Micronta DMM help needed! - diyAudio
Go Back   Home > Forums > Design & Build > Equipment & Tools

Equipment & Tools From test equipment to hand tools

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 6th May 2008, 08:42 PM   #1
KP11520 is offline KP11520  United States
diyAudio Member
 
KP11520's Avatar
 
Join Date: Apr 2007
Default Micronta DMM help needed!

Hi All.

I have a Micronta DMM model 22-185a. It was $50 to $60 some years back. So it shouldn't be total junk!

Recently, when I check DC voltages and I am looking for a "X.XXX" voltage reading, it won't range down to below "X." and I have it set on the correct range (I get whole numbers only with no decimals and inaccurate). The resistance testing seems to be working fine.

Does anyone have any experience with this who can offer some suggestions on how to knock it back into proper function? Maybe even know how to ensure it is calibrated properly and how to calibrate it if it is out? Or should I trash it?

I want a used HP LCR and a used HP DC/AC volt and amp meter, but I am waiting for decent deals on eBay. And the Fluke 289 is $500. I need to hit the lottery! LOL

Any help would be appreciated!

Regards//Keith
__________________
If Wile E. Coyote had enough money to buy all that ACME ****, why didn't he just buy dinner?
  Reply With Quote
Old 7th May 2008, 10:00 PM   #2
KP11520 is offline KP11520  United States
diyAudio Member
 
KP11520's Avatar
 
Join Date: Apr 2007
I guess Micronta DMMs are kinda like mo-peds.

They are useful and even fun but you certainly don't want your friends to know and man you would be embarrassed if they found out!

At least I have a real motorcycle so I can admit it.... That I have a Micronta that needs help.... That is!
__________________
If Wile E. Coyote had enough money to buy all that ACME ****, why didn't he just buy dinner?
  Reply With Quote
Old 8th May 2008, 01:48 PM   #3
KP11520 is offline KP11520  United States
diyAudio Member
 
KP11520's Avatar
 
Join Date: Apr 2007
Well, it looks like I am going to have to get on my mo-ped, I mean motorcycle and go as fast as I can. Then drop it on the road and deem it as road kill!

Only then, will someone make a post! LOL
__________________
If Wile E. Coyote had enough money to buy all that ACME ****, why didn't he just buy dinner?
  Reply With Quote
Old 8th May 2008, 04:18 PM   #4
diyAudio Member
 
leadbelly's Avatar
 
Join Date: Dec 2002
Location: Calgary, Alberta
I don't understand the problem you are describing; to me it sounds like the correct operation of a manual ranging meter.
__________________
Aerodynamics are for people who can't build engines. Enzo Ferrari
  Reply With Quote
Old 8th May 2008, 05:09 PM   #5
diyAudio Member
 
unclejed613's Avatar
 
Join Date: Dec 2006
if it's reading correctly on ohms, the ADC is working properly, could be that the resistor ladder for voltage has a bad resistor in it, or the range switching has a problem. there really are no calibration procedures that can help you here. i was a calibrator in the Army, and when we encountered a handheld DMM that was malfunctioning or out of spec, we NERTS'ed it (Not Economically Repairable This Shop) and ordered a new one. we were a Secondary Transfer shop, so were the highest level a DMM could go, and if we had to NERTS them, nobody could fix them. most handheld DMMs are permanently (thick film resistors printed directly on the PC board and laser trimmed) calibrated at the factory and there are no adjustments inside. Micronta DMMs, being made on the cheap are made to basically be throw-away meters. if you want, you could send it to me and i could send you a video of me shooting it with a .50BMG rifle
__________________
Vintage Audio and Pro-Audio repair ampz(removethis)@sohonet.net
spammer trap: spammers must die
  Reply With Quote
Old 8th May 2008, 11:07 PM   #6
KP11520 is offline KP11520  United States
diyAudio Member
 
KP11520's Avatar
 
Join Date: Apr 2007
Hey unclejed613,

Do you have a Sloooooow Moooootion videooooo camera? That could be worth it and I'll save some of the "Sacred Fluid" (gasoline) with my motorcycle! Or maybe I should suffocate it in a plastic bag with duct tape!

