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  #1  
Old 01-26-2017, 03:12 AM
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Tubejunke Tubejunke is offline
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SEMCORE RC 115 Capacitor Analyzer

In my ever growing fondness for vintage capacitor "checker", "analyzer" or simply testers', I stumbled across this unit not by Sencore, but Semcore out of Puerto Rico. Though foreign made, it's certainly designed for the American market as a knock off of the ever popular (and increasingly expensive) Sprague TelOhmike units. Namely the TO-5 as far as function.

I actually got this and a Sprague TO 4 at the same time and frankly the Semcore has the Sprague licked hands down IMO as far as build quality. The Semcore is more compact and is built like a tank, where the Sprague is quite decent, say a few steps up from a Heathkit or any of their similar cousins. Some say the Spragues' are the Cadillacs' of analog bench analyzers, and they do pretty much cover every aspect of testing caps and/or reforming. I think I have already posted some rant on the current Ebay popularity trend driving prices through the roof. Give me the Semcore any day over anything I have seen yet!

For those not familiar with this type of tester; they are basically every way to properly test electrolytic caps for leakage at rated voltage up to somewhere around 500V(?). For all other non polarized caps, there is an insulation resistance test. All tests are read on a combination analog meg-ohm, volt, mill-ammeter. Also, there is a transformer turns ratio function, and finally a Wheatstone bridge to give the values of caps and resistors using the ever popular "magic eye" tube.

Units like this are to me at least pretty essential for anyone working with vacuum tube equipment on a regular basis. There are however much cheaper units available such as Heathkit C3 (most common) that frankly do less, but that adds to simplicity of use, lightweight and very compact. I have a number of these that upon recapping make great testers, again for not a lot of money. I sold several a year or two here in as found condition with no complaints thus far. I did ensure the buyers that the power transformers, switches and tubes were good. Beats taking a chance on a smoker from Praybay! LOL!

I have several more that I will be moving soon.
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File Type: jpg Semcor RC115.jpg (4.8 KB, 23 views)
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Last edited by Tubejunke; 01-26-2017 at 03:49 AM.
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Old 01-26-2017, 08:50 AM
WISCOJIM WISCOJIM is offline
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Can't see much detail in your 140 by 140 thumbnail.
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Old 01-26-2017, 09:37 AM
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What can it do beyond leakage to 1KV, value down to 0.2pF, ESR and dielectric absorption? Accuracy?

Can it measure resonance of an LC tank or series circuit? Calculate the length of a cable based on capacity?

I've got an Sencore LC102 and it does pretty much everything. I'm in the process of building an SCR250 accessory for mine -way cheaper than buying one...
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Old 01-26-2017, 11:37 AM
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Quote:
Originally Posted by WISCOJIM View Post
Can't see much detail in your 140 by 140 thumbnail.
Here is a video of one in operation.
https://m.youtube.com/watch?v=3-sWuYbnrMw

jr
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Old 01-26-2017, 01:01 PM
WISCOJIM WISCOJIM is offline
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I found the ebay listing still up with pictures: http://www.ebay.com/itm/VINTAGE-SEMC...p2047675.l2557

.
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Old 01-27-2017, 03:58 AM
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Tubejunke Tubejunke is offline
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Wow! First sorry folks, I honestly don't know much about altering the size of picture files. I know that can picture size can be be a pain in more than one way. Having little love (for digital stuff) or need for much more than basic Internet connectivity, I have a very slow connection speed at my home. Still in the Kbytes! LOL!

So if my Dad (who is way more up to date than I in digital gadgets) sends me a pic from his "smart" phone, I must ask him to doctor it up so my computer isn't slowed down to a crawl for 20 minutes all to get a pic so big that I have to scroll up, down, left & right to see it. Wisco always reminds me that the easily uploaded small pics I use suck. Guess he's right. We will work on that. Hey; better than nothing I guess...

