[Hammarlund] HX-500 power supply service bulletin

[jeff]

Thanks Al!
Finally got the chance to get the rig on the bench. The power supply was completely hacked up. 
Somebody was in there and had put all kinds of power resistors in series and in parallel, some values were greater than, and some less than, the schematic indicated. 
I've got the supply back to where the addendum says it should be. Here's where the problem is- I have very high vtages across the board. I am feeding it a line voltage of 115. My HV is over 1000 volts (with the 5R4 tube in place), the LV coming off of the 6CA4 is over 400 volts, and the 15 ohm resistor at the LV choke input is still above 400. I'm seeing about 270 volts at the junction of R122 and R119.
I've disconnected the 15 ohm resistor and I see about 330 volts; still high, but where it would be more reasonable. LV choke resistance is 260 ohms, and all new electrolytic of course.
Bias supply is right on:-90 volts.
Any thoughts? 



-------- Original message --------
From: Al Parker <anchor at ec.rr.com> 
Date: 03/20/2016  3:56 PM  (GMT-05:00) 
To: hammarlund at mailman.qth.net 
Subject: Re: [Hammarlund] HX-500 power supply service bulletin 

Hi Jeff,
     Here's the info on the p.s. mods, which incl. what you wanted, on 
the rectifiers, plus the change to an improved pwr xfmr.  I can't 
remember if my HX-500 has the better xfmr or not, but it does have the 
rectifier mods.
     The .pdf att won't get thru to the reflector, but if anyone else 
wants it, send me a note.
     I hope it helps.
73,

Al, W8UT
www.boatanchors.org
www.hammarlund.info

"There is nothing -- absolutely nothing -- half so much
worth doing as simply messing about in boats"
Ratty, to Mole

On 3/20/2016 1:32 PM, Jeff wrote:
 > Does anyone have a copy of the service bulletin that shows what 
modifications were done to the supply? This would be the change between 
the 12 AX 4S and the 5R4, along with a semiconductor device for the bias 
supply.
 >
 > Thanks!
______________________________________________________________
Hammarlund mailing list
Home: http://mailman.qth.net/mailman/listinfo/hammarlund
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Hammarlund at mailman.qth.net

List Administrator: Duane Fischer, W8DBF
** For Assistance: dfischer at usol.com **


This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html