The AM Forum
March 28, 2024, 12:09:38 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1] 2   Go Down
  Print  
Author Topic: Harris MW-5 Conversion  (Read 24493 times)
0 Members and 1 Guest are viewing this topic.
ke5pme
Guest
« on: July 06, 2010, 01:37:01 PM »

Hello everyone,

I had a few questions that maybe someone could assist me with. I started work on converting my Harris Gates MW-5 for opperation on 160M and have been working a few issues out with the OSC/IPA. Being that this machine works in the range of the broadcast band I need to adjust my exciter a bit. My question is if I bypass the dual oscillator board and feed the IPA amp with 160m signal from a VFO will the IPA amplify this signal being that it is slighlty above the range of 1640 kc? On the IPA there is a set of four coils with a strip of adjustable ferrite rods that may control the matching? Any help or insight would be greatly appreciated.

Thanks
-Ben
Logged
DMOD
AC0OB - A Place where Thermionic Emitters Rule!
Contributing
Member
*
Offline Offline

Posts: 1768


« Reply #1 on: July 06, 2010, 02:37:46 PM »

Since BAMA doesn't have a schematic` of the MW-5, could you scan one in so we can help?

Phil - AC0OB
Logged

Charlie Eppes: Dad would be so happy if we married a doctor.
Don Eppes: Yeah, well, Dad would be happy if I married someone with a pulse.NUMB3RS   Smiley
ke5pme
Guest
« Reply #2 on: July 06, 2010, 09:30:32 PM »

Sure,

Here is a block diagram of the IPA chain. Its located in the upper right hand of the drawing. I have also included a picture of the IPA section if it is of any help. The final transistors or Motorla SJ7349's in the picture.

Thanks


* IPA Block2 001.jpg (1058.55 KB, 2330x1200 - viewed 1083 times.)

* IMG00352.jpg (596.23 KB, 1600x1200 - viewed 783 times.)
Logged
ke5pme
Guest
« Reply #3 on: July 06, 2010, 09:33:28 PM »

One more schematic.


* IPA Block2.jpg (1045.83 KB, 2272x1696 - viewed 1113 times.)
Logged
ke5pme
Guest
« Reply #4 on: July 06, 2010, 09:58:13 PM »

And here is the text portion.


* IPA Block2 002.jpg (1069.35 KB, 1312x1712 - viewed 713 times.)
Logged
DMOD
AC0OB - A Place where Thermionic Emitters Rule!
Contributing
Member
*
Offline Offline

Posts: 1768


« Reply #5 on: July 09, 2010, 12:22:39 AM »

Those are not really what we call block diagrams but it appears a 30 V P-P sine wave from the oscillator is feeding the broadband IPA that is peaked by L1 and associated caps.

The broadband IPA appears to be a switch-mode amp for higher efficiency. The output of the IPA is filtered by L2 and associated caps to turn the pulses back into a sinewave.

The C1 cap in the IPA may would have to be modified for a change in frequency.

Some questions are:

1. is your VFO capable of supplying a 30 V P-P since wave into the BB IPA switcher
2. Does your VFO have a low enough impedance to drive it
3. Are you going to change components in the Final as well to tune to a higher frequency
4. Do you have the test equipment and an electronics background sufficient to make these changes

Phil - AC0OB
Logged

Charlie Eppes: Dad would be so happy if we married a doctor.
Don Eppes: Yeah, well, Dad would be happy if I married someone with a pulse.NUMB3RS   Smiley
w3jn
Johnny Novice
Administrator
Member

Offline Offline

Posts: 4620



« Reply #6 on: July 09, 2010, 06:46:14 AM »

Feed the VFO input thru a .01 cap or so to the base of one of the oscillator transistors.  You might have to play with the level a bit so as not to overdrive the transistor.  It doesn't appear that there are any tuned circuits between the oscillator and the driver output.  Tune L2 for max on the inputs of the IPA modules.  If you run out of room, you'll probably have to trim the inductor and/or remove one of those C3 capacitors.

