T/R switch and Mute

[IK1LBL]

Hi ! it's my first post here ! i h to do all right !
I have a Johnson Ranger recently bought on eBay, finally a transmitter for my four receivers. SX-101MkIII, SP-600, SX-28 and 75A-4 coming to my shack
I did the first tests, I assembled a relay, as AD5X scheme.
Everything ok!
But since it's my first time ever, I come from 'use of the Drake twins. Where the MUTE mutes the receiver completely.
Today I connected Johnson to the SX-101, the relay works fine on CW hear my note, this is perfect .. But in phone, there's no way to mute the receiver at best in Drake?
I mean, by using the RECEIVE / STANDBY still hear to my voice.
What is the correct procedure? how did the OLD TIMER? I have to manually turn the volume down every time, decrease the gain? to avoid the annoying LARSEN I have to use headphones?
The next time I'll try to connect the SX-28 then will be the turn of the SP-600. I expect the same result?
Thanks to all who help me to understand better.
73s Mario IK1LBL

[kf4qkr]

All receivers are different.You shouldnt have that problem in your 75-A4. If its like my 75-A2 it should cut the B+ when in standby.I had a Drake 2B and you could hear your voice when you were transmiting and the receiver was in standby so I just muted the speaker while I was in transmit mode.You can use a switch or a relay.If you are worried about the audio output not having a load on it you can use a single pole double throw switch or relay and switch your hot speaker output into a 10 watt 8 ohm resistor with the other end of the resistor tied to ground.

[WQ9E]

Mario,

For your SX-101 you can access the muting circuit through the accessory socket on the back.  The SX-101 is muted via the AGC line, connect a set of normally closed relay T/R relay contacts to the proper points on the accessory circuit and leave the receiver panel switch in standby.  When your T/R relay is in transmit the receiver will be muted.

With the SX-101 (and other members of this Hallicrafters receiver family) you can easily add an auxiliary sensitivity control to allow you to monitor your signal on CW.  This control is put in parallel with the relay contacts (and existing high value resistor-see schematic).  This control was built into the SX-88 (marked monitor) but left off later family members.

[IK1LBL]

Hi !
For Mike.. yes is a good idea switch the speaker, i use a 3 pole ralay.. so... i can do that easily !
And for Rodger.. yes, the 101 mute of course! but I'm used to total silence..  my audio causes an annoying Larsen .. why do I gain and / or lower the volume .. I'll try to disconnect the 'speaker with a free contact of the relay.
Thank you once again to everyone for the suggestions!
73s Mario IK1LBL

[KE5YTV]

Mario, Welcome to the board! There is a lot of great information here.  It sounds like you have some great boatanchors. Where are you located?

Mike

[IK1LBL]

Hi Mike !
Ther is a really gold mine of infos this forum !
I'm in Nord Italy, on Italian riviera near SanRemo..
On QRZ.COM you can see the 2010 shack..  soon i upload new pics!
Yes i try to collecting and use some vintage gear! here on Europe it's not so easy like on US. to find heavy Radios hi hi hi...
On EU we have some AM net on 40 and 80 meters...  every week-end on morning time we use 7.190 +/- QRM
Many France OM on 3.600 every days at 18:00 to 19:00 CET.. other European QRG is 3.710..
Some OM on European Early morning or late nigth try to listen americans stations..  it's not "piece of cake"  !
Unfotunately hera we don't have the 75 meter... 

It's my first steps on AM whit true boat anchors gear.. usually i'm using my Drakes Radios...  but on the side of my "new" Johnson Ranger it's like to use a Full DSP Jap Black Box hi hi hi hi

I apologize for my poor english !

73s Mario IK1LBL

[WQ9E]

Mario,

You have some wonderful vintage gear, it looks like a very nice setup!

Your English is fine so please do not apologize, otherwise many of us will have to apologize for having no ability to read or write any Italian.

I recently acquired my first piece of Italian gear, a Geloso 4/215 receiver.  Now I have to decide on a transmitter to match.

