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In Reply to: RE: Cit II Doubler Filter posted by Triode_Kingdom on April 02, 2017 at 14:52:02
I've snipped from Jim's site the minimum level of Cit. 2 PSU overhaul he offers. Jim offers stuff beyond this.
For the Citation II Power Supply
1. (2) 820 uf 250 volt 105 degree Celsius very low ESR clamp mount caps that increase the capacitance from
100 uf total in the doubler to 410 uf. (2) clamps are included.
2. (4) General Instruments fast/soft recovery diodes that replace the existing top hat diodes. They fit nicely in the
fuse holder right where the old top hats are now. The GI diodes are very good, and quite reasonably priced too.
If you increase the capacitance, you really need to replace those diodes. And the DO-41 packaging is ideal for replacement.
3. (1) JJ 100/100 dual section 500 volt clamp mount cap, and...
3a. (1) Nichicon 220 uf/500 volt clamp mount cap. The Nichicon replaces the 40 uf 525 volt original twistlock,
and the JJ replaces the dual 50/50 V1/V4 decoupling cap. (2) clamps are included.
Note: This amp responds very well to improved decoupling of the input 12BY7A tubes!
4. (1) .01uf high voltage film cap to replace the existing ceramic unit.
5. (1) Gen'l Instruments fast/soft recovery diode to replace the bias selenium rectifier
6. (1 ea.) 220uf and 100 uf radial electrolytics, a new 1.8K ohm resistor, and a terminal strip for the bias circuitry.
Two new 4.7K ohm resistors to increase the range of bias adjustment.
7. A copy of the schematic, and kit installation notes and diagrams.
You end up with 630 uf (vs. 140 uf stock) of high quality capacitance for the B+, and twice the decoupling
Yes, Jim's basic mods to the doubler create a much better supply. I modeled it yesterday, based on the info on his Website. It's not likely I'll ever own a Cit II, but the concepts Jim is using would be applicable to any supply of this type. Below is the model of the modified doubler. It's scaled the same as the factory PS I posted earlier. Quite a difference!
Buy Chinese. Bury freedom.
Thanks for running the model! I know you didn't have all the best info to run it with either - so your effort was greatly appreciated.
Just FYI - the DCR of the Cit II choke is 11 Ohms at room temperature - it may be a bit higher when under the hood of a Deuce which does get warm underneath.
Also the ESR of the doubler caps is .187 Ohms each - so even stacked in the doubler the total ESR is under .4 Ohms.
Finally (again just FYI) there is 220 uf of high quality capacitance after the hash filter so the spike you saw isn't there.
One last time - THANKS!!
NO need to thank me, it was a necessary exercise for my own work. I was glad to see such a remarkable improvement from your upgrade design (not that I expected anything else). I have a number of HK amps and receivers to rebuild using the transformer sets on new chassis designs. Most will probably be sold off, but One of these, the A500, will be for my own use. I just picked up a spare power transformer for this amp, so now I'm thinking about re-configuring as two isolated channels or maybe monoblocks. Anyway, I'll probably be looking to you for the filter caps in some or all of these. The extremely low ESR of the components you're selling has really caught my attention. Send me a PM if you ever have any pending designs you'd like to see modeled in SPICE off the forum.
Buy Chinese. Bury freedom.
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