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 29th March 2010, 09:18 PM   #11
fredlf is offline fredlf  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Portland, OR
Send a message via AIM to fredlf
Quote:
Originally Posted by PB2 View Post
I bought one of these on ebay recently and the X1/X10 switch was put in upside down so that they were opposite to the labels.
Figured out what was wrong with mine. See if you can guess...

Yep, upside down and wired backwards. Now my IT-18 works fine, readings jibe with my DVM. Yay!
  Reply With Quote
Old 30th March 2010, 12:21 AM   #12
PB2 is offline PB2  United States
diyAudio Member
 
PB2's Avatar
 
Join Date: Sep 2004
Location: North East
Blog Entries: 1
Quote:
Originally Posted by fredlf View Post
Figured out what was wrong with mine. See if you can guess...

Yep, upside down and wired backwards. Now my IT-18 works fine, readings jibe with my DVM. Yay!
Excellent! Seems that was a common mistake!
__________________
Pete Basel
http://www.linkedin.com/in/petebasel
  Reply With Quote
Old 30th March 2010, 02:14 AM   #13
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi Fred,
"Struck by technician"
or TIM
which stands for Technician Induced Failure.

I've seen enough of this and these things can be difficult to find. So congratulations! Now it's time to get to know your meter better.

-Chris
__________________
"Just because you can, doesn't mean you should" © my Wife
  Reply With Quote
Old 30th March 2010, 05:37 PM   #14
sonidos is offline sonidos  United States
Libertador de la Música
diyAudio Member
 
sonidos's Avatar
 
Join Date: Jul 2007
Location: Round Rock, TX
Chris, I sent you an email last night, but here is the best place to discuss all things IT-18.

Hmmm, so builders turned the x1/x10 switch backwards. I have a sneaking suspicion that mine was built the same way too!

I'll run some of the checks that you suggested. I've kept it on my desk next to my computer and my guess is that it won't be put on a shelf any time soon!

I do have a question about setting beta calibration. Does the meter jump like crazy during cal? Mine is sooo sensitive and I just nudge the dial ever so slightly to get it lined up to the right over 'CAL' on the meter.

Last edited by sonidos; 30th March 2010 at 05:48 PM. Reason: add question
  Reply With Quote
Old 30th March 2010, 06:56 PM   #15
diyAudio Member
 
Steve Dunlap's Avatar
 
Join Date: Sep 2008
Location: Here
Quote:
Originally Posted by PB2 View Post
Excellent! Seems that was a common mistake!
It must have been. I picked up a IT-112 Curve Tracer with a switch in backwards. I don't remember which one, that was a long time ago.
  Reply With Quote
Old 31st March 2010, 02:46 AM   #16
fredlf is offline fredlf  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Portland, OR
Send a message via AIM to fredlf
Quote:
Originally Posted by sonidos View Post

Hmmm, so builders turned the x1/x10 switch backwards. I have a sneaking suspicion that mine was built the same way too!

I'll run some of the checks that you suggested. I've kept it on my desk next to my computer and my guess is that it won't be put on a shelf any time soon!

I do have a question about setting beta calibration. Does the meter jump like crazy during cal? Mine is sooo sensitive and I just nudge the dial ever so slightly to get it lined up to the right over 'CAL' on the meter.
It's easy to tell if the switch is in backwards once you know what you're looking for. Compare it to the illustration in the manual and look for the two little marks that represent the two unused slots for solder tabs on the switch. The switch needs to be oriented as illustrated. You can see why people made the mistake!

My needle is quite sensitive when calibrating, just as you describe.

Good luck!
  Reply With Quote
Old 31st March 2010, 03:13 AM   #17
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi sonidos,
Did I reply? I can't remember if I saw it or not. Please let me know as I've been told I have missed a few.

Setting the beta cal. is actually adjusting the transistor under test for a collector current of 1 mA. The adjustment is very touchy when testing lower gain transistors, try some high gain transistors like 2SC2240 or similar, even a real 2N3904 should be much easier to set up. The other possibility would be bad connections somewhere. Check the actual connections to the transistor, the leads for breaks and even the switch contacts inside your IT-18. Don't forget the calibration control.

It's best if you don't clean these parts unless they need it, otherwise you will wash out all the lubricants. Add oil to the shaft bearing. If the adjustment with a high gain part is smooth, you probably do not need to clean anything.

Hi Steve,
Was that an IT-121 you are talking about? They were pretty useful back then

-Chris
__________________
"Just because you can, doesn't mean you should" © my Wife
  Reply With Quote
Old 31st March 2010, 04:10 AM   #18
sonidos is offline sonidos  United States
Libertador de la Música
diyAudio Member
 
sonidos's Avatar
 
Join Date: Jul 2007
Location: Round Rock, TX
Default Thanks - got some work cut out for me

I definitely have some work cut out for me. I think the beta cal dial just was a bit gunky and seems to be working better now after playing with it a bit, but I got some numbers that I think are way off the mark.

