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 Post subject: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Jul Sun 16, 2017 2:31 am 
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Joined: Sep Sat 13, 2014 7:05 pm
Posts: 30
Could someone read the capacitance of an original cable for one of these Sencore capacitor meters.
Spec for RG62 is 13.5pf per foot. Just curious what an original cable reads.
Just thinking 35" should be somewhere in the neighborhood of 39.375pf and 36" somewhere around 40.5pf
Thanks for any information on the above. after years my cable needs new life LOL
If so would be awesome info for building a replacement cable.
Thanks again


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Jul Sun 16, 2017 4:31 am 
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Joined: Sep Tue 30, 2014 6:08 am
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Location: The Old Dominion VA 23518
It's my understanding that the LC101 and LC102 autozero out any cable capacitance when you perform the short/open procedure. This negates the cable length, although at lengths greater than 3 meters, the capacitance of the cable becomes a problem for the autozero. The test frequencies generated by the LC101 or LC102 don't approach a point where the cable becomes a problem. Use a low capacitance cable, an keep it short - mine is a mirror of the original LC102 cable, which I lent/gave to my Dad for his LC75. He passed in 2011, so I should probably get it back someday.

I guess to measure the cable, you'd do the short/open without a cable connected, and then connect the cable and read the capacitance - with some accuracy lacking - my LC102 has only +/- 5% stated accuracy in the lowest pF range, IIRC. The LC53 field calibration standard pf cap ( with the caps and inductors in the little box) always reads a bit high on my LC102. My standard is spot on, except for the tantalum - the ESI bridge at work reads it about .7uF higher than what Sencore wrote on the data plate.

Not knowing what Z-meter you have, this is all I can offer. Me? I'd love to find a free (PDF) set of calibration instructions and service manual for my LC102. The ones available free on the web are incomplete by about 40% of the schematics - some schematics are duplicated, others omitted entirely. The pay sites (at least two) want 140 bucks for the manual, and one is selling a PDF CD for $70 - with no response to my query as to the completeness of the manual....

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Brian
"Capacitor Cosmetologist since 1979"
USN Retired 1984-2006 (Avionics/Cal)


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Jul Sun 16, 2017 8:24 am 
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Joined: Sep Thu 23, 2010 6:37 am
Posts: 9988
Location: Powell River BC Canada
The cables also have to have a minimum resistance or the error message will appear,
and the ESR test wont work properly.

That aside, the cable capacitance of my LC 102 cable is:

45 pFd @ 3.0 mHz on my MFJ Pro269 antenna analyzer, and

44 pFd on my Daetron MC 300 Capacitor Tester.

_________________
de
VE7ASO VE7ZSO
Amateur Radio Literacy Club. May we help you read better.
Steve Dow
ve7aso@rac.ca


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Jul Sun 16, 2017 10:38 am 
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Joined: Feb Tue 07, 2012 9:32 pm
Posts: 1789
Location: Middlesex,NJ
HI:

HERE ARE THE CABLE SPECS THANKS TO DAWN.

The original cable is made from a 35" piece of weird 93 ohm cable RG-62 with the positive lead connected to a 2 1/2" piece of 50 ohm RG-174 to the positive mini grabber clip with the shield grounded to the rg-62 shield and the grabber end unterminated . The negative grabber clip is connected by a 3" piece of about #14 wire.


WALTER-W2WIQ


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Jul Sun 16, 2017 2:17 pm 
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I measured 50 pf on my LC-53 cable.


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Jul Sun 16, 2017 3:32 pm 
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Joined: Sep Sat 13, 2014 7:05 pm
Posts: 30
Thanks for all the replys I have a CA55 and a LC102 the CA55 came without a cable but the unit will zero with the LC102 cable. The instructions for the LC53 and LC77 to zero test leads
TO ELIMINATE TEST LEAD CAPACITY
1. Place the test leads (with no capacitor connected)
on the work area in such a way that they will not be
moved when the capacitor to be tested is connected. Be
sure that the test leads are not on a metal surface or
near an AC power outlet or AC operated device. Stray
AC may affect the reading of small values of
capacitors.
2. Depress the VALUE button and adjust the LEAD
ZERO control until the meter reads 00.0, with negative
sign appearing occasionally.
3. Carefully connect the capacitor to be tested to the
Lest leads. Depress the VALUE button and read the
actual value of the capacitor on the meter.
So I want to make a new lead for my LC102.
Your information is a great help, hope it helps some other owner of a great piece of test equipment.
xxx2fan


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Jul Sun 16, 2017 6:16 pm 
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Joined: Sep Thu 23, 2010 6:37 am
Posts: 9988
Location: Powell River BC Canada
Also remember that LC-102 can test large value electrolytic capacitors with up
to 999 volts, and safely discharge them. So above all the cable assembly is an
important safety item.

