DX 100 B

[WB4AM]

More pics....

[WB4AM]

and more pics...

[WB4AM]

Last pic...

[K4RT]

Ken,

Nice work. Thanks for posting the photos. Have fun with that DX 100B.

Brad

[WB4AM]

Hello Brad, how's going?

Thank you.  Thanks for your help.  If you and everyone else didn't chime in, I am not sure where I would be?  So again Thank You.

I powered it up today and it seemed to be working okay from 15 meter on down, or is up?  To 160 meter anyway.

The strange thing is I thought this was a 100 watt PEP transmitter? 

I tuned it up on 75 meter in the "CW" mode the way the manual instructed and then switched to the "AM" mode.  I was getting around 150 watt carrier.  When I turned up the Audio up, and begin to talk into the Mic, it was modulating roughly to 320 watts.

It seem the same from 15 meter to 160 meter.  When going to 10 meter I could not peak the Grid meter to 5 MA's, which also met that I could not get the plate current to 250 MA's.  But on 10 meter I was able to get the transmitter to transmit about 30 watts and with modulation the watt meter was peaking 120 watts.

So I am not sure what is what!  Or is that What is What Watts!!!

Is the DX-100 a 100 watt carrier rig or is it a 100 watt peak rig?

I am wondering what I should really be seeing on the output?

Again, Thank you Brad.

Ken

[K4RT]

Ken,

With two 6146 tubes in the PA, it's a 100W +/- carrier (unmodulated) rig.  Generally, modulating the carrier results in peaks up to four times the unmodulated carrier power.  So, the peaks of between 300-400W you are seeing would seem about right.  You seem to be seeing the same results on 10M (30W carrier x 4 = 120W). I can't address the low power output on 10M. Perhaps low drive.  Someone else here will surely have some advice.

Brad

[W3NP]

Hi Ken,

Good work on your DX-100B project. I did up my DX-100 (non B) about 10 years ago. I did quite a few mods plus repairs and updates.
With low power on 10 I would first (if you haven't already) sub in a fresh set of 6146's. 6146 or 6146A - not B.  Maybe same with driver tube.

As was already said - A 100 watt carrier output plate modulated rig if fully 100 % modulated and with a stiff power supply and all else optimum will put out about 400 watts PEP as measured on a peak reading meter. Do a search on average vs pep power and see the power distribution. The reason SSB has more talk power for any given power output is mostly due to fact that all of the power is concentrated in the one sideband. With AM, the intelligence (sound, voice) is usually only received one one of the sidebands and the carrier doesn't add anything to the "punch".....but is sure sounds good when it "thumps" on.

Good luck, Dave - W3NP

[Jim, W5JO]

Try adjusting that plate coil for the driver tube.  Spread the turns or compress them for max grid current in the finals.  That little coil is for 15 and 10 meters.  Sounds as if the 15 meter section is ok.

[WB4AM]

With two 6146 tubes in the PA, it's a 100W +/- carrier (unmodulated) rig.  Generally, modulating the carrier results in peaks up to four times the unmodulated carrier power.  So, the peaks of between 300-400W you are seeing would seem about right.  You seem to be seeing the same results on 10M (30W carrier x 4 = 120W). I can't address the low power output on 10M. Perhaps low drive.  Someone else here will surely have some advice.

Brad

Okay, so it is a 100 watt rig unmodulated...that explains it.   

I do understand the 4:1 ratio meaning 4 times the carrier equals PEP.  I had someone set me straight on this when I was first getting into "AM".  For some reason I was believing the DX-100 was like a 25 watt carrier with 100 watts PEP???

Thanks for setting me straight on the DX-100.  It's nice when you know what is going on and what to expect!

Hi Ken,

Good work on your DX-100B project. I did up my DX-100 (non B) about 10 years ago. I did quite a few mods plus repairs and updates.
With low power on 10 I would first (if you haven't already) sub in a fresh set of 6146's. 6146 or 6146A - not B.  Maybe same with driver tube.

As was already said - A 100 watt carrier output plate modulated rig if fully 100 % modulated and with a stiff power supply and all else optimum will put out about 400 watts PEP as measured on a peak reading meter. Do a search on average vs pep power and see the power distribution. The reason SSB has more talk power for any given power output is mostly due to fact that all of the power is concentrated in the one sideband. With AM, the intelligence (sound, voice) is usually only received one one of the sidebands and the carrier doesn't add anything to the "punch".....but is sure sounds good when it "thumps" on.

Good luck, Dave - W3NP

Thanks Dave. I guess the DX-100 will be a work in progress.  I have another DX-100 B and I think 3 standard DX-100's along with 2 Apaches and 2 Mohawks, so I should be able to find some tubes to compare.  I picked up this DX-100B hoping I wouldn't have to do any work on it due to working on my house.  Time is what I need more of!

The transmitters and such are stored away, so I guess I will have a look to see what I can find.

I'll let you know Thanks.

Try adjusting that plate coil for the driver tube.  Spread the turns or compress them for max grid current in the finals.  That little coil is for 15 and 10 meters.  Sounds as if the 15 meter section is ok.

