The old insulator (the thin, flat insulator, that is, placed between primary and secondary windings) was made of a nitrocellulose material (same as old stock film which self-destructs). As that stuff starts breaking down, it eats the insulation off the coil's primary winding, then starts working on the wire itself. If left alone long enough, it will also start negatively affecting the secondary underneath the insulator as well. This can cause the wacky resistance readings.
Good to know thank you! Well now I have to wait for my new wire to come in the mail. In the mean time, I tested all the dog bone resistors and surprisingly they are all decent! Not too much drift. The only concern I have is the replacement electrolytics. The original cans were 8 microfarad, but someone in the past replaced them with 16 microfarad! So I will replace those, and eventually the Bakelite blocks. One step at a time though
Okay maybe someone can point out whether or not this was done for a reason, but I’m seeing 3 filter cap replacements that was clearly done a long time ago judging by the age of the caps. Usually when you replace the original filter cans, you disconnect the cans, and then solder in 2 replacements underneath the chassis. But I’m seeing 3. Looks like 2 are going to the rectifier for some reason. I’m guessing the “Atom” yellow caps were done first, then someone later down the line threw in that back one. I have new caps on order, and was planning on cutting out the old ones and soldering in the new ones. But that third black one is confusing me
It looks to me as though that upper-left Atom electrolytic is attached to pin 6, which may be a filament pin, of the tube there. That would suggest to me that that tube is actually the rectifier.
Further, it looks to me as though the bottom two electrolytics, an Atom and that dark blue one. are connected in series, which could indicate that either there was a higher voltage at that point than one cap could handle by itself, OR that the original cap there was only 8 MFD and the repairer wanted to replace that original cap with one of the same value, but he only had 16 MFD caps to do the job with.
Also, that wire wound resistor which is connected to the + end of the blue cap has gotten awfully hot at some time in the past. In fact. it looks suspiciously like it has been burnt open. I'd be checking that out closely.
Can you make out what the writing is on that blue cap? Maybe that would give us a clue.
Can't really tell what connected to what but looks like the 2 16 mf caps connected to the filament of the 80 tube. The other end is connected the B- or the hv center tap. Also looks like 47 got a little hot and bothered. This could be from having 32mfd rather than 8mf
.
By adding 24mf to the input capacitor there is a good likelihood that the hv would increase and cause more current flow thru 47. 8mf aren't a common value any more but 10's are. Those are fine. There's also a temp rating typically 85 and 105 deg. 105 are the preferred.
There are also film capacitors in the mf range. Last forever, physically large, and a bit more pricey. Generally most folks go for the electrolytic.
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 didn’t know that by adding two 16mf caps in series creates one 8mf cap! Still new at this! That makes sense now! My guess is the wire wound resistor got burnt with the 16, so the repair person installed an additional cap to bring the capacitance down to 8 before any further damage occurred. That’s my guess anyway. Thank you so much!
The wirewounds fail... that is pretty common. As for the 16 MFD condenser, that would most likely not have caused a problem... what is the voltage rating of the 2 16 MFD condensers? When you put 2 16s in series like that, the capacitance is 8 MFD, but the VOLTAGE is the sum of the voltage of each individual condenser, so if he only had say, 250 volt, but needed at least 450 volt, he put the two 16s in series to have 8 MFD at 500VDC, which would work.
OK. I have downloaded the bunch of schematics for the various model 60s. None of which show three filter caps.
Looking more closely at your photo, it looks as though the 4-pin socket for the 80 rectifier must be the one at the bottom of the photo between the bottom Atom and the blue or black electrolytic cap.
Also, looking more closely at your photo, it seems that the upper-left Atom cap's + lead is not connected to the tube-socket's filament pin, but to a lug above that. In any case, none of the various schematics for the Model 60 shows more than 2 capacitors with a value as high as 8 mfd.
Secondly, yes capacitors in series act like resistors in parallel: the total value is less than the value of the individual component. Two equal value resistors in parallel equals 1/2 the value of either and the same goes for caps in series, assuming their ESRs are equal.
Thirdly, if it was me, I would replace the original capacitors with ones of the same value, or as close as one could get. As Terry says, raising the filter capacitance significantly will raise the HV in almost all cases.
Fourthly, can you read what is written on the masking tape that is on the dark blue or black capacitor? If so, what does it say? Learning what is written there MAY give us a clue.
Maybe I should get a spare wire wound resistor to have as a backup since mine is looking bad. Saw one for sale on eBay that looks nice. But hey it’s testing perfect though!
The voltage on those caps is 450, so it’s good there. I’m just going to put the same value replacements in there for now since I know they work. Plus it comes out to 8 anyway. I thought it doubled if they are in series, but it makes sense now! Once I get the oscillator coil rewound and back up and running, I’ll do some voltage checks on the tube pins.
So I figured it out after trying to understand the schematic, the two negatives of the atoms are tied together, and then lead to the terminal of the wire wound resistor. One positive goes up to a compensating condenser I believe, and the other goes to the rectifier. The black and blue is indeed parallel with the atom that goes to the rectifier. So according to the schematic, it is indeed wired up correctly. It just has two 16mf in parallel.
That would total 32 MFD, which IMHO is really too much for that particular radio. That would raise the HV quite a bit. Even so, that higher HV probably wouldn't damage anything.
32? I thought two of them in series makes 8? They are not hooked up back to back. They are both hooked up to the same terminals. I get confused with the difference between “parallel” and “series”
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