Tube tester advice and help please

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Tube tester advice and help please

Post by xtal_01 on Sun Jan 21, 2018 1:39 am

Hey!

So, I an not a radio guy. I am a machinist by trade. I just like to "play". I have built a couple of regenerative tube radios and own a couple of tube sets (R390A, Hallicrafters s-38E, ....). I also have a collection of about 200 tubes (just kept getting them given to me).

Years and years ago ( maybe 30 ), I got an Eico 666 tube tester (without the 610A adapter). Probably paid $20 for it.

I have used it ever since to test tubes. Never had it calibrated. I died once and a friend who knows about electronics (newer electronics but not tubes) fixed it ... this was about 15 years ago, don't know what was wrong.

Two questions:

1) I see people talking about calibrating tube testers .... how can I do this?

2) I would like to get another tube tester ... a spare ... with 200 or more tubes, it would be good to have another. I see them all the way from $20 to $1000 on ebay. This is just a spare (and I only dabble in this hobby .. not a full time obsession) but I do want it to work and test in case mine dies. I don't want to spend a fortune ... say $20 to $100 (including shipping .... money is a bit tight right now). What tube tester do you recommend (or maybe what tube testers should I stay away from)? Where is the best place to find one at a reasonable price?

3) ... sorry, just thought of a third question. Any idea where I can find the 610A adapter for my Eico 666 (again for a reasonable price)?

Thanks so much!

Mike
Jericho, VT

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Re: Tube tester advice and help please

Post by Chas on Sun Jan 21, 2018 4:59 pm

Mike,

1 - To calibrate any tube tester the manufactures manual is generally required. Sometimes a reference tube is used that has been identified as to providing a certain reading. Generally it is a 6L6 metal tube that has been aged so its reading will be stable. Calibrating inexpensive emission tester generally is not done, more often there is no way to do it. Often all the resistors are checked for tolerance and the paper/electrolytic capacitors replace. All the switches cleaned, using any cleaner that does not leave a residue. Sockets can be cleaned with a pipe cleaner and same contact solvent, sometime the contacts can be teased to improve connection.

I have three testers. There is no one tester that can cover all tubes since 1921 to the end of the era without some kind of adapter and a compromise at best.

2 - Best place to find a tube tester IMHO is from a retired or the estate of an electronic technician. That is a reasonable guarantee that the tester has not been "hacked" by a ham & egg'r I would suggest, even though you don't want to get more involved, to have some slick "Biz" cards stating your hobby (no mention of "money") that you collect tubes and tube test equipment. IMHO looking at your location overall, another active collector may some distance away... You can always use ebay, etsy, Craigs List or any local swap medium to find your desires. The card(s) thumb tacked to the local grocery bulletin board are a big help. Yep, I have been contacted some five years after stopping posting of cards.

Hickok 539B is about top of the line, any higher price will not test either early or late tubes. Another is the military TV-7 and its variants. Both these testers s will do a good job. An emission tester is good for your own purposes, there are many of them, recognized by having multiple tube sockets the same, like the drug store tube tester.

3 - Set a search on ebay that emails you when an adapter appears for BIN or auction...

You could consider joining a radio club with due caution.

Flipping tubes is a way to support the hobby. Establish sound principles dealing with problems, the reputation will grow.

You could also consider providing machinist service to radio collectors. There are radios that the construction contains fragile metal parts. The services of a machinist are often needed...

4 - It might be helpful to get a copy of:

Tube Testers and Classic Electronic Test Gear by Alan Douglas

https://www.amazon.com/Tube-Testers-Classic-Electronic-Test/dp/1886606145

GL

Chas

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Re: Tube tester advice and help please

Post by xtal_01 on Sun Jan 21, 2018 6:30 pm

Awesome! Thanks so much for the advice. I actually saw two TV-7's on ebay ... $150 not working and no enclosure ... $1000 working and calibrated. Honesty, I say 200 tubes .... that is how many I assume are useful (radio or amplifier and will test good) .... There may be more like 500 in all the boxes I have (filled the back of a full size pick-up truck). I am thinking though some of them must be TV tube and such which I figure most people will not want.


I love old technology (and just about anything old ... still use a rotary phone, have two old crank phones connected together to show how they work, keep a hit and miss engine and a steam engine running, have slot cars and erector sets in the rec room). As I said, I really only wanted tubes to keep my couple of SW radios working (still love listening to radio from countries far away crackling through the air) and also to build a few "old time" regenerative radios. I wanted them to be build as close to way they would have been constructed in the day.

