Entropy

Relax in southern comfort on the east bank of the Mississippi. You're just around the corner from Beale Street and Sun Records. Watch the ducks, throw back a few and tell us what's on your mind.
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mediatechnology
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Re: Entropy

Post by mediatechnology » Mon Nov 20, 2017 10:10 am

I have a Heathkit digital clock that has a similar problem to your car battery's sulfation.

The clock used SP-352 gas discharge displays and the right-hand hours digit is starting to dim particularly on the segments illuminated almost continuously throughout the day.

On one of the Nixie tube sites there is a post about burning off cathode crud by operating them at increased current for a short time to rehabilitate them.
I think I want to try that first since a NOS SP-352 runs about $50.
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JR.
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Re: Entropy

Post by JR. » Tue Nov 21, 2017 10:11 am

Good luck... Interesting that an electronic display could wear out....

JR

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mediatechnology
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Re: Entropy

Post by mediatechnology » Wed Nov 22, 2017 9:51 am

JR. wrote:
Tue Nov 21, 2017 10:11 am
Good luck... Interesting that an electronic display could wear out....

JR
Cathode crud, bad lead to substrate junctions in the PanaPlex and low gas pressure cause them to age.
Lots of MCI JH-series and SSL consoles have aging Burroughs PanaPlex displays which are unavailable.
I feel bad for the owners wanting to keep them running particularly the SSLs.
Some of the MCIs might best be sent out to pasture.
There were a ton of the Sperry displays used in Avioncs as well which have long service lives.

See also:

Sperry Gas Discharge Display Catalog 1973 viewtopic.php?f=12&t=691
Plasma Bar Graph Meter Documents for MCI and SSL viewtopic.php?f=12&t=429
"There does seem to be a pattern where, the more difficult a truth is to stomach, the higher the hysteria levels go internally at Google."
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JR.
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Re: Entropy

Post by JR. » Wed Nov 22, 2017 3:26 pm

For my it's always something file... my VOM stopped reading voltage today... worked yesterday.

Looks like maybe a broken solder connection on the ground lead, but this old (rat shack) soldier is tired and could use a rest.

JR

PS: Yesterday I measured the parasitic drain by my car on the battery and 85 mA is neither high nor low... but definitely not low... More than 100mA is considered a problem. I suspect the stock car alarm, that hasn't worked properly for years may be responsible for much of that drain.

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mediatechnology
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Re: Entropy

Post by mediatechnology » Wed Nov 22, 2017 3:42 pm

I just "restored" my Radio Shack 22-049 VOM. The batteries hadn't been replaced since the 1990s.
It uses a square 15V "504" battery for the 10K Ohms scale which were discontinued by Eveready. I found a round replacement made by Exell that I need to order. http://www.exellbattery.com/

Image
"Classic" vintage Radio Shack 22-049 VOM

Despite having numerous DVMs using the old 22-049 VOM was like finding an old friend. I've had that thing since the late 1960s or early 1970s.

I also cleaned up an old Simpson 260 that had been given to me. It has the roll top case. Fortunately the 260 uses a 9V battery for the high Ohms.
"There does seem to be a pattern where, the more difficult a truth is to stomach, the higher the hysteria levels go internally at Google."
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Re: Entropy

Post by JR. » Wed Nov 22, 2017 4:17 pm

I loved the old simpson 260... learned how to troubleshoot transistor junctions using the resistance scale back in the 1960s.
Image only a few hundred dollars. :o

I probably need to buy a new cheapo VOM,,, the new stuff has many useful features the old stuff didn't..

probably one IC inside. :lol:

JR

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Re: Entropy

Post by mediatechnology » Wed Nov 22, 2017 6:35 pm

I probably need to buy a new cheapo VOM,,, the new stuff has many useful features the old stuff didn't.. probably one IC inside. :lol:
No ICs in the 260. EMP-proof.

I do have one of those credit card-sized DVMs and recently cleaned the selector switch.
Its one IC chip-on-board inside an epoxy blob.
"There does seem to be a pattern where, the more difficult a truth is to stomach, the higher the hysteria levels go internally at Google."
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Re: Entropy

Post by JR. » Thu Nov 23, 2017 2:43 pm

I had a heathkit vom with a big mechanical meter, but finally threw it away with other detritus cluttering up my lab.
======
I was afraid the old ratshack VOM had finally rode it's last rodeo. After I re-soldered the ground lead that I have fixed before it still was not behaving...

Another thing I realized is how hard it is to troubleshoot a broken VOM without a working VOM. :o

In a nice ratshack feature I noticed a spare fuse inside, so for chuckles swapped out the old fuse... and magically the meter is now back in business. 8-)

Apparently the fuse opened when I tested the parasitic current draw for my car, but the 85 mA should not have popped the fuse. The meter claims 400mA max on the fused lead, 10A on the unfused lead. Perhaps there was a huge initial surge??? or just an old tired fuse.

I decided to upgrade to a decent meter... the entry level Flukes look reasonable but they nudge you up from the $50 basic model to $90 or so with selectively limited features... I'm pretty sure the features don't cost another $40 but it worked to get me to pay up...to buy the 107 model.

JR

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Re: Entropy

Post by JR. » Fri Dec 01, 2017 12:11 pm

I completed my first battery experiment... Battery was topped off with trickle charger last wednesday (no voltage measurement.

During week battery voltage slowly sagged down to 12.54V thursday morning before leaving for my weekly shopping trip.

8 miles to store, two more starts getting gas when first pump didn't work correctly.

Returned from 16 mile round trip with 4 starts and battery voltage measured 12.70V , so alternator definitely works... BUT

Trickle charger took about 6 hours to declare battery fully charged. After leaving trickle charger on battery overnight this morning that battery measures 12.66V

I think the smart charger first charges to higher voltage to clear sulfation (guess), then lets it relax to some nominal voltage.

Next experiment may be to not trickle charge for a few weeks... My suspicion is that 85mA parasitic draw causes the battery to sag a hundred mV /week or more.

JR

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Re: Entropy

Post by JR. » Sat Dec 02, 2017 11:16 am

Got another repair win yesterday, my favorite kind, didn't cost me anything. I had to wait overnight to confirm the fix held, but like I said success... The problem that only started a few months ago was smelly water coming from my bathroom sink... I already fixed the smelly hot water coming from my water heater by cranking up the thermostat above 140'.

This new stink was coming from the aerator threaded onto the end of the faucet... I unscrewed it, and it was full of detritus... I scrubbed it with a toothbrush and clorox solution. While the flow restrictor was removed I cranked the faucet wide open and the water ran dark for a second as loose stuff was flushed from the plumbing.

This morning the water smells like nothing :D :D exactly what water should smell like. 8-)

Apparently I could buy a replacement part for $5 and may, but the crisis is over for now.

JR

PS: My two new VOM arrived today, the several times more expensive Fluke cost another $10 more for the diode function, while the $10 only meter has diode function standard. :lol: Now with 3 different VOMs I will never know what voltage I read.

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