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Check the supply rails are correct, I cooked one when the -5V rail did not come up correctly and the chip latched up and cooked. Check that ICL7660 and the tantalum capacitors attached to it that it can deliver -5v and can deliver at least 20mA into a resistive load without dropping below -4V, use a 270R resistor as a test load and check across it for excessive ripple.
These icl series chip fail quite frequently. Most just show strange values (or strange digits) or show non linear behaviour. Havent seen any draw too much current though.A lot of (older) 3,5 - 4,5 digit lcd voltmeter modules use these chips too. Thankfully you can still get new chips after 15-20 years.
Is it an idea to replace all of the 7 segment units?The new ones give a lot more light and as they are multiplexed you end up with one bright 7 segment, and 3 lesser?
Waiting on parts again, I thought I'd try to clean up the case. I ran into a problem. It looks like it has specks of paint on it. I've tried all these cleaners -AlcoholSimple GreenPaint thinnerSoap and waterOrange degreaserI can't get rid of the specks.Any ideas?
I can't get rid of the specks.Any ideas?
Must be some difficult 'Sh!t' to remove if none of what you tried made any impression at all!!.what about ;WD40, kerosine, mineral turps. Best to try a small spot first if the case is plastic.Cant say if you will have any luck with those either, so maybe just live with the specks.You should be looking at the display not the case anyway .If you do get it off post back the magic liquid that did it.
Seems you have a bit of a thing for old multimeters !.
You know the HP3435a had a touch hold probe assembly similar to the Fluke 80T-H which is used with the 8010, 12 and 50 series.The 34112a, (the small hole between the V/ohm and COM terminals is for this probe!).If you want to add to your collection of oldies see if you can get a HP3476a/b, (that's one odd looking beast!).
Use a magic sponge with any of the cleaners above. It may take quite a bit of rubbing and I would be very careful on the printed info as it may take the print off also. You may also see if the individual specks will pop off with a soft plastic scraper. It looks a lot like house fly crap which is fairly hard to get off also.
I've had good luck with "goop" brand hand cleaner, but sometimes it works very slowly. Apply, let set, wait, rub, wait, apply more, wait, rinse off, evaluate, apply more, rub, wait, apply more, and on and on
Can you scrape any of them with a fingernail ?
Alternate idea would be an old toothbrush with a bit of toothpaste. Toothpaste, depending on the brand, is a mild abrasive. Might try the baking soda and peroxide kind.
It looks a lot like house fly crap which is fairly hard to get off also.
Quote from: Excavatoree on February 19, 2015, 01:08:30 amI've had good luck with "goop" brand hand cleaner, but sometimes it works very slowly. Apply, let set, wait, rub, wait, apply more, wait, rinse off, evaluate, apply more, rub, wait, apply more, and on and onYea that's what I meant by orange degreaser - tried it and no effect.
If you need to know how to remove the innards from these types of banked switches for cleaning the trick is shown below.
By the way, does yours take some strange battery? I can't figure out what mine is suppose to use. (So I use alligator clips and a power supply)
Good repair and restoration. Thanks for the tip on these switches. I will have to remember this thread for the future.