im just getting into radio restoration, and this is the third radio i have attempted repairing.
the little radio actually still worked when i got it, but it obviously needed recapped and generally gone-over, so i found the schematic and ordered up my caps.
well, like a dummy, i went ahead and ordered one of everything off the parts list, while neglecting to look at the radio itself to see what was actually in there. most everything was correct, except i found wildly different values when it came to the three section electrolytic can cap.
the parts list calls for a 40mfd/150v, a 20mfd/150v, and a 20mfd/25v
the actual can cap in my radio is a 50mfd/150v, 30mfd/150v, and a 100mfd/25v
i know the voltages dont really matter as long as you exceed the working voltage of what was intended to be in there, but im not sure why the capacitances are off by so much. the schematic says that it covers several different models, but it does not specify different can caps for the different models, so that ones got me scratching my head.
i guess the bottom line is i should probably replace the old caps with ones of equal value, regardless of what the schematic says, because the dang thing worked before, therefore it will work again, right?
Somebody probably replaced the filters before, but it doesn't really matter, either will work. The only real consideration is the maximum first filter rating for your rectifier tube - you have to look it up.
Here is the deal. If the first filter cap is too large it is like putting a short on the rectifier - well any cap is like putting a short on the rectifier - as it is being charged on power-up. The rectifier is rated to deal with this to a point and it is usually listed in the tube manual.
Hi Brian and Merry Christmas,
Good practice would dictate that C-10 should be 50mf or less. If C-10 is a high value it can damage to cathode of the 35Z5 thru excessive current during warmup. R-11 helps limit the current. C-11 isn't critical, typically they are 30mf but you can go a bit large for better filtering like 47mf. C-12 is normally 10-20mf @ 20-35v. 100mf was probably meant for a portable set to filter the filament circuit. A bit overkill for the cathode bypass.
If you want to get something that looks somewhat correct https://www.tubesandmore.com/products/ca...0v-22-f25v or replacing them with single units.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
i just looked up the 35Z5GT in the tube manual, it says the input filter should be 40mfd, which is exactly where they have it on the schematic.....hmmmm. so maybe i did myself a favor by not even looking at the chassis before i ordered parts, ill just drop the correct caps in there per the schematic and see how it goes!
terry,
merry christmas to you as well, and thanks to both you guys for responding so quickly! im going to keep the old multisection in there, and just undo the leads going to it underneath, then stuff my new electrolytics under the chassis as need be. that way i can retain the original look of the radio and not have to worry too much about finding just the right size or value of can cap.
thanks again to both of you for your help! i really appreciate it!
OBTW these caps are polarized (they have a + and -) and it is very important that they are installed in the proper polarity. The schematic doesn't show it. Here's a quick drawing. All of the -'s are connect together and go back to the off/on switch.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
I've heard and read that about the value of input filter caps being limited to a certain value, however I am not sure whether that still applies anymore. The reason I say this is that I have run across values for input filter caps that run across the board, some as low as 30 uf and others as high as 60 uf or more, and this is in factory service literature. Also I'm not certain that this still applies as modern electrolytic capacitors have different construction and different formulas for electrolyte then caps did 50-60+ years ago, they charge faster and have a lower ESR current then vintage caps do, even general purpose caps today do. I'm not suggesting that you ignore the tube manual, or the service folder, but it is something to consider.
Happy Christmas
Arran
man, you guys are going to think im a real idiot now...
so im looking at my schematic the other night, and i suddenly realize something is very, very wrong with it.
it features 4 tubes.
my radio has 3. none are missing. no empty sockets.
what!? i knew the 442 was based off the schematic for the 444 and the 444-AH, but used some different components, but they dont say anything about removing an entire tube from the chassis! so now im really questioning if i should go with the general guidelines outlined in this post, or if i should go with what the tube manual says with respect to the rectifier tube, at the least, and then go with the general guidelines for the other two, or do i just replace the old multisection with caps of equal value since it did seem to operate fairly well with those values in place...
just for anyones reference, i AM an idiot kid (well, 35 year old kid) who is just learning this stuff. i think the lesson today was that you should go through ALL of your literature before loading up the parts gun and opening fire.
any thoughts or ideas are greatly appreciated! if time permits today ill get a few photos of the radio so maybe someone can tell me if ive misidentified it, or what the heck i did wrong here...
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 12-27-2017, 06:36 PM by Radioroslyn.)
the second of those schematics looks the closest so far...here are some pictures for you! there was no sticker or chassis marking to tell me a model, so when i was looking for schematics i literally just typed in "small arvin radio" and went through google images until i found one that looked exactly like mine, and the page said it was a 442...apparently i could have researched that a little deeper...
first picture is the case of the radio, the second is the case with no knobs, then you see the top of the chassis and then lastly the underside of the chassis....obviously some new caps i put in there, but not all of them yet.
by the way, what in the world is that blue thing in there? i had initially figured it was a capristor, because ive never seen one of those, and ive never seen anything like this, so the two must be the same. but then i read someplace that capristors generally have 3 legs on them, and this blue thing has only two. no real markings on it, just a redish brown dot.
The blue thingy is called a sandstone or fuseable resistor.Mostly use for surge protection. Usually a very low resistance.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
