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Boyuu EL34 A9 Tube Amp
Boyuu EL34 A9 Tube Amp
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Old 3rd February 2015, 11:16 PM   #21
sundaycyclist is offline sundaycyclist  United Kingdom
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Hi chaps. Apart from soldering my fingers a few times I'm progressing! I can't make out from the diagram or the photos what the correct pins are to connect the power supply to for both the EL34 and 6N9PJ valves. I think the EL34 may be 2 and 7 but can someone tell me what the pins are for both vales please?
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Old 4th February 2015, 02:46 AM   #22
mdamp is offline mdamp  Australia
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EL34 Pins 2,7 are for heaters, 3 is connected to opt, 4 is connected to B+ are main power. the 6N9P Pins 7,8 are the heaters and pin 2 is main power. make sure on the EL34 you join pins 1,8 together.
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Old 4th February 2015, 04:30 AM   #23
VictoriaGuy is offline VictoriaGuy  Canada
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Boyuu EL34 A9 Tube Amp
Quote:
Originally Posted by sundaycyclist View Post
Hi chaps. Apart from soldering my fingers a few times I'm progressing! I can't make out from the diagram or the photos what the correct pins are to connect the power supply to for both the EL34 and 6N9PJ valves. I think the EL34 may be 2 and 7 but can someone tell me what the pins are for both valves please?
By 'power supply', you mean the heater/filament supply?

Even with a good schematic, I usually have copies of the tube data sheet (first page) for each tube with me when I'm working...useful for that double and triple-checking.....

You can find those online by searching on 'tube data' for each tube...

I also print extra copies of the schematic and use a highlighter marker to remind me which connections I've made. Everybody will have their own methods of avoiding nasty fireworks.....
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Old 4th February 2015, 05:29 AM   #24
ygg-it is offline ygg-it  Italy
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Quote:
Originally Posted by VictoriaGuy View Post
By 'power supply', you mean the heater/filament supply?

You can find those online by searching on 'tube data' for each tube...
Remember tube datasheet pin out are always from "bottom view", not from the top! and numbering should be clockwise.

Post a detailed photo hand by hand where you are with the kit: it is better we get a look before you switch the power on.
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Old 4th February 2015, 01:30 PM   #25
sundaycyclist is offline sundaycyclist  United Kingdom
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Thanks for the useful info. I've found the specs for EL34 easily. The 6N9PJ was more difficult but I think it goes by different codes too. I'm ready to go now. More later.
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Old 5th February 2015, 12:57 AM   #26
sundaycyclist is offline sundaycyclist  United Kingdom
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I'm nearly done but I have another question. On the output I'm assuming that the black wire is the earth/ground - but which colours go to the 8 and 4 ohm outputs?
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Old 5th February 2015, 04:02 AM   #27
VictoriaGuy is offline VictoriaGuy  Canada
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Looking at the schematic (and knowing how output transformers are wound), I'd measure the resistance from the black wire to the other two output leads. There will be a higher resistance across the whole secondary (0 black wire-8 ohm lead) than from the black wire to the 4 ohm tap.

BTW, I always double-check the transformer leads by measuring continuity (resistance) to make sure I'm working with the correct connections. I wouldn't trust a photo or diagram completely, since checking is only a matter of a minute.
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Old 5th February 2015, 06:24 AM   #28
ygg-it is offline ygg-it  Italy
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Quote:
Originally Posted by VictoriaGuy View Post
Looking at the schematic (and knowing how output transformers are wound), I'd measure the resistance from the black wire to the other two output leads. There will be a higher resistance across the whole secondary (0 black wire-8 ohm lead) than from the black wire to the 4 ohm tap.

BTW, I always double-check the transformer leads by measuring continuity (resistance) to make sure I'm working with the correct connections. I wouldn't trust a photo or diagram completely, since checking is only a matter of a minute.
Mine should be similar to yours.
http://www.diyaudio.com/forums/tubes...eview-mod.html

You should measure like about 1.1 ohm (or about 19 mH) ground to the 8 ohm and 0,8 ohm (or 11,3 mH) ground to 4 ohm. Measurements are not doubling linear but follow exponential rules. Since the resistance are very low, if you have difficulty just put across the primary a 12-24 AC voltage via an extra small transformer and measure the mV AC voltage across the output: the hightest voltage one is for the 8 ohm tap.

In this case you can also determine which will be the primary load. Voltage should be in the ratio of 1:20 for the 8 ohm tap, so resistance in the ratio of 1:400 so (8ohm * 400) you will get 3200 ohm of primary tube load.

OR, in the ratio of 1:28 for the 4 ohm tap so resistance in the ratio of 1:800 so (4 ohm * 800) to get the same 3200 ohm of primary tube load.

If you put 12 VAC at the input of the output transformer you should get 0,6 VAC for the 8 ohm tap and 0,45 VAC for the 4 ohm tap, or values similar to these.

If you put 24 VAC across the input of the output transformer you should get 1,2 VAC for the 8 ohm tap and 0,9 VAC for the 4 ohm tap, or values similar to these. The output taps must be open, without any load, during these measurements.
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Old 5th February 2015, 08:00 AM   #29
mdamp is offline mdamp  Australia
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On my OPT Black is 8 ohm tap Yellow is 4 ohm tap Green is 0 ohm Ground
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Old 5th February 2015, 07:14 PM   #30
sundaycyclist is offline sundaycyclist  United Kingdom
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It would be useful if there was some documentation to go with these Chinese transformers. My colours are black, red and blue!
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