_________________
de
VE7ASO VE7ZSO
Amateur Radio Literacy Club. May we help you read better.
Steve Dow
ve7aso@rac.ca


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Jul Sun 16, 2017 6:42 pm 
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Joined: Sep Tue 30, 2014 6:08 am
Posts: 2913
Location: The Old Dominion VA 23518
radiotechnician wrote:
The cables also have to have a minimum resistance or the error message will appear,
and the ESR test wont work properly.


???

Most coax, even with a solid conductor, is only 41-63 ohms DCR @1000Ft length, making a 3 footer well less than an ohm. 3 ohms of resistance in the short test zeroes out on my LC102 just fine, so a cable 40 feet long would still pass the zero test for resistance.

The LC102 also measures capacitance in long cables for determining their length (by measuring capacity, so again, length and resistance don't matter once the test lead is zeroed. The dynamic resistance feature bottoms out at 100 ohms (and tops out at 999 Megohms... :shock: ) so an ohm or two in the test lead is negligible (only when unzeroed).

The whole point of the zero/open test is to "define" the cable resistance and capacitance parameters and negate them. The cable does get reactive at long lengths and high frequencies, neither of which we are dealing with here.

You don't mention what Z meter you have, so your meter may not handle a test lead like the LC101/LC102/LC103 with the Zero/open feature.

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Brian
"Capacitor Cosmetologist since 1979"
USN Retired 1984-2006 (Avionics/Cal)


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Jul Sun 16, 2017 6:56 pm 
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Joined: Sep Tue 30, 2014 6:08 am
Posts: 2913
Location: The Old Dominion VA 23518
Incidentally, I do recommend everyone with an LC101, LC102 or LC103 get and use the Sencore Tech Tips - they are available still on the web at various sites, and are valuable in using the Z-meter for much more that capacitor testing/reforming and inductance/ringing.

https://drive.google.com/file/d/0BxaJyY ... FWNmc/view NOT mine, but put out there for the public. Only 20 ors so deal with the Z-meters.

I've used mine to test nixies (with a 12K dropper resistor...set the Z-meter for 140V and depress the leakage button), to verify carborundum varistors (XXmA @ 900V, say..), to measure a cable going 230 feet into the ground for opens/shorts, and to test some surplus neon bulbs, also with 18K dropper resistor and Z-meter set for 100V. In a pinch, I've also used the ringing signal (60Hz) to verify a vibrating reed frequency meter.

I finally got the parts to build my own SCR250 - schematics are on the web, and it adds to the usefulness. My Eico 965B just sits in awe. :mrgreen:

Handy!!

_________________
Brian
"Capacitor Cosmetologist since 1979"
USN Retired 1984-2006 (Avionics/Cal)


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Apr Tue 17, 2018 1:55 am 
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Joined: Apr Tue 17, 2018 1:30 am
Posts: 1
Has anyone tried to make a cable for these units? I have an LC75. I read in thisr thread on July, 2017 by Walter about the original cable:

"The original cable is made from a 35" piece of weird 93 ohm cable RG-62 with the positive lead connected to a 2 1/2" piece of 50 ohm RG-174 to the positive mini grabber clip with the shield grounded to the rg-62 shield and the grabber end unterminated . The negative grabber clip is connected by a 3" piece of about #14 wire."

Has anyone tried to actually make the cable? Should I be aware of any build issues when I go ahead and make it up?

Thanks
John Justin


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Apr Tue 17, 2018 2:45 am 
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Joined: Aug Fri 12, 2016 1:49 am
Posts: 191
Location: Houston, TX
Actually, the OEM cable is RG-62 B/U (the B version is stranded center conductor). The electrical specs are the same as U and A/U, but using a solid center conductor in a cable that's going to see lots of flexing is not such a good idea.