It appears all the coils on the IPA outputs are ganged together.  Since you're going for a frequency well above 1640 they should most likely be all the way out (ie min inductance) or close to it.  I'd guess you'd then tune the slugs for max signal out of the IPA.  If that coincides with absolute min inductance, you'll probably have to trim the inductors a bit.
Logged

FCC:  "The record is devoid of a demonstrated nexus between Morse code proficiency and on-the-air conduct."
DMOD
AC0OB - A Place where Thermionic Emitters Rule!
Contributing
Member
*
Offline Offline

Posts: 1768


« Reply #7 on: July 09, 2010, 08:03:08 PM »

Quote
Feed the VFO input thru a .01 cap or so to the base of one of the oscillator transistors.

What are you going to do about the JK FLip FLop divider (U1)?

You might be able to inject a 3-5 volt TTL signal into R19 with the strap removed if the VFO has a digital output.

Phil - AC0OB

Logged

Charlie Eppes: Dad would be so happy if we married a doctor.
Don Eppes: Yeah, well, Dad would be happy if I married someone with a pulse.NUMB3RS   Smiley
w3jn
Johnny Novice
Administrator
Member

Offline Offline

Posts: 4620



« Reply #8 on: July 09, 2010, 11:37:47 PM »

You run the oscillator at 2X the carrier, or whatever the divide ratio of the flippy flop is.  A good strategy anyway, to keep RF leakage from the xmitter into the VFO.  

But yes, you could certainly feed 5V or so into that jumper arrangement.  I don't think it would need to be a TTL square wave, but a TTL Schmitt trigger would easily solve that.

The more stages isolating the input from the output the better, and it's generally easier to use the existing signal shaping and level circuits.  However I point out that all of this is edumacated conjecture as I've never seen, much less converted, a MW-5.
Logged

FCC:  "The record is devoid of a demonstrated nexus between Morse code proficiency and on-the-air conduct."
ke5pme
Guest
« Reply #9 on: July 10, 2010, 01:10:05 AM »

You run the oscillator at 2X the carrier, or whatever the divide ratio of the flippy flop is.  A good strategy anyway, to keep RF leakage from the xmitter into the VFO.  

But yes, you could certainly feed 5V or so into that jumper arrangement.  I don't think it would need to be a TTL square wave, but a TTL Schmitt trigger would easily solve that.

The more stages isolating the input from the output the better, and it's generally easier to use the existing signal shaping and level circuits.  However I point out that all of this is edumacated conjecture as I've never seen, much less converted, a MW-5.

Thanks for the varrious ideals so far. I finallialy got a chance to run 3 phase ac into the garage this evening so now some real work can start. For the sake of simplicity, and just for a good experiment I think I will try to feed 5v into the jumper setup to get an ideal what what this thing wants to do. If its comes down to brass tacks Im sure I could buid a simple oscillator/amplifier with all the tube junk around here to act independently of the existing setup.

-Thanks!
Logged
flintstone mop
Contributing
Member
*
Offline Offline

Posts: 5055


« Reply #10 on: July 10, 2010, 03:55:42 AM »

WOW lucky guy......3-phase power at your fingertips!

This would be interesting to read your progress of a solid state TX, and a big one, to the ham bands.
Reading the circuit description, you could get legal limt from the solid state part of the TX. They mentioned something about the tube final. Where is the modulation taking place?
Some operating tips and stuff

http://www.oldradio.com/archives/hardware/MW-5tips.htm

Little more gooogling reveal the MW5 might be a smaller cousin to the MW50. Hence a similar technical configuration. Watch out for the 15KV supply
Fred
Logged

Fred KC4MOP
KX5JT
Contributing
Member
*
Offline Offline

Posts: 1954


John-O-Phonic


« Reply #11 on: July 10, 2010, 05:19:19 AM »

Hey Ben,

Congratulations on your acquisition of the Big Harris.  Hope to hear you on the air again with your Valiant while you work on getting the Harris up and running.  It was nice talking to you the other day on 75m AM.

