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garbage 19th November 2004 09:36 AM

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

audiousername 19th November 2004 10:29 AM

Garbage,

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

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.

Stixx 19th November 2004 10:37 AM

C3g
 
2 Attachment(s)
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

garbage 19th November 2004 01:54 PM

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 :D

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.

audiousername 20th November 2004 08:40 AM

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 :)

316a 22nd November 2004 05:18 AM

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

audiousername 22nd November 2004 06:17 AM

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!

garbage 22nd November 2004 10:55 AM

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

yagoolar 16th October 2010 09:51 AM

Have you finished the amp yet? Can you share your impressions after couple of years?


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