Hello Jim,

I guess this might be something to try first, before trying to locate the other gear for spare parts.
If doing so will this effect the 15 meter band or some of the others as well?

Like I mentioned 15 on down are okay.

Thanks Jim,

Ken

[Jim, W5JO]

Try adjusting that plate coil for the driver tube.  Spread the turns or compress them for max grid current in the finals.  That little coil is for 15 and 10 meters.  Sounds as if the 15 meter section is ok.

Hello Jim,

I guess this might be something to try first, before trying to locate the other gear for spare parts.
If doing so will this effect the 15 meter band or some of the others as well?

Like I mentioned 15 on down are okay.

Thanks Jim,

Ken

The coil is the one near the divider between the final and driver, I believe it is mounted on a wafer of the bandswitch.  It has been a while but I believe it is about 3/4" in diameter and is one long coil with a tap.  The long part up to the tap is for 15, the shorter part is for 10.  Since 15 is working so well, try not to disturb that part, just move the part from the tap to the end with fewer number of turns.  If it is already wide spaced, push it together just a bit and see what happens.  If that does not help, move the turns apart.

Every DX 100 radio I have had would, after adjusting that coil, have more than adequate grid current to drive it to about 70-90 watts.  That part of the coil does not affect any other band.

Even if you move the 15 meter, you can always readjust it.

[w1vtp]

Very nice job Jim.  It's good that you documented it with these pics.  Great resource for someone who might be going to the same experience.  I looked at the wiring and the job overall and I consider it a thread I would recommend to anyone without reservation,

Thanks, Al

[WB4AM]

Thank you Al,

I take it you met to say Ken?  I like good forums like this one.  For one there are so many here to learn from.  And of course if someone has an issue or even a question, there are many who jumps in! 

Plus for everyone who documents their procedures and such they're always here for everyone including the the original "Author" who may want or even need to come back to see what he or she has done for what ever future reasons!

So I am happy too!  But most of all I am thankful for all of those who help.

Well I have to get back to spreading and leveling stone in my driveway!  (Not That I Want To!)  I was on my break.

Thanks again Al,

Ken

[WB4AM]

Try adjusting that plate coil for the driver tube.  Spread the turns or compress them for max grid current in the finals.  That little coil is for 15 and 10 meters.  Sounds as if the 15 meter section is ok.

Hello Jim,

Thanks for the suggestion.  It did increase the power on 10 meter, but it only brought it up to 60 watts.  With that being said, I found 15 meter on down in frequency the wattage was lacking more then before.  So I decided to place the coil back as before.

One question I have if the carrier let say is 100 watts, and with audio the PEP is only let say 300 watts, and the PEP is suppose to be 400 watts, is this due to a weak component in the modulation circuit / weak audio tube perhaps?

I would think (my lack of knowledge) that the final output tubes generate the 100 watt carrier, and the modulation transformer combine with the audio output tubes would generate the PEP wattage?   

Just trying to figure all this out...

Thank you.
Ken
 

[WD8BIL]

B+ supply sag?

[W3GMS]

Try adjusting that plate coil for the driver tube.  Spread the turns or compress them for max grid current in the finals.  That little coil is for 15 and 10 meters.  Sounds as if the 15 meter section is ok.

Hello Jim,

Thanks for the suggestion.  It did increase the power on 10 meter, but it only brought it up to 60 watts.  With that being said, I found 15 meter on down in frequency the wattage was lacking more then before.  So I decided to place the coil back as before.

One question I have if the carrier let say is 100 watts, and with audio the PEP is only let say 300 watts, and the PEP is suppose to be 400 watts, is this due to a weak component in the modulation circuit / weak audio tube perhaps?

I would think (my lack of knowledge) that the final output tubes generate the 100 watt carrier, and the modulation transformer combine with the audio output tubes would generate the PEP wattage?   

Just trying to figure all this out...

Thank you.
Ken
 

Hi Ken,

Looks like your having fun! 

I would strongly suggest looking at the percentage of modulation with a scope.  That way you can see whats happening.  Not saying anything wrong with your PEP wattmeter, but I would measure percentage of modulation with a scope or the REA modulation monitor that I believe you have.   You need to see what things look like. 

Joe

[WB4AM]

Hello Joe!

My scope was borrowed from someone down the road.  They're finished with it, I just need to go there to pick it up.

I did take the REA Monitor out of storage a while.  Your right I need to connect it so I can see what's going on.  I am still having issues with the output of the DX100.  I think when I find time I will hunt for the other transmitters and borrow some tubes from them.

But I am having some fun!

Thanks Joe,

Ken
 

[kb2vxa]

Again a late post is better than no post I suppose. Having a repair and modification business on the side, whenever I encountered one of those boat anchors I did almost the very same things. The almost was instead of installing fuses I installed push button resettable circuit breakers of the same rating as the original fuses including the internal LV transformer fuse. Obliviously this saved digging inside replacing fuses and the easy part was my "day job" supplied them and plenty of goodies for my various projects. (;->)