Hallicrafters P-2000 power supply rebuild

Discussion in '"Boat Anchor" & Classic Equipment' started by WB3JIH, Aug 11, 2018.

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  1. WB3JIH

    WB3JIH Ham Member QRZ Page

    Hi all -- currently going through a very badly hacked up P-2000 power supply.

    It appears that the 5Kv 1 A diodes have been replaced. There are a couple of wirewound resistors in series with the diodes (between the transformer and the diodes themselves.) I'm assuming they were put in for inrush current limiting, but the schematic shows no such components.

    Second, the B+ supply has a 10 watt 25K resistor across C318B (second filter capacitor after choke), which also does not appear on the schematic. I'm assuming this is a bleeder resistor for the B+ supply, but again, since it isn't in the original design, I'm wondering what negative effects it might cause. I suppose it saves me the drama of discharging the filter capacitors before working on the supply...

    The bias and screen supplies are rebuilt, so all good there. If the HV supply resistors don't really serve a critical purpose, I'd like to take them out since it's just another heat source. They clearly run hot as the lettering has long burned off of them.

    The HV supply is a standard voltage doubler circuit BTW.

    Thoughts appreciated.

    Jeff
     
    Last edited: Aug 11, 2018
  2. K9STH

    K9STH Ham Member Volunteer Moderator QRZ Page

    There should be a bleeder resistor across every electrolytic capacitor.

    As for the resistors in series with the rectifier diodes, with modern silicon diodes they definitely are not needed!

    Glen, K9STH
     
  3. K9AXN

    K9AXN Ham Member QRZ Page

    Have you tried the radio on 10 Meters yet?

    Regards Jim
     
  4. WB3JIH

    WB3JIH Ham Member QRZ Page

    Jim -

    I'm able to tune the rig on 10, but it's probably not 100%. It's OK by me, as I don't really use the vintage stuff on 10 anyways. Not that 10 is usable these days.

    Of course I won't remove the bleeder resistors from the HV supply -- I was just referring to the 10 ohm wirewound resistors that were in series with the 5 KV recitfiers (and not on the schematic). Goal is to simply restore the supply to schematic specifications.

    --Jeff
     
  5. WD0GOF

    WD0GOF Ham Member QRZ Page

    Hi Jeff,
    If you have the proper diodes I think the limiting resistors are a waisted effort. As for the bleeder resistor, I would say it is on the border of over kill, if you are concerned about depleting the 280vdc at power down. The dynamic load on the 280v line is approx. 2.1K. That will yield a TC (time constant) of 0.063 seconds. It takes about o.75 seconds for the filaments to cool to cutoff. That is almost 12 TC. The magic number for discharge TC's is 5. So at the instant of turn off, the 25K resister across C318B is swamped by the dynamic 2.1K of rig. By the time the dynamic load fades away C30 is already discharged. It harms nothing being there (o.0112 amps 3.1 watts) but it is just unnecessary. The original designers of these old classics did not make a lot of errors. By the time the SR-2000 got to its 4th and final production run there were few real design flaws left. It performed as advertised. BUT WE IN THE HOBBY are never satisfied we must IMPROVE everything. And that, Jeff, my friend is why we sometimes get a rig like yours ;).
     
  6. WB3JIH

    WB3JIH Ham Member QRZ Page

    That will work! -- Thanks!

    Throughout the process of this rebuild, I've hewn as closely to the schematic as possible. I'll use modern parts and materials because they are just safer and more robust, but I firmly believe that the guys that built her knew a heck of a lot more than I do.

    This was the most torn up rig I've worked on to date, but each one teaches me a little more: a new technique, how to fabricate a new part from scratch, how to use a grid dip meter for real, and best of all, likely the opportunity to add a new tool to my toolbox and bench...

    I'll replace a 4H4c with a LM317, because I'm pretty sure the Hallicrafters engineers would look down and approve. I'm just the current caretaker of this rig. The point to me is to let them have their dignity. They are history; let them be what they were at the time. And if you get annoyed with me drifting a few dozen Hz, well, then don't answer my CQ.

    :cool:
     
  7. W9GB

    W9GB Ham Member QRZ Page

  8. K9AXN

    K9AXN Ham Member QRZ Page

    The VFO's in the SR-2000, SR-400, and SR-400A are the finest CTO's of the era and drift comparable to Collins if the VFO has been restored and temp comp adjusted.

    It can be made to drift maybe 100 HZ in the first 15 minutes then dial up an SSB QSO go on vacation and it will still be there --- doesn't need any help. Stanford and Orwin of Hallicrafters were wizards. The VFO had some design improvements that were not included in the production radio because of expense and inadequate bang for buck value.

    Regards Jim
     
  9. WA6MHZ

    WA6MHZ Subscriber QRZ Page

    Already went thru the whole recap and renewal project. When I couldn't find the time delay relay I designed one using a 555 and made pins on the bottom of the project so it would plug in the existing socket (in case I ever found a correct time delay relay)

    This is all documented in the QRZ archives somewhere.

    the diode stack in mine was OK so I left it as is, but should I replace it, I'd just use a stack of 1N5401s like the Pros do in a SB-220.
    The power supply worked great, but it is ridiculously heavy so; and I never got the SR-2000 to work quite right, so it wound up in the MUSEUM of FUTILITY!

    I have ALOT of money in this rig (well over $1000) so I am not about to just sell it to some clown for $20! The NUN might though!

    HINT: If you want to hurry up my Estate Sale, take out a HIT on me. I just ask that you instruct the Hitman to make it quick and painless.
    Then give the Nun the $20 for the SR-2000 and PS
     
  10. WD0GOF

    WD0GOF Ham Member QRZ Page

    $20, I guess not. The last fully functional SR-2000 I saw for sale was listed for $4100 with money back if it did not function to spec. It sold in one day. I am asking $7500 for mine, but I don't want to sell it :).
     

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