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Need help on B+ output

celestar32

Member
2013-12-29 5:59 am
Can anybody help to calculate what is my B+ output if the configuration is like this power supply circuit. How to get 435V output if this configuration is wrong.
 

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TNoll

Member
2016-06-08 6:11 pm
You will need to know the dc resistance of the choke, too.

Rayma's advice is good. Breadboard it and use a power resistor for a dummy load which will draw the current your device will draw.

Two points, though:
Where is your bleeder resistor? You Need to have one. Its job is to discharge the filter caps so they don't hold high voltage and discharge through your body. It goes on the B+ line, after the last cap.

What's that cap doing across the switch? That's a leakage path, and will somewhat energized the transformer at all times. With the snubber (marked NL), which is a very good idea, you do not need anything else.

Good luck with your project!
 
NL = neon lamp. It's a pilot light. The series resistor is a voltage dropper/current limiter.

The breadboard suggestion is spot on.

A 20 muF. cap. in the 1st position and a 100 muF. part in the reservoir position gives an option to use a "potato masher" 5R4, instead of a 5U4, should the rail be too tall. At the rated 250 mA., the forward drop in a 5R4 is a whopping 67 .
 
I tested it with this configuration. I got 315V on my B+ but the rectifier will red plating. The choke resistance is at 45ohms.

You are drawing more than the 250 mA. allowed with a 5U4GB. Other 5U4 variants allow only 225 mA. Increase the value of your "dummy" load, to hold the draw down.

Look at the 5U4GB data sheet. That 47 muF. 1st cap. is suspect.

Back in the day, all sorts of liberties were taken with published tube limits. :mad: Tubes were inexpensive and performance claims helped sales. Definitely adhere to published limits, until you accumulate experience. With experience, you will learn where small liberties can be taken. Beating the living guano out of your tubes is very bad for your bank balance.