In other news: Yes, pour around a couple grand into a nice Sencore LC102 and perhaps you can build add something that will just spit out a replacement cap! I guess we are all here for similar reasons, but we have the right to approach it all how we want and with what we want to use. I started off years ago doing quite a bit of successful repair work with an analog VOM and a soldering iron. That doesn't mean I would recommend it, or want to use just that as like many things in life; we evolve.

And I think that there are many of us here who don't just want to fix obsolete stuff. We like many other things about using it and repairing (restoring) it. LONG story short, I find the old cap analyzers very interesting in a world where many think that their DVOM can do the job, or perhaps an ESR meter. It only took the computing power of a calculator to put a man on the moon. How much science and/or money must we put into finding a bad cap in tube driven equipment?

Besides Sencore's high dollar stuff, I don't know of anyone else making cap testers that at least test under real world conditions (rated voltage). So some folks like me are bringing these good old units back up to snuff and do just fine with them. Accuracy? They can be made to be very accurate for what they are. The old bridge can be persnickety measuring value! LOL! That's where the DVOM comes into use.

I do understand those who don't want to restore their restoration equipment though! LOL! The stuff were trying to fix gives us enough fits; right?
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Last edited by Tubejunke; 01-27-2017 at 04:34 AM.
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Old 01-27-2017, 07:09 AM
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If you have friends that own smart phones you hay want to invite them over and see if they have good service at your house. You can get a smart phone with a large to unlimited data (several such plans are under $60/mo) and use the smartphone as a WiFi internet hub at home, and get a bluetooth to POTS adapter to run your wired phones off your cell line when you are at home. Depending on how much you are paying for POTS phone service and dial-up internet dropping those and switching to a smart phone configured to provide those services to your home devices might even save you some money.

I can understand the frustration of living with dial up...I used to have it, and honestly that waiting was wasting enough of my life that I'd never go back to it if any other option exists.
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Old 01-27-2017, 11:38 AM
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Quote:
Originally Posted by Tubejunke View Post
Yes, pour around a couple grand into a nice Sencore LC102 and perhaps you can build add something that will just spit out a replacement cap!
It didn't cost me one tenth of that. You called the Sprague a "Caddilac" of testers - I guess my Sencore is just a Buick... I'm cheap, hence my building of my own SCR250 clone.

Quote:
Originally Posted by Tubejunke View Post
Besides Sencore's high dollar stuff, I don't know of anyone else making cap testers that at least test under real world conditions (rated voltage).
ESI made the good stuff - $14K testers/variable frequency LCR bridges that did it all, and even characterized the dv/dt (pulse charge/discharge characteristics) - something no one in the real world needs. I've seen one - turned on maybe 2-3 times a year for ISO proofing, and sent out every 2 years to get calibrated.

Bottom line for me is cry once, get a decent tester, but you'll find your time to be more precious than the $ to buy a decent replacement capacitor.

Time vs. cost of replacement....
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Last edited by Findm-Keepm; 01-27-2017 at 11:44 AM.
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Old 01-27-2017, 06:17 PM
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Tubejunke Tubejunke is offline
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[QUOTE=Findm-Keepm;3177393]It didn't cost me one tenth of that. You called the Sprague a "Caddilac" of testers - I guess my Sencore is just a Buick... I'm cheap, hence my building of my own SCR250 clone.

"Some say the Spragues' are the Cadillacs' of analog bench analyzers" is my quote based on what a quy has to say on a page I found dedicated to vintage cap testers. He doesen't get into stuff like you have mentioned except I do think he has something about a certain Sencore. I know that the Sencores are very nice and $very$ sought after. Just look at what they go for on Praybay and the amount of bidders.

When I read about your unit that seemed to do things I haven't even thought about, I Googled it and the first thing I saw was like $1,800 in an ad. And again, to each his own, but what I saw (and I may have looked it up wrong) looked like one of these modern overkill instruments with 30 small buttons with 40 functions each. Just not my cup of tea. Same as these digital o-scopes. Some have some really neat functions that my old Techtronix analog scope doesn't have, but for ease of use to view a waveform within vintage equipment, I'll keep mine & the money.