Thanks for your response. Your experience makes your advice about the best I could expect!

I think you have it right with the range switch going bad. It was fine, then intermittent and then completely gone and I now have about 100 JFETs to test the Idss.

I am testing them with a 1K resistor and a 9-volt battery in series and measuring the voltage at both sides of the resistor for a mA value. That is why I need the value to go to 3 decimal places. Like 2.609 volts which would equal 2.609 mA in my test setup. All I am getting is 4 volts for all of them with no variation. I smell toast! (burnt toast)

Looks like I have to steal, gamble, etc. so I can buy what I need! What an expensive hobby!

Thanks for the help!

Regards//Keith
__________________
If Wile E. Coyote had enough money to buy all that ACME ****, why didn't he just buy dinner?
  Reply With Quote
Old 9th May 2008, 11:14 AM   #7
diyAudio Member
 
unclejed613's Avatar
 
Join Date: Dec 2006
is the range switch a rotary switch? if it is, then it can be cleaned with a pencil eraser. you said it was intermittant at first. i was thinking it was an autoranging meter at first.
__________________
Vintage Audio and Pro-Audio repair ampz(removethis)@sohonet.net
spammer trap: spammers must die
  Reply With Quote
Old 9th May 2008, 02:50 PM   #8
KP11520 is offline KP11520  United States
diyAudio Member
 
KP11520's Avatar
 
Join Date: Apr 2007
Hi unclejed613,

Yes, it is a rotary switch. I needed to be more clear when saying it wouldn't range down to the setting I needed. I should have been more clear and said it acts like it is on a higher voltage switch setting where decimals aren't used, even though the switch is on the selection for low voltage with 3 decimal places.

So maybe I can save you a heavy slug! (Is that a 50 calibre you were going to use to execute it? black powder? I hope you would offer a blindfold!)

I guess I should take it apart and clean the contacts. You suggest a pencil eraser but if the contacts are delicate, should I use De-Oxit or something like that?

Thanks for giving my little friend another chance at life! She needs to work to earn her keep! (like all of us!)

Regards//Keith
__________________
If Wile E. Coyote had enough money to buy all that ACME ****, why didn't he just buy dinner?
  Reply With Quote
Old 10th May 2008, 05:11 AM   #9
diyAudio Member
 
unclejed613's Avatar
 
Join Date: Dec 2006
the contacts are most likely gold plated copper on a circuit board. they're not delicate. i've used pencil erasers on plated contacts for years, just don't use a gritty pen eraser on them.

that's not a black powder rifle i'm talking about. it's a .60BMG rifle. see pic below. this one is more fun than any human should be allowed to have.
Attached Images
File Type: jpg ferret50.jpg (72.1 KB, 101 views)
__________________
Vintage Audio and Pro-Audio repair ampz(removethis)@sohonet.net
spammer trap: spammers must die
  Reply With Quote
Old 14th May 2008, 07:11 PM   #10
KP11520 is offline KP11520  United States
diyAudio Member
 
KP11520's Avatar
 
Join Date: Apr 2007
Hey unclejed613,

Is that yours? What can you shoot with that, a Micronta DMM from a half mile? YIKES It looks like fun (with proper ear protection!).

Micronta DMM

So I borrowed a digital camera to show the kind of switches that are in my Micronta target! Do I un-assemble these by taking out the e-clip and then use an eraser on all contacts or do not un-assemble the switches and use a non-residue spray cleaner or a cleaner/lubricant? (see attached picture)

Thanks!

Regards//Keith
Attached Images
File Type: jpg micronta switches 1.jpg (21.6 KB, 93 views)
__________________
If Wile E. Coyote had enough money to buy all that ACME ****, why didn't he just buy dinner?
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Help needed ! Inter M R300 schematics needed ! alexclaire Solid State 30 9th September 2009 06:14 AM
LT1964-adj Help Needed or Part Needed lgreen Parts 2 29th June 2007 02:50 PM
Micronta Road Patrol XK buzzer doesn't work xplod1236 Parts 1 12th April 2006 10:20 PM


New To Site? Need Help?

All times are GMT. The time now is 12:22 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2