Quote:
Originally Posted by Ed_Dinning
Hi Richard, back on the 1155 PSU, I have seen an AM unit that used the LcL configuration and I'm sure the first choke was a swinging type.
Some earlier users of 1155's reported that it was useful to be able to vary the HT voltage over a small range as an aid to reducing frequency drift, I've never tried to verify this
Ed
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Ed,
the only AM (=Air Ministry I presume) power units for the 1155 I am aware of are those monsters described in AP1186E, which I posted further up this thread. The chokes in there are fixed values - no swinging chokes there - see the note about L3 and L4 in paragraph 11, where the values are given as 10 to 12H at 110mA.
There may of course be some other AM psu designed solely to run a R1155. Can't comment about that - except to say I have never heard of one.
I should also say that I will have to back out of offering to simulate the swinging choke version of any psu. I've actually done a bunch of such simulations, but I then spoke to the designer of the PSUD2 simulation software, and he pointed out that simulating a swinging choke is actually vastly more complex than his simple software package will allow for.
The ripple current through the choke can easily vary from 0 to 200mA over one cycle - and of course the inductance will vary too through the cycle. Add in magnetic hysteresis and you have a very complex situation here.
One last thought on swinging chokes.......and that is that they were apparently only used as a cost saving measure. To some extent they can reduce the amount of copper and iron required, since the inductance at the high current load is allowed to fall to some quite low value. That's a bit academic these days - and I rather doubt any seller of old chokes is going to give a discount because its a swinging one! Probably double the price because its a "rare item".
I can't comment on your point that there some "sweet spot" for HT+ voltage for the R1155. I am surprised anyone has done the measurements and analysis to find out such obscure information. Sounds like a whole other topic for another thread to me...!
Richard