I'm building a Brownface-type amp - Single channel -Brown pre/bass+treb tonestack(6G)- Brown 6v6 outputs-
Have it up and running but i can't seem to get the V1 voltages right.
Using an old hifi chassis-
Everything works, i just can't dial in the plate voltages on V1
Using a 100K on the first plate stage, 220k on the second plate stage.
1.5k+25/50v on the first stage cathode. 820/25+50v on the secong stage cathode.
I have the Driver tube (V2) dialed in - plate voltages and cathode-
I started at 10K and I've lowered the resistor in the supply between V2 and V1 to 470 ohms and i can't get any more voltage than 150v(100k)/80v(220k) on the plates of V1. Cathode voltage is wrong at 2v+(100k) and under 1v(220k)
swapped in a bunch of different tubes in V1, triple checked the resistors.
The Amp chassis was originally powering MORE tubes than i am now, so i know its should have the juice
Voltage before the V1 100k/220k plate resistors is a bit above 300v
The schematic for most browns shows about 220v(100k side) and 195v(220k side) for V1 and i've built a couple Browns before - they do sound best(to me) at those voltages
Should i not worry about the 100k/220k and corresponding impedance and adjust them?
I literally can't go lower on the supply resistor.
I also don't know why its such a problem. I've adjusted the supply resistors on other builds and found what i needed. Stumped here
Brown Voltage question/help
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Stevem
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- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Brown Voltage question/help
So V1A is idling hotter than it should with the 2 volts across the cathode, and V1B is idling colder and pulling less current by reading only 1 volt across that cathode.
How do you have the amp built, with terminal strips and point to point, or tag board and post?
If that is a used tube socket I would get a short section of a round wound string that fits a bit tight into each tube pin reciver of the socket and run it in and out of each with some light oil on it or some contact cleaner and see if it's a crud / tarnish condition that is adding gost resistance to what you have the components set at in circuit!
How do you have the amp built, with terminal strips and point to point, or tag board and post?
If that is a used tube socket I would get a short section of a round wound string that fits a bit tight into each tube pin reciver of the socket and run it in and out of each with some light oil on it or some contact cleaner and see if it's a crud / tarnish condition that is adding gost resistance to what you have the components set at in circuit!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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Voxacthirtee
- Posts: 10
- Joined: Fri Jun 14, 2013 10:25 pm
Re: Brown Voltage question/help
Thanks for the reply and the suggestion.
I did actually replace all the tube sockets and rewire everything.
Only things old are the actual chassis and the transformers.
It's a combination of point to point/term strip with a small generic tag strip/posts
And it ultimately works as is, its just a bit grungy and gets compressed too quick. Need to solve this somehow.
Original tube compliment was 5y3/2-6v6/6an8/+4 more tubes in am/fm tuner
Current compliment is 5ar4/2-6v6/2-12ax7
I did actually replace all the tube sockets and rewire everything.
Only things old are the actual chassis and the transformers.
It's a combination of point to point/term strip with a small generic tag strip/posts
And it ultimately works as is, its just a bit grungy and gets compressed too quick. Need to solve this somehow.
Original tube compliment was 5y3/2-6v6/6an8/+4 more tubes in am/fm tuner
Current compliment is 5ar4/2-6v6/2-12ax7
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Brown Voltage question/help
It's just not making sence!
If you pull out one of the outputs to free up some current does it let you make changes to that gain stage and have them make results ?
If you pull out one of the outputs to free up some current does it let you make changes to that gain stage and have them make results ?
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Brown Voltage question/help
It's a bit of a guess in the dark without a schematic. Right now I'm looking at a Princeton 6G2 schematic, which fits your tube compliment pretty well: 2x 12AX7 and 2x 6V6. There are two gain stages, one triode tremolo, and a concertina for the PI. Is that what you are working with?
In the 6G2, V1 and V2 are both fed from the same filter cap node, with no dropping or decoupling resistor between them. You might try this and see if it works for you. The schematic shows 135V on V1 , 200V on the tremolo, and 230V on the concertina plate. So, by this reckoning, what you report is consistent with the design. The schematic shows 1.5V on the V1 cathodes, so your 2.0, while high, is not that far from what's expected. You should be able to knock down cathode voltage by tweaking Rk.
If you could be more specific with a schematic or model number (not just 6G) it might illuminate the discussion for us.
In the 6G2, V1 and V2 are both fed from the same filter cap node, with no dropping or decoupling resistor between them. You might try this and see if it works for you. The schematic shows 135V on V1 , 200V on the tremolo, and 230V on the concertina plate. So, by this reckoning, what you report is consistent with the design. The schematic shows 1.5V on the V1 cathodes, so your 2.0, while high, is not that far from what's expected. You should be able to knock down cathode voltage by tweaking Rk.
If you could be more specific with a schematic or model number (not just 6G) it might illuminate the discussion for us.