Old Radio Shack tester

[bob91343]

I picked up an old multimeter free yesterday.  It doesn't work.

Inside, I discovered a 9 Volt battery that is about 8 Volts.  There is also a little circuit with two transistors in it, as well as a copper oxide rectifier.  I tested the meter and it's fine, I think 200 uA full scale.

It presumably measures ac and dc volts and ohms and capacitance but there is no sign of the familiar nonlinear resistance scale on the meter.

No clue on the web.  There is no model number anywhere.  Is this unit familiar to anyone?

[soldar]

You don't need to post a photo where we can appreciate each single atom. My slow internet connection has great difficulty downloading that photo without timing out. As a courtesy to those of us with limited connections it would be better if you resized the photo to a size that shows the needed details without incurring in unnecessary size.

[bob91343]

I thought of that too late to take care of it.  Sorry.

[DDunfield]

Nice one! Took a bit to find a reference:

Appears on page 33 of a 1970 Radio Shack/Allied Radio flyer:

EDIT: Found a more readable Page 102 from 1970 RS general catalog.
Looks like the part number is: 22-009
That's an early RS part number!

Unfortunately if you google this part number, you get a LOT of hits on a Radio Shack "Battery Tester".
I happen to have the battery tester that comes up, and the part number is: 22-090

Dave

[floobydust]

It came out in 1969. Micronta 22-009 Multi-lab multitester.
It seems to have a 400Hz and 455kHz signal generator, three leaded part must be a transistor.
1971 says a bit more about it's features.

source: http://www.radioshackcatalogs.com

[bob91343]

The blurbs are conflicting on the frequencies.  Apparently it doesn't measure R and C but has subs.  Yet, reading the description it seems confusing.

Nowhere can I find info on how to use it.  I have tried many things and can't seem to get the meter to deflect from the panel terminals.  Yet it does move when I activate the movement directly.

There are two transistors in it.  Also an adjustable coil, plus an rf choke.  There is what appears to be a germanium diode but my tests show it not to have a low forward drop.

Has anyone used one or even seen one?  I mean, $15 when new doesn't make you think it's anything special but I would like to know more about it.

[bob91343]

Okay!  Armed with at least a description of the unit, I made more tests.

I now get dc voltage readings but it's around 4000 Ohms per Volt, not terribly useful.  The reading is remarkably accurate.

I measured the substitution values and sure enough that's what it seems to be, although the accuracy is abominable.  It's around 30% off or more except the 100k resistance which is pretty close.

I don't get signal output (don't know where that's supposed to be) but I attribute that to a weak battery.  It measures 8V open circuit so I'm sure it collapses under load.  And of course the frequency will be anyone's guess depending on which blurb you read.

I have yet to test ac volts or rf field.

Regardless of the results of the remaining tests, I intend to scrap this thing.  Or maybe put it on the freebie table at the next swap meet.  I'd offer it free here but any shipping cost would be far in excess of the value.

[DDunfield]

Regardless of the results of the remaining tests, I intend to scrap this thing.  Or maybe put it on the freebie table at the next swap meet.  I'd offer it free here but any shipping cost would be far in excess of the value.

Be a shame to scrap it, it's a nice piece.. bit of hobby electronics history from late 60's. I doubt there are many of them around these days.

To bad you are so far away, I'd love to have it on display in my lab, but really is worth far less than shipping, especially "over the pond".

I hope it finds a good home.

Dave

PS: Yeah I like old tech: http://www.classiccmp.org/dunfield/
other than slide rules, there's not much there from before mid-70's.

[bob91343]

Further testing has revealed that it generates about 1 kHz and 500 kHz (didn't measure exactly) and in the RF field position it takes about 1/2 Volt input to read full scale, all the way to over 100 MHz.  I assume the high generated frequency is 455 kHz or can be adjusted thereto.

So this thing sort of works okay.  Replacing the out of tolerance substitution components probably will put it into original specification.

The rf input is at the ANT terminal and the generated signals come out the red jack.

You sure you don't want to pay for overseas delivery?  With this device you can replace all your expensive test gear.

[jkj1962]

Sorry for the late entry, but I was just curious as to what you ever did with this.

Thanks.

[bob91343]

I scrapped it.  The switch is worth more than the unit.  I had fun playing with it but had no desire to pack and ship it.  I still have the meter; I can't throw stuff away.

[jkj1962]

Ah, sorry to hear that.  It was an odd device for sure.  I've never seen another one, not even on eBay, and they've got some odd testers on there.

[bob91343]

You want an old tester, I have an Acro-Set Sr from many years ago.  It's still accurate but has no use for me.

Google it and you probably can see what it is.  It has two meters and seems intended for automotive testing.  There are shunts and stuff.  It's portable and has a fold-down steel handle.

https://www.google.com/search?q=acroset+sr&rlz=1C1AVNE_enUS701US725&sxsrf=ALeKk021xKzm1PrYqK9vJUDX0OpQZel9SA:1582593169975&tbm=isch&source=iu&ictx=1&fir=5sedSFS59VDbZM%253A%252CkBjXOiSm8fqTfM%252C_&vet=1&usg=AI4_-kT9MaO97FkLXEpPasbwanyERfe1Pw&sa=X&ved=2ahUKEwj8lOH9wuvnAhUhLX0KHdaUALMQ9QEwAHoECAoQBQ#imgrc=5sedSFS59VDbZM:

[jkj1962]

I FOUND ANOTHER ONE!!  eBay is your friend.  I found a listing for an "estate sale find" for a MultiLab tester, and Micronta Transistor tester, some odds and ends, all with a nice wooden case.  $17 plus shipping.  Should be here tomorrow.  Now, if I can just find a Micronta Home-Auto Tester, 22-011 in 1966 catalog.  It was a re-branded Eico "Redi-Tester 540".  In fact, Radio Shack sold the Eico version in kit form and assembled before 1966, then the Micronta version.  Basic voltage/resistance, with appliance "leakage" thrown in.  Missed one in very good condition on eBay in June, there's a couple on there in fair condition.

[jkj1962]

Well, for those still paying attention, I found a Micronta MultiLab tester on eBay.  Unfortunately, it does not work, at least not totally.  From what I can tell. the actual meter itself is non-functional.  I can select the 15v range, connect a 9V battery and...nada.  No meter movement.  I have verified that there is voltage at the terminals on the back of the meter, but it will not deflect.  The R/C substitution works, but I haven't been able to test the AF/RF generator.  And the RF signal strength...well, no meter, no measure.

I'm still looking for the Micronta Home-Auto Tester.  I have found several variants, from CalRad, Midland, Eico, and even one from Elenco.  I did find a "Handi-Tester" from National Technical Schools, brand new, still in the box a previous owner received it in, with a postmark of 1984.  When I opened the tester, I found a 36-year-old Ray-O-Vac AA battery that, to my surprise and relief, had not leaked.  And it measured 1.2V.  It is similar to the Home-Auto tester, but has separate jacks for the various functions/ranges instead of a rotary switch.  So far it works perfectly.  And like the Home-Auto tester, you shouldn't try to measure anything with the leads when the line cord is plugged in because one side of the line cord is connected to the "Common" jack.  Definitely wouldn't pass UL testing.  Oddly enough, a later revision of the Elenco version of the Home-Auto tester has a switch to isolate these.  It has a note included in the box mentioning the switch and why.