I have been looking for someone to test tubes where I live , but they are a little hard to find. i was wondering if any of these would be good to buy. Can anyone recomend one of these, that are listed on E-Bay http://shop.ebay.com/items/__tube-t...C65%3A12%7C39%3A1&_trksid=p3286.c0.m14&_pgn=1
Any help would be appreciated,
Thank You ,
Matt
Any help would be appreciated,
Thank You ,
Matt
What is your budget?
If you can swing the $$, look for a mutual conductance type tester, such as a Hickok or equivalent.
For a basic education, look here:
http://www.tone-lizard.com/Tube_Testers.html
If you can swing the $$, look for a mutual conductance type tester, such as a Hickok or equivalent.
For a basic education, look here:
http://www.tone-lizard.com/Tube_Testers.html
I have an Eico 666 "Satan's Choice" which is a "dynamic conductance" tester (a term they coined themselves, I think). Simpler than a mutual conductance tester, but better than a basic emissions tester. Look up the Eico on the site that boywonder posted.
I bring it up because it does a fairly decent job, the manual has a full schematic and theory of operation, they have no tubes inside, and they are not as desirable on eBay. A better value for the $$$ IMO. I've used mine to go through my stock of random NOS and used stuff to find any duds. Other than that, I mostly use it for testing tubes for friends. The readings are more meaningful when I have a known-strong tube to compare it with.
I bring it up because it does a fairly decent job, the manual has a full schematic and theory of operation, they have no tubes inside, and they are not as desirable on eBay. A better value for the $$$ IMO. I've used mine to go through my stock of random NOS and used stuff to find any duds. Other than that, I mostly use it for testing tubes for friends. The readings are more meaningful when I have a known-strong tube to compare it with.
I have an EICO 625 (basic emission tester) an a Hickok 600a which I use to test practically all of my tubes. The 600a is very versatile and does mutual conductance, but a decent one goes for about $200.
One interesting fact about the EICO 625....the switch tips are the same ones that were used on late 60's Telecasters (tophat style), so if you pick one up, the vintage switch tips (and probably switches) are worth more than what whole testers go for.
Speaking of my Hickok, I have not tested my 300b's on the 600a, since they are not in any of the roll chart data that I have. Can I test these as 45's with 5V on the filament?
One interesting fact about the EICO 625....the switch tips are the same ones that were used on late 60's Telecasters (tophat style), so if you pick one up, the vintage switch tips (and probably switches) are worth more than what whole testers go for.
Speaking of my Hickok, I have not tested my 300b's on the 600a, since they are not in any of the roll chart data that I have. Can I test these as 45's with 5V on the filament?
My issue with tube testers is that they do not test under real working scenarios, except for a very few and VERY EXPENSIVE ones. TV-7, but try getting one for less than $1000.00 !!! A tester can be useful for weeding out plain DEAD tubes, but a problem may manifest itself at operating voltage that the tester does not reveal. Blow up an output tube once at 450V and see what else can happen to your amp. Also, to be safe, you should have your tester calibrated when you get a new one and few people are still doing that nowadays. 
I would say that is a bit of an exaggeration. Yes, the less-expensive only test the tube at one operating point and yes that won't uncover an issue with a tube that may not show up at that operating point. And so no, you can't take a box of tubes from eBay and/or someones' attic/barn, jam it in the tester, get a reading in a green and say it is super-awesome-A++++.
It will however give you an indication of the overall tube's health and more often than not (especially for NOS stuff) it's a pretty accurate conclusion. Yes, sometimes the tube will test fine in the tester but is all wrong in a circuit. If you use the tester right and it is calibrated, more often than not a "good" tube is indeed good and a "bad" tube is indeed bad. Obviously the final and most meaningful test is in the final circuit. I've tried weak 45s in the TSE and they work fine.
Other things that many testers don't test for is gas and leakage. The Eico does have a nice test for leakage and I have modified mine so that I can measure grid current and check for gas. The Eico is also very easy to calibrate. No special tools other than a meter are needed.
It will however give you an indication of the overall tube's health and more often than not (especially for NOS stuff) it's a pretty accurate conclusion. Yes, sometimes the tube will test fine in the tester but is all wrong in a circuit. If you use the tester right and it is calibrated, more often than not a "good" tube is indeed good and a "bad" tube is indeed bad. Obviously the final and most meaningful test is in the final circuit. I've tried weak 45s in the TSE and they work fine.
Other things that many testers don't test for is gas and leakage. The Eico does have a nice test for leakage and I have modified mine so that I can measure grid current and check for gas. The Eico is also very easy to calibrate. No special tools other than a meter are needed.
bereanbill said:
This is true, but they're not supposed to. They're designed as a screen to weed out the probably good from the definitely bad. To test under more stringent real working conditions, you need what's generally refered to as a tube analyzer. These include the RCA WT-100A, Daystrom/Weston CA-1630 and the New London 901A seen below. Hickok also made one but I forget the model.
