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Old 15th May 2013, 01:12 PM   #121
Pdwhitt is offline Pdwhitt  United States
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The output transformers are labelled in Chinese. Best I can tell, it looks like black is ground, yellow is 4, and green is 8 ohms. Red is P coming from pin 3 on the 6p3p, and blue is B coming from pin 4. Can anyone confirm this?

Thanks!
Paul
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Old 15th May 2013, 06:15 PM   #122
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Quote:
Originally Posted by Pdwhitt View Post
The output transformers are labelled in Chinese. Best I can tell, it looks like black is ground, yellow is 4, and green is 8 ohms. Red is P coming from pin 3 on the 6p3p, and blue is B coming from pin 4. Can anyone confirm this?

Thanks!
Paul
Blue is B+ you can take it from anywhere after the power supply usually at or shortly after the third cap C3 22uf 450V. You can connect the blue to pin4 OR + terminal on C3.

Red connects to pin3 (signal out for output tube)

Output wires

Black is 0 (Neutral) - be sure you get both connected together and run a wire (black) back to your star ground point (bolt on the transformer).

For the output transformer color codes - I'll have to check when I get home, I don't remember which color is which.

Here's a way to tell....
Measure ohms reading from Black to yellow and black to green. The reading with the lowest resistance to common will be your 4 Ohm tap.

Hope that helps.

Cheers,
Bob
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Old 19th May 2013, 03:25 PM   #123
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Hi guys, was wondering if anyone else has tried the diode mod Bobrown has suggested.
With further reading on other posts on the subject, i got the impression, at least with the 5y3 tube that this becomes a solid state rectifier and the tube itself becomes redundant.
Can anyone clarify this for me that i understood this right (Bobrown if your out there, any thoughts on the subject).
If so, i don't see the point in buying a new rectifier tube just yet if i try this mod.
In the meantime i have some russian 6p3s tubes and a tocos volume pot i have read good things about on there way, so hopefully can let you all know of any improvements these might add.

Scratch
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Old 19th May 2013, 08:39 PM   #124
Pdwhitt is offline Pdwhitt  United States
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Just finished my 6p3p and will post some pics and building notes later. This can be a very good first diy tube amp if you study the schematic and wiring diagrams. The stock amp looks awesome, is quiet, sounds good, and with a few simple mods (rectifier diodes, new power tubes, and feedback resistors) is plenty loud enough and sounds great!

Paul
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Old 19th May 2013, 08:46 PM   #125
Pdwhitt is offline Pdwhitt  United States
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I ended up with 330k feedback resistors, and these sound about right for my 6p3p. Has anyone tried installing a variable feedback resistor?
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Old 19th May 2013, 09:10 PM   #126
kevinkr is offline kevinkr  United States
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Wire both primaries in parallel or you may fry the transformer. The primary windings are sized based on the primary current when the windings are wired in series for 220-240V operation, when operating on 120V the current consumption will be twice that at 240V which could result in excessive heating in a single primary, the winding current is correct when both are wired in parallel..


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Originally Posted by Pdwhitt View Post
Bob,

The extra pair of red black seem to be identical to the first pair. If i connect 120v AC to the first pair of red black, the second pair reads 120 and all the other voltages (300, 6.3, 5, and 3.15) are correct. If i connect the second pair of red black to 120 wall outlet, then the first pair reads 120, and all the others again show correct voltages. So I guess I will not use the second pair of red black wires, and will secure them out of the way.

Thanks!
Paul
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Old 19th May 2013, 09:31 PM   #127
Pdwhitt is offline Pdwhitt  United States
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Quote:
Originally Posted by kevinkr View Post
Wire both primaries in parallel or you may fry the transformer. The primary windings are sized based on the primary current when the windings are wired in series for 220-240V operation, when operating on 120V the current consumption will be twice that at 240V which could result in excessive heating in a single primary, the winding current is correct when both are wired in parallel..
So, I will put the two red wires together and wire them to one side of the wall AC current, and put the two black wires together and run them to the other side of the AC inlet.

Thank you Kevin!

Paul
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Old 21st May 2013, 07:43 PM   #128
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Quote:
Originally Posted by mr scratch View Post
Hi guys, was wondering if anyone else has tried the diode mod Bobrown has suggested.
With further reading on other posts on the subject, i got the impression, at least with the 5y3 tube that this becomes a solid state rectifier and the tube itself becomes redundant.
Can anyone clarify this for me that i understood this right (Bobrown if your out there, any thoughts on the subject).
If so, i don't see the point in buying a new rectifier tube just yet if i try this mod.
In the meantime i have some russian 6p3s tubes and a tocos volume pot i have read good things about on there way, so hopefully can let you all know of any improvements these might add.

Scratch
Diode mod is there to protect transformer in the case of arc over in the rectifier tube, primarily a safety feature. Does not make the rectifier tube redundant. You keep all the properties of the rectifier tube (slow start & resistance & voltage drop) these all make a difference in performance of the power supply & subsequent circuits.

Arc over in rectifier tube = toasted transformer for this amp, add diodes no more worries.
Of course there are many ways to tame that cat. Some rectifiers are getting pricey so you can protect the rectifier tube and the power transformer with this simple $.24 mod.

Cheers,
Bob
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Old 23rd May 2013, 10:33 AM   #129
6n1 is offline 6n1  Spain
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Default Bad expierence with tube seller

Hi there , I have had a bad expierence with a Russian tube seller :ruTube.com I ordered some capacitors and tubes payed trough paypal and started to wait after 3 weeks I cancelled and this guy ( Nikolay ) sended me an Email explaining that there were holidays in Russia , so he convinced me I opened the acount and since then nothing he does not aswer my Emails . If you guys have some good experience post the names . With regards Paul
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Old 23rd May 2013, 11:12 AM   #130
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Quote:
Originally Posted by 6n1 View Post
Hi there , I have had a bad expierence with a Russian tube seller :ruTube.com I ordered some capacitors and tubes payed trough paypal and started to wait after 3 weeks I cancelled and this guy ( Nikolay ) sended me an Email explaining that there were holidays in Russia , so he convinced me I opened the acount and since then nothing he does not aswer my Emails . If you guys have some good experience post the names . With regards Paul
The holiday is May day (May 8th & 9th) - 2 days off work. I've had to wait a month from a few Russian sellers to get parts, and others I've only had to wait a week or so. Last order from RU took a month, I've always gotten parts.

Cheers,
Bob
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