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Bijou All Tube Futterman Headphone Amplifier - Page 95

post #1411 of 3976
9/27/08 at 9:36am
and thats at max turns of the pot? you have will have to adjust when you plug in the amps.

also, is that with the EZ81 or 80.

Fishki, the stainless donuts are a tube guards bought from vt4c taken aparts. Looks really good!
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post #1412 of 3976
9/27/08 at 10:10am
Quote:
Originally Posted by pabbi1 View Post
Well, I was thinking more Stacker, or whatever it is you are doing with the 'Super Bijou'... but, seriously, we really need you looking at electrostatics.

snip
Is there an update on the Super Bijou?
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post #1413 of 3976
9/27/08 at 10:11am
Yes, it is at max turns of the pot with the EZ81.
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post #1414 of 3976
9/27/08 at 10:30am
Quote:
Is there an update on the Super Bijou?
Apart from that, what would be the exact difference between the standard Bijou and the Super Bijou?

Regards
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post #1415 of 3976
9/27/08 at 11:07am
Quote:
Originally Posted by miky View Post
Yes, it is at max turns of the pot with the EZ81.
miky, what is the voltage at the exposed lead of R7 and R8?
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post #1416 of 3976
9/27/08 at 11:32am
Quote:
Originally Posted by runeight View Post
miky, what is the voltage at the exposed lead of R7 and R8?
Power Supply
R7 - 248v
R8 - 301v
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post #1417 of 3976
9/27/08 at 11:35am
Wow, that is a huge current draw from the PS. What tubes are you using and are you using the stock resistor values in the amps?
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post #1418 of 3976
9/27/08 at 11:52am
Tubes - EZ81 JJ, ECC99 Gold JJ, Amperex Gold Pin 8416. I am using the stock resistor values + Regal's mods & 470 ohm in R2 (R3-30K, R5, R6, R7 - 10K).
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post #1419 of 3976
9/27/08 at 12:41pm
OK. Things are now making more sense.

One more measurement please. What is the voltage at the plates of the input tubes (pin 6).

The voltage drop across R7 and R8 says that your amps boards are drawing 80mA. This is outside the design capability of the PS, even with EZ81. So we have to reduce the current draw to more like 70mA in order to increase the voltage at R7 (the input to the regulator). I'm not sure exactly how we'll do this, but there is always a way.
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post #1420 of 3976
9/27/08 at 1:49pm
Thank you runeight
It is 93-94v (pin 6 of 8416 - ground).
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post #1421 of 3976
9/27/08 at 11:24pm
OK. This says that the first stage is drawing about the right amount of current. Which means that the ECC99s are drawing a huge amount of current.

Are you using 1N4002 diodes in the O/P stage?

Also, could you please disconnect the amp boards from the PS, re-attache the 100k resistor, and measure the voltages at R7 and R8 again.

Thanks.
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post #1422 of 3976
9/28/08 at 2:34am
I am using 1N4004 diodes from JRossel's kit.
The voltages with the 100k resistor:
R7 - 352v
R8 - 359v
I have 283VAC from R0080-036 R-Core transformer (260-230-0-230-260).
And the fuse was blown twice (1A fast blow).
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post #1423 of 3976
9/28/08 at 11:07am
OK. Those are all good voltages and the right diodes.

So, at the moment I don't know what's happening. You have plenty of HV secondary. What is the HV AC voltage when the amp boards are attached?

Your input stage is biased about 5mA. I'm not sure about the O/P stage yet.

Try using a slo blo fuse.

Try running it for a while. Perhaps a little breakin will help.
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post #1424 of 3976
9/28/08 at 11:19am
Miky, when you an opportunity, could you also try another ez81? Your ez81 is dropping quite a lot of voltage. I'm wondering if it's a bit below spec.
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post #1425 of 3976
9/28/08 at 2:24pm
Bijou is finished



more pics in the post your builds thread. Really pleased with the way this sounds and looks!
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