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Author Topic: HEATH KIT DX-20 REPAIR  (Read 2530 times)
WB8VMW
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Posts: 29




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« on: April 22, 2012, 01:19:19 PM »

I JUST RECEIVED A DX 20 THAT WAS ON A SHELF FOR MANY YEARS AND WOULD LIKE TO GET IT ON THE AIR AGAIN. I CHECKED THE TUBES AND THEY ARE OK, I FOUND THE FIL. WIRE ON 6CL6 BROKE AND RECONNECTED IT. IT LOOKS LIKE SOMEONE HAD A VFO ON IT AT ONE TIME, THERE'S A HOLE FOR A SOCKET IN THE BACK BUT IT'S EMPTY. I PLUGGED IT IN AND IT LOADS UP LIKE THE BOOK SAYS BUT THE XTAL. I HAVE IS 7156 AND IT TRANSMITS OK THERE BUT ONLY THERE. THIS RIG IS LIKE THE FIRST ONE I HAD AS A NOVICE THEN A HW 16 THEN A 101. BUT I GUESS THERE IS ALWAYS A SMALL SPOT IN YOUR HEART FOR THE FIRST ONE. SO ANY HELP WOULD BE GREATLY APPRECIATED.
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W9GB
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Posts: 2623




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« Reply #1 on: April 22, 2012, 05:31:10 PM »

Plenty of VF-1 VFO on used market.  
Do not power this VF-1 from the DX-20, usually can not handle add'l current load.
« Last Edit: April 22, 2012, 08:55:28 PM by W9GB » Logged
K8AXW
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Posts: 3839




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« Reply #2 on: April 22, 2012, 05:50:04 PM »

VMW:  Help with what?  Sounds like it's working fine!!
« Last Edit: April 22, 2012, 06:05:17 PM by K8AXW » Logged
K8AXW
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Posts: 3839




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« Reply #3 on: April 22, 2012, 06:04:45 PM »

GB:  My first rig was the Heath AT-1 transmitter.  It powered the VF-1 VFO.  Later, when I used the Globeking 400B I used the VF-1 VFO for it, still being powered by the AT-1.

The DX-20 came later and I'd seriously have to evaluate rather it could or could not be powered by the VF-1.

A check at the Heath Museum gives the following power requirements for the VF-1:

"Requires a power source of only 250 volts DC at 15 to 20 ma, and 6.3 VAC at 0.45a, available on most transmitters."

The 0.45A for the filaments would be my main concern.  What do you think?
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W9GB
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Posts: 2623




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« Reply #4 on: April 22, 2012, 09:00:37 PM »

The Heathkit DX-30, DX-40 suffer from transformer failures -- attributed to under capacity or poor quality of the OEM potted transformer originally sold to Heath in 1950s.
The DX-20 is unknown (to me) if it suffers from this same failure rate/cause.
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K2OWK
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Posts: 1061




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« Reply #5 on: April 22, 2012, 09:15:55 PM »

I had a Heathkit DX-35 back in the fifty's. I used the VF-1 powered by the DX-35 without incident. I think the DX-20 was the CW version of the DX-35. If memory serves me right the VF-1 has the old 11 meter ham band on it. I do not know if the DX-20 power supply will handle the VF-1, but it was supposed to.
Just for safety sake I would power it up with an external supply, because of the difficulty of getting components for this transmitter if the power supply fails.

73s

K2OWK
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K7MH
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Posts: 339




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« Reply #6 on: April 22, 2012, 11:24:38 PM »

Replace all the electrolytics in it if it hasn't been done already.
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K4EJQ
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Posts: 101




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« Reply #7 on: April 23, 2012, 06:29:17 PM »

Jim; Welcome to the DX-20 "Club". I've been using one for a number of years with a VF-1 VFO powered from it's own dedicated well-filtered and regulated power supply. Works like a champ. Just replace the original filter caps in the power supply and add a fuse to the rig's primary 115 VAC input if it hasn't already been done. Works like it did when new. Enjoy, but remember it's an old piece of gear and you don't want it to sound like an IC-XXXX. A little chirp is good for the soul!!! 73, Bunky, K4EJQ
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WB8VMW
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Posts: 29




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« Reply #8 on: April 24, 2012, 04:40:29 AM »

WELL NOW I KNOW JUST HOW MUCH I HAVE FORGOTTEN ABOUT MY EQT. A FRIEND LOCALLY READ MY QUESTION AND CALLED ME AND TOLD ME THE SAME AS ONE OF THE ANSWERED I GOT HERE. IT'S DOING WHAT IT'S SUPPOSED TO DO. SO EXCUSE THE LACK OF SMARTS( THAT'S WHY I CAME HERE TO GET THE ANS. )AND HOPE THE NEXT TIME I CAN POST A REAL QUESTION. THANKS AND HOPEFULLY SOON YOU WILL HEAR ME BANGING AWAY ( WITH A SMALL CHIRP) ON MY UP AND RUNNING DX-20.
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K8AXW
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« Reply #9 on: April 24, 2012, 10:54:45 AM »

Quote
A FRIEND LOCALLY READ MY QUESTION AND CALLED ME AND TOLD ME THE SAME AS ONE OF THE ANSWERED I GOT HERE.

VMW:  That's great, I guess.  Do you mind sharing what you found out from your friend?  This information may be used later to help another ham with the same question.
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WB8VMW
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Posts: 29




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« Reply #10 on: April 24, 2012, 01:49:34 PM »

MY FRIEND SAID THAT IT'S WORKING THE WAY IT SHOULD. IT TRANSMITS ON ONLY THE FREQUENCY OF THE CRYSTAL THAT'S PLUGGED IN TO IT,THE ONLY WAY TO TUNE THE WHOLE BAND IS WITH A VFO.   
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KB3YLB
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« Reply #11 on: May 11, 2012, 09:09:48 AM »

I have a DX-20 that I picked up at an auction for $10. Was wired all wrong. Rewired and replaced caps. Loads up real nice now.
On your crystal, I have a crystal 3558 for mine and I would set the DX-20 up on 40 meters and transmit on the 2nd harmonic
at 7116. I had 3 contacts using that routine with just a 30 foot end fed wire strung out the window and tied to a tree. It was
putting out near 40 watts. SWR wasn't good! It is a nice simple rig but a VFO is really a must. The power supply in the DX-20 does not supply
enough power to power up a VFO so you will need a separate power supply for the VFO. I found a Knight VFO on ebay that is
self powered and works just fine. I just wired in a BNC connector in the back to the crystal terminals to connect the VFO.
Hope you have fun with your DX-20. Maybe I'll see you on the air. I have a new callsign whichis K2DEP. I operate in CW mode.
Steve K2DEP
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