You mentioned pulse charge/discharge characteristics, Simpson once made and attempt at doing something with that back in the 50s I think. I believe the name was CapacOmeter, but may be wrong. They come up for sale here and there and supposedly did quite a job when working, but a little investigation told me that they were a bull to try to revamp and it seems like I read that they stopped making them partly at least as people were getting injured messing with them. Don't quote me on this, but it was an interesting read.
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Old 01-27-2017, 06:33 PM
WISCOJIM WISCOJIM is offline
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Originally Posted by Tubejunke View Post
Simpson once made and attempt at doing something with that back in the 50s I think. I believe the name was CapacOmeter, but may be wrong.
Capacohmeter

Info here: http://www.byan-roper.org/steve/stev...acohmeter.html



.
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  #11  
Old 01-28-2017, 09:30 AM
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Back in the day when you could easily get 90V Photoflash batteries, we made our own cap tester - two 90v batteries, a VTVM, and a "pinch stand" - essentially a couple of Grayhill 020 component clips. Wired up in series with the VTVM, you could watch the cap charge up - proof it was good. Simple, elegant, and easy, but told you nothing about the value. The first one I built for myself was huge - all 9V batteries, formed up to make a 162V battery, and I just used a piece of copper clad to make two pads to "touch" the capacitor leads.

The Sencore testers aren't difficult to use - each "button" is dedicated, with no duality. I use the leakage test the most, but not for caps - suspect caps just get replaced - it's too easy to just replace the cap. Instead, I use the leakage feature to test neons, Nixie tubes (along with a 12K resistor...) and to measure high resistances like focus dividers and high-megohm (>75Meg) bleeders. It's good to about 3% or so, about what an analog megger would measure to.

The Sencore's low range is good for characterizing variable caps I've pulled from stuff over the years, and I'll admit I've used the ESR test to check a resistor or two. I prefer my Dick Smith tester for capacitor ESR measurements - with the Sencore I have to press a button while holding the leads, not cool when you've got a whole board of electros to check.

Again, I don't test film caps - I just replace them. Panasonic ECQ-E caps from Digi-key are(or were at the time) less than 15 cents each, and an entire set could be recapped for about 5 bucks or so. I don't use the yellow caps for any work - tried them, but one shorted (from new) cap swayed me back to the brand name stuff.

I do some SCR and Triac work, so the SCR250 seemed helpful, and I have all the parts already to build one. Pretty simple to use, and will augment my hobby SCR tester I built from a Popular Electronics article. It doesn't lie, but is limited...

Now to find a cap with a 15Kv, 2nsec transitiion and 4-second recharge.........rail gun, anyone?
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Old 01-28-2017, 09:48 AM
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Originally Posted by WISCOJIM View Post
Is the pulse a steady train of pulses on a one-shot deal?

Philips made a pulse tester good for about 2Kv and up to 60Khz - I used to play with one, connecting 1600V rated TV safety caps at 1200V, with a 9.9 Khz pulse rate, the highest rate above 1Kv. Cheap (read: non-Sprague) safety caps would get warm after a few minutes. At 900V and 15.8 Khz (closest i could get to 15,750...), none of the caps would get warm...

For fun, we'd flash burn foil gum wrappers with the Philips - one pulse at 2KV, and you had a wisp of smoke, and a carbon trail across the foil. I'd love to have had a high-speed camera to film it - you could see the foil buckle as the pulse traveled across it - most likely from the heat.

We used it to pulse test HV cables for airborne fire-control radar pulse-forming networks....I can remember that all the cables I ever tested passed. But sea-level testing proved little - get that cable in an unpressurized aircraft bay, and at altitude, it was a different animal. Arcs, blow outs (where the center conductor burned a trail to the outer jacket) and opens occurred. Hard to do real-world testing. A failed cable showed itself easily - no testing required...
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