The TV-7 is certainly not in this category, and is one of my least favorite testers. I've owned and used many different testers over the years. For some dumb reason the TV-7 has obtained cult status. Probably because it's small and military. My personal favorite is the Hickok USM-118B military cardmatic because it's very fast, durable and stays in cal for a long time.
Attachments
Practical Wireless
At an antiques shop I came across some old issues of 'Practical Wireless' that had designs for multimeters, oscillators and a design for a tube tester. The tube tester is one of the things I may not have a go at building, but it might be of an interest to anyone here. Its very detailed, showing full circuit and construction diagrams and component lists. I can post the article if anyone wants to see it?
Cheers
Charlie
At an antiques shop I came across some old issues of 'Practical Wireless' that had designs for multimeters, oscillators and a design for a tube tester. The tube tester is one of the things I may not have a go at building, but it might be of an interest to anyone here. Its very detailed, showing full circuit and construction diagrams and component lists. I can post the article if anyone wants to see it?
Cheers
Charlie
BillEpstein said:Now I can calibrate it AND perhaps figger out how to test tubes not on the roll chart
Yeah, that's fairly easy too as long as you have a few of the tube specs. They explain it in the manual. I sometimes forget to ground one side of the heater...they sort of mention that in passing....
With power tube testing....
Keep in mind that transconductance testing is a test best done in CLASS A , SINGLE ENDED.....
With that being said.... Doing a "real life condition" 450V test is not valid.... Tubes such as 6L6..ect will not bias into CLASS A at those higher voltages... So what do you expect for results??? A broken waveform due to cut-off ???? I would like to see what meter would give the RMS AC current average for that???
ALso....small signal injection is useless for power tube gm testing...The gm varies durring dynamic operation over the AC swing of the load-line.... SO large signal injection is more accurate...
Most of the old school tube manuals have defined the power tube transconductance testing to be done at typicall 250V/250V at a specified input grid bias.... This means 250V plate 250V screen...
This is actually a great spot for testing small signal injection... First if you are running your valve CLASS A , then it is right on center with symmetrical operating conditions... If you are running your valve in CLASS AB like 450V to 500V...your also in luck since the 250V/250V test will be the geometrical center of swing, thus will show the average gm you would get over full large signal operation at voltage twice as high...
Chris
Keep in mind that transconductance testing is a test best done in CLASS A , SINGLE ENDED.....
With that being said.... Doing a "real life condition" 450V test is not valid.... Tubes such as 6L6..ect will not bias into CLASS A at those higher voltages... So what do you expect for results??? A broken waveform due to cut-off ???? I would like to see what meter would give the RMS AC current average for that???
ALso....small signal injection is useless for power tube gm testing...The gm varies durring dynamic operation over the AC swing of the load-line.... SO large signal injection is more accurate...
Most of the old school tube manuals have defined the power tube transconductance testing to be done at typicall 250V/250V at a specified input grid bias.... This means 250V plate 250V screen...
This is actually a great spot for testing small signal injection... First if you are running your valve CLASS A , then it is right on center with symmetrical operating conditions... If you are running your valve in CLASS AB like 450V to 500V...your also in luck since the 250V/250V test will be the geometrical center of swing, thus will show the average gm you would get over full large signal operation at voltage twice as high...
Chris
cerrem said:
Yes, agreed.
A Hewlett-Packard type 3400A RMS meter would. With a pair of matched thermocouples in the feedback loop, the true DC heating power of a waveform is established. Square waves and waveforms with a crest factor ratio of 10:1 full scale are valid. (100:1 at 1/10th scale) That's why I chose it for the Gm indicator on my industrial tube tester. But such a distorted measurment would indeed be virtually useless.
Re: Re: Practical Wireless
Hi Kevinkr,
Ill post in in the next few days, my friend and I split up the stack of PW's, and I think hes got it.
Seeing as they are quite old, I assume I am ok to scan in the article and post it here? could a moderator confirm that for me please?
Im not sure im ready to give them away right now, but I was thinking of starting a topic with all the old schematics and designs from the Practical Wireless copies I have, and other peoples of course. It certainly interests me, and maybe it will be nostalgic for the older members
Cheers
Charlie
kevinkr said:
Hi Charlie,
Please post! I would definitely be interested and if you are ever looking for a new home for some of those PW you scored think of me..
Hi Kevinkr,
Ill post in in the next few days, my friend and I split up the stack of PW's, and I think hes got it.
Seeing as they are quite old, I assume I am ok to scan in the article and post it here? could a moderator confirm that for me please?
Im not sure im ready to give them away right now, but I was thinking of starting a topic with all the old schematics and designs from the Practical Wireless copies I have, and other peoples of course. It certainly interests me, and maybe it will be nostalgic for the older members
Cheers
Charlie
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