FOUND! ARVIN 9219-cm-uhf television. - Page 11 - Videokarma.org TV - Video

Yamamaya42 · #**151** 06-22-2021, 07:46 PM

Sigh, I sill have not been able to find another local TV to feed my restoration addiction yet.

Yamamaya42 · #**152** 06-30-2021, 09:28 PM

Well, i did manage to find something to play with in the meantime, a rc1121a radio.

being sent to me now.

https://www.radiomuseum.org/r/rca_rc1121a_2xf931.html

series heaters and DEATHTRAP design. :O
I'm sure this was common when it was made, but it's a good way to get someone shocked/ hurt.
https://i.imgur.com/E04YZfR.jpg
you have to wonder WTH were they thinking?

And I have found a potential TV restoration project, but it may be a hopeless case, no idea yet, it appears to be a CRT ( 21 inch bw ) and chassis that was crudely removed from a cabinet for some reason, fish tank or pet bed or something?

I have NO idea if the tube is any good or not, of if the chassis is is savable, but I can't turn down the price $0
I will try to get that this weekend.

Electronic M · #**153** 06-30-2021, 09:39 PM

Quote:

Originally Posted by Yamamaya42

Well, i did manage to find something to play with in the meantime, a rc1121a radio.

being sent to me now.

https://www.radiomuseum.org/r/rca_rc1121a_2xf931.html

series heaters and DEATHTRAP design. :O
I'm sure this was common when it was made, but it's a good way to get someone shocked/ hurt.
https://i.imgur.com/E04YZfR.jpg
you have to wonder WTH were they thinking?

And I have found a potential TV restoration project, but it may be a hopeless case, no idea yet, it appears to be a CRT ( 21 inch bw ) and chassis that was crudely removed from a cabinet for some reason, fish tank or pet bed or something?

I have NO idea if the tube is any good or not, of if the chassis is is savable, but I can't turn down the price $0
I will try to get that this weekend.

By the 1950s the knobs were captive to the cabinet, the chassis bolts thread into nylon insulators on the chassis, and the back prevented touching the chassis....A complete set would have no direct chassis electrical connections exposed and the chassis would have a bleeder resistor that would limit shock to non-lethal levels....not as safe as a transformer but as long as owners don't defeat the safeties and don't bathe with it they'd never know the difference...

Go back to the forties and you get fun stuff like my Sonora radio/phono...the metal toggles for motor power and radio/phono and the metal pickup arm are tied directly to the hot chassis and you get to choose whether you want them to shock you with the power off or the power on.

Yamamaya42 · #**154** 06-30-2021, 10:33 PM

Quote:

Originally Posted by Electronic M

By the 1950s the knobs were captive to the cabinet, the chassis bolts thread into nylon insulators on the chassis, and the back prevented touching the chassis....A complete set would have no direct chassis electrical connections exposed and the chassis would have a bleeder resistor that would limit shock to non-lethal levels....not as safe as a transformer but as long as owners don't defeat the safeties and don't bathe with it they'd never know the difference...

Go back to the forties and you get fun stuff like my Sonora radio/phono...the metal toggles for motor power and radio/phono and the metal pickup arm are tied directly to the hot chassis and you get to choose whether you want them to shock you with the power off or the power on.

but was it really so safe to be 1 missing knob or leaky cap from getting the crap shocked out of ya?

something like that could never be sold to day, I'm sure! :p

kvflyer · #**155** 07-02-2021, 01:15 PM

Quote:

Originally Posted by Yamamaya42

...
something like that could never be sold to day, I'm sure! :p

And sets in Australia during this time period, being 240 volts almost always were transformer sets. Quite a different era.

Yamamaya42 · #**156** 07-08-2021, 07:23 PM

the radio came today

first thing I did was put the dial cord back on.. FUN FUN!

and I saw that it had been worked on before
https://i.imgur.com/MwglCyb.jpg

this is a NO NO!

you don't just bridge the bad selenium rectifier...

Yamamaya42 · #**157** 09-30-2021, 11:30 PM

got a little bored, so started to look at that old RCA radio, and i can't believe what i am seeing.

https://i.imgur.com/cb6DSOo.jpg
someone made a mess of it..

someone tacked in a Silicon rectifier in parallel to the selenium rectifier m1, C1a failed, but was NOT removed from the circuit, it was originally a 80uf 180v, they have in there now a 80uf 450v in parallel, R29 has been replaced with a 3 OHM 5 WATT resistor, meaning that B+ was way way too high, and all the paper caps are still in it.

it's any wonder the damn thing did not catch on fire!

Tom9589 · #**158** 10-01-2021, 11:16 AM

I couldn't tell you how many instances I saw of silicon diodes bridged across selenium rectifiers. Many techs were too lazy to mount a single terminal strip on which to mount the silicon diodes.

old_coot88 · #**159** 10-01-2021, 12:25 PM

Quote:

Originally Posted by Tom9589

I couldn't tell you how many instances I saw of silicon diodes bridged across selenium rectifiers.