73, John KX5JT
Logged

AMI#1684
DMOD
AC0OB - A Place where Thermionic Emitters Rule!
Contributing
Member
*
Offline Offline

Posts: 1768


« Reply #12 on: July 10, 2010, 01:10:23 PM »

Here is an interesting 4-part read on the Harris/Gates years in Quincy:

http://www.thebdr.net/articles/prof/history/Quincy1.pdf

Phil - AC0OB
Logged

Charlie Eppes: Dad would be so happy if we married a doctor.
Don Eppes: Yeah, well, Dad would be happy if I married someone with a pulse.NUMB3RS   Smiley
w3jn
Johnny Novice
Administrator
Member

Offline Offline

Posts: 4620



« Reply #13 on: July 10, 2010, 02:53:16 PM »

Believe this is a PWM rig, Fred.
Logged

FCC:  "The record is devoid of a demonstrated nexus between Morse code proficiency and on-the-air conduct."
VE3BNB
Guest
« Reply #14 on: July 24, 2010, 12:57:49 AM »

Hi Ben!

I just became the proud owner of a Harris, Gates 2 Transmitter. I think it may be a more modern version of what you have.

Converting it to 160 or 80 is also a project of mine. I plan to feed a VFO into the crystal osc. area and take it from there. In checking for RF-frequency sensitive components....they are only after the IPA and in the PA and Final matching circuits. With parts changed out they are spec'd to 1.705mHz so it souldn't be too too hard to convert.

I have gotten some excellent reading info from the "Class-E" transmitter group. Please google them!

Good luck! I'll Keep you posted.

Mike VE3BNB
Logged
W2PFY
Contributing
Member
*
Offline Offline

Posts: 13312



« Reply #15 on: July 24, 2010, 12:37:01 PM »

Quote
Here is an interesting 4-part read on the Harris/Gates years in Quincy:

Great read!!
Logged

The secrecy of my job prevents me from knowing what I am doing.
VE3BNB
Guest
« Reply #16 on: July 25, 2010, 07:38:57 PM »

Hi Ben,

I powered up the low level sections of my Harris Gates 2 transmitter and found that the metering, oscillator board and IPA are working. Since I don't have a 1N4056 I couldn't get the high power or the modulator tested.

But I did test the oscillator board and the IPA with a crystal that I have that works out to 1,926.6665kHz and found that the osc. board works and the IPA puts out around 15watts and gets warm. I brought the signal up a fair amount by tuning the IPA output roller inductor that is located before the power divider. I believe your MW-5 is similar in layout and board stages. On the schematic for the IPA it shows the output tuning is the first stage of frequency sensitive components. Specifically there are about 5 doorknob type capacitors that bring the roller inductor into resonance. Later on this week I'll try and remove some of them to try to get the unit up in frequency.

My transmitter was factory tuned for the bottom of the AM band and I'll be reducing a lot of "C" to bring it into the 160m band.

The crystal I used was from an FM lowband radio. Let me know and I'll send you one. At least then you can test and modify your TX chain before you hook up a synth. to it.

Take care. Mike VE3BNB


 
Logged
ke5pme
Guest
« Reply #17 on: July 25, 2010, 09:18:10 PM »

Hello again,

Its been a bit since Ive got a chance to re post due to studying for another enginnering test for work so I havent be able to really tinker with the MW5a. I hit a small snag in the 3 phase and my AC unit so I may have to go another route as far as powering this thing up. Luckly the rest of the transmtter is powered just by 240vac with the exception of the B+ transformer. With a quick rewire of the xfmr I think I can have it opperate from 240 as well, just need to move a few things around.

