I was able to solve the problem thanks to some help from the Elecraft reflector.  I had a mismatch between the Mark pitch in the K3 and the Mark setting in MMTTY.  Changing MMTTY to match the K3 fixed the problem.   In several years using MMTTY I  had never run into this before - blind luck I guess !

I changed out my old Dell for a newer and faster dell OPtiplex GX620.

Now I can not get MMTTY to run.  I first started with the newer 1.68 version but then went back to 1.65 which was running fine on the old machine. Still not go! The Sound card in the GX620 is Analog Devices Sound Max.

I am getting audio into the soundcard because I can hear it on headphones on the Line Out port.  My K3 is set up OK because it will decode RTTY and display it.  Instead of two-ring figure the MMTTY XY plot, I only get a blob and jibberish printing out.  When running WriteLog, the sound card is able to take WAV files and input them to my K3 transceiver.  So the sound card is not totally dead.

I have been over and over the MTTY setup and am confident that the setup is OK.  Of course I could be missing something.  I am beginning to suspect the motherboard mounted sound card is messed up.

Any tips/tests will be greatly appreciated.  My next step is desperation and to try an outbouard USB sound card.  I read some reports that this might be better anyway.

Problem solved.  It turned out that with the new-faster PC, the COM port was not completely "idle" after XP booted.  It appears that DTR or RTS was in a state such that it operated the PTT circuit on the K3.  The K3 PTT configuration of Rts-Dtr worked OK on the old PC where the serial port was completely idle.  But not so with the new PC.  Changing the K3 PTT configuration to OFF-dtr fixed the problem.  I think this means the K3 ignores the state of rts.

Yes - The K3 is infact keyed by one of the seial pins - DTR if i remember correctly.  Is there a way to make the port inactive until opened by a program or change something in Windows?

I moved to a faster PC - Dell OPtiplex GX620 running Windows XP3.  Now when I connect COM1 to my K3 radio, it keys the radio.  But if I launch Writelog, the port behaves as it should - reads freq, mode, and sends CW.  The port also supports the K3 utility to store the radio configuration.  Device manager says the port is working OK.  Looking at Setup before Windows launch, it seems all is OK with the port.  But when I plug the cable inthe K3, it keys the radio.  This did not happen on the older Dell.  Any suggestions.  I have spent two frustrating days on this.

Thank you for your reply.  The 756/3 fan kicks in when I key the rig, but I do not detect any air flow out the rear panel as evidenced by a small strip of paper positioned in front of the holes. I can hear the fan kick in and when I open up the top cover, the fan is rotating.  HOwever, it does not seem to be moving any air.

I wonder if you could do me a favor and check whether, with the fan running, you can detect any air flow out the rear panel of your 756 using the "paper strip indicator" method.  My paper strip is about 1/4 inch wide and about 4 inches long.  The paper is just standard printer paper.  I would very much appreciate this information as I never performed this test before I started having signs of trouble.  There are several controls on this fan and perhaps the controls are defective are not delivering a high enough voltage. 73 Bob AF4OX

I do not seem to have any appreciable air flow out the back of my IC-756 Pro3.  I know the cooling fan is running because I can hear it and because I have looked inside.  Using a small piece of paper as a flow detector does not indicate any air flow out the holes in the back.  Is this normal?

Reading carefully revealed that I need to change out the 6AU6 Osc.-Buff - with a 6BA6 !!!  That is the answer to that question.  I only wonder then if you have any suggestions aout the Keyer sub-chassis?  73

Thank you very much for the reference.  I downloaded the file and began to study the schematic.

There seem to be some differences between the schematic shown in the download and the Viking 2 schematic.  The Osc-Buffer in my Viking 2 is a 6AU6, vs. the 6BA6 shown.

The dimensions of the Keyer sub-chassis are not given.  I wonder if you have a suggestion - especially the depth?  Am I correct that the sub chassis is U-shaped

Thanks + 73 Bob

Does anyone know of a modification for the Viking 2 that converts it and the Model 122 VFO to grid block keying? One source told me that the schemtaic for this modification was made available by Johnson to avoid nasty key clicks.  He said he was once-upon-a-time cited by the FCC until making this mod.

The Viking 2 has 75 volts of bias available which is used to bias the 6AQ5 buffer and 6146 finals.  However, the "oscillator" (sometimes frequency doubler) and VFO are simple cathode keying.

Jim

Thanks for the reply and boost/buck reference.  Just what I was looking for.  I did not recognize the autotransformer immediately from the circuit since an autotransformer usually has all the windings on the the same "side" of the core.  But then the light came on!  I see Mouser has a 6.3V/3 amp filamant transformer that will probably do the job - especially for $7.  You are right ont the rating - the manual states the Chief requires 1.5A and it is fused for 3A, so the 3A transformer should be OK.  It will drop the line voltage enough to be able to run with no sweat.  Also looks like fun project to rig up.

