DX 60B...AM?

[wa2tak]

I'm presently restoring a vy nice 60B.
Also have a nice HG-10 working with it.
Right now getting 40 watts on CW with 175 ma plate...xtal or VFO.
Alas, my AM is less than 10 watts with 50 ma plate...xtal or VFO.

Swapped out all tubes except the 6DE7...only have one.

1. what AM output should I shoot for?

2. any ideas on where to start?

Tnx,
Steve

[WQ9E]

Steve,

The DX-60 is controlled carrier so the resting carrier level is low and your results sound normal.  It will increase with modulation level so the best check of it is either a scope or on the air reports from someone who understands it is controlled carrier.

The DX-60 sounds nice but people used to full carrier AM will question why their S meter is moving up and down as their receiver AGC tracks the carrier level.

Controlled carrier rigs allow low cost AM operation that sounds good AND controlled carrier is highly compatible with amplifiers primarily intended for SSB operation because the reduced duty cycle of controlled carrier allows them to run at or very close to their SSB power rating which is definitely not the case when these low duty cycle designs (both power supply and cooling) are confronted with the duty cycle of high level AM modulation.

Many entry level rigs (i.e. the Knight T60) also used controlled carrier as did Drake with their 4 line gear.

Rodger WQ9E

[wa2tak]

Thanks for the lesson...never stop learning in Ham Radio!

Yup...AM output does go up with audio.
Curiously, it topped out at 30 watts immediately AFTER my speech..then came down.

My next 'lesson' for today:
When I first fired it up...my AM output ( no speech ) was 20 watts.
Did my 'lesson 1' as above....say about 10 minutes...
during this time...the AM output went DOWN to that less than 10 watts that I had yesterday.

CW output no change at all.

Seems like I have a 'time' problem in AM.

[wa2tak]

Things are getting more "interesting".
I had tested all the tubes before firing up the rig.

Today tested this 6DE7...looked 'funky'.
Previous one had a short.
Put one of the 6CL6 in...heard a low noise...vintage tube tester 100% now not working...

More 'lessons' in the works!

[wa2tak]

Luckily it was only a fuse.
10 AMPS...should be 1 amp!!
Second time this has happened to me...the other was my PS23 power supply.
What the heck are these folks thinking???

6DE7 might be 'sorry'...got to get another.
Next...my "time" problem...as I don't have a thermal imager...( to find a bad resistor )..got to get some gas...CO2

[Pete, WA2CWA]

Luckily it was only a fuse.
10 AMPS...should be 1 amp!!
Second time this has happened to me...the other was my PS23 power supply.
What the heck are these folks thinking???

6DE7 might be 'sorry'...got to get another.
Next...my "time" problem...as I don't have a thermal imager...( to find a bad resistor )..got to get some gas...CO2

Always good to check that all the correct parts and values are installed before applying power.
Harbor Freight has cheap  infrared thermometers to detect hot resistors or other parts:
https://www.harborfreight.com/search?q=infrared%20thermometer
Watch the cold spray. You don't want to shock a part into failure. I prefer the "medical" type of cold spray, It's not as severe and it's less expensive:
https://www.webstaurantstore.com/medi-first-23017-4-oz-cold-spray/57723017.html
Don't remember if drug stores carry something similar.

[DMOD]

Here is a DX-60B in which enhancements can be made to increase modulation percentage and vary power output.



Phil - AC0OB

[wa2tak]

Welll.....it appears that the only "hot" thing is my MIKE CABLE.
In AM...my output is 12 watts...then...when I GRAB the mike cable...it goes to 20...speech puts it to around 30.
In PTT hold just the mike...its at 8 watts.

The mike is a Shure 404C high impedance.

[wa2tak]

PS...have some ferrites over the cable.

[WD5JKO]

"when I GRAB the mike cable...it goes to 20"


Try running a wire from the microphone to the front panel of the rig. If there is a lot of RF in the shack, this will shunt away the RF flowing on the coaxial cable shield.

Jim
Wd5JKO

[wa2tak]

Have a LOT of RF 'output'...the chassis..6164 box 100% 'in the air'...as I"ve been 'working' on it.
Will button it up.
But heck...watts out is watts out..hihi...

Like antennas...folks 'complain' about common mode current radiating from the coax line...
"watts out is watts out...

[wa2tak]

Hello Jim:

"Good eye" you have.
Buttoned it up.
All fine.
Just about done with it....except my ignorance on L1.

Rig-work...looks like new...even polished the screws.

Permit me to call your attention to my "DX100 ala GTO"...my spot on QRZ...only took me 1-1/2 years...

Tnx,
Steve

[DMOD]

Welll.....it appears that the only "hot" thing is my MIKE CABLE.
In AM...my output is 12 watts...then...when I GRAB the mike cable...it goes to 20...speech puts it to around 30.
In PTT hold just the mike...its at 8 watts.

The mike is a Shure 404C high impedance.

Some more suggestions

1) Check your mic shield grounds, with an ohmmeter, to see if you have continuity from the shield to the chassis ground and to the 1/4" mic plug.

2) change R17 to a 10k 1/2W.

3) change C29 to a 150pF Silver Mica

4) place a .005uF 500V ceramic disk cap at the junction of  R21 and R22 to ground.



Phil