Motorola VT-71 (TS4H)

[fox_rivers]

I ordered a pair of Panasonic ECQ-E2106KF 10uf 250v film capacitors, a 200 ohm 5w and a 30 ohm 5w resistor from Mouser. I removed the innards of the old ballast and desoldered the copper leads from the pins using a solder sucker. I placed the resistors on a piece of PCB I cut out of an old power supply and I used this schematic to wire the caps and resistors to the base of the ballast. I spray painted the metal can for the ballast black and installed the newly rebuilt unit into metal can thus looking awesome.

[compucat]

Originally Posted by fox_rivers

I ordered a pair of Panasonic ECQ-E2106KF 10uf 250v film capacitors, a 200 ohm 5w and a 30 ohm 5w resistor from Mouser. I removed the innards of the old ballast and desoldered the copper leads from the pins using a solder sucker. I placed the resistors on a piece of PCB I cut out of an old power supply and I used this schematic to wire the caps and resistors to the base of the ballast. I spray painted the metal can for the ballast black and installed the newly rebuilt unit into metal can thus looking awesome.

Does it generate a lot of heat in operation? It looks like a good solution, one of several ways to deal with these old ballast tubes.

[fox_rivers]

This ballast will run 80% cooler and eliminates the current surge when the set is powered so it will prolong the tubes as well as the 7JP4. This thread explains more about how they work. http://videokarma.org/showthread.php?t=249434

[miniman82]

Neat fix, but I prefer the glass ballast.

[fox_rivers]

Originally Posted by miniman82

Neat fix, but I prefer the glass ballast.

I have to admit, the glass ones do look cool.

[compucat]

Originally Posted by fox_rivers

I have to admit, the glass ones do look cool.

The glass ballasts run just a little cooler than the metal ones and I suspect they are more reliable since they are under vacuum. I am using a glass ballast in my Motorola with good results. I would like to build one of the alternative types as a backup.

[polyphase]

I'm delighted you chose to use the cap balast I described back in Nov 2010 for your project. They are still working great for me.

For best results, it may be necessary to tweak the 30ohm resistor lower to get correct filament voltages. This is due to normal tolerances of the caps.

This is easily done at the socket, by connecting a 2w resistor of between 100 and 300 across pins 1 and 6. You can always change out the ballast R later with the newly established value.

Note: To get stable filament voltage measurements, you need to wait at LEAST 5 minuets from a cold start.

[fox_rivers]

Originally Posted by polyphase

I'm delighted you chose to use the cap balast I described back in Nov 2010 for your project. They are still working great for me.

For best results, it may be necessary to tweak the 30ohm resistor lower to get correct filament voltages. This is due to normal tolerances of the caps.

This is easily done at the socket, by connecting a 2w resistor of between 100 and 300 across pins 1 and 6. You can always change out the ballast R later with the newly established value.

Note: To get stable filament voltage measurements, you need to wait at LEAST 5 minuets from a cold start.

I really liked the idea of the soft start as well as it looking original. I appreciate the tip and the build design.

[fox_rivers]

Well I finally got all the electrolytics replaced and the 2 diodes in the power supply. I put a 40watt bulb in line to limit the current to the set. Flipped the switch and nothing, no power. I took the bulb out of line and still the same.

I went through all the caps and everything and it all checked out so the only thing I suspected was the ballast and sure enough the ballast schematic i used was incorrect for my tv. Pin 5 which was one side of the ac line wasn't used so I have to figure out which parts in the ballast go to what pins. I'm not exactly sure how I'm gonna figure that out.

[Phil Nelson]

Originally Posted by fox_rivers

the schematic i used was incorrect for my tv.

The VT-71 had more revisions than I've seen in any TV or radio.

Phil Nelson

[miniman82]

The 'H' version is the same one I have, when I put the glass ballast in I remember having to move one pin in the socket over to make it work. Maybe it's the same pin for you?

[fox_rivers]

This ballast was designed to replace the 17A485459 ballast in the vt-71. My ballast is a 17A470303. I didn't realize that that various chassis these sets used also used different ballasts. I have to hit up polyphase and see if he has an alternate method otherwise I have to use the glass ballast.

[fox_rivers]

Originally Posted by miniman82

The 'H' version is the same one I have, when I put the glass ballast in I remember having to move one pin in the socket over to make it work. Maybe it's the same pin for you?

I wouldn't know which pin to move. I also think its more then that since pin 5 and 8 aren't used in the new ballast design. The schematic for my chassis utilizes all the pins.

[bandersen]

You might find this thread on my VT71 with a TS-4H chassis helpful: http://www.videokarma.org/showthread...=233337&page=4

I just had to move one wire to use a 17A485459 in a set design for a 17A470303.

However, if you have a really, really early TS-4, you will need to add an addition resistor between pins 6 and 8 which the 17A485459 does not have.

[fox_rivers]

Cool. Moving the ac line to 6 did the trick but now i only have one tube that illuminates which is the 6201 (12AT7). When i turn the lamp on the bulb glows dim and only the 6201 lights up but after a few seconds after the tube warms up the bulb suddenly brightens and the 6201 tube gets much brighter then its supposed to be. No other tubes light and this issue might explain why the 12AT7 that was originally in the set was dead.