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 Post subject: HeathKit IT-21
PostPosted: Jan Mon 11, 2010 6:54 pm 
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Location: Tyler, Texas 75707-4212
I have aquired an IT-21 tube tester, sans all documentation. Any pointers as to sources of schematics, manual, etc? The setup data is on the roll, but I have no idea of its version and whether it has been updated. I'd like to go through it before I power it up, and see if it needs service. I suspect it does.
All help appreciated, and comments as well!

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PostPosted: Jan Mon 11, 2010 11:07 pm 
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Location: Oswego, NY, USA
Tony, As you probably know, most of the websites stopped posting the Heathkit manuals (except for some of the circuit diagrams) and data charts. I could mail (by First Class envelope) to you the Heath # 597-1442-01 (1979) data booklet (28pp) which includes all the chart data listings for the Models IT-17, IT-21, & IT-3117. These 3 models are the same testers, except for being from different years & different case colors. I also have the "Condensed" (contains everything except for the Construction steps) manuals for Models IT-3117 & IT-17, so could easily make up a good manual for your IT-21...but minus the construction steps.

The Eico Model 628 was Eico's equivalent/competing tester; I could also include its 1-1-76 (published by Coletronics) data booklet, which would also provide some additional tubes and different editing. The Heath capital letters and the Eico numbers run consecutively in order, except that Heathkit eliminated the letter "I" (H=8, J=9). Please PM or email if interested.

Your IT-21 can also use the available Heath TC, Eico 625, NRI 66 thru 69, Knight KG600's, & Triplett 3413 data charts. These testers have only ten toggles, so their cap (flying) lead is connected to "K"/10; on the 13 toggle testers like yours it's connected to "N"/13. A kit should get checked for correct wiring (compared to circuit diagram) & inspect the quality of every solder joint; check tolerance of each resistor; replace any capacitors; check the meter for response (1ma fs); check every switch..clean them if necessary; check the Line-Reg calibration (R10, 75K must be good; then fine adjust R9, 1K to calibrate); then check the merit/value readings of the ranges with your known good tubes.

Fred


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 Post subject:
PostPosted: Jan Tue 12, 2010 2:19 am 
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Thank you, Fred. PM en route!

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PostPosted: Jan Tue 12, 2010 3:34 am 
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I read here and there about folks replacing resistors with metal film precision in place of carbon comp. I know the difference, but going through an instrument such as this, is it worth it to do that? It doesn't seem to be a large expense, or a lot of work. It's not original, so is the decision one of preservation versus function? Is this tester worth worrying about preservation at all? Are there any enhancements viable on this unit? It is a fair emmision tester as I understand it.

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PostPosted: Jan Sat 16, 2010 1:30 am 
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A bit late in replying to your post but here's the assembly manual and tube chart for the IT-21:

http://www.jogis-roehrenbude.de/Roehren ... eitung.pdf

http://www.jogis-roehrenbude.de/Roehren ... beData.pdf


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 Post subject:
PostPosted: Jan Sat 16, 2010 2:15 am 
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Dan,
no complaints here. I appreciate the links. I have d/l the info and filed it for printing as needed. I can now open the unit up for a quick look before power.
Many thanks!

And, if you go up a level there are all sorts of goodies: http://www.jogis-roehrenbude.de/Roehren ... e-Pruefer/

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 Post subject:
PostPosted: Jan Mon 18, 2010 2:54 am 
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Location: Montreal, Canada
Glad I could help. :)


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 Post subject:
PostPosted: Jan Mon 18, 2010 4:17 am 
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Location: Ceres, CA 95307
My CTI tester uses the same settings. I only have 4 tabbed sheets of tube settings with it.
Thanks,
Bill


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 Post subject:
PostPosted: Jan Mon 18, 2010 2:56 pm 
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Location: Potomac, Md.
GrayLox wrote:
I read here and there about folks replacing resistors with metal film precision in place of carbon comp. I know the difference, but going through an instrument such as this, is it worth it to do that? It doesn't seem to be a large expense, or a lot of work. It's not original, so is the decision one of preservation versus function? Is this tester worth worrying about preservation at all?...


I don't think anybody advocates going through a radio, tube tester, or what have you and replacing every carbon resistor with metal film, the way many folks automatically replace all electrolytics. Nor is there any need to use precision resistors unless replacing other precision resistors.

The idea is that if you HAVE to replace a carbon composition resistor because it is way out of way out of tolerance or shows signs of overheating, metal film would be a good choice because metal film is more stable over time and these resistors can tolerate overloads better than carbon comp can. It's not a matter of preservation or function (if by function you mean works better than carbon comp).

I can't speak specifically to the IT-21.

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 Post subject:
PostPosted: Jun Sat 12, 2010 1:13 am 
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Is the IT-21 a mutual transconductance (Micromhos) tester? I have a Hickok 539B, but the main meter is broken, I was wondering if this tester would tell me if the tube is actually good? Does that make sense?


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 Post subject:
PostPosted: Jun Sat 12, 2010 2:27 am 
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Location: Pocasset, Cape Cod, MA
All the Heaths (except the TT-1) are simple emission testers.

An emission tester will tell you about 80 to 90 per cent of what you want to know about a tube's condition.


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 Post subject:
PostPosted: Jun Sat 12, 2010 2:59 am 
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Ah, no...you'd be better off hunting a replacement meter, or having that one rebuilt.

Trust Mr. Douglas. It will tell you something, but not as much as your Hickok would if it were operational.

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 Post subject:
PostPosted: Jun Sat 12, 2010 3:27 am 
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I have almost no money to spend on the Hickok, but I have much skill in fabrication. Can anyone tell me what the full swing specs are for the 539B?


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 Post subject:
PostPosted: Jun Sat 12, 2010 5:00 am 
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Location: LONG BEACH CA.( 90808}
tube data sheet is the same as my heathkit TC2 Jewel

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 Post subject:
PostPosted: Jun Sat 12, 2010 5:17 am 
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Location: Tyler, Texas 75707-4212
Tundrawolf, that's a loaded question. Do you mean the meter movement only?

Stuff to read:

http://www.alltubetesters.com/articles/tester_guide.htm

http://www.cathedralstone.net/Pages/Hickok539B.htm

http://bellsouthpwp.net/p/a/padgett46/cal539c.htm

New meters sold here:

http://www.alltubetesters.com/parts.htm

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I'm right 97% of the time. Who cares about the other 4%!

-.-. --- .-.. -.. / ---.. ----- --...


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 Post subject: Re: HeathKit IT-21
PostPosted: Apr Sat 05, 2014 9:56 pm 
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Joined: Apr Sat 05, 2014 9:49 pm
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April 5, 2014

Can anyone help me get an owner manual for IT 21 by mail or online at reasonable price?
Don't need assembly instructions. I am in Delaware. Thanks.
audidoc


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