Tube socket extension cord cable?

[Axtman]

I considering building a tube socket extension cord using an empty tube bases, wire cable and sockets.







The purpose of this device is so I can check voltages and bias on different tubes without opening up the amp and without trying to crawl around under the dark chasis.

I don't like the individual cables and would perfer to make it neater. Can I just use some Cat 5 cables or do I need thicker guage wires?

[Helmholtz]

Two concerns:

1) The dielectric strength of the wire insulation must be able to cope with high voltages. First there is the DCV given by B+ and with signal the peak plate voltage is about twice that value, say up to 900V peak (and more with some amps).

2)The cable adds inductance and capacitance which may give rise to HF oscillation. When oscillating, peak plate voltages may get as high as 2kV.

[Leo_Gnardo]

I considering building a tube socket extension cord using an empty tube bases, wire cable and sockets. - - - - I don't like the individual cables and would perfer to make it neater. Can I just use some Cat 5 cables or do I need thicker guage wires?

Consider please, what current it takes to run the filaments in whatever tube you plan on plugging into your "extension." Then, multiply that figure by a factor of say, 6 to 10. Because you can expect a large current surge when tubes are lit up cold. Cold filaments draw lots of current until they start to heat up, a current pulse that can last half a second. Not much time admittedly, but it's enough to destroy a cable - and connectors - if they are not of sufficient size. I can imagine a carefully prepared CAT cable to go up in smoke when starting up an amp with output tube(s) on a remote test stand attached with such cable.

Overall I think this isn't a good idea. But don't let that slow you down. Maybe you're on to something big, and before long everybody will be doing it like you. Have fun!

[Chuck H]

Indeed! To responses thus far.

Not sure where you'll find 20ga nine conductor cable with 2KV insulation!?! And there's still the matter of the bundled leads inducting and capaci (ah?) tating

[mozz]

Any good tv repairman worth his salt, opps, nevermind. Look for these in old tube caddies or repair benches, they come in all sizes.

[Axtman]

Thank you for everyone's responses but here is the problem and the need for the "extension cord".

[nosaj]

Thank you for everyone's responses but here is the problem and the need for the "extension cord".

The problem here is you don't want to do exactly what you should do and that is to remove the chassis. Half the time you will have to do that anyways to change the bias.
nosaj

[Enzo]

And as to crawling around under the dark chassis, just turn the amp over and put the handle on the benchtop. Now the tubes are facing up and easily visible.

[J M Fahey]

Build it if you wish but out of real cable, proper gauge and insulation.

Of course, use as short as possible.

No need for cable stretching to limits, but,say, 15-20 cm tops-

[Chuck H]

I've never been inside one of those, but might there be a way to simply recess the sockets a little? That might be easier, and certainly in the long term, than building purpose made tube socket extensions and having to mount them somewhere or just have the tubes flopping around. Not to mention the potential safety and electrical/electronic matters that may need trouble shooting in the process.

[J M Fahey]

They make chassis as short as they can, leaving only enough wiggle space to replace tubes.

I bet if they recessed sockets, they would make it even shorter.

[Chuck H]

They make chassis as short as they can, leaving only enough wiggle space to replace tubes.

I bet if they recessed sockets, they would make it even shorter.

Well, yes. But I'm talking about a retrofit at this juncture. Use some washers or standoffs to remount the sockets 'up in' the chassis by another quarter inch or whatever. Maybe the socket holes have to be opened a little so everything fits without trouble. Just not a big deal I think. I may be wrong but I perceived from the tape measure photo that getting the tubes out is a problem?

EDIT: Or, like Jason said, just accept that to remove the tubes you need to remove the chassis from the cabinet. How often will the tubes need to be removed? Once a year at most? And as noted, whenever that's done the chassis will be out for a bias check/adjustment anyway. As to testing, just do as Enzo said and flip the amp over. The tubes aren't orientation sensitive. This is still better than tubes wagging around on cords I think.

[Mick Bailey]

I've used the very same method as the OP suggests. A salvaged tube base with some hefty hookup wire and then part filled with epoxy, plus an octal relay base. I never had a single problem with using this, but YMMV, as they say.