[IK1LBL]

Rodger !
Geloso 4/215 is too modern !!! hi it's a joke ! :-) BtW from previus line, only AM/CW the great transmitter are the G 4/222 and 4/223...   the 215 it's match whit the G 4/225 but is the  SSB  era...
The G4/222 and 223 it's well know to have a very beautiful modulations! but only a single 6146....

Good infos here:
http://www.qsl.net/i0jx/geloso.html

and a nice funny video of my good friend LU7YS from Argentina on his local Radio Club using Geloso 215 - 225...
http://www.youtube.com/watch?v=pHQ9CGtFI6c

Regarding my MUTE story... what doing others?  cut speaker seems to be a easy choice...

73s Mario IK1LBL

[WQ9E]

Mario,

Thank you for the information on the Geloso line.  At some point I will try to find the matching SSB transmitter but at this point it fits fairly well with my Multi-Elmac AF-68.

With the SX-101 in standby you should not hear your voice in the speaker.  I have used an SX-101 and other family members (SX-88, 96, 100, and 115) with AM transmitters running the legal limit (Johnson Ranger/Desk KW, Viking 500, etc.) and the receiver is completely quiet.

Is it possible someone already added an auxiliary sensitivity control to your SX-101 so that in standby it is not muting completely as intended?  Look for an added control, probably on the chassis back or top.  Or is there a jumper where it does not belong on the back (pins 5 and 2 on the accessory socket are for standby control and they should only be shorted with your T/R relay in the receive condition.  Check also to make sure that the receive/standby switch on the front is properly in standby and teh switch is functioning properly.  You could also try measuring the resistance to ground from the "hot" terminal of the standby switch with the switch set to standby.

[KE5YTV]

Mario, Thanks for the picture. The shack looks great. I would love to visit the Italian Rivera some day. Your english is fine and we'll look forward to your posts.

Mike

[IK1LBL]

Hi ! good morning !
I checked everything, and everything seems fine.
But even in receiving. with the control sensitivity to a minimum, and the radio in STANDBY. antenna disconnected. if you tune a strong signal. you get a bit of signal.
So imagine my transmitter with a few inches closer.
The only question is by .22 mF capacitor C85 connected to the potentiometer control sensitivity. measured value that represents a double. may be important?

Mario,

Thank you for the information on the Geloso line.  At some point I will try to find the matching SSB transmitter but at this point it fits fairly well with my Multi-Elmac AF-68.

With the SX-101 in standby you should not hear your voice in the speaker.  I have used an SX-101 and other family members (SX-88, 96, 100, and 115) with AM transmitters running the legal limit (Johnson Ranger/Desk KW, Viking 500, etc.) and the receiver is completely quiet.

Is it possible someone already added an auxiliary sensitivity control to your SX-101 so that in standby it is not muting completely as intended?  Look for an added control, probably on the chassis back or top.  Or is there a jumper where it does not belong on the back (pins 5 and 2 on the accessory socket are for standby control and they should only be shorted with your T/R relay in the receive condition.  Check also to make sure that the receive/standby switch on the front is properly in standby and teh switch is functioning properly.  You could also try measuring the resistance to ground from the "hot" terminal of the standby switch with the switch set to standby.

[IK1LBL]

Hi ! the pics is of the shack on summer 2010... now when im ready and all in order i shot new pics :-)
Also i have the idea to recording some video for youtube :-)
I want to visit USA ! rent a container and ship them back at home full of boat anchors radios hi hi hi
Here we can easily find some nice receiver at reasonable price.. But it's not so easy find Transmitter and due to weight it can't be easily purchased overseas... Just my little Ranger i have recived by USPS...  impossible to ship at human price a HT-32, a 32V/1/2/3....  i don't mean a KWS-1 hi hi hi
Next month we have e great Ham Fest here on Italy, Hams coming from any side! i hope to find an HT-32 !!
Please feel free to ad a look at some pics shoted on 2009 editions.
http://www.flickr.com/photos/ik1lbl/sets/72157617859507069/show/

Mario, Thanks for the picture. The shack looks great. I would love to visit the Italian Rivera some day. Your english is fine and we'll look forward to your posts.

