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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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4th Nov 2014, 11:53 am | #41 |
Heptode
Join Date: Apr 2014
Location: Wigton, Cumbria, UK.
Posts: 728
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Re: Variable HT regulator circuit.
Even better. BTW the seller accepted an offer of $15, so all-in including postage it was less than £13.00!
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4th Nov 2014, 2:21 pm | #42 |
Dekatron
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,670
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Re: Variable HT regulator circuit.
Hope it does the job Nick, but at an OP power of 20-30mA / 9W ,you might it be severely constrained to what valves you can test.
Andy.
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4th Nov 2014, 3:59 pm | #43 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
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Re: Variable HT regulator circuit.
Andy, Nick's measuring small signal valves and a low power output valve, not line-output or transmitting valves. He'll be fine. If not, just one MOSFET has to be replaced - 2 mins work and a quid's outlay.
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Al |
13th Nov 2014, 2:13 pm | #44 |
Heptode
Join Date: Nov 2004
Location: Ripon, N.Yorkshire, UK.
Posts: 782
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Re: Variable HT regulator circuit.
Back again. I'm assembling the bits to build one of these. Is there any need to have an AF choke/capacitor smoothing circuit following the rectifiers?
Jim |
13th Nov 2014, 4:56 pm | #45 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
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Re: Variable HT regulator circuit.
Hi Jim, if you're talking about the circuit that was posted early in this thread, no, you don't need a choke, but you do need the big electrolytics shown.
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Al |
13th Nov 2014, 5:59 pm | #46 |
Heptode
Join Date: Nov 2004
Location: Ripon, N.Yorkshire, UK.
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Re: Variable HT regulator circuit.
Hi Al,
This is the circuit I eventually ended up with, Jim |
13th Nov 2014, 6:17 pm | #47 |
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Re: Variable HT regulator circuit.
Good result, I would have it variable down to zero (you never know, a ten turn pot is good here) and put a switch and a fuse (FETs go short on failure) on the output (after the meters). I was going to mention an output bleed but the volt meter will do that, talking of meters, a protection diode across the ammeter is a good idea. I like the gate series and protection too, well thought out and simple as all good designs are.
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13th Nov 2014, 8:29 pm | #48 |
Heptode
Join Date: Nov 2004
Location: Ripon, N.Yorkshire, UK.
Posts: 782
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Re: Variable HT regulator circuit.
Cheers Merlin,
I do intend adding a fuse but hadn't thought of the diode across the meter. The LED and its resistor will bleed the 220uF capacitor. I'm thinking I might publish this* as I'm sure there are others out there who would like to build one. Jim *With due acknowledgements to the Forum of course! |
13th Nov 2014, 8:38 pm | #49 | |
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Re: Variable HT regulator circuit.
Quote:
One thing I like to use on high voltage stuff is a neon (even inside), very reliable. Rather guiding the lilly in this case though. |
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13th Nov 2014, 9:47 pm | #50 |
Heptode
Join Date: Nov 2004
Location: Ripon, N.Yorkshire, UK.
Posts: 782
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Re: Variable HT regulator circuit.
Yes, I realised you meant the output Merlin and I'll do that as well I think. I considered using a Neon indicator too as even taking just 5mA extra from the transformer for the LED is quite a big percentage of the 100mA available with the transformer I'm using and Neons take less than that.
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14th Nov 2014, 12:43 am | #51 |
Heptode
Join Date: Feb 2010
Location: Heysham, Lancashire, UK.
Posts: 669
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Re: Variable HT regulator circuit.
Could you replace the string of Zenners with small wire-ended neons (with shunt resistors to help striking...)
Stuart |
14th Nov 2014, 8:46 am | #52 |
Nonode
Join Date: Aug 2007
Location: South Bradford, West Yorkshire, UK.
Posts: 2,573
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Re: Variable HT regulator circuit.
Rather than put the LED, and its series resistor, across the supply put it in series with R1. You'll still get 5mA through the LED and save a resistor and get an extra 5mA available at the output.
Keith |
14th Nov 2014, 1:35 pm | #53 |
Heptode
Join Date: Nov 2004
Location: Ripon, N.Yorkshire, UK.
Posts: 782
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Re: Variable HT regulator circuit.
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14th Nov 2014, 1:36 pm | #54 |
Heptode
Join Date: Nov 2004
Location: Ripon, N.Yorkshire, UK.
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Re: Variable HT regulator circuit.
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14th Nov 2014, 3:04 pm | #55 | |
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Re: Variable HT regulator circuit.
Quote:
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14th Nov 2014, 11:26 pm | #56 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
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Re: Variable HT regulator circuit.
Nice one Jim.
This may just be the icing on the cake, but that Mosfet can source a lot of current..would it be an idea to add some simple crowbar s/c protection?
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Al |
14th Nov 2014, 11:35 pm | #57 |
Heptode
Join Date: Nov 2004
Location: Ripon, N.Yorkshire, UK.
Posts: 782
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Re: Variable HT regulator circuit.
Yes Al, I've been mulling that over. I'll see what I can come up with tomorrow.
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15th Nov 2014, 1:27 am | #58 |
Dekatron
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 4,935
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Re: Variable HT regulator circuit.
I know that this has been devised as a VV supply, but would it also be a good way of dealing with limiting the very high off-load HT voltage which occurs during the period when a valve receiver is warming up? If the power supply uses silicon diodes, the HT volts can be surprisingly high - and close to the limits on various caps - prior to the time when the valves start conducting. Usually, I've used some crude combination of resistors/zeners/neons to keep things under some degree of control, but these can be a drain on the current available when the valves are on.
B
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15th Nov 2014, 3:39 am | #59 | |
Dekatron
Join Date: Nov 2006
Location: London, UK.
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Re: Variable HT regulator circuit.
Quote:
My sketch is a bit rough but I didn't tag the original circuit. Cheers
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Al |
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15th Nov 2014, 1:41 pm | #60 |
Heptode
Join Date: Nov 2004
Location: Ripon, N.Yorkshire, UK.
Posts: 782
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Re: Variable HT regulator circuit.
Nice one Al. I remember my boss having problems with the electrics on his boat many years ago. The solution there was to have a built in delay so I designed and built a unit based on a 555 which solved the problem for him. I never got a trip on his boat though!
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