I am very pleased with the keying of the Globe Chief compared to my Globe Scout 65B.  The Scout pulls the oscillator very hard under keying - real 50's sound!

This is not exactly a new topic, but maybe there are new ideas out there.

My "Lazarus" Globe Chief is producing ~ 60W output.  I redid the power cord, power supply filter caps and some misc. items and it came right back to life on the bench.  However, I notice the filament voltage for 6AG7 Osc and 2 x 807 PA is 7.1 volts vs. 6.3 nominal  I assume this is due to my 121 VAC line voltage vs. what was design voltage for the transformer primary (supposedly 115VAC).  I have the rig on a Variac for the moment, but would like to have my Variac back! The B+ is also higher than spec, but well below max ratings for the 807's so I don't see that as a problem.  I can think of several alternatives:

1. Do nothing on the assumption the higher filamant voltage will not practically affect the life of the tubes.  My duty cycle is so low they will fail due to some other cause.

2. Put a dropping resistor in the filament circuit.  Current draw is 2.45 amp and need to drop 0.8 v =  about 0.3 ohms @ 5W should do it.  Would also need a dropping resistor in the 5V rectifier circuit.

3. Buy another Variac and keep it for this purpose.  This will up my investment in the rig.

4. Home brew some type of bucking transformer, but not sure about how to do this.


I will appreciate any comments/suggestions.

Bob AF4OX

Hi OM

I am working on getting a Globe Chief back on the air.  I notice that the filament voltage is 7.1 V with 120.1 VAC on the primary (my normal line voltage).  This is without the 5V rectifier plugged in or any load on the rig.  When I reduce the line voltage to 110V with my Variac, the filament voltage drops to 6.47 VAC = OK.  I can think of several solutions:

1. Do nothing on the assumption the filament life will probaably not be reduced significantly with the duty cycle I will have.  Not sure if this is good assumption.

2. Put a Variac in the circuit when using the rig.  Disadvantage - Expensive and more stuff to hook/unhook.

3.  Bucking transformer.  Not sure how to hook this up.

4. Put a dropping resistor in the 6.3V filamant circuit.  But I would probably need to do the same in the 5V rectifier circuit.



Any suggestions, advice???





Bob AF4XO

4.  

I now have my "lazarus" Globe Scout 65B putting out about 35W CW into a dummy load.  This was after I reformed the filter caps, changed out the 6146 final,(low output when substituted in DX60), changed out the 6V6 (low grid drive to final), replaced a couple of resistors and shorted bypass caps. etc.

The key down plate voltage measures 508VDC vs. 500VDC in the scout manual.  That seems OK.  However, the screen voltage measures 282VDC vs. 230 VDC in the manual and 150VDC in tube specs for 6146 in typical Class C with 500 Plate volts.  When I began, the screen voltage was even higher at 305 VDC so I increased the screen dropping resistor from 12.5K to 27.5K.  This increased the power output at the same meter loading of 125 ma. (meter is in cathode lead so I assume that the screen was drawing heavy current.
but not producing any RF.

I get about 2ma.grid drive to the 6146.  This should be enough, but maybe I could get a bit more very slightly raising the Osc. screen voltage.

I would appreciate any input on what I might do to squeeze out a bit more output.  The voltage regulation is dreadful on the Scout - key up 685 VDC, key down 508 VDC (choke input filter.  Incidently, most RF bypass caps are rated at 500 VDC, but many see 685 VDc in key up, so I plan to swap all the bypasses out.

I wonder about further increasing the screen dropping resistor to reduce the screen voltage even more in hopes of being able to get more output at the same cathode current, but I wonder if this will mess up the Heising modulation when I try to get AM running.

The schematic shows a 6AG7 as well as 6V6 in the Osc. position, but this is hard to understand as the tubes have very different pin-outs.  An article by W8JI on the Scout shows a 6F6 substiuuted for the 6V6. These tubes have identical pinouts, but I would have guessed the 6V6 to have more output.

Anyway, I would very much appreciate any input.  

Allen

Thanks for the reply and tips.  As a teenager I converted several old broadcast radio power transformer into 5V rectifier filament windings for the HV supply for my home brew station.  I remember winding, taping with electricial tape, then reassembling the transformer plates to check the voltage under load and calculate the turns/volt in order to make a correction to get 5V.  But I only did a few transformers and don't remember if the winding order was predictable.  All I can remember was the primary was at the core, and I did not have to mess with that.  I will pull this one out and make a closer inspection looking for bad joints etc.  Bob