Mike

[IK1LBL]

I have just upload on youtube  my SX-101 to show how behavior the RX

http://www.youtube.com/watch?v=U1ej8tRlemg

TNX 73 Mario IK1LBL

[WQ9E]

Mario,

I watched your video and that is definitely not proper behavior.  With the switch set to standby, measure pin 4 of the accessory socket (rear of the receiver) to ground.  It should be above 200K.  The sensitivity/standby circuit controls the cathode bias on several stages.  A leaky bypass capacitor either on the sensitivity control or on one of the controlled cathodes could be the cause or it could also be from significant heater/cathode leakage in one of those tubes.

Your audio not going to zero with the volume control down is probably just a bad potentiometer.  This part of the circuit is very simple.  Measure from the center tap of the volume control to ground with the volume at minimum and it should show very close to 0 ohms to ground.

[IK1LBL]

Pin 4 to ground mesure about 2K...   and center tap of volume potentiometer to  ground is 0!

Mario,

I watched your video and that is definitely not proper behavior.  With the switch set to standby, measure pin 4 of the accessory socket (rear of the receiver) to ground.  It should be above 200K.  The sensitivity/standby circuit controls the cathode bias on several stages.  A leaky bypass capacitor either on the sensitivity control or on one of the controlled cathodes could be the cause or it could also be from significant heater/cathode leakage in one of those tubes.

Your audio not going to zero with the volume control down is probably just a bad potentiometer.  This part of the circuit is very simple.  Measure from the center tap of the volume control to ground with the volume at minimum and it should show very close to 0 ohms to ground.

[WQ9E]

Mario,

Now you need to find out why the resistance only measures 2K, there is either a circuit failure or someone has modified the circuit and added an auxiliary/monitor sensitivity control (I bet there is an added control).  The resistance should be much higher.

I am at a loss with the volume control circuit.  The volume control pot is a 500K unit that forms a voltage divider with the grid of the first audio stage fed from this tapped divider.  With the center at ground the grid of the audio stage should also be at ground for audio.  What happens when you set the response control to the "phono" position?

Do you have an oscilloscope?  It will be useful for tracking down the audio issue.

[IK1LBL]

Rodger,
In phono position nothing happens, radio is mute,
I searched for modifications. but I appears all Original. there was only a strange TV connector. on the rear panel.
But it was not connected to anything. still had traces of an old soldering.
I've removed.
now I am completely blocked. I am a farmer. I try to learn a bit.
Visually there are no damaged components.

Mario,

Now you need to find out why the resistance only measures 2K, there is either a circuit failure or someone has modified the circuit and added an auxiliary/monitor sensitivity control (I bet there is an added control).  The resistance should be much higher.

I am at a loss with the volume control circuit.  The volume control pot is a 500K unit that forms a voltage divider with the grid of the first audio stage fed from this tapped divider.  With the center at ground the grid of the audio stage should also be at ground for audio.  What happens when you set the response control to the "phono" position?

Do you have an oscilloscope?  It will be useful for tracking down the audio issue.

[WQ9E]

Mario,

Try adjusting the sensitivity control and see if that varies the 2K reading.  Then you will need to trace through the circuit to find the problem.  It is unlikely that a heater/cathode short is the problem but you can easily check this by removing the tubes which have their cathode bias circuit connected to the sensitivity control circuit.  If this is not the issue then check the bypass capacitors on this line one by one.

Rodger

[IK1LBL]

Rodger, Volume problem fixed !!!! 
was a bad soldering to ground! "piece of cake" !
Now im going to deep invesigate the real problem on sensitivity area...
ASAP i hope to let you know any positive news or i make more question 
Thank's a lot for helping me !

Mario,

Try adjusting the sensitivity control and see if that varies the 2K reading.  Then you will need to trace through the circuit to find the problem.  It is unlikely that a heater/cathode short is the problem but you can easily check this by removing the tubes which have their cathode bias circuit connected to the sensitivity control circuit.  If this is not the issue then check the bypass capacitors on this line one by one.

