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Cordovox CG Trouble Shooting Unlit Tubes

VASANTORO

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Hi All
None of the six tubes in the "Quality Control" section of my tone generator (see tube chart attached) will light up.
Opened the tube panel to examine wiring and rear of tube sockets. There is no evidence of failure or damage.
Any advice on trouble shooting this issue is greatly appreciated!
Thanks in advance...

I am the original owner of this instrument ....purchased in May of 1965
 

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that is basically the audio pre-amp section

none/zero of the tubes heater elements lighting up would indicate
the 12 volt power supply voltage is not reaching that shared circuit

that is not like a superheterodyne tube radio where the
total heaters circuit = 110 volts.. in the c-vox if one tube is
burnt out that is the only one out, the rest of the heater
circuit is not dependent on every tube element being whole

i am assuming the 6x8 and 6fh8 (6 volt) tube sections
DO still light up, further indicating this is not a catastrophic
power supply failure, but a localized one

you should be able to use tube pin-out info to help you
focus on the heater part of the circuit, then trace it out
and test back toward the power supply to find the
open component

there was a schematic posted by CAPS on the forum, if you can
find that it will help a lot
 
Thank you for the quick response and the information...
Yes....all of the 6 volt tube section lights up.

I only have a limited knowledge of electronics ( had to lookup superheterodyne! ) but you
have given me a clear direction to proceed. A schematic would be a big help but I could
only find a Cordovox manual and an interesting promotional sales brochure posted by CAPS.....(?)

Trouble shooting is postponed for a bit as the amp and tone generator
occupy the floorspace I use for my Holiday Lionel train layout. The amp and generator are
squirreled away in a closet for now. The perils of living in a small house.

I hope you are well and have an enjoyable holiday season......
 
back in Electronics shop during high school, we each built
from a rough kit of components one if those "super" radio's that
taught us to add up to 110 (volts) and when a tube went out
in one of those types, yes it was like a string of old christmas lights
gone dark where you had to find the bad one

enjoy yoiur trains and holidays.. we can work on this again in the new year
 
that is basically the audio pre-amp section

none/zero of the tubes heater elements lighting up would indicate
the 12 volt power supply voltage is not reaching that shared circuit

that is not like a superheterodyne tube radio where the
total heaters circuit = 110 volts.. in the c-vox if one tube is
burnt out that is the only one out, the rest of the heater
circuit is not dependent on every tube element being whole

i am assuming the 6x8 and 6fh8 (6 volt) tube sections
DO still light up, further indicating this is not a catastrophic
power supply failure, but a localized one

you should be able to use tube pin-out info to help you
focus on the heater part of the circuit, then trace it out
and test back toward the power supply to find the
open component

there was a schematic posted by CAPS on the forum, if you can
find that it will help a lot
Oh my gosh... How do you remember this stuff Ventura?. I posted a partial schematic like 20+ years ago on the predecessor of this forum. I no longer have it as I gave the service manual away years ago. As I recall though, the 12Volt tubes were wired in parallel direct to the 12 volt winding on a transformer so the fault should be relatively easy to find. The wiring was pretty straight forward.
 
Oh my gosh... How do you remember this stuff Ventura?. I posted a partial schematic like 20+ years ago
lol

and i cannot remember most peoples names,
could never remember a phone number whispered in my ear
can't remember where i set my keys down
(which is why they are carbiniered to my first left beltloop)
couldn't remember which side handle was the hot or cold water
till i was like 40 years old

but i remember 1000 of songs and riffs..
you can drop me anywhere i have ever been and i
won't need a city street map to find my way back to
the turm above the heiligenberg across from the Castle
 
back in Electronics shop during high school, we each built
from a rough kit of components one if those "super" radio's that
taught us to add up to 110 (volts) and when a tube went out
in one of those types, yes it was like a string of old christmas lights
gone dark where you had to find the bad one

Ah, that's familiar. In the 1960s my father worked as an electrician at a steel works, mostly working on power control for motors, floodlighting, etc. But as an apprentice he had a time working on the computer, which was made with tubes. He said it was like Christmas lights, and if it stopped working you had to rush to find the tubes - as long as only one tube was broken it was a matter of working along the line of tubes, swapping them out one after another until it started working again. Two tubes broken meant removing them all to put in a tube tester. I seem to recall the swapping out was done live, though that seems a bit unlikely through the prism of 21st century safety attitudes. (NB: I used 'tubes' but we call them 'valves' in the UK)
 
lol

and i cannot remember most peoples names,
could never remember a phone number whispered in my ear
can't remember where i set my keys down
(which is why they are carbiniered to my first left beltloop)
couldn't remember which side handle was the hot or cold water
till i was like 40 years old

but i remember 1000 of songs and riffs..
you can drop me anywhere i have ever been and i
won't need a city street map to find my way back to
the turm above the heiligenberg across from the Castle
Wow, I have made that hike from the town up to the turm along philosophers way several times. Good times!
 
lol

and i cannot remember most peoples names,
could never remember a phone number whispered in my ear
can't remember where i set my keys down
(which is why they are carbiniered to my first left beltloop)
couldn't remember which side handle was the hot or cold water
till i was like 40 years old

but i remember 1000 of songs and riffs..
you can drop me anywhere i have ever been and i
won't need a city street map to find my way back to
the turm above the heiligenberg across from the Castle
I would be happier if I could remember tunes rather than where my keys are.
 
Wow, I have made that hike from the town up to the turm along philosophers way several times. Good times!
the Philosophenweg

yes, i wondered if anyone would "get" the reference


i loved poking around Heidelberg
 

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