I have a bunch of small toroids lying around.
How can I decide if they are usable with a voltage doubler?
So far I've been looking at a full wave voltage doubler.
The trafo ratings are:
Prim: 230V@50Hz
Sec: 7.5V 1A, 15-0-15V 75mA, 20-0-20V 420mA.
I've been toying with some sims using LTspice and it's causing me some headaches.
The load will draw roughly 26mA.
I need approximately 150VDC from the PSU. (B+ for some 6CG7)
Using these figures everything looks ok if I hook the 15-0-15 and 20-0-20 secondaries in series. I have the trafos already so it's free...
Now, sims will show a peak current draw from the trafo in the 400mA range.
How much peak current can it handle? It's Toroid brand and it's number is
TI-78038-8?
(I'll save the 7.5V secondary for the heater.)
How can I decide if they are usable with a voltage doubler?
So far I've been looking at a full wave voltage doubler.
The trafo ratings are:
Prim: 230V@50Hz
Sec: 7.5V 1A, 15-0-15V 75mA, 20-0-20V 420mA.
I've been toying with some sims using LTspice and it's causing me some headaches.
The load will draw roughly 26mA.
I need approximately 150VDC from the PSU. (B+ for some 6CG7)
Using these figures everything looks ok if I hook the 15-0-15 and 20-0-20 secondaries in series. I have the trafos already so it's free...
Now, sims will show a peak current draw from the trafo in the 400mA range.
How much peak current can it handle? It's Toroid brand and it's number is
TI-78038-8?
(I'll save the 7.5V secondary for the heater.)
Hi,
quite unusual to generate B+ from a low voltage transformer, but do-able.
Doublers and more do not like to provide lots of current, but your current load is low.
Doublers and more do have a lot of ripple under load.
I would suggest you aim to go over voltage and bring the voltage back down to operational B+ using RCRC or RCLC or extended to more stages or similar.
quite unusual to generate B+ from a low voltage transformer, but do-able.
Doublers and more do not like to provide lots of current, but your current load is low.
Doublers and more do have a lot of ripple under load.
I would suggest you aim to go over voltage and bring the voltage back down to operational B+ using RCRC or RCLC or extended to more stages or similar.
if 25Vdrop is too high and leaves B+ a bit low then consider replacing one or more of the R with an aircored LI'm dropping something like 25V over a symmetrical three-stage RC filter.
A 100gm bobbin of 0.5mm diam wire will have quite a bit of inductance and only 5r of resistance. Expect L~4mH to 8mH
My current sim leaves me with 140VDC at the plate and that's good enough for me.
If the need arises it's always good to have a trick up your sleeve, I think I'll save the inductances for "in case of emergency". Thanks for the tip though.
BTW, does the 100gm stand for 100 grams? or what? (to me gm is something you find with tubes?)
Andy, I'm not sure I'm getting what your saying? It's one Toroid? Either you hook it up to a secondary or a primary? Anywho, I need the 7.5V @ 1A for the heater so I can't run it in reverse.
If the need arises it's always good to have a trick up your sleeve, I think I'll save the inductances for "in case of emergency". Thanks for the tip though.
BTW, does the 100gm stand for 100 grams? or what? (to me gm is something you find with tubes?)
Andy, I'm not sure I'm getting what your saying? It's one Toroid? Either you hook it up to a secondary or a primary? Anywho, I need the 7.5V @ 1A for the heater so I can't run it in reverse.
My current sim leaves me with 140VDC at the plate and that's good enough for me.
If the need arises it's always good to have a trick up your sleeve, I think I'll save the inductances for "in case of emergency". Thanks for the tip though.
BTW, does the 100gm stand for 100 grams? or what? (to me gm is something you find with tubes?)
Andy, I'm not sure I'm getting what your saying? It's one Toroid? Either you hook it up to a secondary or a primary? Anywho, I need the 7.5V @ 1A for the heater so I can't run it in reverse.
Sorry. I thought you had a number of transformers.
In the valve World it is quite usual to use back to back transformers to replicate those bygone age power transformers.
In this case I fed you with a complete load of b******s.
Andy
I considered that as well, but apart from the fact that you'd need an extra transformer, the 15V tap in this xfo is apparently only about 2VA, so it wouldn't do. Otherwise, it'd have been my preferred solution as well.Why not just use the 240V - 15V to drive the 20V - 240V in reverse.
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