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PostPosted: 09 Aug 2010, 12:58 
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Joined: 22 Feb 2010, 20:57
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I got around to testing it with a DMM and there is only a 100 milivolt drop on pin 1 and 6! (using the wallwart for testing, so B+ is measure around 11.56V, and pin 1 and 6 is a around 11.45V) :confused:

heaters check out just fine. 12v across pin 4 and 5 and 6v on 9.


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PostPosted: 09 Aug 2010, 15:01 
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homik wrote:
I got around to testing it with a DMM and there is only a 100 milivolt drop on pin 1 and 6! (using the wallwart for testing, so B+ is measure around 11.56V, and pin 1 and 6 is a around 11.45V) :confused:

heaters check out just fine. 12v across pin 4 and 5 and 6v on 9.

Did you measure the resistors before mounting them ? i were thinking about especially the 4,7 kohm ...is it the right value at all ?


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PostPosted: 09 Aug 2010, 15:10 
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Yes. I checked all resistors and rechecked them now, they were fine. Also, the same symptoms exist in both channels, so what are the chances of two bad resistors? :?

I'm thinking its a bad tube. I'll put it in my pre (which happens to also use ecc82's) and see what happens.


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PostPosted: 09 Aug 2010, 16:24 
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If you've checked (also measured ) the resistors and they got the right value they are in fine condition. You can see it, if they are burned ...i guess they aren't.

You say a bad tube ...hmm, I've never seen a tube where both channels are bad ( defect ), but who knows. I think it's a good idea to test the tube in your preamp.


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PostPosted: 09 Aug 2010, 16:32 
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i did got a bad tube

it did not glow

and when it did glow it was with 24V on the heaters

i kept it for decorations


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PostPosted: 09 Aug 2010, 20:01 
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Joined: 22 Feb 2010, 20:57
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Yup, definitely a bad tube. Turned out the heater is borked, does not glow. It was by no means a new tube, just something i dug up from my grampa's stock.

Grabbed another ecc82 from my stock. Good news is, i can hear music. :headphones:
Bad news, tons of hum, but that is most likely do to the really poor PtP. I'll tidy things up and that will hopefully tidy up the sound.

Thanks a bunch. :thumbsup:

I'll post a pic of the final product once i tidy up and assemble the case.

Happy tube rolling! :headphones:


Last edited by homik on 09 Aug 2010, 20:48, edited 1 time in total.

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PostPosted: 09 Aug 2010, 20:44 
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Joined: 22 Feb 2010, 20:57
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Separated input and output grounds from power grounds and the buzz went away! I'll have to read up on grounding schemes for future projects. There is still a very slight hum, most likely from the mains or some other wiring issues, but i'm happy with it for now so i will tackle that problem some other day.

Also got my Grados today so looks like i'm headed for an extended listening session. :headphones:

assembled chassis:

Image

tiny update: the hum was from a ceiling fan in my room. Turned it off and hum went way, except for slight fuzz and white noise, and of course tiny pops, but that comes with the territory as far as headphone amps go. :D


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PostPosted: 10 Aug 2010, 10:48 
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homik wrote:
Yup, definitely a bad tube. Turned out the heater is borked, does not glow. It was by no means a new tube, just something i dug up from my grampa's stock.

Yep, the glow is necessary :lightbuilb: ...no glow no sound ;)

But, something must have been glowing, when you wrote following :?: ...because of that i didn't ask you about it.
homik wrote:
heaters check out just fine. 12v across pin 4 and 5 and 6v on 9.

Anyway, great you've got it working homik ...congrats :headphones:


Last edited by KrammeAcoustics on 10 Aug 2010, 11:00, edited 4 times in total.

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PostPosted: 10 Aug 2010, 10:50 
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a few post agow a asked if it glowed but it seems no one lisens to me


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PostPosted: 10 Aug 2010, 11:11 
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robot797 wrote:
a few post agow a asked if it glowed but it seems no one lisens to me

sorry about that. thats because when power was applied the heaters would glow for a second, so i did not really bother checking up on that. but when i compared it to other tubes i saw there was a significant difference in how much it glowed, which was pretty much not at all.

But hey, everything turned out well in the end. no hard feelings. :headphones:


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