[Amps] Amp Supply LK-500ZBx or generic P/S capacitor Question

Carl km1h at jeremy.mv.com
Tue Jul 8 15:21:09 EDT 2014

The PM 800 caps are superior and modern technology. The other set goes back 
to 1970's designs and once called computer grade.

If you look at the MFJ catalog they are selling 270uF screw terminal caps in 
under half the height which are what is used in all their amps and the cap 
internals are a modern design for those still using screw terminals.


----- Original Message ----- 
From: "KB8NTY" <kb8nty at wowway.com>
To: <amps at contesting.com>
Sent: Tuesday, July 08, 2014 2:24 PM
Subject: [Amps] Amp Supply LK-500ZBx or generic P/S capacitor Question

> Appreciate all the help this group provides.
> I have a nice clean unmodified LK-500ZBx (not sure what the x means), an
> early
> serial number 500x,  the all gray front not the colorful
> version.
> P.Dahl transformers, QSK option, no ALO, step start, or fan speed option.
> Original 8438 code Eimacs, producing 1400 out on best band.
> As an admitted somewhat novice in the amp theory I look to the group for
> valued help
> / advice.
> H/V seems to read 2900 +/- Idle, 2500 key down,  but more concerning is 
> the
> steady "buzzing"
> coming from the P/S board (not the transformers) when powered on and when
> keying
> amp as well.
> In the thoughts to save a impeding disaster a P/S replacement is in order.
> I am a recovering leukemia patent, disabled, and recovering from both L&R
> shoulder reconstructive surgeries from a fall after being discharged home
> from long hospital stay.
> Not complaining, I am blessed to be here and appreciate every day!
> So not being up to repair/replace the original board, or ship out for
> upgrade, I plan to purchase the PM-800 P/S from Harbach:
> http://harbachelectronics.com/shop/amp-supply/pm-800-replacement-power-supply-module/
> My question..I also see he offers a capacitor:
> http://harbachelectronics.com/shop/misc/cp-210-set-of-eight-8-220-%ce%bcf-450vdc-filter-capacitors-with-sems-screws/
> Similar to the original's in my LK-500ZB, these are physically larger than
> the modern caps supplied with the PM-800 kit.
> Any thoughts or opinions regarding the newer smaller modern caps compared 
> to
> the older larger caps?
> His smaller caps are 105 deg hi-temp rated, which is good. So considering
> with
> the values being close to the same 210/220 mfd, any reason to not go with
> the smaller modern size?
> Of-course the PM-800 board will be much easier for me to deal with and all
> components & new board are all supplied, based on vintage the complete P/S
> component replacement should be a good thing!...However if there is
> compromise by use of the smaller size caps compared to the original larger
> types, I will have to step back and re-evaluate my purchase plan.
> I'm overthinking but if the smaller size, modern caps are equal or better,
> has me overthinking then why dont present day tube amps such as ameritron
> use the smaller caps?
> Thank you very much for your thoughts and experience. I value your
> contribution.
> -73- Ross KB8NTY
> RossRadio: RF Ground Radial Website
> http://www.rossradio.net/
> Ground Radial Discussion: Please Visit & Join In!
> https://groups.yahoo.com/neo/groups/groundradial/conversations/messages


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