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Old 26th October 2010, 12:06 AM   #11
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by yagoolar View Post
How can I tell they are "series 3"?
I no longer remember the specifics unfortunately - you'll need to Google for additional information - probably specific date code range. I gave up on them 10yrs ago and haven't looked back.

Consider them as fodder for experimentation and if they are better than that consider yourself fortunate..
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Old 26th October 2010, 09:36 AM   #12
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The tubes have the new logo: latin letter "S" not cyrillic "C".
BTW.
Your remark made me reconsider NOS 6C4C as an output triode.

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Old 26th October 2010, 04:37 PM   #13
kevinkr is offline kevinkr  United States
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Originally Posted by yagoolar View Post
The tubes have the new logo: latin letter "S" not cyrillic "C".
BTW.
Your remark made me reconsider NOS 6C4C as an output triode.
They might be late enough not to have the issue.. Mine were either winged "C" or Svetlana branded.

I think the 6C4C might be a safer choice, it's basically equivalent to the 6B4G, note the maximum plate voltage is only ~250V (fixed bias -45V) for these types and you'll get maybe 3W out in A1.
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Old 26th October 2010, 06:43 PM   #14
45 is offline 45  Italy
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Originally Posted by kevinkr View Post
I think the 6C4C might be a safer choice, it's basically equivalent to the 6B4G, note the maximum plate voltage is only ~250V (fixed bias -45V) for these types and you'll get maybe 3W out in A1.
Kevin the 6C4C can take up to 360V anode voltage and as far as I have seen (directly) up to 16-17W without any problem. It's an improved copy of the RCA design, IMHO. The higher plate dissipation actually stands also for NOS 2A3's and good quality chinese production (like Golden Dragon and Billington Gold which I think come from the same factory...). You can get easily 4W and up to 6W (in class A2 using a simple source follower).
Actually there are some old American amps which used the 2A3's at 22W plate dissipation! I cannot remember the name now...they were from DIYers
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Old 12th November 2010, 05:17 PM   #15
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Question C3g + 6C4C parafeed with mains xformer as OPT - sim

Kids are at their garndmother, there was a national holiday in Poland and at last I had time to proceed with the work with an amp. The result is the below shown schematic.

On one Polish forum I found interesting discussion on using mains transformers as OPT. www.trioda.com • Zobacz w?tek - trafo sieciowe jako g?o?nikowe. I measured inductances of primary and secondary windings of one toroid mains transoformer (50VA / 230V / 9V). The values are shown on the schematic.

On the next picture frequency response is shown, as simulated in LT Spice IV.

I also simulated the circuit with LED biased 6C4C (4 x 26 LEDs), yet the outcome is not satisfactory. Still some analysis to be done.

Comments are welcome.
Attached Images
File Type: png 20101112 C3g 6C4C noled PF.png (29.0 KB, 644 views)
File Type: png 20101112 C3g 6C4C noled PF 1-1MHz.png (60.1 KB, 635 views)
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Old 12th November 2010, 07:02 PM   #16
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The frequency response attached in the previous post seems unreal. What is worse, I cannot replicate the result.
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Old 12th November 2010, 08:43 PM   #17
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I am a bit confused: why those two circuits make such a difference? Only a cap position changed.

Oh, and the OPT is not mains / power xformer. It is custom SE OPT: two primaries + two secondaries. In the schematics pris and secs are connected in parallel respectively.

20101112 C3g 6C4C noled PF cap cath-trafo.png

20101112 C3g 6C4C noled PF cap ano-trafo.png

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Old 12th November 2010, 09:32 PM   #18
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well, I was about to say that the ones I have seen had the cap connected to ground

and shouldnt the cap be bigger ?

what does two secondaries mean ?
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Old 13th November 2010, 02:16 PM   #19
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Find attached a circuit with C2 in range of 1uF to 100uF. Dark green line on the left refers to 100uF; more to the right - C2 goes down to 1uF
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File Type: png 20101112 C3g 6C4C noled PF cap ano-trafo 1u-100u.png (68.3 KB, 561 views)
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Old 13th November 2010, 02:26 PM   #20
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Here you have the simulation with the other variant. Strange - the response does NOT depend on the C2 value. My guess is it is not real.
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File Type: png 20101112 C3g 6C4C noled PF cap cath-trafo 1u-100u.png (61.0 KB, 544 views)
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