SK129-38 is an industry standard. No need to go to ebay for that kind of stuff, RS stocks it as well
Is the circuit mostly assembled? A common beginner mistake is to BOTH ground the negative leg of a DC heater supply AND connect a raised heater voltage divider if part of the schematic.
No one said anything about earth ground. He was talking about circuit ground. Right now the middle pin of the 7806 is "grounded" as far as it's connected to circuit ground. Is anything else connected to the heater circuit other than the output of pins 2-3 of the 7806?
Try only a load resistor sized to draw the same DC current as the 6V filaments will. Use a 12VDC input.
Does it work now? If so, it's the turn-on surge. If not, is your input still 12VDC under load?
Does it work now? If so, it's the turn-on surge. If not, is your input still 12VDC under load?
Last edited:
Use a 12VDC input for a 6V regulator. If it is a lab power supply, make sure it is not in current limiting.
Last edited:
Post a picture of your setup, and a close up of the regulator clearly showing the writing on it.
Your description suggests it has gone into current limiting.
The data sheets seem a bit vague with regard to maximum current capability.
The St data sheet states
"If adequate heat sinking is provided, they can deliver over 1 A output current."
and "Output current up to 1.5 A"
With two ECC88s you will get 1.46A with 3 you get 2.19A.
It looks like you will need to use a different regulator with a higher current rating.
Sid
Your description suggests it has gone into current limiting.
The data sheets seem a bit vague with regard to maximum current capability.
The St data sheet states
"If adequate heat sinking is provided, they can deliver over 1 A output current."
and "Output current up to 1.5 A"
With two ECC88s you will get 1.46A with 3 you get 2.19A.
It looks like you will need to use a different regulator with a higher current rating.
Sid
Picture as requested, 50va transformer 2 x 9v out measured at 10.4v ac with load connected. One side feeds 12v regulator with two ECC88's in series giving 10v out ( I expect that as measured DC in to regulator is only 11.7v ) Other side 6v regulator with 12v in and 4.8v out with just one ECC88. ECC88 data sheets advise heater current at 365mA so even with two or three times start up current I would expect the 6v regulator to supply close to that. I have now tried 3 regulators and they all give roughly the same voltage but then they did all come from the same place !
I'm seeing a CRC filter AFTER the 3 pin regulator...of course that will drop voltage. When we were asking you for voltages, we meant the voltages at the regulator PINS.
You have better eyesight than me Leadbelly I missed that but the photo looks like a "Google satellite " view to me, it would be better if it was nearer and a side-view.
I guess you don't do much troubleshooting. At this point Ohm's Law is far more useful than any picture.
It's actually a resistor the value is so low there is virtually no voltage drop, I only put it there to make the connection !!!
Thanks Jabiru I cant understand why some people make unsubstantiated wrong remarks -- probably makes them feel better .
What's the value of the resistor that's "so low there is virtually no voltage drop"? And once again what is the voltage on the pins of the reg? 1-2 and 2-3.
Duncan is right about the photo - a much higher res picture would be nice: 4K perhaps?
Duncan is right about the photo - a much higher res picture would be nice: 4K perhaps?