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Tuesday, June 26, 2012

HW-7 fixed after 36 years!

Give this man a license!  He deserves one.  Great job David. 
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Bill,

Found your podcasts (137 & 8) about the HW-7. Really enjoyed hearing your enthusiasm. I have owned one since 1976...my dad purchased it for me while at the Dayton Hamvention. Unfortunately it didn't work when we plugged it in. Dad didn't have the money to fix it at the time and as a 15 year old, neither did I. So it went into a box and was stored. 
Fast forward to 2008 and my youngest son asked me what Morse Code was. I told him and showed him...I didn't remember hardly any code. He wasn't interested in learning that didn't deter me and I wondered about the HW-7. So I went to the attic and found the box with the old rig. It still didn't make a sound when turned on so I decided to crack the case open and go through the troubleshooting guide...I had the manuals for both the radio and power supply. I determined the 40673 was bad. 
Got online and snooped around and couldn't find a source for a replacement so I started looking into equivalent parts and ran across the NTE454. Ordered it, made some "soldersmoke" and replaced it, turned on the radio and was happy to hear hum from the power supply in my headphones. Switched over to a 9 volt battery, attached a long wire and was blessed to hear CW coming through loud and clear! 
Dad, a ham from years past, almost didn't believe me when I called to let him know. "Fantastic!" was his response when I explained how it happened. (He's an EE and I'm a graphic designer.) 
During the investigation I also discovered that the original owner never finished the assembly guide. Found a tool at Radio Shack that I could tune the coils with, borrowed a frequency counter from a local TV station's tech and with dad's help aligned the rig according to the manual. Got the dial into rock solid sync with the FC. Both on RX and TX. 
I never heard what it sounded like with the 70673, however, looking at the data sheets for both Mosfets, the noise level of the NTE454 is lower. Typical for the NTE454 is 1.8 compared to 3.5 of the 40673. The max is 4.5 compared to 6.0 according to RCA. I have ears, thank you, and have copied a station located halfway down the Baja peninsula running 100 watts into a vertical. I was using a dipole 12' up in Indiana. I say copied because I have yet transmitted with it. Because of life I have been delayed (many years) in getting my ticket. However I will be taking the Tech exam...possibly even the General exam in July...but I have a bit more study to do for General. As a tech I would only be able to use 40 meters 
I have retrieved dad's J-38...still sporting the 76 Dayton Hamvention sticker on the bottom, polished it up and have been practicing for when I can get on the air. 7 1/2 WPM currently, but slowly gaining. I hear that working stations on the air will help the speed increase.
Anyway, the HW-7 is going to be my rig for a while...thought about selling it...because of the stories I've read...but I like listening to it JUST LIKE YOU for the SSB rag chews near the top of the 40 meter band. I also listen to the slower guys on CW to get my ear tuned to it. You also confirmed how to tune and listen so I will have possibly, an easier chance in making contacts. I also know a few local hams that can schedule with me. 
The HWA-7-1 power supply needs mods though. Plan on putting in place some caps and some magnetic beads to hopefully reduce the hum to a respectable level. Anyway, I appreciate your sharing and hope to work you sometime.

David Oldham
Greenwood, IN


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2 comments:

  1. Update -- Granted a license today. Couldn't wait to make a contact. Took just a couple of minutes. Heard Dave, N9KKY, calling CQ and I answered him and he heard me. The very first contact this old radio has ever made. Based on his location he was 237 miles from me as the crow flies. My dipole is between 12' to 18' off the ground, so it was NVIS since Dave was off the ends of my wire. Anyway, between whipping the dial back and forth to hear and be heard plus other close stations and my newb status to both sending and receiving Morse, the QSO was short and mostly missed by me. But it was neat hearing my new call sign, KC9WIP, come back to me on this ole girl...I'm happy! 73

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  2. FB OM! Congrats on your first QSO, on the old HW-7 no less! Because really, how could OM "Oldham" not have a ticket?

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