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Your own tube tester

C

Chessycreek

New Member
Does anyone here who doesn't repair gear professionally have their own tube tester. I have an opportunity to buy a Eico 667 in good working order. I am about to dive into building my first tube power amp and wasn't looking for this kind of gear - it just showed up. As new tube are becoming harder to come by (thanks putin), I was wondering if this might be a reasonable acquisition.

I am kind of a tool hound anyway. Don't need much encouragement.

Thanks
 
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If tube audio is your interest, it is good to have, I have the same model as a backup, and it will not lose value, if cared for.
 
I also have a 667 and have been using it for years at this point. Mostly works fine, just make sure you get the most current charts from BAMA. There are a few random tubes that the chart is simply wrong for. The 7199 happens to be one of them. Making your own settings is not very difficult though.

If you need to test pre-octal big pin tubes, its not difficult to make either single socket adapters or an external box with a full set of pre-octal types. Any types not listed in the 667 charts you can use the 666 charts for. Same machine, just different sockets and a couple extra switches. I built an adapter for mine so any 4-7 pin tube can be tested with no fuss.
 
I have a Eico 666 tester. I don’t use it much anymore, but when I need it, it’s there.

I say grab the 667 if the price is right. These don’t go for big bucks like the Hickoks, but they’re a solid tester for usually a pretty decent price.
 
Had one and got rid of it. Have had for years all the parts to build a digital one and cannot find the motivation to make one.

Tube's working can change a lot depending on under what conditions it is being used - it may test bad in the tester yet work fine for years to come in the circuit. Or the other way round - test fine yet won't work.

I've had more use out of a distortion meter to weeding out bad tubes in circuit.(I've got a HP 339A) A good digital oscilloscope ($$$$) can do as well, the normal el-cheapo oscilloscpes are good for fault hunting but not for more.

You may want to read the last post in this thread: https://forum.intactaudio.com/viewtopic.php?f=15&t=538 basically mentioning that a change of 40% in Gm and 20% in mu can be regarded as normal variation.

The US military discovered that more tubes fail by repeatedly being taken out of their sockets to test than if they were left in place and a "test through" in circuit was used.

A tube tester is only needed if you start buying used tubes in quantities and need to test them quickly.
 
Many IECO's were sold as kits. Not sure about the 667. If so, having the assembly manual would be a good thing. You can use the assmbly manual to locate the parts and test for bad and out of spec components much easier.. Having all of the docs is a great thing. Make sure the meter movement is in good order and if you buy it you'll want to see if the chart is the latest.

I came across a Knight KG-600B tube tester several years back and that was a kit. It came with all of the books including an assembly manual and a substitution manual. IMHO the documentation is just as important as the tester. The assembly manual helped me go through all the resistors and replace all that were out of spec, cleaned the switches and sockets, cleaned and lubed the chart mechanism, and replaced the only cap. It is a basic emission tester (as is the 667 I assume) and does a short test and gas test. Serves me very well. I haven't found a tube that it won't test yet. The tester will help weed out obviously bad tubes. Most of the bad tubes I've found are shorts, but I do find an occasional weak one. I compare weak ones to a good tube when they turn up to be sure it isn't a false reading as all testers aren't perfect testers for every tube. Trust but verify. I keep some bad examples and mark them in case I need to remind myself as to what a bad one of that type looks like in the tester.

Others are correct that the real test is when you put the tube into use. I use my ears and measure voltages (and currents where appropriate) when I get that far. What I never do is put untested old manufacture tubes into my unit. It's just my habit. I use a lot of old manufacture tubes and you just never know the condition without checking on them.

So yes, having a tube tester or access to one is a good thing.
 
The 667 could be had in kit or factory-wired form. Pretty sure mine is a factory wired unit. Assembly and operations manuals can be found at BAMA

Its not an emissions tester either. Its what they called "dynamic mutual conductance". Emissions testers strap all the elements together and test it as a diode. The 667 applies an AC signal to the grid and measures the current swing on the plate.

no its not the final word in tube condition but if you have total unknowns it'll tell you if they are safe to run in an amp, totally wasted, strong, etc. One specific caution I can offer, if you ever get a tube that tests abnormally strong, like the meter pegs into the corner and vibrates, chances are its no good. Every tube I've had that red plated and ran away for no obvious reason tested like that. No other signs of problems though.
 
I have two Hickoks (different models). Besides all the opinions provided above, I just think they are fun to play with and helpful in understanding how tubes work.
 
gadget73 said:
The 667 could be had in kit or factory-wired form. Pretty sure mine is a factory wired unit. Assembly and operations manuals can be found at BAMA

Its not an emissions tester either. Its what they called "dynamic mutual conductance". Emissions testers strap all the elements together and test it as a diode. The 667 applies an AC signal to the grid and measures the current swing on the plate.

no its not the final word in tube condition but if you have total unknowns it'll tell you if they are safe to run in an amp, totally wasted, strong, etc. One specific caution I can offer, if you ever get a tube that tests abnormally strong, like the meter pegs into the corner and vibrates, chances are its no good. Every tube I've had that red plated and ran away for no obvious reason tested like that. No other signs of problems though.
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The Eico is useful for tracking mystery problems to specific tube faults thru deduction, as the various controls track to specific tube pins and a tube pinout chart and deductive reasoning can help solve them.
 
Chessycreek said:
Does anyone here who doesn't repair gear professionally have their own tube tester. I have an opportunity to buy a Eico 667 in good working order. I am about to dive into building my first tube power amp and wasn't looking for this kind of gear - it just showed up. As new tube are becoming harder to come by (thanks putin), I was wondering if this might be a reasonable acquisition.

I am kind of a tool hound anyway. Don't need much encouragement.

Thanks
Click to expand...

I have a 667 and find it very useful, particularly the heater/cathode leakage test.

Keep in mind though it won't test 4 pin tubes such as the 300B, or the 5 pin 807, so if you plan to use triodes or other tubes with pre octal sockets you may need a second tester.
 
You can test 807 as a 6BG6G with a suitable socket adapter. Probably likewise with an adapter for the 300B as a similar octal triode with suitable settings.
 
Pio1980 said:
You can test 807 as a 6BG6G with a suitable socket adapter. Probably likewise with an adapter for the 300B as a similar octal triode with suitable settings.
Click to expand...

Fair enough but that's what the TV7 is for. On the other hand the 667 tests compactrons and magnoval tubes and the TV7 doesn't.
 
I have a TV-7 from a flea mkt that had several for $12 each, your choice. Most folks can't afford one now, adapters are doable and Eicos are affordable, adaptable, and owner serviceable.
 
maxhifi said:
I have a 667 and find it very useful, particularly the heater/cathode leakage test.

Keep in mind though it won't test 4 pin tubes such as the 300B, or the 5 pin 807, so if you plan to use triodes or other tubes with pre octal sockets you may need a second tester.
Click to expand...

adapters are easy to build. Eico made one but they are very rare and expensive. Its stupid easy to make one though. The sockets are all just pin to pin wired, so every pin 1 connects together, pin 2, etc. Can make individual adapters from junk tubes and a socket or put it all in one box like mine is.
 
I don't really see how you move forward with tube equipment without having an essential tool like a tester to make certain the basics are covered. I use a Hickock 800. Very helpful.
 
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