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 Post subject: TV-2/U tester - advice on calibration
PostPosted: Jun Sun 09, 2019 7:15 pm 
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Location: Galena, Ohio
Just picked up a TV-2 and would like to get it back to working condition. Any advice on calibrating these things? I've calibrated TV-7 testers before, but this appears to be a totally different beast from what I'm seeing.

If you have a guide or document of some sort that you can share that walks you through the TV-2 calibration/repair, that would be great to get a copy of that!

It's also missing the roll chart piece and the pin straighteners. Anyone happen to have these sitting around in their parts pile? :)

Here's a few pictures of it...


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 Post subject: Re: TV-2/U tester - advice on calibration
PostPosted: Jun Sun 09, 2019 9:36 pm 
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Location: Sunbury, Ohio 43074
Manuals are on bama:

http://bama.edebris.com/manuals/military/tv2u/

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 Post subject: Re: TV-2/U tester - advice on calibration
PostPosted: Jun Sun 09, 2019 11:50 pm 
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viewtopic.php?t=306423
viewtopic.php?f=8&t=346503

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 Post subject: Re: TV-2/U tester - advice on calibration
PostPosted: Jun Mon 10, 2019 12:04 am 
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Keep in mind as you start working through the testing procedures for the unit per the manual, the TV-2 is not exactly a "tube tester" in the normal sense of the word. It's more of a tube analyzer by virtue of the fact that you can vary just about all the operating parameters of the tube under test.

It also has no real "calibration" adjustments, as noted in the other threads Steve listed. Read those. And do NOT start shotgun replacements of either capacitors or resistors until you fully understand how this unit works, or you will end up with an actual boat anchor. Mine has most of the original electrolytics, for example, and works just fine. I don't use it much, but it does, or did work, last time I pulled it out to play with.

To what level you try and restore it depends, I suppose, on what you intend to do with it. As a daily tube tester, it's rather involved and time consuming to use although extremely high quality.

BUT>..... I sure do like all those needles and dials and switches and other thingies....... :-D

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 Post subject: Re: TV-2/U tester - advice on calibration
PostPosted: Jun Mon 10, 2019 3:30 am 
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Joined: Mar Thu 29, 2018 3:41 am
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Location: Portland Oregon
Hi,

I recently went through my TV2/U that is made by Columbia. I cannot see your serial number, but it looks like we have sister testers. I *really* like the TV-2 tester, but I'm an engineer and I like to know what my tester is really doing and know the limitations of the tester.

I suggest you read the -35 manual numerous times so you can understand the way that the tester works and how to qualify it. This will help you understand what you have to do.

Eventually, I replaced all of the capacitors with modern capacitors and left the original ones in the tester. I found that some of the capacitors were shorted and others were very high ESR. I don't recommend using NOS canned cap's. I know that there are different philosophies on this, but I believe that one should use new capacitors. The new capacitors are probably much better than the old capacitors and they definitely had lower ESR values. The T2 transformer is one of the weak links in the tester and keeping the power draw in this transformer to a minimum is probably important for the life of the tester. The new caps will help reduce the load on the T2. I also, eventually, replaced all of the resistors except for the wire wound resistors with 1%, metal film resistors. The metal film resistors are relatively cheap and much more stable than the original carbon comp resistors in the tester. I rewired R59 (I believe - a 47Ohm resistor in plate circuit) with a 10, 15, and 22 Ohm resistor in series. I tapped off of either side of the 10 Ohm resistor and ran wires to the dummy two prong plug on the pannel so I could read plate current with a DVM (actually 10X plate current when on the voltage scale). When I was replacing the resistors, I did change some of the values a little so that the meters were more correct.

I found that the linearity of my plate and screen meters was not the best, hence I went through and made a correction table chart. That get's me close, but I eventually purchased and Octal and 9 pin mini test socket and measure the true voltage being delivered to the tube with a DVM. I use a fluke 189 on the grid voltage so I can independently measure the AC signal voltage with the DC grid bias at the same time. The other voltages are easily measured with a reasonably good DVM.

I *highly* suggest that you measure your shunt pot on, say, 5 increment intervals and create a linearity calibration chart. This will help you set the shunt values very precisely. The shunt pot is very difficult to find and I expect that your TV-2 shunt pot will still be OK. Also, if you do the plate current modification listed above, you can then calibrate each Gm range quite precisely by doing a simple grid shift method to calculate the Gm (Gm - dIp/dVg) by selecting range F on your Gm/Signal switch, zeroing your quality meter, and then adjust your shunt pot to the right value for that range. You don't need to depend upon a "bogey" tube nor the 10KOhm/!0W resistor method described by Allan Douglas. I use the same meter multiplier suggested by Douglas for each Gm range but set the shunt to get the ranges calibrated. I found that my quality meter was pretty good for linearity (close to 1%).

Be sure to turn all of the knobs multiple times so you make good contact and I did the q-tip with deoxit on some of the switch contact areas.

I haven't done it yet, but you may want to think about changing the 83 with a good SS83 which uses the 10V/5W zener diodes and the 10Ohm resistors for the filament circuit. These will create a very balanced, repeatable tube and reduce the power in your tester significantly and I'm always for minimizing the power in these sorts of electronics. Of course, this change is highly debated.

This is a lot of work, but I think with special care you can have on of the more accurate, precise portable tube testers.

