Just a thought but if it is indeed choke input, you might consider putting the choke on the negative side if a bridge, or the center tap if otherwise. That way, way less voltage across the choke.
Jeep K3HVG
On 10/22/2022 7:49 PM Rick WA6III <myr748@...> wrote:
Ok,
I am going to probably show my ignorance of choke input power supplies but here goes!!
I am rebuilding my HT45 power supply.? My HT45 is Hallicrafters branded but probably like many, has the Radio Industries PS-2A power supply. I am guessing that Hallicrafters probably had a LOT of them laying around and used them until the supply was exhausted and then started putting their own name on them.? No matter, there doesn't appear to be any electrical difference.
Testing mine, I have noticed that if I use only the existing 210K ohm total bleeder resistors (series 100k + 100k + 10K), I hear what is best described as a faint "clicking" sound in the choke!? And the voltage is upwards of 3750V.? (too high in my book)
Although I don't see any discussion of it in the manual, the schematic shows the 4-16H (swinging) choke with what I would call an "arc-gap" (maybe internal) for protecting the choke (I guess) .
With no load (but with the 210K resistors) on the power supply the voltage is a little more than 3700V.? If I add some load (an additional 50K like an idling 3-400) drawing a total of 87 ma, The voltage drops to about 3460v and the clicking stops!
And before someone tells me how a choke input power supply works (needs a minimum load etc)? I did read the handbook discussion on choke input power supplies!
My question (and I'm hoping Walt jumps in here) concerns the jumper on the back of the HT45.? This terminal allows "shorting" across a 150 OHM resistor in the 3-400 cathode circuit that is there to increase bias and reduce cathode current during STBY.
The manual talks about using a T/R relay controlled by PTT from the exciter with additional contacts for this purpose.? This is also done with the HT33 I have and many other amplifiers. (Note 5.)
I am just wondering what to expect with the reduction?? I have experimented with the power supply a little and have discovered that with the current swinging choke I have, the existing 210K ohms aren't enough, an additional 100K isn't enough, and I had to put another 100K in parallel to get the choke to stop "ticking"
210K + 100K + 100K? all in parallel (about 40K) produced enough current to stop the ticking and clicking and put the output at 3460V with 122VAC on the primary.
Anyone have experience with one of these?
--
73/Rick
WA6III
__________________________________
No critters were injured transmitting with Hallicrafters transmitters except
the ones that wandered into the final amp cage Bug-Motel!!
Bugs check-in, but they don't check-out!
