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Old 12th October 2012, 06:03 AM   #31
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So, an LM317 configured as current regulator, a better choice than LM317 as voltage regulator, to avoid overcurrent at startup.
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Old 12th October 2012, 04:56 PM   #32
tomchr is offline tomchr  Canada
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Originally Posted by Bigun View Post
As soon as I get back in front of a PC (all Mac at home) I'll try those mods.
Dude! Ever heard of VMware, Parallels, or VirtualBox? The latter is freeware, the other two payware (I think I paid $40 or $50 for VMware). Works great.

Originally Posted by Bigun View Post
Whilst we don't appear to need fast feedback perhaps it helps. In a way it's a lazy way to deal with any h.f. hash from the mains that gets through the transformer and any h.f. hash generated by the rectifiers.
I highly doubt you'll be able to make a feedback loop that's fast enough to compensate for mains hash and rectifier spikes. Filtering - or just not generating the noise in the first place - works better here. But at least ensure that your circuit doesn't have gain at HF.

Originally Posted by Bigun View Post
I mean that the current through the filament, when no signal is present, doesn't change over time.
So low drift? That probably depends mostly on the tempco and drift of your reference as well as that of the op-amp input offset.

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Old 12th October 2012, 05:09 PM   #33
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Originally Posted by tomchr View Post
Dude! Ever heard of VMware, Parallels, or VirtualBox? The latter is freeware, the other two payware (I think I paid $40 or $50 for VMware). Works great.

VMware player is free of $. You can install and run one image at a time.
VMware Virtualization Products for Virtual Servers, Virtual Desktops, and Data Center. However not for Mac, AFAIK
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Old 19th August 2015, 12:33 PM   #34
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Sorry to resurrect this old thread but I'm currently in for the same type of regulator.

Look at the attached schematic for what I came up with. It's supposed to heat a 2A3 from either 5V or 6.3V spare windings. Excess voltage & power can be dropped in the CRC input. The mosfet max Pd is ~6.5W.

The CCS is adjusted such that 2.5V appear across the filament, much like the Tentlabs regulator. Unfortunately I had to use 3 opamps, whereas the Tentlabs piece seems to require only a dual.

Originally Posted by Bigun View Post
The real trick would be a dc heater supply for a 2A3 that can hook up to an existing 2.5V heater transformer. Not a lot of spare voltage to play with there.
My regulator requires 3.0Vdc after rectification, which, in theory, should be obtainable from a 2.5Vac winding using a synchronous rectifier and huge caps... In practice, it will probably not work with real 2.5Vac 2.5A windings because of voltage sag, when drawing more power than made for.
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