGC and everything would be near impossible.

But on the upside, it looks like the input to the video output , right out of the detector is 1.5v ptp, so it would be easy to feed in composite video.

I have a tuner and all the controls from a similar Mag set I scrapped.
Unfortunately, I can't get to my warehouse because of health issues.
Be patient, that set don't have to be finished in the next day or so!