Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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  #31   Report Post  
Old March 21st 14, 10:27 PM posted to sci.electronics.repair
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On Thursday, March 20, 2014 10:44:20 AM UTC-7, William Sommerwerck wrote:
"John Robertson" wrote in message

...


Actually considering that the battery leaks an alkaline, I can only imagine
that using additional alkaline will only make matters worse.


He's trying to unstick the battery. You want something that will dissolve an
alkalai -- another alkali.


I'm not sure that's relevant: the alkali (usually potassium hydroxide) will have
corroded the aluminum, and you cannot dissolve the corrosion!

There's a few options for removing batteries in this situation, including
lathe-and-boring-tool, but I'd trash the flashlight.

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Old March 21st 14, 10:44 PM posted to sci.electronics.repair
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On Thursday, March 20, 2014 12:16:03 AM UTC-4, wrote:
I found this circuit somewhere, (I can't remember) to replace the 1.50 volt battery in a VTVM. I have an RCA WV98C Senior Voltohmyst VTVM that is in perfect condition but doesn't get used very often. This battery retrofit circuit takes power from the 6.30 volt filament transformer and is built around an LM317. With a trim pot you set it for 1.55 volts and you never have to change a battery again. It also needs to occupy an area no larger than the battery presently does.



As much as I like keeping things original, I'm worried that the battery is going to leak and rot the inside of the unit. I was going to build the circuit but it occurred to me that I should probably be concerned about the current that the LM317 will be dissipating when the meter is used on the low ohms range. Does anyone have a feel for the size that an adequate sized heat sink should be in order to handle this? Thanks, Lenny


I finally found the Website where I originally found the circuit. I liked the second schematic. It's isolated from chassis ground. Here's the link:

http://mikeyancey.com/VTVM_battery_eliminator.php
  #33   Report Post  
Old March 21st 14, 11:45 PM posted to sci.electronics.repair
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On Fri, 21 Mar 2014 14:27:08 -0700 (PDT), whit3rd
wrote:

On Thursday, March 20, 2014 10:44:20 AM UTC-7, William Sommerwerck wrote:
"John Robertson" wrote in message

...


Actually considering that the battery leaks an alkaline, I can only imagine
that using additional alkaline will only make matters worse.


He's trying to unstick the battery. You want something that will dissolve an
alkalai -- another alkali.


I'm not sure that's relevant: the alkali (usually potassium hydroxide) will have
corroded the aluminum, and you cannot dissolve the corrosion!

There's a few options for removing batteries in this situation, including
lathe-and-boring-tool, but I'd trash the flashlight.

Lye will dissolve the corrosion. Too bad it will dissolve the
flashlight too.
Eric

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Old March 22nd 14, 04:37 PM posted to sci.electronics.repair
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Default ohm meter battery

Trevor Wilson scribbled thus:

On 20/03/2014 3:16 PM, wrote:
I found this circuit somewhere, (I can't remember) to replace the
1.50 volt battery in a VTVM. I have an RCA WV98C Senior Voltohmyst
VTVM that is in perfect condition but doesn't get used very often.
This battery retrofit circuit takes power from the 6.30 volt filament
transformer and is built around an LM317. With a trim pot you set it
for 1.55 volts and you never have to change a battery again. It also
needs to occupy an area no larger than the battery presently does.

As much as I like keeping things original, I'm worried that the
battery is going to leak and rot the inside of the unit. I was going
to build the circuit but it occurred to me that I should probably be
concerned about the current that the LM317 will be dissipating when
the meter is used on the low ohms range. Does anyone have a feel for
the size that an adequate sized heat sink should be in order to
handle this? Thanks, Lenny


**Crazy idea, Lenny:

Move yourself into the 1970s and buy yourself a digital multimeter.
Most of them operate on a 9 Volt battery. Replace the battery every
year and you'll be sweet. Even a US$20.00 meter will give you a vast
improvement in every performance parameter over your ancient POS,
which is likely well outside it's original performance specs.


Like this one:


http://au.mouser.com/ProductDetail/E...qaRLKRQ5wis%3d

One of my meters measures the usual Volts, Amps & Ohms AND light
intensity, sound pressure level, relative humidity and transistor
gain. I recall that it cost me AUS$50.00.

I have a nice collection of analogue meters (I recently acquired a
beautiful AVO 8 Mk7), but I never use them anymore.

Go digital. You will not be sorry.


There is no way that I will give up using my AVO8...

--
Best Regards:
Baron.
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Old March 22nd 14, 07:47 PM posted to sci.electronics.repair
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Default ohm meter battery

On 03/21/2014 2:27 PM, whit3rd wrote:
On Thursday, March 20, 2014 10:44:20 AM UTC-7, William Sommerwerck wrote:
"John Robertson" wrote in message

...


Actually considering that the battery leaks an alkaline, I can only imagine
that using additional alkaline will only make matters worse.


He's trying to unstick the battery. You want something that will dissolve an
alkalai -- another alkali.


