Need help on B+ output
- Thread starter celestar32
- Start date
Several pieces of information are missing.
380*1.4=532
You have a theoretical max voltage of 532.
Now you need to know the DC load current, the source resistance of the transformer secondary, the voltage drop across 5U4 vs load current provided in datasheet, and the DCR of the choke being used.
380*1.4=532
You have a theoretical max voltage of 532.
Now you need to know the DC load current, the source resistance of the transformer secondary, the voltage drop across 5U4 vs load current provided in datasheet, and the DCR of the choke being used.
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!
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 .
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 .
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.
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.Hope you switched it off immediately!
http://frank.pocnet.net/sheets/127/5/5U4G.pdf
Look at this datasheet, if you had only 315V, you must have seriously overloaded the rectifier tube. Or the smoothing capacitor is defective.
That wouldn't cause the issues you are having. What is being presented to you is that the first cap is defective and not just sized incorrectly. I am willing to bet this is the case if you do not have any other load connected.