[Heathkit] DX-60 Repair Adventure, or DX-60 only Works on its Side

Tue Sep 5 10:18:04 EDT 2006

Over the past several of years I've casually collected an HR-10B, HG-10,
DX-60B but I haven't gotten around to assembling the station yet.  

Friday I got the bug to get the Heath station up and running so I moved it
down off the shelf and into the one of the operating positions.

Last year I realigned the HR-10B receiver, so I didn't have
to do anything with it other than wire up the mute contacts to the
antenna relay. I was listening to 40 meter CW while I was
working on the transmitter.  That HR-10B sounds pretty nice and was probably
a nice beginning ham receiver.  It sounds alot better than some of the junk
that was sold as a 'ham receiver'.  The Conar 500 comes to mind, or the
Ameco R5.

I hooked up the VFO and TX and just fired it up.  There was very little
grid current and the frequency wobbled with out any provocation, so I put
the TX on the bench and opened it up, set it upside down. I checked the voltages and they were 
good (at where I was measuring them... hint hint).  Then checked the tubes and the 
6146 was bad so I replaced it.  I was now getting grid current.... ok.... that was
easy.  I had a crystal in and I listened to the signal on the receiver.  The oscillator was
stable and sounding very
good.  I turned it over, closed up the PA cage, and went to measure power but got nothing.
No grid current again.  Huh?

So I set it on its side to start probing and got grid current right away. 
I started tapping around the chassis and found it was intermittant.  It seemed to be the worst
when I tapped on the PI Network box, so I shut it down and pulled the box off the chassis.
I found a burned up silver mica on the last stage, but that wouldn't account for the
intermittent problem.  I replaced the silver mica and then touched up all the solder
joints in the box, reattached it, powered up the DX-60, and it was still intermittent. By the
way, those PI filter box screws such are a bugger to get at.... 

I was now tapping under the chassis with the Red Heathkit plastic nut driver, tapping components, 
sections, and I found an unsoldered joint.  AH HA.  Soldered it, turned it back on, and... and...it
was still intermittent.  

By now I'm starting to notice that it often works on its side but it never
works when its sitting down on the table...  Up/down, Up/down, work/no work :))) With the TX on its side,
I continued tapping but I couldn't find a sensitive area.  I got down on the
floor so I could peer up under the chassis as I lowered it down to the table, and I saw a brief ZZZtttt.
It was in the high voltage section, a lug had a couple of HV connections on it, and one of them
was not soldered.  It was hidden under the soldered joint above it. So what apparently was 
happening was the connection was made when the TX was laying 
on its side or upside down, but when the TX was placed flat on its feet, the weight of the power 
transformer tweaked that
joint slightly, opening the connection... Sheesh.... So I 
soldered it up and that was the end of
the intermittent problem.  After than I went through and looked at the rest of the connections,
hunting for any more unsoldered joints.   I should have recapped the high voltage electrolytics
but I didn't have the right value so I'll order them from Mouser.  I also retighted every screw and
nut in there, relubed up the rotary switches, a little DeOxit here and there.

I just started going through the HG-10 VFO before calling it a day.  Maybe I'll get to that this 
week and have the classic Heathkit station on the air by the weekend.  I love CW and hope to have
a ball with this station on CW.  While I hear an occasional DX-60 on AM, I'm not
that much of a masochist  :)

I thought you guys would get a kick out the sideways adventure.

Did Heathkit ever give away blank QSL cards for Novices to use?

73, Scott WA9WFA

-----Original Message-----
From: heathkit-bounces at mailman.qth.net
[mailto:heathkit-bounces at mailman.qth.net]On Behalf Of Duane Fischer,
W8DBF
Sent: Saturday, September 02, 2006 10:29 PM
To: Jim Brannigan; Robert & Linda McGraw (K4TAX); David Thompson; David
Rose; heathkit at mailman.qth.net
Subject: Re: [Heathkit] SB 220 on AM

Suck it up James! The Heathkit SB-220 is a decent HF amplifier, a real work 
horse in fact. So unless the former owner/owners assembled her incorrectly 
you should be as happy doing eons worth of DX bank shots off the D layer of 
the ionosphere as Ben Franklin was after that solid Brass key he was holding 
between his wet lips evolved into the dance step of the century that 
historic electron Cha Cha, Proton puddle piddle and neurotic Neutron 
necromancy when that inspired bolt of wisdom from the great blue beyond 
ignighted his mustache, abundance of 12 gauge nose hairs and bushy eyebrows 
transforming his bifocal parking place into what put one in mind of a 
seriously char burned super sized marshmellow! So Jim should a 'Headless 
Horseman' pull up in a horseless carriage and deliver into your trembling 
hands an envelope bearing your Colonial family monogram. Easily verified as 
an authentic manual, bold sprawling script listing slightly to starboard 
from Peter The Scholar of Schematics, the Master of manuals and Lord 
Laffayette the only guy in Benton Harbor, Michigan who could seamlessly 
solder up a sword shank withouta cold shoulder joint!

