Revisiting my 7S363 - Printable Version
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Revisiting my 7S363 - LedHed - 06-15-2012
Today I pulled the chassis from the Zenith 7S363 console that I "finished" a few months ago. It was an OK player and received the close local stations without too much trouble.
As this was my first attempt, there were quite a few issues I wanted to revisit and plenty of "should haves" and "wish I had knowns."
My major goal is to get the best I can out of this set. I know it's not a crown jewel kind of set, and will never be the black hole of RF that I wish it was but I love the cabinet and it will forever be the first one. Along with my major goal, I am getting basically zero action on the eye tube. I already checked the resistor in the tube socket, and have come up with almost bang on 1 Mohm. My plan is to go back through and check the resistors. Did I mention the should haves or wish I had knowns? After looking at the underside, I realized my old resistor knowledge is far from complete. I have the color codes for the dogbones (I think) with the body, end and dot colors. The problem is that I see some that look like modern-ish colors with bands, but they don't ohm out like I think they should as well as some that are not quite dogbones but don't look like the others.
Does anyone have a link to a primer of the different types of codes and how to read them? I want to do this right and have the set at 100% before I start the hard stuff including a 16B cathedral and my latest acquisition an RCA 9T. Quite frankly, these two scare the crap out of me and I don't want to booger up two highly collectible set that will be the RF black holes that I seek!
RE: Revisiting my 7S363 - rghines1 - 06-16-2012
http://www.eeweb.com/blog/andrew_carter/how-to-read-resistor-color-coding-scheme
RE: Revisiting my 7S363 - morzh - 06-16-2012
Look at the sch and go by the values in it. Old resistors won't "ohm out" as they should simply because they mostly were carbon types and have detriorated to become 30-70% above normal value.
RE: Revisiting my 7S363 - codefox1 - 06-16-2012
Just replace 'em. Nickel apiece, right?
RE: Revisiting my 7S363 - LedHed - 06-16-2012
After reading your responses and some more thought, I decided to go the route Codefox suggested. I wrote down a parts list from the schematic, and looked at it. Something didn't seem right to me... Before you guys start laughing, bear in mind that I am in my early 30s and all my knowledge is based on Navy training for modern components.
Looking closely at the list, I realized I didn't have a single value below 1 Megohm!? I thought "That can't be right, why would there be 470 Megohm resistors in this thing?" A little Google-Fu later, and I now know that the annotation of M Ohm in the old schematics is notation for thousand! No wonder everything looked funky to me!
Armed with my new knowledge, I will replace all the resistors in the set. I didn't trust any of the paper caps, why would I trust old carbon resistors.
This brings up a new question. The candohm resistor has one 220 ohm section reading way too high. I have 10W power resistors to make a new one. Is 10W enough dissipation or should I source higher wattage? Is 10W too high?
RE: Revisiting my 7S363 - morzh - 06-16-2012
No...not nickel. I usually use a minimum 1 Watt to keep the size, otherwise leads may not be long enough, and sometimes higher rating is warranted, and this is in tens of cents.
RE: Revisiting my 7S363 - TA Forbes - 06-16-2012
I should think that 10W is plenty.
Personally, I check resistors and replace those outside 20 percent of their stated value.
Bear in mind that you may have to pull one side of your resistor to get a good reading.
RE: Revisiting my 7S363 - codefox1 - 06-17-2012
If you gotta pull one side free, for a nickel on fractional watt resistors, just put a new one in and be done with it.