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Old 6th November 2011, 10:55 AM   #1
elgsdyr is offline elgsdyr  Denmark
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Default testing my simple se

Hello

I am new on these forums. but i have spent alot of time reading here before building my simple se.

I just finished my PC board yester day and wired it for testing. I followed Ty_bowers test guide

Checkout :: ohm00.jpg picture by Ty_Bower - Photobucket

Everything was fine i then put in the tubes hooked on some very cheap speakers.

I measured B+ at R4 its 459V
I use JJ 6L6GC tubes with a 680ohm cathode resistance.
the cathode voltage measured at R17/R27 is 37,4V and 37,2V that around 55mA.
The datasheet on the tubes says Ia = 72mA Is that fine or could/should I use a smaller resistor for R17/R27.
The cathode voltage on the EH 12AT7 is 1.9V at both R10 and R20 thats 8.6mA.
One of the output tubes have one spot glowing brighly. is that something i should be aware of, it sounds fine.

besides that
OPT = hammond 1628SEA
PS = hammond 374BX
choke = hammond 193H
Motor run cap = 50 microF 370VAC
C1 = JJ 47microF 500V
C2 = JJ 100microF 500V
C11/C21 = mallory
rectifier tube = JJ GZ34S / 5AR4
GE sensing CL90 and fairchild diodes.
50K ohm stereo log pot
1.25A slow blow fuse
the rest is from mouser. from some list ive found on this forum

I have tried on my focal chorus 816v for some hours now and depending on the type of music its rather fantastic. My other amp is a rotel RA-1062 and the simple se is a strong competitor. Some types of music sound better on the SE, and some better on the rotel. But i need to build a cabinet for it and listen some more. By the way its running triode mode without CFB.

this is my first amp build, i am overall very satisfied with the result.

what do you guys think does it make sense what ive wrote, are there some voltages or currents i should be aware of, or more i need to check.
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Old 6th November 2011, 04:03 PM   #2
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Quote:
Originally Posted by elgsdyr View Post
I measured B+ at R4 its 459V.
The cathode voltage measured at R17/R27 is 37,4V and 37,2V that around 55mA.
Should I use a smaller resistor for R17/R27?

The cathode voltage on the EH 12AT7 is 1.9V at both R10 and R20 thats 8.6mA.

One of the output tubes have one spot glowing brighly. is that something i should be aware of, it sounds fine.
Take your B+ and subtract the cathode voltage. That's roughly the voltage across the tube (ignoring whatever is lost in the transformer winding). Multiply by the idle current, and I get 23 watts idle for your setup. That should be fine for 6L6GC.

Voltage for the driver tube look spot on.

When you say "glowing brightly", I'm guessing you are seeing a white/yellow glow coming from the heater that is poking slightly out one end of the cathode sleeve. That's perfectly normal, and nothing to worry about.

If you are seeing a dull red to bright orange glow on the surface of the plate, that's bad. These usually appear somewhere near one of the seams or folds in the plate structure. They occur because the distribution of the the electron beam is not uniform across the plate. One section gets to much current, usually due to poor screen alignment, and that area of the plate gets too hot.

If you do have a bright red spot at 23 watts, the tube is most likely bad and should be replaced. If it is only a dim red glow, you might be able to try lowering the idle current (by increasing cathode resistance) and it might go away.

Here's a couple examples of what I mean by dim red glow. In both photos, look at the tube on the left. The bright white/yellow heater glow can also be seen clearly at the top and somewhat at bottom of each tube.

Click the image to open in full size.
http://i69.photobucket.com/albums/i4...E/P1130044.jpg

Click the image to open in full size.
http://i69.photobucket.com/albums/i4...s/P1070380.jpg
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Old 6th November 2011, 07:01 PM   #3
elgsdyr is offline elgsdyr  Denmark
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I have uploaded some photos

simple se pictures by elgsdyr - Photobucket

Its the one to the left at the top.

Not much glow in mine, compared to yours. what type is that?
Does it depend on the type or how hot you run them.
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Old 6th November 2011, 07:40 PM   #4
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Originally Posted by elgsdyr View Post
Not much glow in mine, compared to yours. what type is that?
Judging by your photos, the tubes in your amp are perfectly fine. What you are seeing on the top of the left side tube is only the end of the heater poking out of the cathode sleeve. Due to production variances, sometimes they stick out a tiny bit and you see them a little more. It's no big deal.

The tubes in my top photo are Reflektor 6550 tubes. They have some kind of issue with the alignment of the beam formers, and they tend to show excessive plate dissipation at much lower wattages than they should. The bottom photo is a pair of perfectly good EL84, except one of the pair is biased too hot. I tend to take long exposure photographs (8 seconds) on a tripod, so glowing things are a little easier to see in my pictures.
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Old 6th November 2011, 07:40 PM   #5
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Quote:
Its the one to the left at the top.

Quote:
When you say "glowing brightly", I'm guessing you are seeing a white/yellow glow coming from the heater that is poking slightly out one end of the cathode sleeve. That's perfectly normal, and nothing to worry about.
It looks like normal heater glow to me. The rod down the center of the tube must glow red for the tube to function. The heating element that provides the glow sticks out of each end and will be the hottest point in the entire tube.

The outer metal shell around the guts of the tube should not glow, although some of us tend to ignore that warning and run them into the red zone. Just like spinning the tach needle into the red zone shorter tube life and possible catastrophic failure are the risk for a bit of extra power.
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Old 6th November 2011, 08:30 PM   #6
elgsdyr is offline elgsdyr  Denmark
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When the amp is off i can see the end of a rod on the left tube. So yes its just the heater. no worries then.

I will just enjoy listening to some more music. Build a cabinet. And later try some other types of tubes.

Thank you both for your help and quick response.
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