Harris MW-5 Conversion

[ke5pme]

Thanks for the headsup on the PDM deck. Have you ever had any issues with the mosfets dying on you? Last night I got around to buiding and doing a quick tests on a phase converter. Ill take a look at it on the scope tonight.

-Thanks
Ben

[KA3EKH]

I have not had much history with IPA failures, the stupid class D modulator driver tends to fail but have not had any issues with the IPA. Running them at 5 kW they do go thru a modulator tube every year and a PA tube every other, also have seen the choke in the PDM stage burn out,  replaced plate transformers and best of all the two solenoids that short out the HV supply will sometimes fail and its very colorful when that happens. I may have a IPA deck from a MW-5 that I squashed up with a backhoe, that was a particularly nasty bad tempered and highly modified by a past engineer MW-5b and it deserved to die but did save lots of the innards first so if you need parts I may have them.  If you have a strong stomach take a look at:  http://staff.salisbury.edu/~rafantini/gates&collins.htm

[w3jn]

Nice!

[flintstone mop]

That'll teach it!!!!!!!!

BTW Timtron might have some tips about the MW5. He solved a very expensive problem in the WBCQ MW50 with damper diodes. Harris wanted $5000 for the diode stack. Timmy uses 4 tubes (?) to act damper diodes.

FRED

SORRY the link below would not save the pic from this link:
http://www.flickr.com/photos/28334187@N07

[Opcom]

Hey any more news on this?

[ke5pme]

I got around to tinkering with the MW5a today. To start I had ordered a 80 meter xtal at 3.6700 kc from ebay last week for 4 bucks and got it friday. After doing a quick conversion to run everything with the exception of the HV transformer I hit the filliment button and the machine came to life. I checked all the filliment readings with a VOM and everything was where it should be. In the manual it states to run a clip lead from ground to pin 5 on the OSC pcb to start the oscilator devider. The first test was on the original 2600 xtal from where it lived (1300) Kc broadcast band. I also had connected my frequency counter to the IPA and it read out 1300 kc. Next trick was to run my 80 meter xtal and see if I could get out 1.835 which I was aiming for. I used another set of clip leads from the xtal socket to my FT-243 crystal , flipped over the switch and watched the frequency counter display read out 1.8347! I made a a few adjustments to the trimmer cap to relight the led to full brilliance and called it good.


The next trick is to get the phase converter and HV xfmr up. Or find a line distrobution transformer.

Thanks
-Ben

[ke5pme]

New Pictures

[ke5pme]

Updated pictures

[ke5pme]

Glowing 3cx2500

[KA3EKH]

Harris developed a phase monitor kit that attaches to the front panel of the power supply cover that is a three phase detector. This kit looks at the ripple frequency on the HV (30 kV) supply and if it does not see the correct frequency it will turn off the plate contactor. It’s a PC board that mounts right on the front panel and you can easily bypass this because if you don’t you may have some issues getting the transmitter to keep the plats contactor locked in when you push the HV on, being that you do not have real three phase. Also remember that everything in the PDM/PA compartment is at extremely high potentials and although it’s a huge hassle do not operate the HV with the back cover removed! On the PDM control board will be power controls for high and low power, start with them turned all the way down. This will allow you to turn on the plate with no output from the PDM stage and no RF out but will give full grid drive to the PA tube and you should see grid current and be able to peak the grid then if your anywhere near resonance. The oscillator and IPA deck always run at full power regardless of the output power and all power control is a function of the PDM amplifier, the two little pots on the PDM control board. The little lights behind the window for the PA deck are 115 vac although they look like 12 volt car bulbs. They should come on with the filament power; let me know if you need any.
Ray Fantini KA3EKH

[flintstone mop]

The glowing 3CX2500 would get some juices flowing as the excitement builds. Sounds like your taking a nice, thought-out approach to get the TX up to 160M. Hopefully it's smooth sailing.
It's gonna be hard to keep the ole girl tamed down, though. Build strong antenna components and tuner............hi

Fred

[ke5pme]

I would like to thank everyone again for the support, parts and help.

I have been asking everyone for there ideals and insight on getting this machine up on 160 so I have a better understanding of pit falls that may be advoided and the fact if I crunch a tube im done ha!

Fred, thats the next stunt is the tuner. I get chills thinking about it.

Thanks again Everyone, half the fun has been updating this page.

more to come

73
-Ben
-Ben