Westinghouse H14T17 Restoration/Questions
 

Picked this Westinghouse 14 inch "portable" set from 57'
Few questions as I'm still new to the field of television repair (patience appreciated):D

There's a 4.7 ohm resistor placed right before the half wave rectifier that's gone bad. According to the datasheet, it should be 1/2w although it looks like a much higher wattage resistor. Is this a typo or am I reading this wrong?

Datasheet and resistor(R82)
http://i50.photobucket.com/albums/f3...psiponvcba.jpg

Looks to be in the 5-20w range. Word to the wise Sam's are full of typos, and even the good ones are not the last word... There were often many production changes throughout the life of a chassis... Sam's are usually a snapshot of one. Whether it was the first, last, best, or worst is not usually known.

When you restore a set it is best to go by the original parts instead of the schematic... granted if someone has worked on it before you and hacked up the wiring or made questionable replacements, or if the originals are damaged beyond identification the schematic is your best guide.

That resistor is probably for current limiting the selenium rect. Resistance is not critical ( wattage will be though) and may be increased to compensate for the reduced voltage drop across the diode that you're presumaby replacing the selenium with.

The preceding was a message from your friendly neighborhood insomniac TV restorer.

You'd be correct in assuming that, is it just trial and error to see what gets the proper voltages? I had heard that each plate on the selenium drops somewhere between 1 and 2 volts. Is that a good ballpark?

Also, the 4.7ohm resistor was before the selenium, could the value be added to the resistor or would it have to be placed after the new diode?

That is a fusable resistor and they act like a slow blow fuse. You can sometimes find them on the auction site or replace with a fuse and a resistor. I would use a 10 watt resistor if it were mine.

Gregb

4.7 ohm 5 watt

So I replaced the 4.7 ohm resistor with a 10watt resistor of the same value. Unfortunately it's blowing the resistor, any recommendations on how to isolate the problem?

Blowing the resistor or just getting really hot? Hot would be normal, burning it out would probably indicate a shorted filter cap.

It burned out, I checked the caps prior to putting them in, and now they've fried as well. So the real question is why did the filter caps burn out when they're brand new? Is this something I should troubleshoot further before putting in new caps?

Check that you had the polarity to the filter cans correct, backwards or too many volts is about all that could kill them.

Did they smoke or get hot?

New diode?:saywhat: Did you shunt the selenium with a Si diode? If so, is the polarity correct? (Banded end goes to the 'downstream' end of the selenium, usually marked '+'.)

When using a Si diode, the selenium can be left in place but with the 'upstream' end disconnected so the selenium's out-of-circuit.

Well that'll about do it, in my excitement to install it I flipped the whole mount backwards, diode and all.

Once I purchase new caps, I'll do a power test and see how it goes. Stay posted for updates and likewise, more questions.

Thanks all,
Zach

If the 4.7Ω 'fuse' resistor popped quickly enough, there's a chance you didn't kill the caps.

Good idea to replace at least the first one anyway, since it wouda took the hardest hit.

Well success, replaced the diode and filter capacitors. Set warmed up with no problems, still no raster, although I can hear the flyback's distinctive whine.

Found that the 1X2B was faulty and replaced it with a working tube.(thought I had tested all of these :dunno:) Alas, still no raster. Checked the damper tube along with surrounding connections, and main voltages appear within 1-2 volts.

Finally pulled out my capacitor checker and tested the single 4kv 160pF ceramic capacitor in the flyback circuit just to find that it had failed. Well, time to order parts, it's always one thing or another

Anyone know where I can purchase caps like this?
Cheers,
Zach

Are you getting any high voltage to the top of the 1X2? Just touch the tip of a (well insulated) ungrounded screwdriver to it and you should draw an arc.


I have this same set by the way, it's a Raymond Lowey design.

http://www.vintagetvsets.com/images/lowey1.jpg

Yes, it does arc though not very far, and it's a fun set, good learning process for me