Philco Town and Country restoration - Page 4 - Videokarma.org TV - Video

bandersen · #46 07-15-2012, 02:46 AM

I spot tested a few and almost all were high so I just replaced them all. It really didn't take that long. These PCBs are fairly well made and I didn't have any trouble with traces lifting off.

bandersen · #47 07-16-2012, 03:26 AM

I finished reconnecting everything and tried firing it up.

B+ is fine now and I have full horizontal width, but still no vertical. I did resistance check on the VOT and yoke and they're fine.
Also no sound. At least I had very weak sound before.
I'll fire up the scope tomorrow and poke around.

bandersen · #48 07-16-2012, 03:47 AM

Doh! I think I know what the problem is. I had to order a 0.0015 @ 1000 volt cap for the vertical circuit and I never got around to installing it

kvflyer · #49 07-16-2012, 07:27 AM

Quote:

Originally Posted by bandersen

Doh! I think I know what the problem is. I had to order a 0.0015 @ 1000 volt cap for the vertical circuit and I never got around to installing it

Bob, sounds like you have joined our club, "CRS". It comes with maturity. Seriously, waiting to see a picture. CRT looks healthy!

Phil Nelson · #50 07-16-2012, 11:49 AM

Love the tinfoil hat on the CRT. Looks like something I would do

Phil Nelson

bandersen · #51 07-16-2012, 02:41 PM

Quote:

Originally Posted by kvflyer

Bob, sounds like you have joined our club, "CRS". It comes with maturity. Seriously, waiting to see a picture. CRT looks healthy!

I hope it's more because I'm working on it at 3am

Quote:

Originally Posted by Phil Nelson

Love the tinfoil hat on the CRT. Looks like something I would do

Phil Nelson

Hey it works

I figure I'll go with tin foil for now and spray on some slip plate once it's working.

Luckily, I was able to easily install the missing cap from the topside and we have full raster

Next problem - no sound and no video. I did hear some sound briefly as the set warmed up though. I'll do some voltage checks on the IF board.

DavGoodlin · #52 07-16-2012, 03:14 PM

AGC issue? maybe

Now that you have vertical, you can be sure it was Westinghouse!

The value of this TV keeps going up and up.

bandersen · #53 07-17-2012, 03:21 AM

Good call on the AGC. I found some really weird voltages throughout the keyed AGC circuit leading all the way back to the flyback.

At one point my DMMs overload indicator was lighting up even though I only showed about 150 VDC. I switch to AC mode and the reading were off the scale.

That leads me to suspect something in the circuit where a pulse is picked off the flyback for the key pulse. Possibly a 120 pF 5,000 volt cap on the flyback frame.

I popped the plate cap off the HOT to kill the HV and test my theory. Bingo! We have sound

I'll have to disassemble the set again and go poking around for the culprit.

bandersen · #54 07-17-2012, 04:11 PM

Progress

Rather than pulling the set apart, I did some more experimenting.
Finally, it occurred to me to just hook up a battery to the AGC bus (like when doing an alignment) to force it into the correct voltage range.
That got me some harsh video and sound.
I disconnected the battery and was surprised to still have sound and video. After some head scratching, I realized that if I rotated the contrast control to one extreme I could get sound and video without forcing the AGC bus.
So maybe it just comes down to a bad contrast control ? More testing later tonight....

Reece · #55 07-17-2012, 05:36 PM

If it's a matter of not enough resistance at the extreme of the control, maybe try a series resistor to add some.

bandersen · #56 07-17-2012, 09:37 PM

It seems the 36K control is shot. I get about 0 ohms at one extreme but after a few degrees of travel, it jumps to 500K and stays there. DeOxit didn't help.
It's an oddball control with a shaft running through it to the volume pot/power switch.
One good thing though is that only two legs of the pot are used so I can easily stick a fixed value in there that gives me a decent picture for now.

Maybe AUdubon5425 saved this control from his set

dieseljeep · #57 07-17-2012, 09:52 PM

Quote:

Originally Posted by bandersen

It seems the 36K control is shot. I get about 0 ohms at one extreme but after a few degrees of travel, it jumps to 500K and stays there. DeOxit didn't help.
It's an oddball control with a shaft running through it to the volume pot/power switch.
One good thing though is that only two legs of the pot are used so I can easily stick a fixed value in there for now that give me a decent picture.

Maybe AUdubon5425 saved this control from his set

Another of Philco's odd-ball controls. The control you have looks like a CTS made one. Maybe you can find a resistance element that's close in resistance from another control. I've done that on a few occasions.

AUdubon5425 · #58 07-17-2012, 11:05 PM

Let me hunt around for a box and you can have the whole chassis for shipping. Think I saved the yoke too.

bandersen · #59 07-17-2012, 11:38 PM

Quote:

Originally Posted by AUdubon5425

Let me hunt around for a box and you can have the whole chassis for shipping. Think I saved the yoke too.

Thanks

bandersen · #60 07-18-2012, 02:46 AM

I went to temporarily tack in a 50K pot when I noticed the remains of a wire on the unused terminal. I bet this pot fried and someone switched this wire to the other side to keep it running.

The 50K pot plus some control tweaking made a big difference.

Here's some stuff from an over the air DTV receiver fed into the antenna terminals on channel 3. Cartoons look especially sharp.