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Old 19th November 2004, 08:36 AM   #1
garbage is offline garbage  Singapore
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Question c3g connections

hi all

i am getting lower current than stated on datasheet of c3g.
just wondering if i connected it correctly as a triode strapped pentode.

datasheet can be found here

as a triode strapped pentode,
i have connected Ua = U2 = anode voltage, U3 = 0v, U1 = grid, pin 5 and 7 to cathode.

is that right?

cheers
garbage
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Old 19th November 2004, 09:29 AM   #2
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Garbage,

I've been posting in a lot of your threads... I assure you I'm not following you around

Pin 1: heater
Pin 2: g3 - tie to anode
Pin 3: anode
Pin 4: g2 - tie to anode
Pin 5: cathode
Pin 6: grid
Pin 7: cathode
Pin 8: heater

(valve pins are numbered clockwise with from the key/gap from bottom view)

What are the anode-cathode and g1-cathode voltages you are measuring, and the current? Sometimes valves deviate a little from spec.
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Old 19th November 2004, 09:37 AM   #3
Stixx is offline Stixx  Germany
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Default C3g

Quote:
i have connected Ua = U2 = anode voltage, U3 = 0v, U1 = grid, pin 5 and 7 to cathode
Hi Garbage,

don't know whether I can be of much help, but since I am in the process of building a headphone amplifier using the C3g , I might as well post part of my original schematic. This is how the originator of the schematic, one Mr. Siemens, wired things up.

Good luck,
Oliver
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Old 19th November 2004, 12:54 PM   #4
garbage is offline garbage  Singapore
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Default Re: C3g

Quote:
Originally posted by audiousername

I've been posting in a lot of your threads... I assure you I'm not following you around

Pin 1: heater
Pin 2: g3 - tie to anode
Pin 3: anode
Pin 4: g2 - tie to anode
Pin 5: cathode
Pin 6: grid
Pin 7: cathode
Pin 8: heater

(valve pins are numbered clockwise with from the key/gap from bottom view)

What are the anode-cathode and g1-cathode voltages you are measuring, and the current? Sometimes valves deviate a little from spec.
i realised, and i appreciate your replies, no worries mate.
i only measure the anode voltage and the drd choke with current passing thru it. the voltage is 182.3 and 7.36mA with 2.7v bias.

will follow your suggestion to measure the p-k voltage and g1-k voltage.

Quote:
Originally posted by Stixx


don't know whether I can be of much help, but since I am in the process of building a headphone amplifier using the C3g , I might as well post part of my original schematic. This is how the originator of the schematic, one Mr. Siemens, wired things up.

Good luck,
Oliver
it's a great help. it is a triode strapped pentode right? i notice from another datasheet that pin2 is connected to pin 5/7 too.
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Old 20th November 2004, 07:40 AM   #5
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That's odd. From ~180Va-k and ~-3Vg1-k you would be expecting about 12mA of current, almost twice what you are getting!

This is a strange one....

Don't worry about measuring the voltages, what you told me is fine
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Old 22nd November 2004, 04:18 AM   #6
316a is offline 316a  England
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Default Hmmm...

Quote:
Originally posted by audiousername
That's odd. From ~180Va-k and ~-3Vg1-k you would be expecting about 12mA of current, almost twice what you are getting!

This is a strange one....

Don't worry about measuring the voltages, what you told me is fine

A strange one ? Not really . I'd put this down to device variation which is a typical of high gm valves . If it's not a new one then there also may be the possibility the valve under test is a little on the weak side

cheers

316a
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Old 22nd November 2004, 05:17 AM   #7
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Default Re: Hmmm...

Quote:
Originally posted by 316a
A strange one ? Not really . I'd put this down to device variation which is a typical of high gm valves . If it's not a new one then there also may be the possibility the valve under test is a little on the weak side
Of course what you're saying is correct. Although 17mA/V isn't super-high, device variation is always something to consider with high transconductance valves.


Garbage,
You could always just swap the valve drawing too little current with the other channel or a spare. I can't believe I hadn't said it before. It should have been the first thing I said!
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Old 22nd November 2004, 09:55 AM   #8
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Default Re: Re: Hmmm...

Quote:
Originally posted by audiousername


Garbage,
You could always just swap the valve drawing too little current with the other channel or a spare. I can't believe I hadn't said it before. It should have been the first thing I said!
right, i actually wanted to do that over the weekend. i have 4 in all to play around with.

but was pretty tied up with sanding the aluminium panels for the chassis.

i did solder pin 2 to cathode as Oliver suggested, that raised current to 8.15mA, but could be due to the batteries losing some charge. i measured across the batteries and they are 2.66v.

cheers
garbage
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Old 16th October 2010, 08:51 AM   #9
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Have you finished the amp yet? Can you share your impressions after couple of years?
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