James, this final tidbit that I trust will help you distinguish the properly 
assembled Heathkit from one that really should be used to anchor a boat! If 
when you remove the bottom plate that covered the inside of the chassis, 
turn it back rightside up and observe what gifts befall you. The General 
class rule of thumb is, assuming you still have said digit, having niether 
burned it off due to poor soldering iron habits or slipped with a razor 
blade knife and whittled flesh and bone into a living toothpick, if you can 
fill the Anthrancite Coal car of a 1952 Tom Thumb 1/50 scale model with 
loose solder, don't buy it! Because some kit clutz kid, or Bozo The Clown 
drop out, lived in a joint with no heat and a lot of cold solder!

If you should need them Jim, I still retain copies of the original assembly 
and service information manuals. A great amp, 'provided' you DO NOT 
overdrive it. If you let her run about 800 watts keydown and watch the grid 
current, the 3-500Z's can last twenty years. According to a note from Jim 
H., he was still using the original finals he put in his SB-220 in the early 
seventies.

If you need "good" quality original, or reproduction, manuals then utilize 
WA2CWA, Pete or NI4Q, Al Bernard. Excellent detail, sharp contrast, well 
bound, reasonable prices and prompt shipping. Two gentlemen! There are 
others who also do nice work, but Pete and Al get the old blind dude's 
"thumb and a third" up! (LOL!)

Duane Fischer, W8DBF

 ----- Original Message ----- 
From: "Jim Brannigan" <jbrannig at optonline.net>
To: "Robert & Linda McGraw (K4TAX)" <RMcGraw at Blomand.Net>; "David Thompson" 
<thompson at mindspring.com>; "David Rose" <w4dja at hotmail.com>; 
<heathkit at mailman.qth.net>
Sent: Saturday, September 02, 2006 8:11 PM
Subject: Re: [Heathkit] SB 220 on AM

> Thanks for the tips. I've been chugging along with a Ranger on AM and have 
> been a bit "chicken" about using the SB-220 for all the reasons noted.
> I have a schematic for a Ranger attenuator, time to get the parts and 
> build it!!!
>
> BTW: The Harbach(sp?)  fan is just a bit noisier, but it moves a lot more 
> air.
>
> Jim
>
>
>> Agreed, the SB-220 will do OK on AM although I consider it a wee bit 
>> light in the power supply and cooling areas.  Keep in mind that carrier 
>> level modulated 100% will then be a PEP value equal to carrier times 4. 
>> Thus 350 watts of carrier equals 1400 watts PEP.  Legally one can run 375 
>> watts of carrier modulated 100% for 1500 watts PEP.  Also, keep in mind 
>> the duty cycle of the SB-220.  I seem to recall it to be something on the 
>> order of 50% or less.  Thus the transmit time must not exceed the 
>> non-transmit time.
>>
>> Regarding tune-up.  With the FT-990 in tune mode drive the SB-220 to max 
>> output, watch the grid current which is the most critical parameter to 
>> observe during tune-up.  Don't exceed 260 ma, as I recall, for 2 tubes 
>> and adjust tuning and loading on the SB-220 for max output.  Maximum 
>> plate current should not exceed 800 ma for two tubes.  Increase the drive 
>> as necessary but not so much as to exceed the grid current rating of the 
>> tubes. This can be done in the SSB mode for the SB-220.  Switch the 
>> FT-990 to AM and adjust the drive for about 250 to 300 watts output.  Do 
>> not change the tuning or loading of the SB-220.  Remember, it should be 
>> tuned for some 1200 watts output PEP although the un-modulated carrier is 
>> only 250 to 300 watts. Ideally you have and use a monitor scope to look 
>> at the waveform to assure that the negative peaks do not exceed 100% and 
>> the positive peaks are not flattened.
>>
>> I've run everything from a Heath DX-60 with control carrier modulation, 
>> then converted it to classic screen modulation and used it to drive a 
>> pair of 3-500's to legal AM limit of 375 watts output (1500 watts PEP). 
>> At present I use a Heath TX-1 Apache at 150 watts output (600 watts PEP) 
>> but with high level modulation.  For this application I don't use an 
>> amplifier.  Then there is the retired BC transmitter that weighs in at 
>> 3.7 lbs per carrier watt or 1400 lbs.
>>
>> Good luck on AM
>>
>> 73
>> Bob, K4TAX
>> 1885 KHz and 3885 KHz
>
> _______________________________________________
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