I never thought about making parts for radios ... just never occurred to me there would be any. I do a lot of little jobs that big shops don't want to touch ... making parts for antique cars, hit and miss engines, antique steam engines .... about anything you can't buy or find.

This fall I poured the pad for a 3500 sq ft workshop. When the snow breaks here in VT, I will start putting the shop up. By fall, I want to unpack the transport trailer here beside the house with all my machines, radios, tubes and such in it (moved from SC to VT a couple l years ago ... put everything in a transport and parked it here on the lot while I built the house first ... house is almost done, time for the shop).

Anyway, I do appreciate all the information. I do a lot with industrial electricity ( wiring in equipment, building control panels, instrumentation, ...) but that is a far cry from electronics. I have just enough knowledge to be dangerous.

I know even just keeping this as a hobby, I really should invest in a better tube tester ... just don't want to spend a small fortune on one.

Thanks so much again .... Mike

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Re: Tube tester advice and help please

Post by xtal_01 on Sun Jan 21, 2018 7:12 pm

What about a "NRI Professional Model 70 Tube Tester"?

I may have found one cheap (maybe). The top of the wooden case looks rough (like it got when and de-laminated ... might have gotten wet .. but looks clean inside from what I can tell ... need more pictures).

Would this be an OK model? I did not see much on the web ... one page talked about making some changes to make the grid leak more sensitive. The only con listed "No compactron capability makes it not suitable to Ham Radio operators that use Compactron sweep tubes" .... I have no idea what this means!

Thanks .... Mike

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Re: Tube tester advice and help please

Post by xtal_01 on Sun Jan 21, 2018 8:22 pm

The one in the above post is $20. Here is another I found "NRI Professional Model 71 tube tester".

A day left on ebay ... $25 right now ( plus $30 shipping) ... probably go for $50 ... so fits my budget.

Is this a good model or ????

Thanks again ... Mike

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Re: Tube tester advice and help please

Post by stachowiak on Tue Apr 24, 2018 11:18 pm

Mike,

The Eico 666 and 667 testers are pretty good testers that actually put a signal on the grid of the tube and the meter measures plate current. The biggest problem is the early charts had lots of errors. Try to find the Coltronics updated charts that came out in the late 70's. Here's a good link on the Eico 666 and 667 testers.

http://www.fourwater.com/files/restr666.txt

The NRI tester is a very basic tester that test each tube as a simple diode, I think you would do better to fix up the Eico that you have. Hickok testers are nice but most of them have big problems. The good ones are very expensive. The fixer-upers on ebay can end up being non repairable as some parts just don't exist anymore. The meters on them haven't haven't held up with age and most have a bad bias or shunt pot. They used a custom control that was only made for Hickok. The bias pot is 3,000Ω wirewound with a non standard taper, and testing a shorted tube would burn it open. Substituting anything else is simply not an option.

Dick Stachowiak
Sound Services

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Re: Tube tester advice and help please

Post by W3IRE on Wed Apr 25, 2018 6:50 am

Precision tube testers are a great all around testers. I have a 612 that works great. Bought it on ebay 20 years ago and had been working great. The only thing I did was replaced the capacitor and check the resistors. They are very inexpensive, middle of the road testers.
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Re: Tube tester advice and help please

Post by stachowiak on Wed Apr 25, 2018 2:20 pm

Precision made some very nice testers. The 900 series and the 10 series use a circuit similar to the Eico 666 667 testers. The 612 circuit is more like the NRI tester mentioned above. The only downside is the birch ply cabinets tend to delaminate when stored in damp locations. I've had a few of them that had open meters, so if your looking at one on ebay you need to confirm that the line test will deflect the meter. A fantastic resource for Precision testers is at:

http://oldradios.50webs.com/precision/

This guy did a fantastic job putting all the tube data into searchable PDF files. He also has manuals and schematics available for download.

Dick Stachowiak
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Eico 666 Socket Adapters

Post by mr_ed01 on Thu Apr 26, 2018 10:48 am

If you have access to some old octal base type relays, remove the relay components and install old style 4, 5, 6 and 7 pin sockets in the plastic covers (hot glue or epoxy in place).  wire sockets pin for pin.  When testing old tubes, install the correct socket adapter in the Eico 666 octal socket.

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