Smoothing to Swinging Choke Conversion

[AB9ZG]

I have a UTC CG-1S, rated 10H at 1A.
UTC also made a CG-1C is rated at 5-25H at .1-1A.
They are both listed to have the same size, weight, and DC resistance, suggesting that the core and windings are the same.

Can I convert my CG-1S into a CG-1C simply by removing the cardboard spacing in the core gap and butting the core tightly together, or do the core laminations have to actually be interleaved?

[KA2DZT]

You're right about REDUCING the gap between the "I" and "E".  But, you're better off leaving the choke as is.  You don't need a swinging choke for the input choke.  Swinging chokes were used way back when most supplies were lucky to have a few mfds for caps.  The choke was used to help regulate the output voltage.  As the current increased the choke would reduce in inductance thus bringing the filter closer to a cap input filter which would bring up the voltage somewhat.

You don't need this, leave the choke as is, 10Hy is plenty of inductance for an input choke.

Even Thordarson did away with this concept with the last series of chokes they made (21 series).  They made chokes that were a cross between the swinging and smoothing type thus having only one choke for each size.  But, this series doesn't due a very good job at filtering compared to the older straight smoothing chokes.

Swinging chokes were only helpful with modulators were the current load is always changing.  The power output stage in an AM xmtr never needed a swinging choke.

Fred

[w1vtp]

Don't change the choke.  Use it as is

[AB9ZG]

My motivation to change it was to prevent the power supply key up voltage from soaring. But it looks like the unanimous opinion is to leave it as-as. I'll put the power supply together and see how well the 10H input choke works.

Thanks for the responses.

[KA2DZT]

Your key up voltage is not the problem, it's the in rush current charging the capacitors.  If you're going to key the supply on and off with xmit and receive use a step-start circuit on the primary to the xfmr.  Very simple to build.  If the supply is for an AM xmtr, the high voltage soar is less of a problem because the finals are pulling current at the on set.  Although, the in rush current is greater, use a step-start, solve the problem.

Fred

[N2DTS]

Some people keep the voltage on all the time and key cathodes, and I guess some amplifiers leave the voltage on?
In AM rigs, its typical to put a resistor across the relay so the tubes draw a bit of current.

[AB9ZG]

Keying the power supply is alright for AM. However, it would be good to have the versatility of CW capability as well.  I think CW would require cathode keying or another system that involve the power supply being on without a load other than the bleeder. I do have two more 1A chokes that I could put in series with the UTC, but this seems a little wasteful.

[KA2DZT]

Keying the power supply is alright for AM. However, it would be good to have the versatility of CW capability as well.  I think CW would require cathode keying or another system that involve the power supply being on without a load other than the bleeder. I do have two more 1A chokes that I could put in series with the UTC, but this seems a little wasteful.

You didn't mention what voltage you are using and what type xmtr or is it an amp?  What xfmr??  Leaving the supply on can work, but you need to use a bit heavier bleeder and caps with a high enough voltage rating.

You need to build up the supply and test the voltage with just the bleeder current to see how high the voltage will get.  Not all chokes work the same even though they may be the same rated inductance.  So you need to do some testing.

Fred

[Opcom]

The "see-saw bleeder" as seen in 73, 1961 January, page 56, could help.

It does not require using the expensive PA or modulator tubes as a bleeder, which in the former case some people complain makes RF noise.

How about using a cheaper tube as an electronic switch?  In the article the HV is left on and the load is electronically keyed along with the bleeder. In the article the bleeder resistor is electronically switched by a small TX tube like a 6146 or 807. The see saw bleeder appears in an unauthorized collection of old AM related circuits here http://69.36.164.11/kb/goth/AGH-AM-027p.pdf (260MB)

Higher voltage tubes could be used, including Triodes. The reason to suggest that is because the circuit in the article may not completely cut off the bleeder at higher voltages depending on the 'idling' current of the switch tube. Tubes like the 4-65 and 811 can be held to cutoff at higher voltages than the 807, etc.