Mike,

Thanks for the information and Im about at the same step your at with this machine here at the house. The MW5a was built in 78 so your Harris Gates II is a few years younger but from what I can tell about its has similar circuitry for the most part. The transmitter here was tunned up on 1300kc and there are a few things they changed around in the pi networks from the IPA and amp section. For instance on the OSC/IPA deck there are locations for three caps in varrious areas. The transmitter only has 2 caps in the input and output stages for matching at the frequency, furthermore I have found a list of parts to be change in determining frequency. So Im going to have to mess around with that next. I may have to take you up on the offer for the xtal. I tore appart my shack last night looking for a crystal that might work and set me up on 160 but that didnt work out as well as I hoped. Ill include the scan of the list that I found. Hearing that your having luck with the Gates II makes me motivated to work on this machine again.

Thanks again to everyone and Ill get more pictues and junk like that up soon.

-73
Ben


* IPA Block2 005.jpg (518.59 KB, 1584x1072 - viewed 577 times.)

* IPA Block2 004.jpg (1013.68 KB, 2256x1134 - viewed 583 times.)
Logged
ke5pme
Guest
« Reply #18 on: July 25, 2010, 09:22:33 PM »

Would this work with out burning the house down?

73
-Ben


* transformer re wire.JPG (30.87 KB, 613x512 - viewed 702 times.)

* IMG00371.jpg (486.73 KB, 1600x1200 - viewed 688 times.)
Logged
ke5pme
Guest
« Reply #19 on: July 25, 2010, 09:55:51 PM »

MW5a pictures


* IMG00367.jpg (580.06 KB, 1600x1200 - viewed 701 times.)

* IMG00368.jpg (489.17 KB, 1600x1200 - viewed 637 times.)

* IMG00370.jpg (634.37 KB, 1600x1200 - viewed 734 times.)
Logged
ke5pme
Guest
« Reply #20 on: July 25, 2010, 09:58:28 PM »

More pictures


* IMG00372.jpg (553.15 KB, 1600x1200 - viewed 656 times.)

* IMG00380.jpg (315.12 KB, 1600x1200 - viewed 881 times.)

* IMG00373.jpg (569.2 KB, 1600x1200 - viewed 613 times.)
Logged
ke5pme
Guest
« Reply #21 on: July 25, 2010, 10:16:12 PM »

Even more pictures.


* IMG00374.jpg (498.86 KB, 1600x1200 - viewed 662 times.)

* IMG00375.jpg (531.64 KB, 1600x1200 - viewed 738 times.)

* IMG00369.jpg (514.68 KB, 1600x1200 - viewed 689 times.)
Logged
flintstone mop
Contributing
Member
*
Offline Offline

Posts: 5055


« Reply #22 on: July 26, 2010, 12:33:58 AM »

VERY nice looking transmitter.
the TX audio should be unbelievable!!!
WBCQ 7415 audio, even though shaped for short wave transmission is about the best I have heard. Probably the only MW50 ever converted to short wave!!!!

Just get those solid state guys to behave.

Get whatever power you can out of it. Coz we need static crushers and QRM crushers on the bands

Fred
Logged

Fred KC4MOP
ke5pme
Guest
« Reply #23 on: July 26, 2010, 11:05:52 PM »

Thanks alot!
Hopefully if all goes to plan 160m will be alot more interesting. Getting mosfets working is half the battle.


-Ben
Logged
KA3EKH
Member

Offline Offline

Posts: 772



WWW
« Reply #24 on: July 27, 2010, 09:56:44 AM »

Wow, congrats on the MW-5 At one time I had three that I kept in service, two 5A and one 5B but now down to just one as a backup for a DAX. The PDM modulation system works great in the MW but if you have not ever worked on one before you will find that the power control and start up systems will be a task to master. Reducing power for "ham" services may allow you to get away with a smaller HV supply then the original three phase 10 kV monster. Also keep in mind that the PA deck is in series with the PDM modulator tube and floats at that potential above ground so be careful!
Logged
Pages: [1] 2   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone © 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.082 seconds with 18 queries.