Quote:
Originally Posted by Jon F
Hey all, I've got a Motorola 9T1 I'm getting ready to restore. I have some questions I'll list below-
-I audited the paper and electrolytic caps with help from the photofact and ordered a cap kit online. I also ordered 1N4007 diodes to replace the silicon rectifiers. Are these directional? Anything special I should know?
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Yes, they are directional. They are marked, but if you get confused by the markings, measure the resistance both ways and the diodes should be inserted so the low resistance is the same direction in the diodes as it was in the seleniums.
Quote:
Originally Posted by Jon F
-I ordered parts to make a replacement ballast per the attached schematic I found on antiqueradio.org. It was for a Moto VT-73 TS-4J chassis. Will this work with my TS-18 chassis or do I need to swap pins around or change something?
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If you don't yet have the
correct schematic for this set go to
http://earlytelevision.org/tv_schematic_diagrams.html
and download one. Usually I prefer the manufacturer's service book.
From this you will see that your ballast drawing is incorrect for this set.
On the ballast tube, pin 6 is a common tie point, a 105 ohm goes from there to pin 7 and a second 105 ohm goes from pin 6 to pin 2. Originally a 37 ohm went from pin 3 to pin 1, but since you are replacing seleniums with diodes, I'd suggest raising this value to 50 ohms to limit the start up current and lower the B + voltage. The final resistor in ballast is a 200 ohm between pins 3 & 4.
>>> Edit: Jon, I made an error here. Bob Anderson is correct and he made a good catch on Motorola's math error! I did not realize that you were using the large capacitor to replace the 105 ohm resistors, in the circuit described by Phil Nelson. That should work, and be more gentle to the tube filament, especially the CRT, in this set. This is the same ballast. However, if it were me, I'd first get the set working with the resistor equivalent ballast while testing, before switching to the cooler capacitor current limiting circuit Phil described, just in case it caused an unexpected prolem. <<<
Quote:
Originally Posted by Jon F
-Can I restore the speaker fabric shown in my picture? It is wavy and the color dulled.
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I tried to soak my cloth off to restretch and it completely came apart. If you try it, I wish you better luck.
Quote:
Originally Posted by Jon F
-What is the best way to clean and shine the Bakelite? I was thinking of trying a magic eraser to clean the years of crud off the surface but not sure it will ruin the finish.
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The simplest way is to use Windex and clean soft rags. Once the cabinet is clean, give it a good coat of paste floor wax (preferred, but auto wax can be substituted.)
One possible issue you may find is the adjustment for the gimmick on the 1B3/8016 is slightly different from the illustration since modern 1B3/1G3 has a different cathode-to-plate spacing. If you have to replace the tube, or if someone has moved the spring, you will have to do a little playing to find the sweet spot.
I owned one of these sets and used it as my daily driver from 1956 to 1964. I still regret selling it.
Today a good 8BP4 is almost impossible to find. I've seen the smaller and much more common 7JP4 substituted in these sets.
James.