I got my hands on some Belden 8255, which is B/U. Although its insulation is a little stiffer than the Consolidated brand Sencore used, it's still plenty flexible for daily bench use.

There's a guy selling some 8255 on eBay right now from a large spool.

Most BNC connectors meant for RG-59 will fit the RG-62. When using B/U version, you'll probably want to twist and solder the end of the center conductor before you try to make your BNC assembly. This helps when you use solder style connectors, and you'll likely have probs with compression BNC's if you don't prep the stranded conductor.


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Apr Tue 17, 2018 7:39 am 
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Joined: Mar Thu 15, 2018 2:23 pm
Posts: 24
Findm-Keepm wrote:
Not knowing what Z-meter you have, this is all I can offer. Me? I'd love to find a free (PDF) set of calibration instructions and service manual for my LC102. The ones available free on the web are incomplete by about 40% of the schematics - some schematics are duplicated, others omitted entirely. The pay sites (at least two) want 140 bucks for the manual, and one is selling a PDF CD for $70 - with no response to my query as to the completeness of the manual....

I have the LC102 calibration instructions. I'm unable to upload to this site. Let me know if you still want them and I'll setup a link for you


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Apr Tue 17, 2018 3:08 pm 
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Joined: Aug Fri 12, 2016 1:49 am
Posts: 191
Location: Houston, TX
A "Sencoretech" posted the LC102 cal procedure at eevblog.


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Apr Tue 17, 2018 10:57 pm 
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Joined: Sep Sat 13, 2014 7:05 pm
Posts: 30
Thank you so much for the cal info. I'm sure there are going to be many who thank you for the Cal. info


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Apr Wed 18, 2018 1:02 am 
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Joined: Aug Fri 12, 2016 1:49 am
Posts: 191
Location: Houston, TX
xxx2fan wrote:
Thank you so much for the cal info. I'm sure there are going to be many who thank you for the Cal. info

I'm happy to do my part, but I'm not the uploader, just passing along the link.
Here is the original post: https://www.eevblog.com/forum/testgear/ ... #msg781812

Perhaps if we let "Sencoretech" know how much s/he is appreciated, we might induce him/her to cough up more juicy bits of literature for us. :D

Sencore corporate isn't much help, other than selling remaining inventory, as they prefer to forget they ever made this old gear. It's largely up to current or former employees to help us out with stuff like this. I don't know that "Sencoretech" is/was actually affiliated with the company, but s/he did have this rare document, so...


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Apr Wed 18, 2018 4:19 am 
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Joined: Sep Tue 30, 2014 6:08 am
Posts: 2913
Location: The Old Dominion VA 23518
Vin Tageman wrote:
xxx2fan wrote:
Thank you so much for the cal info. I'm sure there are going to be many who thank you for the Cal. info

I'm happy to do my part, but I'm not the uploader, just passing along the link.
Here is the original post: https://www.eevblog.com/forum/testgear/ ... #msg781812

Perhaps if we let "Sencoretech" know how much he is appreciated, we might induce him to cough up more juicy bits of literature for us. :D

Sencore corporate isn't much help, other than selling remaining inventory, as they prefer to forget they ever made this old gear. It's largely up to current or former employees to help us out with stuff like this. I don't know that "Sencoretech" is/was actually affiliated with the company, but he or she did have this rare document, so...


Actually, thank Navy Metcal in Corona, CA - the US Navy's calibration HQ. That's a photocopy of the Navy METCAL procedure, cropped to drop the NA17-series markings. 100% lifted from the DoD. I've seen enough of them to spot one right away. It's FOUO - for official use only, but some techs don't play by the rules.. :) For some of the military tube testers, formatting of the cal procedures was changed to easily identify the leaker - turned out to be a public US Army website.....oops.

The DoD agrees to not "infringe" on the copyrights and resale of tech lit by the OEMs by broadly publishing (or "releasing"), so FOUO applies to most tech lit nowadays. NATEC has made most of the PDFs read-only (no local save - just a printout with watermark).

_________________
Brian
"Capacitor Cosmetologist since 1979"
USN Retired 1984-2006 (Avionics/Cal)


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Apr Wed 18, 2018 8:46 am 
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Joined: Aug Fri 12, 2016 1:49 am
Posts: 191
Location: Houston, TX
So, you're saying the Sencoretech person is/was a METCAL insider or at least knows one.

