Magnavox Windsor Imperial - TV Help
 

Hello all, I'm new to the forum, and look forward to getting to know you.

Several years ago I found a Magnavox Imperial Windsor on craigslist for $500. Neither the seller nor I knew what it was. It was a family pass down for him, and my first old radio. I knew it was special by the looks of it.

It is very original, with some cabinet dings from moving the beast over the years. I recapped the radio and amp a couple years ago with success. :-)

Always wanted to get into the TV, but was intimidated. Recent retirement gave some time to recap the (paper and electrolytics) the TV. Getting the Ecaps into the chassis turned out to be a challenge. I ended up placing them schematically correct under the chassis, but fear that I have introduced some noise and unintended performance abnormalities. After reading through others solutions, I have decided to remove the old ecaps mount a board above the chassis.

I am able to power up the unit and light the CRT, but the vertical scanning is only half height ~5" at the full height adjustment. Additionally, it appears to be compressed at the bottom of the scanning. Are there other components I should be looking to replace? Tell me its just a tube :yes:

Thanks in advance!

Greg

Check resistors and tubes in the vertical stage as well as B+ voltages and Boost voltage if the flyback boost powers the vertical as is done in many sets.

Thanks!
 

Thanks Tom!

As a mechanical engineer, I have to admit that I'm still coming up to speed on schematics. Let me see what I can teach myself. Can you direct me to transformer outputs or potentially tube numbers? here is the schematic https://www.earlytelevision.org/pdf/...sams_62-13.pdf

Stay Healthy! Greg

6sn7gt?

V17 a&b?

Yes those tube sections and the resistors around them.

Welcome. I collect tombstone radios and tube color televisions.

thank you Tom!

Tech Question: Measuring Resistance
 

I was able to connect the Magnavox to an Amazon Fire TV and finally get a glimpse of the Twilight Zone (my first goal for the effort) :banana:

I am aware that resistors in a circuit can not be measured without the rest of the circuit elements affecting the reading...

Are these resistors situated such that the tubes or capacitors allow for the resistance measurements without removing them from the circuit?

thanks, Greg

If resistance reads lower than designed on these old carbon comp resistors it almost always means there is something in parallel with them affecting the reading (those resistors usually aren't a problem but you could unhook an end if you're concerned), but if the resistor reads higher than specified by a percentage higher than the tolerance rating to means that the resistor has gone bad and needs to be changed...

Carbon comp resistors usually fail by increasing in resistance. And there is no way external parts in a set that is powered off can make a resistor test as a higher resistance (only lower).

I just finished working on mine. Check the 6SN7 vertical oscillator tube and the resistors close to it. Here’s tonight’s picture on mine.

Pulled the project back out
 

After years of collecting dust, I've decided to give the tv another go. My earlier attempt was to replace all of the paper caps and electrolytics. I took an easy path and placed the Electrolytics physically around the chassis. The TV turned on, but had a vertical compression. I am unable to get the vertical scan to extend more than 4" or so. I have gone back in to replace the electrolytics and build a sub board to mount them. Good news, I still haven't killed the tv or myself :D Bad news, the vertical scan remains at about 4". I exchanged the 6sN7tubes and have the same result. I have now ordered the 8 resistors in the vertical circuit. Come this weekend, I hope to have them replaced. Attached is a pic of the current output. Any other thoughts on repairs?


Greg

Xdevo1973, that picture looks remarkable! grats!

I'll investigate B+ Voltages and Boost voltage as well....though admittedly I'm intimidated to have my hands near this with the power on ;-)

6SN7 very common tube. If the set uses others swap them as a test.
If the vert is small but stable its usually a high ohm resistor. To test
you can nip one wire off & test.
Replace one thing at a time the try set before moving on.
Keep filter cans were they were in the set Mount a terminal strip for them
enuf fer now

73 Zeno:smoke:
LFOD !

thanks Zeno! Definitely stable, just crushed vertically. Looking at the original picture, its almost like the crush is not linear. its crushed more at the bottom than the top?

Looks like there are a few high ohm resistors near the vertical tube. I'll check them out when the new ones arrive.

Best, Greg

The vert out has 3 electrolytic caps C3B, C1C & C1B involved. Double
check them & the wiring. They do not go to ground as normally done.
They can cause the bottom to "pull up" & throw off the vert lin.
Also look into the negative 85 line.
Thats as far as I can go. The power supply is cut off in the schematic & none
of us can get a scroll bar to move it. All my fault for not being a
computer head !

73 Zeno:smoke:
LFOD !

Thanks y’all for the guidance! After replacing all the caps once before, four resistors were the key. Three of the resistors were >1 mega ohm.

It’s been so long since I’ve manually tuned an analog crt that it’s hard to determine if things are operating normally. I notice when adjusting the contrast, that the picture will go askew. Normal?

Again, thanks! Greg
.

Yes, in older designs where the "contrast" pot controls gain of the IF strip. In newer designs, sync is taken off ahead of the contrast control, which controls gain of the detected video signal.

Thanks!