Rodger

[IK1LBL]

Rodger

I do not know where I got this 2k first.maybe I did not think to measure. varying the control.
anyway now. checking the pin 4 to ground.
I read all the 'range of the potentiometer, 10k to 0.5k about...
I'm going to do all the controls that I you have suggested.
Mario

Mario,

Try adjusting the sensitivity control and see if that varies the 2K reading.  Then you will need to trace through the circuit to find the problem.  It is unlikely that a heater/cathode short is the problem but you can easily check this by removing the tubes which have their cathode bias circuit connected to the sensitivity control circuit.  If this is not the issue then check the bypass capacitors on this line one by one.

Rodger

[WQ9E]

Mario,

How does the resistance vary when you switch between standby and receive? 

I am glad the volume problem was simple!

I hope the weather is drier in your part of Italy than it is here in Illinois.  I live away from the city and my neighbors are farmers but they will not be in the fields for awhile after 10 centimeters of rain in the last 3 days.  I work all day at the university around other Ph.D.s but some of the smartest people I know are my farmer neighbors.

Rodger

[IK1LBL]

Rodger
I mesure resistence only when im in standby and vary 10k to 05k when turn the potentiometer on recive   is 0 ! no change using the sensitivity control...

This is a photo of a 560 ohm resistor connected to the line of sensitivity to ground.
i can't find them on schematic.
obviously has a different cut from the original resistors. is known to be of later period.
until now is the 'most modern single component. I've seen. I see no other changes.
I have no idea what they do and why is inserted into the circuit.

Today it's sunny, it rained a little yesterday. looks like a beautiful spring.
I cultivate cactus inside the greenhouses. produce for market to 'wholesale.
I live 80 meters from the beach. in the summer tourist season is a real chaos.
prefer to live away from everyone on top of a hill Hahahahahah

Mario,

How does the resistance vary when you switch between standby and receive? 

I am glad the volume problem was simple!

I hope the weather is drier in your part of Italy than it is here in Illinois.  I live away from the city and my neighbors are farmers but they will not be in the fields for awhile after 10 centimeters of rain in the last 3 days.  I work all day at the university around other Ph.D.s but some of the smartest people I know are my farmer neighbors.

Rodger

[WQ9E]

Mario,

You have found your problem, the 560 ohm resistor does not belong in the circuit.  Remove it and your receiver should operate normally.

It was probably installed by the previous owner so the receiver would operate as a monitor for CW use. 

If you wish to use such a monitor circuit then install another 10K pot in parallel with the existing one with the cold end grounded when the receiver is switched to standby.  See the SX-88 schematic on Bama for an example of how to wire this circuit. 

But in any case remove the existing 560 ohm resistor and save it until you need it for another project

[IK1LBL]

Rodger !!!!! Ohhhhh Yeah !!
Resistor are cut off and the radio perfor well !
these problems are always a great opportunity for me to learn new things.
Thank you very much for your step by step help ! i appriciate very much !!
that's why I love boat anchors radios ! because they are the only ones that can grow a poor farmer in the world of electronics ! do you image try to fix a new DSP plastic RTX full of SMD components ? hhahahaha

Ok now i fit the 101 on his cabite on his place!
next step try to combine the SP-600 whit the Ranger....
I have a 75A-4 on the way ........   when ready a make new shot of my 2011 shack edition!!

Thank's again Rodger and all other friends for helping my !
I promise I'll be back to boring you every time I have a problem.

73s Mario IK1LBL

Mario,

You have found your problem, the 560 ohm resistor does not belong in the circuit.  Remove it and your receiver should operate normally.

It was probably installed by the previous owner so the receiver would operate as a monitor for CW use. 

If you wish to use such a monitor circuit then install another 10K pot in parallel with the existing one with the cold end grounded when the receiver is switched to standby.  See the SX-88 schematic on Bama for an example of how to wire this circuit. 

But in any case remove the existing 560 ohm resistor and save it until you need it for another project

[WQ9E]

Congratulations Mario!

Every repair you complete is building on your knowledge for the future.