I suppose an "outside" cal procedure is useful, but I'd rather have Sencore's official literature. Unfortunately, it is essentially worthless for certain models w/o the proprietary Sencore software that goes with it — they told me they never distributed their cal software to outside labs, and further claim they didn't keep copies for themselves (they'd probably like to sell us a bridge or two, though).
They couldn't or wouldn't even tell me whether it's just BASIC scripts for GPIB controllers or if it's an executable. sheesh!
Perhaps some day a benefactor out there will disseminate the software. I can dream, can't I? Releasing it can do Sencore no harm, since they no longer offer cal service on "obsolete" gear.

At any rate, Sencore isn't bothered by infringement of "obsolete" material. They know their vintage publications are being pirated and sold for profit. They simply don't care. How do I know? I asked them. Their answer? eBay, et al, are still home to plenty of PDF pirates, unimpeded and unchallenged, and I'm confident that very few, if any, have paid Sencore licensing fees or even attempted to obtain permission.

AFAICT, about the only company that's complained recently is Heath, which led to at least one site taking down all Heathkit manuals, because Heath wants to sell them (again), and they want a lot for them (their vintage offerings can be found here).


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Apr Wed 18, 2018 11:12 am 
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Joined: Sep Tue 30, 2014 6:08 am
Posts: 2913
Location: The Old Dominion VA 23518
Vin Tageman wrote:
So, you're saying the Sencoretech person is/was a METCAL insider or at least knows one.


Neither - I can only comment on the procedure. I worked calibration in the Navy for almost 11 years of my 22. With a library of over 23,000 calibration procedures, it comes as second nature to recognize the format/font and "where stuff is supposed to be" - the cropping removed all of the source identification. Pages 4 and 5 are close cropped - deleting the identifying info.

Me, I can care less of the source - just glad to "stick it to the man" :mrgreen: - Sencore abandoned many thousands of people that bought millions $$ of their test equipment and left them hanging without continued piece parts or servioe support. Google "looking for a service manual for a Sencore XXXXXX......" in the mid 2000s, and you'd have seen the vacuum....

ALL Navy Metcal procedures are either developed with the use of the manufacturers info, or are a copy of the original OEM, formatted in the Navy METCAL manner - uniformity prevails in the military. With Sencore, I can say with certainty the Navy procedure is 100% from Sencore - hence the FOUO - gotta protect Sencore's intellectual property rights/copyrights.

Vin Tageman wrote:
At any rate, Sencore isn't bothered by infringement of "obsolete" material. They know their vintage publications are being pirated and sold for profit. They simply don't care. How do I know? I asked them. Their answer? eBay, et al, are still home to plenty of PDF pirates, unimpeded and unchallenged, and I'm confident that very few, if any, have paid Sencore licensing fees or even attempted to obtain permission.


True - but the source is still FOUO - but not that anyone "out there" cares....the population of LC102s (or any Sencore legacy product) in use by the military is probably ZERO these days....

"Sencoretech" is a hero for sharing.

_________________
Brian
"Capacitor Cosmetologist since 1979"
USN Retired 1984-2006 (Avionics/Cal)


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Apr Wed 18, 2018 1:10 pm 
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Location: Ohio 45177
I have used a short BNC jumper cable made of RG 58 before, with one of those molded BNC to alligator test clip ends made by Pomona or someone. But I usually use the OEM cable. They used these at work and with the constant use, the clips would break off the end of the small coax and have to be reworked till they got too short to use. Like they said, it does zero out the cable up to a point. But might affect accuracy on very small values. Probably not on larger caps.


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 Post subject: Re: Sencore LC53 LC77 LC102 LC103 cable
PostPosted: Apr Wed 18, 2018 4:32 pm 
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Joined: Aug Fri 12, 2016 1:49 am
Posts: 191
Location: Houston, TX
Incidentally, for those still looking for the LC102 schemo, it's up on BAMA. The uploader included it with the ops manual, total of 111 pgs., 17MB. I took a look at it, and it includes parts lists, board x-rays and, from my cursory examination, it seems to be complete — the schemos are chopped up, so you'll need to assemble them in a paint program for the ultimate in readability. I might tackle that project after I finish other OEM's of my own that I'm scanning.

http://bama.edebris.com/manuals/sencore/lc102/


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