3 prong on tube tester?

[drewl]

Stupid question, but I should put a grounded three prong cord on a tube tester right?

I haven't worked on one of these since the 80's.

[R.G.]

Depends. Do you feel lucky?

[Tom Phillips]

With a properly installed three prong power cord plugged into a properly powered outlet the exposed metel parts of the equipment will be connected to earth ground. That will protect you by preventing those exposed metal parts from becoming electrified if there is a failure such as loose wiring inside the device. Since this principle applies to a tube tester just as it does to other equipment then your tube tester would be safer if you install a grounded three conductor power cord.

[drewl]

Common sense suggests a grounded chassis, didn't know if there was anything special or different that needed to be done.
After looking inside and at the schematic I can see there is not.

[TomCarlos]

And this is why we do not "toss" old threads. I have a couple tube testers that need new line cords. And I was asking myself, why is it that on all the videos I see where guys are refurbing testers, no one uses a 3 prong cord?

[DrGonz78]

My tube tester was modified to have a 3 prong power cable. I got lucky because they did a good job. I got a good one. Only had to change out the mercury rectifier 83 or something. I added 3 prongs to all of my test gear that needs it.

[Jon Snell]

All of my valve testers, appart from one, that I have restored; AVO CT160, AVO twin panel Mk1 and my Mullard E7600 came with a three core power cable. Admittedly they had round 5Amp plugtops, now fitted with fused 13A plugtops with 3A fuses.
The AVO Twin Panel Mk1 is dated circa 1935 always has had a three core mains lead because the chassis is exposed metalwork.
The only one with twin cable was a B&K Dynajet 707 and as it is in a wooden box, I restored it and sold it on as it was.

[TomCarlos]

Thanks guys.... I appreciate the replies.

From a Facebook post, someone alerted me to the Sencore TC 136. Take a look at that schematic. The incoming line does not go to the mains transformer? So I guess the lesson here is to "know your equipment." When safe to do, ground the chassis and case.

[DrGonz78]

How many times do you hear about someone being electrocuted from crappy test gear? Once would be too many. It’s a threat if you are not coupled to the AC main’s with a transformer. At least a ground connection should help but there is still no isolation without an isolated transformer. A short run of wires helps too.

[g1]

It looks to me like for Tom's circuit in post #8, earthing the unit would mean the unit would always be on, via function switch 'A' (neutral connects to earth at mains panel).