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Old 30th July 2012, 05:20 PM   #1
Divad89 is offline Divad89  Denmark
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Default No sound and low B+?

After been through this:
HTML Code:
http://www.diyaudio.com/forums/tubes-valves/213643-fuse-blows-instantly.html
I've now received a new power transformer (the excact same Edcor XPWR059), and I can get it to start and the tubes are glowing, but at this point there is no signal coming from it to the speakers, so I've tried to measure the B+ (without tubes), and it just shows 60V, even though it measures 375-380 V from the high voltage secondary.

Do you know what I can have done wrong?

---
David
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Old 30th July 2012, 05:37 PM   #2
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Can you post a schematic ?

Something is drawing excessive current from the PSU, either a mistake in your construction or a faulty component.
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Old 30th July 2012, 05:44 PM   #3
Divad89 is offline Divad89  Denmark
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I've based the amp on this schematic:
HTML Code:
http://diyaudioprojects.com/Tubes/KT88/
But that was also something like that I thought of, I just think I been through it all...

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Old 30th July 2012, 05:48 PM   #4
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by Divad89 View Post
After been through this:
HTML Code:
http://www.diyaudio.com/forums/tubes-valves/213643-fuse-blows-instantly.html
I've now received a new power transformer (the excact same Edcor XPWR059), and I can get it to start and the tubes are glowing, but at this point there is no signal coming from it to the speakers, so I've tried to measure the B+ (without tubes), and it just shows 60V, even though it measures 375-380 V from the high voltage secondary.

Do you know what I can have done wrong?

---
David
Using tube or solid state rectification? If solid state you've got a pretty near short somewhere (filter cap perhaps) if not you need to install the rectifier tube in order to have DC to measure. Note that you should probably use a ballast lamp (incandescent lamp in series with the mains voltage) otherwise you are likely to end up with another fried power transformer.
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Old 30th July 2012, 06:03 PM   #5
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Quote:
Originally Posted by kevinkr View Post
Note that you should probably use a ballast lamp (incandescent lamp in series with the mains voltage) otherwise you are likely to end up with another fried power transformer.
Big Idea!! I always use them. In any dubious circuit including unknown PC monitors. For testing frequency inverters I use a star of three of them. Although, since they are going too expensive because the prohibition to manufacture and import such kind of lamps in the "a-s-s of the world".
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Old 30th July 2012, 06:07 PM   #6
Divad89 is offline Divad89  Denmark
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I've been using tube rectification, but then it is therefore the measurement is so low, but there is still no sound coming out of the speakers...?
But I think I will be using a ballast lamp as suggested...

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David
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Old 30th July 2012, 06:08 PM   #7
kevinkr is offline kevinkr  United States
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I use them, and note that halogen replacement bulbs will work just as well.. Not sure what part of the world you are referring to Osvaldo, but the EU led the initiative and certain countries in North America followed suit.. I much prefer incandescent light to LEDs and CFL so far, although LEDs are getting a lot better and a little cheaper - noting that these do not work as ballasts..
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Old 30th July 2012, 06:10 PM   #8
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by Divad89 View Post
I've been using tube rectification, but then it is therefore the measurement is so low, but there is still no sound coming out of the speakers...?
But I think I will be using a ballast lamp as suggested...

---
David
I think you've got a problem elsewhere like a shorted electrolytic capacitor, failed insulation in a choke or output transformer or a bad output tube or bias component.

Don't run it without the ballast lamp because the transformer will fail.
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Old 30th July 2012, 06:20 PM   #9
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In my house I use only fluorescent lamps, 105 or 40W quick start, with electromagnetic ballast. Electronic ones generated too much QRM (man made interference in ham radio language) in the radio equipment, so they are inhibited to my building. And all of them has the corresponding cap for power factor correction. Sincerely I hate very much the red-yellow light of tungsten and love white light from this tubes.

For series lamp only can work purely resistive devices, like incandescent, or heaters I use at bigger loads expected. Led lights are too directional for my taste, and the mpx frequency in some devices is very annoying for me.

Salu2.
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Old 30th July 2012, 06:24 PM   #10
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I can't get the schem's in the early posts......!
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