I tested 8 each of Sanyo 2SD1047 and 2SB817 power transistors. I used the x1 scale and I was getting beta from as low as 6.8 to as high as 15. The NPNs ranged from 6.8 to 11. The PNPs ranged from 12 to 15. Selecting x10 didn't give me any useful results because it was measuring at about 1000 (100 x 10), and the beta for these trannies is supposed to be from 100 to 200 when measured at 1 A. Is it possible that 1 mA gives a different beta value on these boys?

Now I did try a Fairchild KSA992 (pnp type), which is a small signal type and x1 got a reading over 50, so I moved it to x10 and got a reading around 500, which is right in the middle of the published beta of 400 to 600. So that seems right and jibes with what you stated regarding measuring small signal trannies. I've got a few more other varieties and I'll give them a try tomorrow.

I did do some checking vs. the illustration and everything looks fine as far as wire layout, connections to switches, placement of resistors, the diode, and the ceramic cap. So I will probably check to see if maybe switch contacts need cleaning

Chris, no problem on the email. I set it about a day or two ago and it covers what I've added here on this thread. Much obliged to you guys. I hope to have this working right very soon. It's definitely a fun tool.

Last edited by sonidos; 31st March 2010 at 04:11 AM. Reason: changed measured value
  Reply With Quote
Old 31st March 2010, 04:13 AM   #19
sonidos is offline sonidos  United States
Libertador de la Música
diyAudio Member
 
sonidos's Avatar
 
Join Date: Jul 2007
Location: Round Rock, TX
Chris,

BTW, I had these transistors laying on my desk and used insulated needle nose pliers to attach the clips to the leads...so no hand holding to get them warmed up. I got several matches, but those low beta numbers bother me.
  Reply With Quote
Old 31st March 2010, 10:04 PM   #20
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi sonidos,
My IT-18 measures those part numbers just fine. Interesting problem you have there. I have confirmed the readings with other transistor testers and also by setting up a test jig where I measured the values of collector and base currents directly. They agree within the error of the meter and other experimental effects. To be honest, even a change of temperature affects what you get for numbers.

The numbers at 1 mA correspond well with the numbers I get at higher currents. For sure there is going to be some difference, but the readings seem to be in the ball park.

Did you perform the calibration procedure on your meter? If not, start there. You can put a DVM in series with the emitter or collector of a high gain part and confirm your zero set point reads 1.0 mA. This is a very important point as the meter is based on this. Static on the plastic meter cover can throw your reading way off, as can a sticky movement (I hope your meter is okay!).

Quote:
I think the beta cal dial just was a bit gunky and seems to be working better now after playing with it a bit, but I got some numbers that I think are way off the mark.
You don't want to ruin the control, it's a multi-turn control. Get some fine, single weight, light machine oil with zero additives and put some in the front of the bearing where the shaft enters the bushing. There will be some kind of a clip (leave it!), you want to get a bit of oil into the area behind the clip. Around to the rear, apply some of the same oil into the ball bearings and also into the rear of the sleeve bearing if you can. Work the control (it should be much looser) and clean up anything around the outside of the areas where you put the oil. You may need to do this a couple times, depending on how bad the control is. The same treatment is used for any rotating controls or switches. It is very important that you do not use 3n1, WD-40 or anything like those. Sewing machine oil is another to stay away from.

When cleaning a variable resistor, use only enough cleaner (not tuner cleaner !!!) to get things working and no more. There are lubricants inside that protect the carbon track. The problem area is the slip ring, not the carbon track! That's a popular misconception. I use a liquid cleaner with a hollow needle-like applicator and a rubber bulb for applying cleaning fluid. Sprays are a last resort as you get far too much in there, and it goes pretty much everywhere. Even the Caig pump applicator allows too much cleaner out.

The IT-18 will not measure a darlington properly due to the double VBE drops. Don't bother trying as it's a waste of time. Another battery in series with the base might work, but your gain reading will be in that compressed area at the top (bottom?) of the scale.

You can get matches using this meter, but it's difficult. That's why I put together a jig for that one purpose.

-Chris
__________________
"Just because you can, doesn't mean you should" © my Wife
  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
Looking for a manual for a Heathkit IT-18 fredlf Equipment & Tools 9 26th January 2012 07:05 PM
Transistor Tester Current Levels Stocker Parts 87 22nd December 2010 03:30 AM
Best transistor substitutes for Heathkit ar-15 ar15guy Solid State 4 8th April 2008 02:21 PM
HOW to use a Heathkit Model 10-18 oscilloscope Dusk Solid State 7 14th October 2004 10:00 AM
transistor tester janey Solid State 0 4th January 2002 02:44 PM


New To Site? Need Help?

All times are GMT. The time now is 10:03 AM.


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