Capacitor Checker

[NoPegs]

Originally Posted by Tubejunke

I have to hand it to Solar. They made one heck of a good product; at least in their CB1-60(?) I think that's the right no. The most common one. Anyway, I have bought several Heathkits, a Knight, and the Solar. Out of everything there is some need for repair, or in the case of the Knight total rewiring of the multi-function switch. The switch is actually assembled wrong it and the hot shaft terminal is covering the wrong stuff at the wrong time. Lots of mistakes in the these because the were kits.

Anyway,THE SOLAR! Solar rules! Everything on that unit functions as it should and well! Looking inside for hot stuff and prior repair damage I found that at some point like probably the 60s someone tacked in a dual outlet 10mfd with a second in SERIES with one of the two 10mfds (sometimes 8mfd) in the power supply. That gives you what 5mfd and double the working volts. I need to find a schematic and see what is called for because 5 is low. I don't know what effect it would have, but those are almost always 8 or 10mfd

No real concerns other than a noticeable buzz in the transformer, mostly in the first 15 min or so. Nothing is hot. I jumped over the 10mfds individually just to see what may change. Nothing did. There is evidence that the transformer has run hot at some point. It just looks like it is missing a little wax AND there is an oily stain in the bottom of the box. It probably all has to do with why the power supply stuff is all that has been touched.

Everyone's Solar has a different story it seems.

Word to the wise: DO NOT POKE, PROD, BEND, WIGGLE, HEAT, SPRAY, TIGHTEN, LOOSTEN, LICK, or MEASURE the magical can of ohms buried inside. The moment you do anything directly to it (Measuring it by making your connections at the OTHER end of the wires connected to it might be OK.) it will flip its shit.

As to the filter caps: Schematic(Parts list) says 4µF, some have found Solar branded 8µF units in theirs, and mine had what appeared to be the factory original in it, which was a dual 10µF @450WVDC, and I replaced it with a pair of 10µF 700V film caps. (Yes I know, overkill all around, but at the time I was rebuilding it, nobody had a straight answer as to how much voltage they actually see, going consensus was 450v rated caps might not be enough, plus film caps are less likely to fail short and take out the delicious 1V rectifier...) These: http://www.mouser.com/Search/Product...1848S61070JP2C Not really expensive when you note that the only suitable electrolytic replacement which is only 450V is only a tad more than half the price... http://www.mouser.com/ProductDetail/...pA4A0AnJua4%3d Look at the load life figures... 100,000 hours on the film cap, and 2,000 on the good electrolytic. Sure there's probably never been a Solar CB-1-60 that's even seen 2,000 hours of operation, but I'll be damned if the next guy who restores it can fault my choice!


Here's the schematic and parts list out of the operation booklet for anyone who may need it, linked for table-destroying resolution. (Own hosting obviously.)

http://www.funkengine.net/vk-img/201...-Schematic.gif
http://www.funkengine.net/vk-img/201...parts-list.jpg


Regarding the whole 4/8/10µF thing, looking over the datasheets for the 1V rectifier there's no hazard with 20µF of filter caps hanging off of it. I wouldn't go much higher though.

Other tips:

Be sure to swap out R12 and R13 on the eye-tube, and also R4 and R5 up by the neon leakage indicator to be sure of getting proper results.

If your eye-tube is pretty much all used up and nearly dead, you can move the eye tube's plate/target B+ connection(along with the + side of C7) from the original junction of R9 and R10 (both part of cannedohm unit) over to the junction of R8 and R9.(So one lug further away from the grounded end of the cannedohm) This will increase the voltage on the eye tube by ~40%, so only do this to get the very last drips of use out of an already all but dead tube.

I got in on on a few of the Japanese 6E5s produced in the 70s/80s (Nobody knows for sure, but they're of visibly "modern" construction.) and I can actually use mine without difficulty even at 3500+ lux on my workbench. The tube it came with was still quite good, but I pulled it out of service and safely packed it away for future "complete period accurate" uses. My only gripe with the Japanese new-manufacture tubes is that the phosphor used on their target is the standard "ATM screen" grass green instead of the "any non-Tektronix oscilloscope made before 1978 screen" dark green. I'm actually considering splitting R10 into 3 sections and seeing how far down I can turn the wick to extend life via reduced target voltage.

Ok, so maybe the original tube was more like "5.5 ouf of 10" in terms of luminance, looking back over the photos...

Here's one of the "before" reference shots, the Solar badged dual 10µF electrolytic is dead center...


Now looking at the "after" photo I'm ashamed at how terrible it came out... Consider "re-work the Solar to improve mechanical and aesthetic conditions" moved much closer to the top of the "easy evening projects" list...




Edit:

Originally Posted by Tubejunke

There is evidence that the transformer has run hot at some point. It just looks like it is missing a little wax AND there is an oily stain in the bottom of the box. It probably all has to do with why the power supply stuff is all that has been touched.

Show me the (inside) bottom of your lovely maple box. Inside of the lid too. What initially looks like overheating actually turns out to be shellac condensation from being stored in a warm/hot area from the few I've seen.

Originally Posted by Tubejunke

I found that at some point like probably the 60s someone tacked in a dual outlet 10mfd with a second in SERIES with one of the two 10mfds (sometimes 8mfd) in the power supply. That gives you what 5mfd and double the working volts.

Well, sometimes it gives you 10µF and the WV of whichever cap out of the two in series isn't dead-shorted.


Generally though yes, two caps in series works like two resistors in parallell, if they're the same value you get half the capacity, if they're mismatched values you reach for the nomogram and/or slide-rule.