[mike s]

At the weekend I manage to find a few hours to continue my interrupted restoration of a 1947, or thereabouts, Vortexion guitar amplifier.

http://mike.wepoco.com/Home/retro-ge...vortexion-eg20

When I left if a few months back it would amplify weakly, but turning up the volume control just increased distortion, and the treble control didn't do anything.

Anyway, to cut a long story short. I switched it on once again, connected signal generator to the input and scope to the output and placed my hand on each of the output valves. Two were much hotter than the other two. Checking the anode voltages showed they were drawing more current. Not sure if it was a hunch, or an accident, but I prodded the wire connecting the grids of the two hot CL33 and hey presto the output signal increased significantly.

Turns out the very carefully hand wiring had put the rubber insulated wire in direct contact with the aluminium chassis and in 60 years the black rubber had changed from an insulator to a resistor.

I should probably replace all the wires, which is a shame as it is so tidily built. Anyway I'll have to change quite a few as I want to change from series heater CL33 to a quad of EL33 for the output.

After decades of mocking "audiophile wire", I must now accept that not all wire is good.

[Big Bad Bob]

On 04/26/11 14:37, mike s so wittily quipped:
Turns out the very carefully hand wiring had put the rubber insulated wire in direct contact with the aluminium chassis and in 60 years the black rubber had changed from an insulator to a resistor.

thanks for that - it's something that 'old equipment restoration' buffs
can make use of in the future. Modern wire uses teflon or plastic for
insulation. Old wire used rubber (and often had a chunk of cloth
running the length of the wire, not sure why, but you can identify it
that way). Newer wire insulation (especially teflon) should withstand
long-term high temp better, but the old stuff is in a lot of old tube gear.

[Pt]

On Apr 26, 4:37*pm, mike s wrote:

After decades of mocking "audiophile wire", I must now accept that not all wire is good. *

It isn't the wire, it's the insulation.
Put shrink wrap on the wires with bad insulation.

Pt

[Phil Allison[_3_]]

"Big Bad Boob is at it again"


Modern wire uses teflon or plastic for insulation.

** It is very rare to see teflon coated wire in anything - the stuff is
expensive, hard to work with and only worth while in devices that operate at
unusually high temperatures.

One occasionally sees silicone coated wire used but the overwhelming
majority of plastic costed wire uses good old PVC = polyvinyl chloride.



..... Phil

[Phil Allison[_3_]]

"mike s"

Turns out the very carefully hand wiring had put the rubber insulated wire
in direct contact with the aluminium chassis and in 60 years the black
rubber had changed from an insulator to a resistor.

I should probably replace all the wires, which is a shame as it is so
tidily built.


** You might like to get some of this from Farnell:

http://uk.farnell.com/pro-power/bsr3...3?Ntt=146-5863

Made of silicone, feels soft and look just like rubber and several colours
available.

The 3A current rating is nonsense - it can handle 10A and only rise about
10 degrees C in free air.



.... Phil

[Big Bad Bob]

On 04/26/11 17:39, Phil Allison so wittily quipped:
"Big Bad Boob is at it again"

you are an idiot.


Modern wire uses teflon or plastic for insulation.

** It is very rare to see teflon coated wire in anything - the stuff is
expensive, hard to work with and only worth while in devices that operate at
unusually high temperatures.

military equipment often uses EXCLUSIVELY teflon wire. You are an IDIOT
for not knowing that.

[Big Bad Bob]

On 04/26/11 20:03, Phil Allison so wittily quipped:

... Phil

you're STILL an idiot. Troll.

[Phil Allison[_3_]]

"Big Bad Boob is a ****ing IMBECILE"


Modern wire uses teflon or plastic for insulation.

** It is very rare to see teflon coated wire in anything - the stuff is
expensive, hard to work with and only worth while in devices that operate
at
unusually high temperatures.

military equipment often uses EXCLUSIVELY teflon wire.


** Shame the topic here is tube amps and the like, not Space Shuttles.

http://www.hookupwire.org/Teflon_Wire.html



...... Phil

[Big Bad Bob]

On 04/28/11 00:23, Phil Allison so wittily quipped:
"Big Bad Boob is a ****ing IMBECILE"

careful - your FAIL is showing.

military equipment often uses EXCLUSIVELY teflon wire.


** Shame the topic here is tube amps and the like, not Space Shuttles.

http://www.hookupwire.org/Teflon_Wire.html

troll harder, please. you're boring me. Space Shuttles aren't
military, anyway. NASA is a civilian organization. Besides, there has
been a lot of "old school" tube gear out there used by the military,
primarily COMM stuff. Lots of audio there.

you are not the topic police anyway. your trolling is about as
off-topic as anyone can think up. ****head. Grow a brain.