#16
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I picked up a Sprague TEL-OHMIKE T0-6A capacitor analyzer a few years back and now I just shotgun all vintage paper and electrolytic caps. It was 1 in 100 caps that would pass a test on the Sprague and so I found there was really no point in testing them.
Gregb |
#17
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If you don't have the monies to throw at a total recap, and or are a newbie that is not good at finding their own wiring mistakes trouble shooting like this can be a very good thing.
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 Last edited by Electronic M; 01-07-2015 at 03:59 PM. |
#18
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From my prospective its all of them, the newest set I own is a Predicta Princess.
Gregb |
#19
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I work on anything I can lay hands on from 1928 Atwater Kents to 70's SS Zenth TV's, and newer stuff if I have a manual and reason that are both good enough to make me bother.
The reliable plastic types started in the late 50's ~1957/58 and gradually phased out the paper based caps over the next ~5 years (some makers jumped on 'em others lagged badly).
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#20
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Its a strange thing, I do repair work as a sideline and 98% of what comes in is 30's vintage with the balance 40'-50's. I cant remember the last time anything newer than 1955 came in for repair.
Gregb |
Audiokarma |
#21
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If for no other reason, these R/C bridge testers serve a very important role when either totally shotgunning all old caps without testing if their bad or doing piecemeal replacements. That would be using it to verify the replacement cap(s) are indeed value as marked and that they are truly good and have no leakage; especially if they are used or N.O.S. I would doubt that all mfg's do/did 100% production line comprehensive verification testing, and probably just used some sample testing.
Tom (PK) |
#22
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What is sort of interesting about late 1930 paper cap's in the Zenith portable radios of the time are often found with asbestos pads under the chassis of those that are in wooden cases. This was to prevent fires from paper cap's failing and then starting a fire.
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#23
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I am glad to hear some good words about the Heathkit C3. I bought one from a member here that supposedly was "working fine." I had been wanting one of the tuning eye type testers for a while and not being an Ebay customer I got overly excited and paid way too much ($85) for the not so finely working tester.
Basically, all of my outputs are low (around half) on the leakage test, and most of my values are considerably off. In other words I bought a unit that needs restoration. Actually, I can still use the thing to a certain degree, but I must realize that the leakage test voltages are low and take that into consideration. I don't have a big concern on measuring value as I can do that with my digital meter. Yeah, I hate using digital stuff if I don't have to. In this case I have to until repairs are done. I guess buying any old test equipment is a shot in the dark, and many folks think that if something lights up and doesn't smoke out then it is working. I just hate restoring my restoration equipment....
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"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
#24
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__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#25
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http://www.old-timers.tuars.com/index.html jr |
Audiokarma |
#26
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Thanks; that link is great!
__________________
"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
#27
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I recently got disgusted trying to land a Sprague Telohmike TO-6 without some vulture with more dollars than sense jacking the price through the roof. So having pretty good luck with the simple Heathkit C3s (I now have 3), I grabbed a very similarly designed Knight unit AND a vintage (40s) Solar for a third or less than I would have spent on the later model Sprague.
I guess some people go bonkers over extra push buttons and meters, but in reality the simply designed units do about the same thing minus the luxury of the current meter. The "magic eye" tells me all I really need to know about a capacitor and leakage.
__________________
"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
#28
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I have a B&K 879B, which has "all" the bells and whistles. However when checking caps > 100WV I pop open the Solar first, and only if the Solar seems to think it's ok do I turn the 879B loose on it. I picked up a Cornell-Dubilier Capacitance Bridge (Model BN) at Kutztown, the YL and I might tackle it this weekend. |
#29
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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.
__________________
"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
#30
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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: Quote:
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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. Last edited by NoPegs; 07-22-2015 at 10:43 AM. |
Audiokarma |
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