[Hammarlund] HX-500 trials

Mon Apr 25 20:56:17 EDT 2016

Maybe somebody converted a choke input power supply filter to capacitor input? 

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> Date: Mon, 25 Apr 2016 19:12:06 -0500
> From: WQ9E at btsnetworks.net
> To: jeff at podengo.com; hammarlund at mailman.qth.net
> Subject: Re: [Hammarlund] HX-500 trials
> 
> The 6146 tubes will draw a lot of current with those operating conditions.  With the plate and screen potential that high you will need more than -50 volts bias to keep it in check and 900 is really high since there is a load on the supply at that point from the final idle current.  With those plate and screen potentials the tube is going to be idling at higher than rated plate dissipation for a 6146B and way over for an original 6146 or A version.  Take a look at the data sheets with typical operational values and you will need to adjust accordingly.  Any chance choke L40 in your power supply was replaced with something other than the correct part?
> 
> My HX-500 is still in the awaiting restoration queue and I have made a note to check for too high plate and screen voltage when I get to it.
> 
> Rodger WQ9E
> 
> -------- Original Message --------
> > From: Jeff <jeff at podengo.com>
> > Sent: Monday, April 25, 2016 5:46 PM
> > To: hammarlund at mailman.qth.net
> > Subject: Junk E-Mail [Spam] :Re: [Hammarlund] HX-500 trials
> > 
> > Thanks to all of the great responses!  I didn't think that the socket 
> > might be the problem.
> > 
> > Alas -
> > 
> > No.  -50 volts on the pin at the top of the socket.  Both of them. I let 
> > it heat up for a minute to discover both plates on the two 6146s start 
> > to get red; the "first" one in the pair just draws current faster.
> > 
> > So -- -50 v bias on the tubes, 250 volts on the screen, about 900 v on 
> > the plates.  Still the tubes draw current.
> > 
> > Open to any other thoughts... tonight I'll put the ammeter on the plate 
> > choke to see exactly what it is pulling and report back.
> > 
> > And thanks to everybody for the manual information!
> > 
> > Jeff
> > WB3JIH
> > 
> > 
> > 
> > On 4/24/2016 7:21 PM, Jeff wrote:
> > > Oh -- and if anyone has a clean PDF of the manual, let me know.  I 
> > > appreciate the one on BAMA from N9SOR, but the watermark he's put on 
> > > it has washed out some of the text on the schematic and 
> > > voltage/resistance tables.
> > >
> > > I'd be glad to trade perfect quality PDFs of the original HQ-140X or 
> > > the HXL-ONE manual, or Hammarlund HT-32 if you're interested.
> > >
> > >
> > >
> > >
> > > On 4/24/2016 7:17 PM, Jeff wrote:
> > >> Well, been playing on and off with this rig.  Finally reversed all 
> > >> the golden screwdriver "mods" to the rig and have all the specified 
> > >> component values in, including the Hammarlund power supply mods now 
> > >> done correctly.
> > >>
> > >> Still, way high voltages on the meter.  Yes, I'm running a bucking 
> > >> transformer on the input, so I'm only putting about 109 VAC into it.
> > >>
> > >> And... now it is drawing current like crazy in standby mode.  As it 
> > >> warms up, you can hear the power supply start to load then the left 
> > >> hand 6146 will start to get red.  Reversing the tubes has no change, 
> > >> always the left one.  So, checked all the components in the power 
> > >> supply again, replaced all the components in the PA section (some 
> > >> drifted resistors, but not terribly off), checked wiring and 
> > >> grounds.  Still the one tube takes off.  Replaced parasitic choke 
> > >> resistors as the original carbon comps turned to dust in my hands 
> > >> when I started working them out of the choke. Still the same. Removed 
> > >> the 12BY7 driver tube, no change.
> > >>
> > >> Checked the bias supply -- right on the money with -90 and -50 volts 
> > >> where it should be.  I do however note that I have over 3 volts on 
> > >> pins 4 & 6 of the 6146s, when the voltage chart in the manual says 
> > >> between point 6 and point 9.  About 250 volts at the junction of the 
> > >> screen resistors.
> > >>
> > >> I am able to verify that the 1650 KC oscillators are working, so at 
> > >> least it appears that I'll be able to get some sections going. It is 
> > >> also drawing a lot of current though on the LV power supply, and I 
> > >> haven't tracked that one down yet either. Enough to burn up the two 
> > >> watt 15 ohm resistor in the LV supply.
> > >>
> > >> I also notice now the meter is totally dead.
> > >>
> > >> Anybody have any thoughts?  The PA current draw doesn't seem to be 
> > >> related to the driver section -- the tube's out of the rig...
> > >>
> > >> And I thought my CE 100V was a bear to trace out...
> > >>
> > >> Thanks for any thoughts --
> > >>
> > >> Jeff
> > >> WB3JIH