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HART 75 Transmitter




 
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Author Topic: HART 75 Transmitter  (Read 21190 times)
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W9GT
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« Reply #25 on: October 03, 2013, 09:24:24 AM »

The 6DQ5 is a great suggestion, but the base connections are not correct for this rig.  The 6DQ6 works fine, but the plate connector is the small size which is different from the existing connector in the rig.  I just used a slip -on small connector on the tube then attached the larger one over that.  Of course, we could just change out the connector, but I was trying to keep things original.  Still trying to identify the "mystery tube".  A 6DQ6 with a large plate cap??

That 6DQ5 (and 1625 modulator) rig is a really nice example of a great home brew project.  That would be a nice one to build!

73,  Jack, W9GT
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M1ECY
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« Reply #26 on: October 03, 2013, 03:29:15 PM »

I will have a rummage, but I am sure I have versions of the 6DQ6 here with a large top cap.

Will report back once I have nosed through the valve store.

Sean
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W9GT
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« Reply #27 on: October 07, 2013, 09:26:35 AM »

I'm still searching for the EMICO 0-10 mA panel meter to replace the original one that opened up.  Seems that those cheap meters were famous for that, in addition to their total lack of damping and questionable accuracy.  I did find a 0-1 mA model on EBay and I can change the shunt resistors to accomodate that range, but I would still like to find one like the one that came in the rig.

73,  Jack, W9GT
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W9GT
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« Reply #28 on: October 13, 2013, 09:25:00 AM »

Looks like I finally found the Emico meter for the Hart 75 and it should be on its way to me shortly.  Thanks everyone for looking!  I also have gathered all the parts for the AM-1 Heising modulator and I will put that together over the next week or so....maybe I will have the Hart 75 on AM soon.

73,  Jack, W9GT
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W9GT
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« Reply #29 on: November 23, 2013, 05:11:49 PM »

I just realized that I had not informed everyone via this thread that I successfully completed the electrical restoration of this rig and also constructed the matching Heising modulator.  I got it on the air and had several good AM contacts including one with the owner of the rig.  The owner is having the front panel professionally re-done and it will be a real show piece and a great example of a really rare mid-fifties rig.

Hopefully, I will soon submit an article to ER outlining the story behind this rig and my adventures in researching it and getting it running.  Thanks again to everyone for your kind suggestions and comments during the process!

73,   Jack, W9GT


* Hart 75 in action.jpg (180.43 KB, 927x768 - viewed 522 times.)

* Hart 75 in action 2.jpg (170.03 KB, 1024x768 - viewed 578 times.)
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« Reply #30 on: November 23, 2013, 05:43:11 PM »

Nice!...Very cool setup........Steve
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W9GT
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« Reply #31 on: November 24, 2013, 10:15:22 AM »

Another view of modulator and PTT control box for Hart 75.  


* Heising Modulator and PTT.jpg (143.84 KB, 652x768 - viewed 496 times.)
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KA0HCP
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« Reply #32 on: November 24, 2013, 12:21:48 PM »

Congratulations!  I was afraid you would not make much progress due to lack of information.  Another piece of history gets saved from a dark corner or the dumpster.

As a gentle suggestion, please consider posting whatever schematics and information you received from the designer here and on the BAMA Mirror for posterity (if you have permission).

b.
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W3GMS
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« Reply #33 on: November 24, 2013, 02:28:45 PM »

Jack,
Congrats on finishing up the project. You did some great research including finding and ultimately talking to the owner of the company and that makes it all the more fun. 

Doing an article for ER is a great idea and I can't wait to read it. 

Hopefully the owner will put it on the air and use it.  Who did he find to redo the panel? 

Joe, W3GMS 
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W9GT
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« Reply #34 on: August 11, 2014, 07:57:14 PM »

My article describing the Hart 75 project is in the August 2014 issue of Electric Radio.  Also check out an article in the same issue by Don, K4KYV regarding putting a BC xmtr on CW.

73,  Jack, W9GT
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« Reply #35 on: August 11, 2014, 08:03:17 PM »

Congratulations Jack!

bill
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W3GMS
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« Reply #36 on: August 11, 2014, 08:35:43 PM »

My article describing the Hart 75 project is in the August 2014 ssue of Electric Radio.  Also check out an article in the same issue by Don, K4KYV regarding putting a BC xmtr on CW.

73,  Jack, W9GT

ER came today and that is the first article I read.  You did an excellent job and the story for me was somewhat familiar since we followed the trail on AMfone.  Congrats on taking the time to write up the story.  ER has a great audience and I am sure many of the subscribers will enjoy reading the story.

The second article I read was the one Don wrote.  Very interesting article and a practical and novel way to modify the choke input supply in order to not need the typical value of bleeder resistor required on a choke input filter. 

Joe, W3GMS 

 
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« Reply #37 on: August 12, 2014, 10:22:53 AM »

I also very much enjoyed the August ER article.   Very nice Jack.

Got the "ER" out of the mailbox yesterday and immediately crossed the road over to the Maple Lake club house porch to read it. Didn't wait to climb hill back to my house.

"Hmm, where have I seen this before?" In somewhat of a déjà vu fog...

..lights back on in there somewhere.   ..."Oh yeah!"

The documentation and confab with the original builder just about puts the little Hart 75 in priceless territory ; these days worth a video trip with him holding his creation along with a little show and tell interview.
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It's alive. IT'S ALIVE!!!


« Reply #38 on: August 12, 2014, 12:50:39 PM »

I too look forward to reading your article. ER has become my favorite ham rag. QST is a distant, DISTANT, second.
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W6TOM
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« Reply #39 on: August 12, 2014, 11:14:59 PM »

  Got my copy of ER late yesterday, Great Story!!

  If only these old radios could talk, what stories might they tell??
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« Reply #40 on: August 13, 2014, 06:39:05 PM »

Good ER article Jack.  While I was reading it I thought I had seen parts of it before.  Now I know why.  FB work.
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73,  Mitch

Since 1958. There still is nothing like tubes to keep your coffee warm in the shack.

Vulcan Theory of Troubleshooting:  Once you have eliminated the impossible, whatever remains, however improbable, must be the truth.
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« Reply #41 on: August 16, 2014, 09:13:16 AM »

In response to several requests for the schematics, here they are.  Please notice that the transmitter schematic is for the two 807 final version and not for the single 6DQ6 version that I restored.  Also the keying relay was added to this version. This drawing was sent to me by Hart Smith, W8QX.

73,  Jack, W9GT


* H75-807su.jpg (244.78 KB, 1026x787 - viewed 524 times.)
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Carl WA1KPD
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« Reply #42 on: August 16, 2014, 10:11:13 AM »

Thank you Jack
Carl
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Carl

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