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The Quiz of today???

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Posted on September 16, 2014 at 13:09:35
TomWh
Audiophile

Posts: 764
Location: Tucson Az
Joined: August 7, 2003
 Ok to not make this is a really long story I built separate channel for left right buffer gain each completely separate from each other. (6j5 trans output for a dac) So I was checking b+ and current and the one side was around 25 volts higher than the other and the current was higher on the lower B+ side (which makes sense) So I checked caps, dampers, chokes etc etc etc.

So it turned out to be the filament trans I used on the 6j5 where 269ex hammonds which I had and they have b+ voltage which I left idle. How could this cause a voltage drop in the circuit like this???

Thanks Tom

 

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RE: The Quiz of today???, posted on September 16, 2014 at 13:25:12
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 "So it turned out to be the filament trans"

I'm not sure what you mean.

Is the heater voltage high or low on the side that is drawing more current?

I will guess high.

So yes, if the heater voltage is too high or too low it will change the current through the tube and thus change the plate voltage.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: The Quiz of today???, posted on September 16, 2014 at 13:47:18
TomWh
Audiophile

Posts: 764
Location: Tucson Az
Joined: August 7, 2003
 Hey Tre

Let me explain a little bit better. The main power transformers (one for each channel) are hammond 369ex. They are used for the b+ on the 6j5 and the damper diodes filaments. The damper diodes used 2.4 of the 2.5 limit of the filament part so I had to use another transformer for each channel of the 6j5's filaments. (269ex hammonds).

The filaments on all four of the dampers was 6.2v and the 2 6j5's where right at 6.2v. The problem was the one side was pulling more current than the other side resulting in loss of around 25 volts on the b+ of the 6j5.

I check everything multiple time not thinking that a transformer only used for it filament could cause a problem. The only thing that is out of the ordinary is the 380vct of 269ex's are left floating (

 

RE: The Quiz of today???, posted on September 16, 2014 at 15:34:08
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 "The only thing that is out of the ordinary is the 380vct of 269ex's are left floating"

But that's the same for both channels?

So if the heater voltage is the same on each 6j5 then that can't be the problem.

Did you try swapping the 6j5's? I've had tubes that would give that much of a difference.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: The Quiz of today???, posted on September 16, 2014 at 16:18:44
TomWh
Audiophile

Posts: 764
Location: Tucson Az
Joined: August 7, 2003
 Hey Tre

I changed out everything more than once. Just tried a another trans I had lying around and it is very close to the higher b+ of the other trans.


The only thing that is making a difference is changing the filament transformer part of these 269ex's.

I need to get some regular filament trans anyway I just wanted to see what it would sound like and I had these here. I will just use the higher b+ 269ex with the 269ax(they match up to within a couple of volts) and see how it sounds.

I am still at a loss on how if the input is 120 volts the filament is running at 6.2 volts how that could change the b+ of the circuit unless the filament windings are interacting with the unused b+ winding some how, but you would thing that would change the filament voltage.

Thanks Tom

 

RE: The Quiz of today???, posted on September 16, 2014 at 16:33:29
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 "........but you would thing that would change the filament voltage."

Yes, I would too.

It's a mystery.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

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