I'm not sure that's relevant: the alkali (usually potassium hydroxide) will have
corroded the aluminum, and you cannot dissolve the corrosion!

There's a few options for removing batteries in this situation, including
lathe-and-boring-tool, but I'd trash the flashlight.


Yeah, I'd missed the aluminum body bit. Unless this is a collectable
flashlight is should be binned...

John :-#)#

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www.flippers.com
"Old pinballers never die, they just flip out."


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Old March 22nd 14, 08:04 PM posted to sci.electronics.repair
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Default ohm meter battery

On 03/21/2014 5:34 AM, dave wrote:
On 03/20/2014 01:30 AM, William Sommerwerck wrote:
wrote in message
...

As much as I like keeping things original, I'm worried that
the battery is going to leak and rot the inside of the unit.


Only if you use a carbon-zinc cell. An alkaline cell should be fine.


Unless it's a Duracell!

https://duckduckgo.com/?t=lm&q=leaky+duracell


My experience is either Duracell or Everready alkaline batteries will
leak. This is based on batteries that were stored in circuit in arcade
games (pinball and video) since 1980 that I subsequently opened,
serviced, serviced and then sold between 2004 and 2011.

Some leaked, most did not. I have lots of pictures...somewhere.

John :-#)#
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John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
  #37   Report Post  
Old March 23rd 14, 02:55 AM posted to sci.electronics.repair
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Default ohm meter battery

On 22/03/2014 6:12 AM, wrote:
On Thursday, March 20, 2014 12:16:03 AM UTC-4,
wrote:
I found this circuit somewhere, (I can't remember) to replace the
1.50 volt battery in a VTVM. I have an RCA WV98C Senior Voltohmyst
VTVM that is in perfect condition but doesn't get used very often.
This battery retrofit circuit takes power from the 6.30 volt
filament transformer and is built around an LM317. With a trim pot
you set it for 1.55 volts and you never have to change a battery
again. It also needs to occupy an area no larger than the battery
presently does.



As much as I like keeping things original, I'm worried that the
battery is going to leak and rot the inside of the unit. I was
going to build the circuit but it occurred to me that I should
probably be concerned about the current that the LM317 will be
dissipating when the meter is used on the low ohms range. Does
anyone have a feel for the size that an adequate sized heat sink
should be in order to handle this? Thanks, Lenny


Besides the things I've already mentioned regarding digital vs.
analog, I've tried checking transistors and diodes with a digital,
and I suppose that you can do it but perhaps it's because I've been
doing this all my life with something like a 260, trying to do this
with a digital drives me nuts.


**Almost every modern digital meter I've ever seen has a diode test
function. It's easy to use and is often conveniently labelled with a
diode symbol.


And Trevor you asked how you insulted
me. You referred to my meter as a "piece of ****".


**So, not insulted you, so much as called your meter a POS? You have
pretty thin skin, Lenny. I'm pretty certain that if someone referred to
my AVO 8 Mk7 as a POS, I would not be overly concerned. Nor my Fluke 85,
or anything else I own. It's just stuff. If someone called me a liar, or
an idiot, or some other derogatory term, then I would be insulted.


You've never used
it nor have you ever seen it. So where the hell did that come from?


**I've owned VTVMs of the same vintage (in fact, I think I still have
one stored away somewhere). I still own a FETVOM I built (Heathkit) way
back. I never use it, because it is a POS. It was fine when I built it,
but time has moved on and so have I. It's a collector's (barely) piece
only. Same as my AVO 8, my Simpson 260, my Philips PM2403 (now THERE is
one seriously impressive FETVOM) or my General Radio 1564A (the most
beautifully constructed piece in my collection). They're all way past
being truly useful. But I like having them around. All the batteries
have been removed, of course.

You may have your own opinions but there was no reason for that
comment. Lenny


**Sure there was. You're trying to re-invent the wheel. If you want to
keep your VTVM for sentimental/collector purposes, then it's not an
issue. If you want to use it for day-to-day purposes, there are much
better choices available.


--
Trevor Wilson
www.rageaudio.com.au
  #38   Report Post  
Old March 23rd 14, 12:03 PM posted to sci.electronics.repair
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Default ohm meter battery

For what it's worth...

More than a decade ago I bought four toy "Insecto Bots", new. They came with
three AAA alkaline cells installed, from some totally unknown manufacturer.

http://www.amazon.com/247999-I-B-53-.../dp/B000TQC9AO

I'd opened them a few times to check, and the cells had not leaked. They still
powered the units, though a bit weakly. The other day I finally discarded
them. There were no signs of leakage.

Yes, cells leak, and yes, Duracell seems more likely to leak than others, and
yes, I've had leaking cells on rare occasions. But why some people here have
had such terrible experiences, I don't know.

If it'll make you feel better... About ten years ago I bought a box of 1000
AAA Polaroid cells on eBay. They're wrapped in pairs, in cellophane. About a
quarter of them have leaked, producing a powdery deposit.



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