Metropoulos Forum

I know nothing about tube testers but a friends dad hit me up with an old 60s B&K 625 Dyna Tester. Merry Christmas he says after he learned about my little amp hobby. Any good?

No pics??? You got me all excited there.......

I have an old Eico tube tester (probably also from the 60's) that I use to check stuff I pull from old stereos and such. Everyone claims they don't run the tubes at high enough voltage to really see if they'll last in a guitar circuit but at least you'll have some idea of whether the tubes are shorted or how far gone they are.

It looks like some junky old suitcase from the outside. Andy Ill probably me PMing you on how the hell to use it when I have need.

Now I need some nice old tubes to test with it.

No instructions came with it, huh.....ouch......hopefully they're somewhat standardized as to the controls, etc.......

There are huge differences with the tube testers from the old days.

Some simply testers ONLY are measuring, whether the filament is broken, if not they say: Tube OK

On the other hand there are testers, testing so much different tube's parameters, you'd never need to know

In the past I've had a Hickok 600A and a russian L3-3 - but after a while I've sold both again, after I've build my own tube tester.

Maybe not bad, if you take a look to this web link:

http://www.tone-lizard.com/Tube_Testers.html

Larry

Yes, that's a good tester. I'm pretty sure that's a mutual conductance tester. I have a Dyna 707, which is basically just an upgraded version. While not quite as versatile as Hickocks, Dynas are much easier to use.

From what I've read, Dyna simply added more sockets to the later versions like mine to test "newly" invented tubes. Post a pic. If the top plates of our testers are similar, you can probably use my info to get you started.

The tone lizard site is great for info.

Oops, I was wrong. I just read on the tone lizard site that your tester simply tests for emissions. Still good enough for a down and dirty "Is the tube usuable?" kind of test.

I also read that your model has a VOM as well?

The manual is in there that lists what to set all the rotary knobs to for each tube type. I just dont know what the hell Im measuring

Yeah it has a VOM

There are guys on Fleabay that sell repro manuals for al lot of testers. Personally, I scored a nice shape, working Hickok 539C from my work (a factory) Apparently, industrial electronics used to use tubes in vibration analysis and other egghead engineering shenanigans. It was in an old electronics workshop and the old geezer with a zillion years seniority didn't even know it was there, so I "liberated" it.

Most good testers test "mutualconductance", which is a highbrow term for emission quality. There are specific numbers giver as per tube type and tube is considered good if it falls within these certain coordinates. Most old testers are usually in need of re-calibration due to cap drifting etc...so you may still have a good tube-tester is just reading it inaccurately.

My tester came with two separate manuals. One manual lists the tube charts and the other is the actual "owner's manual". It has the schematic, general info about what the tester is doing, directions for testing tubes and directions for calibrating. If you order a manual, make sure it contains calibration procedures. In my unit, I replaced the electrolytics and the 6BN8 found inside. The 707 also uses an 83 rectifier tube but I replaced with a custom solid state unit that has the appropriate voltage drop. If yours uses an 83, I've a spare tube you can use.

When you calibrate it with external resistors, ante up for good precision ones. The adjustments are VERY sensitive to the slightest tweak of a screwdriver. I'm sure you can't wait to stick your hands around the exposed high voltage stuff (gotta adjust tester when it's powered up).