Yeah, with the selenium still in-circuit, it's susceptable to reverse leakage and possible overheating.

Yamamaya42 · #**160** 10-01-2021, 01:22 PM

What really confuses me is why the hell is the 3 ohm resistor in there? When SAMs shows it to be 22, it must seem that who ever had it had no clue as to what they were doing, and as the bias voltage dropped when the selenium rectifier started to fail, tried to put in a smaller value to adjust for it, and when the silicon was put in, never adjusted with a larger value for the higher efficiency of the silicon rectifier.
I wonder what other fun mistakes there are to find in it!

Anyway, it's just something to keep me entertained until it is cool enough outside to build the cabinet for my magnavox project. :P

Electronic M · #**161** 10-01-2021, 05:22 PM

The selenium bridged is a bad but common practice.

Personally I see nothing wrong with that lytic. I only stock 2 voltages of lytic 160V and 450V (except occasional cases where 200V in a capacitance value happens to be cheaper than 160V) and anything over 160V just about always gets replaced with 450V (except odd cases like 250uF 200V doubler caps where I don't stock something that will work and have to order a part).

Yamamaya42 · #**162** 10-02-2021, 01:06 PM

Quote:

Originally Posted by Electronic M

The selenium bridged is a bad but common practice.

Personally I see nothing wrong with that lytic. I only stock 2 voltages of lytic 160V and 450V (except occasional cases where 200V in a capacitance value happens to be cheaper than 160V) and anything over 160V just about always gets replaced with 450V (except odd cases like 250uF 200V doubler caps where I don't stock something that will work and have to order a part).

it's proving to be quite fun indeed.

the old grey Nichicon cap was leaky, the 80uf they had in there, after removing the selenium stack, i put power to it through a 15 ohm 2 watt resistor, and the resistor fried., so that cap has been tossed an new caps put in, and replaced most papers.
this is where the real fun started.

As I still do not know what to replace that 22 ohm main line resistor with ( where the fool had the 3 ohm) I put in a 30 for now, till I can work out what it needs, turned on to watch the fireworks!
tubes lit up, no sound but a faint hum.

https://i.imgur.com/s9aDDXz.jpg

b+ was about 165v
started to smell something HOT!
IR camera said that r28 is very VERY hot.
b+ goes to the center tap of the audio x-fomer and is fed to that resistor, SHOULD be 100v/90v depending on AM/FM, it was 35v, not good!

shut down, pulled audio output tube, there was now 165v on both sides of r28, plugged it back in with it on, instant drop to 35v.
AUDIO OUTPUT BAD!

The fool blew it up by over biasing it...

Yamamaya42 · #**163** 10-09-2021, 02:06 AM

its alive a little

https://www.youtube.com/watch?v=vSzGC29wpLE

AM barely working but is WAY off freq.

FM worked for a few min
will most likely have to change resistors AND the caps in the IF cans

prob has silver mica disease.

yeah i know this is the wrong form for this but

Yamamaya42 · #**164** 02-01-2024, 09:52 AM

Slight horizontal linearity issue now.

As you may or may not recall with this set, when I first got it, the 21EP4 was necked when the seller moved it from storage when I came to pick it up, and thanks to DJ here on the forums, I was able to get a rebuilt 21FP4, which is pretty much an exact replacement deflection angle wise and electronically, however, slightly dif in size, but this was no big deal, fixed with small spacers.

Face to yoke ref-line.
21FP4 - 15 1/2 (+-3/16)
21EP4 - 15 17/32 (+-3/16)
Which should have had no effect on functionality whatsoever, I'm sure!

The set has been working fine for over 2+ years now, however I did notice that compared to the Hoffman Super Receiver Mark V next to it, the display on it was much MUCH wider, I never did adjust it.

So, with a tweaking tool I was able to adjust the horizontal width coil out ( way WAY out) to where it was close to my other sets.
My guess is, as the set got older and older with the paper caps over the years, it was losing width, and they kept cranking up and up to compensate, but with new caps, it's no longer needed to be like that.

But now that I have the width down where it should be, the horizontal linearity is a bit off, which can be seen especially with text scrolling on the screen, more narrow at the L/R edges, and wider in the middle, looks weird! :P

I have not tried to adjust the horizontal linearity yet, as where the horizontal width coil is very easy to reach from the back, the linearity coil is more of a pain to reach, as it's deep in the HV box, there is a hole in the back of the set to reach in and adjust, but it's not easy to get to.

But I'm assuming that this SHOULD be able to be adjusted to where it's equal across the screen.

old_tv_nut · #**165** 02-01-2024, 09:35 PM

Linearity usually affects left side vs. right side. If both edges are too narrow or too wide compared with the middle, this is usually due to the size of "S correction" capacitor in series with the yoke. I can't recall off the top of my head which makes the sides narrower, smaller S cap or bigger, but I think it's smaller for narrower sides.

You could try jumpering a small cap (10% of existing one) across the existing one to see how things change.