Rebuilding an SB-220 (for KJP)

Discussion in 'Amateur Radio Amplifiers' started by W1QJ, Jan 19, 2013.

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  1. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    Here is a photograph of the HT-33A. Maybe it should be called something like HT-33A-1/2! It has the circuitry of the HT-33B but doesn't have the 2nd blower and the layout of the chassis is different.

    As can be seen, it is just not worth trying to get it back to original condition, let alone the cost of a new tube! With a full-wave solid-state rectifier, the large capacitor and the filter choke can be removed, along with the filament transformer. That will lighten the amplifier a good bit.

    Glen, K9STH

  2. W1BR

    W1BR Premium Subscriber QRZ Page

    Looks better than my HT-41. All I have is the chassis, front panel and the power transformer. It is going to be used as the foundation for an amp using a pair of 813s.

  3. AF6LJ

    AF6LJ Ham Member QRZ Page

    From the top side it doesn't look that bad.
    Think of the space you will free up when all the support for that old power supply is removed and a new solid state supply is installed. Not to mention it will run a gob and a bunch cooler.
  4. W1QJ

    W1QJ Ham Member QRZ Page

    Steve, no kidding, Roland is right. If you need to get to the rectifier board on those Commander amps you have to take RF parts out to gain access to the underside of it where the board is hidden. it is a pain to get to it for repair. I guess the thought that anything in there would live past the warranty. I am always impressed with any kind of amp or radio or machine that was designed for easy repair. It shows that the engineers were thinking.
  5. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    The only thing from the power supply that I intend to keep is the high voltage transformer. Since it is center-tapped, the choke is now in the center-tap to ground, I can put in meter shunts to read both plate voltage and grid current.

    There are several broken components on the topside and a lot of dust!

    Glen, K9STH
  6. KM1H

    KM1H Ham Member QRZ Page

    As an authorized service center for the Command HF-2500 and the rest of their amps I have to apologize in advance to customers that a one hour PS job in other amps will be 3-4...yes I got more efficient once I found the tricks. New caps, resistors, including real ones for the HV meter string are automatic and I also do a couple of PM fixes on the control board and elsewhere. I also get in many of the Palstar versions from those who dont want to ship or dont like their pissy attitude on the phone.

    Variety is fun and I work on most all makes but Emtron. This IS my day job and Im never without work. I dont advertise as satisfied customers do it for me on the air.

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