Dave


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 Post subject: Re: TV-2/U tester - advice on calibration
PostPosted: Jun Mon 10, 2019 4:44 am 
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Location: Galena, Ohio
Thanks guys, really appreciate the good advice. I'll definitely read up on it and familiarize myself before touching it. I have read multiple places about the weak transformer, so I think I'll probably go with the SS83 as that will likely reduce power draw the most of any changes I can make to it. Give it a bit more breathing room that way.


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 Post subject: Re: TV-2/U tester - advice on calibration
PostPosted: Jun Mon 10, 2019 9:19 am 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
heh... looks like we're neighbors. ;-). If you need to compare anything in yours to mine, PM me or stop by .. you've probably been past my shop many times.

Probably for less work than "blueprinting" your TV-2, you could build a uTracer, if it's precision you want. As I've stated before, tubes aren't precision devices, and tube testers never were either. Expecting too much is ....well .... time consuming. 8)

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 Post subject: Re: TV-2/U tester - advice on calibration
PostPosted: Jun Tue 18, 2019 3:55 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: St. Paul, Minnesota
You can't calibrate TV-2s or TV-2As. There is nothing that can be varied, not even the meter needle positions. The TV-2Bs are the first in the series you can calibrate.


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 Post subject: Re: TV-2/U tester - advice on calibration
PostPosted: Jun Tue 18, 2019 1:31 pm 
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Location: Brooklyn, NY 11217
Everytime I see one of these threads I want a TV-2...


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 Post subject: Re: TV-2/U tester - advice on calibration
PostPosted: Jun Tue 18, 2019 1:51 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
Quote:
Everytime I see one of these threads I want a TV-2...

I'll see your "threads" and raise you one "picture". I wanted one from the first time I saw a photo. I finally got one from an ARF member. I haven't even fired it up yet. But it sure is purdy ................

Getting back to calibration, no, you do not calibrate a TV2. Everything is adjustable, hence the term "tube analyzer" rather than tube tester that I like to use. It's a little bit of both, but really less of a 'tester' and more of a lab instrument. You can test tubes for any number of different parameters, but you have to know a lot more about what you're doing than when using a regular old fashioned tube tester, whether emission only, or Gm.

The TV2 is one very robust instrument. If the meters are good, it's probably going to work, even with the old electrolytic cans. Just let them reform a bit before putting full voltage on it. If you're going to use it day in and day out, I might suggest replacing the cans however. And of course any paper caps.

You could check the resistors I suppose, but I'd avoid that until you see if the thing works the way it is. Most resistors will need a lead disconnected to test, so personally, i'd leave them be unless there's a compelling reason to mess with them.

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 Post subject: Re: TV-2/U tester - advice on calibration
PostPosted: Jun Tue 18, 2019 5:59 pm 
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Joined: Mar Thu 29, 2018 3:41 am
Posts: 169
Location: Portland Oregon
These tube testers do need calibration. The meter's have resisters that limit the current that need to be correct so that the meter readings correspond to the applied voltages. Getting the resistors correct so the meters are best centered is a calibration.

I went a bit further and did individual calibration curves for the plate and screen meters because their linearity wasn't the best (right on the edge of +/-2% of reading). My quality meter is pretty good (within 1%) and the filament is very close. I find that it is better to use a test socket and measure values on a portable DVM - especially when setting the bias, plate, and screen.


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 Post subject: Re: TV-2/U tester - advice on calibration
PostPosted: Jun Tue 18, 2019 7:49 pm 
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Location: Sunbury, Ohio 43074
your's needed "calibration" because you wanted to make it better than it was designed. Perhaps you did, but it's not necessary

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 Post subject: Re: TV-2/U tester - advice on calibration
PostPosted: Jun Tue 18, 2019 9:38 pm 
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Joined: Aug Mon 04, 2014 9:42 pm
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Suggest (in addition to everything else) checking those blue precision resistors. A couple of them were way out of spec in mine, causing some meter errors


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 Post subject: Re: TV-2/U tester - advice on calibration
PostPosted: Jun Tue 18, 2019 10:45 pm 
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Joined: Mar Thu 29, 2018 3:41 am
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Location: Portland Oregon
Agreed Mark. many of the blue resisters were way off on my tester as well and some of hte caps basically fell off when I removed the resistors.

Many, many of my carbon resistors were out of spec as well so I just ended up replacing them all. Some of the resistor values I changed slightly so the gauges were more in alignment with true voltages (but, I think it was only 3?? - I have this recorded at home).

Good luck on fixing your TV2. Please keep us up-to-date on what you are doing and how it is going.


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 Post subject: Re: TV-2/U tester - advice on calibration
PostPosted: Jun Tue 18, 2019 10:52 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
Interestingly, mine is virtually all original except for one cap that was replaced in the past before I took ownership.

I highly advise seeing if yours works before diving into it. :). must my 2c ... you can always decide to replace every part later. :shock:

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 Post subject: Re: TV-2/U tester - advice on calibration
PostPosted: Jun Wed 19, 2019 3:05 am 
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Running through the 5th echelon tests in the manual will pinpoint the areas that have bad precision resistors.

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 Post subject: Re: TV-2/U tester - advice on calibration
PostPosted: Jun Wed 19, 2019 1:12 pm 
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Joined: Aug Mon 04, 2014 9:42 pm
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Barry - I agree. Check things out before you replace anything. I made mention of the resistor issue, because I spent a lot of time tracing things out - out of spec resistors (especially precision ones) were the last things I was expecting. But hey, what else makes this stuff so fun?


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