Topics

kwm2 signal low


electronicavalvulas@...
 

Hello again, a few days ago, I began to notice a rather curious failure in my kwm2, when I turn it on, the smeter, it goes to the right, it stays there for a few seconds and goes back down almost to 0 and then goes back up and dial signals, but, I have noticed that it is unstable, when it fails, I hear a few clicks and distortion in the audio, to this day, the failure is continuous, and if I lower the antenna gain to the minimum, the smeter barely gives a signal of 3 , I have tried to bring it up with the internal adjustment behind the front and zero, but without success, the plug-in relays are clean and checked. I have the feeling that some resistance is doing its thing, L33 is in good condition, since pin7 of v17 is correct. where would they start looking? agc circuit? I am also looking for edition 9 of the manual thanks


Georges Ricaud
 

Hello
Have a look on V1 (6AZ8) and decoupling caps around 

Envoyé de mon iPad

Le 15 déc. 2020 à 23:16, electronicavalvulas@... a écrit :

Hello again, a few days ago, I began to notice a rather curious failure in my kwm2, when I turn it on, the smeter, it goes to the right, it stays there for a few seconds and goes back down almost to 0 and then goes back up and dial signals, but, I have noticed that it is unstable, when it fails, I hear a few clicks and distortion in the audio, to this day, the failure is continuous, and if I lower the antenna gain to the minimum, the smeter barely gives a signal of 3 , I have tried to bring it up with the internal adjustment behind the front and zero, but without success, the plug-in relays are clean and checked. I have the feeling that some resistance is doing its thing, L33 is in good condition, since pin7 of v17 is correct. where would they start looking? agc circuit? I am also looking for edition 9 of the manual thanks


electronicavalvulas@...
 

Hello again, I have looked at v1, replaced the tube v1 with a new one, and there is no change, I have measured the resistive values ​​on the pins of v1 and they seem correct, I have also looked at the adjustable potentiometers and resistors and also everything OK, I do not have any signal with the internal calibrator, injecting a 50uv signal as soon as the smeter moves, however I have a sensitivity of -127dbm.


electronicavalvulas@...
 

This morning, I have measured the resistive values ​​again, starting with V1, and my surprise on pin 6 that there should be 4.7Megohm there are 3.4Mohm. the associated resistance r74 of 1 megohm appears to be fine, (1.1) megohm. although the measurement on pin 6 is not much different, I think it could be part of the problem. what do you think?


F6FER Roger - CCAE#016
 

Hello
I think it could be part of the problem.
Probably not.
This resistance is variable depending on the KWM2 vintage , for example  it is given as 4.7 Mohms by the 1962 manual  ( 3rd edition) , and 3.2 Mohms by the 1978 manual ( 9th edition ). All this depend on the circuit around to the RF Gain potentiometer.
Anyway, whatever the value, I don't think this is the cause of your troubles.

A  number of component values ( or connections  sometimes ) has been changed over the years. It is better  to have a good idea of which schematics is the closest to the wiring of your transceiver.

Information are available from :
CCAE Europe
http://www.ccae.tm6cca.com/Tools
specially http://www.ccae.tm6cca.com/Tools.html#KWM2SCHEMA for various brands of schematics prepared by our friend F1LAG

CCA USA
http://www.collinsradio.org/archives/

and other places on the net.



Good luck
73
--

73 Roger - F6FER - CCAE#016


Georges Ricaud
 

As stated by Roger , the AGC resistors value can be very different and depends on whenyour ´KWM2 has been manufactured , nevertheless it has no incidence on your problem : if every voltages around V1 are correct , have a look also on K3 : one set of contacts are used to mute the receiver and can affect the agc line and the « s « meter

Envoyé de mon iPad


Peter E
 

Hi,

I had intermittent issues with the power output and ALC indication on my KWM2. After much signal tracing and head scratching it turned out to be one of the ground contacts on one of the valve sockets not making good contact with the aluminium chassis. As the bolts are stainless steel, they react with the Aluminium over a period of time. It may be worth your while to check each these bolts that are used for ground connections - loosen each one then tighten again.

Cheers,
Peter - VK2AN


electronicavalvulas@...
 

Hello, thanks for the ideas, they are of great help, the k3 antenna relay is new, since the original had a faulty coil, I have placed a potter brumfield but contacts for 10 A, this failure in rx was already doing with the relay Original, the scheme that I am using is the 6th edition, since the 9th edition does not look very good, I also look for the 9th edition manual without success, continuing with the problem, I am measuring resistive values ​​in the valve pins. As for the serial number to know the date, this unit seems to be a military one, since there is no normal serial number, but if a number is engraved on an aluminum sticker, I am going to check the anchors to the chassis, due to the problem of galvanic corrosion between the stainless steel. and aluminum. thanks.


F6FER Roger - CCAE#016
 


Hello
On Sun, Dec 20, 2020 at 12:05 PM, <electronicavalvulas@...> wrote  " since the 9th edition does not look very good "
I imagine you refer to the 9th edition of schematics  at  http://www.ccae.tm6cca.com/Tools.html#KWM2SCHEMA
Unfortunately, that is true for the .pdf  file, however the .jpg file is perfectly legible, have a try at it.


73
Roger
 
 
--

73 Roger - F6FER - CCAE#016


thierri.delvaux
 

Salut GEORGE, 

JE POSSÈDE UN VÉNÉRABLE RÉCEPTEUR 51S1,NUMÉRO DE SÉRIE 8261 (CR/ANAMOSA).
Ce qui m'intéresse c'est de connaitre la date de fabrication .???
Merci pour ton retour.
73,sqro.
Thierri. 
On5td.




Envoyé depuis mon appareil Galaxy


-------- Message d'origine --------
De : "Georges Ricaud via groups.io" <f6cer@...>
Date : 19/12/20 17:21 (GMT+01:00)
À : CCAE-Collins@groups.io
Objet : Re: [CCAECollins] kwm2 signal low

As stated by Roger , the AGC resistors value can be very different and depends on whenyour ´KWM2 has been manufactured , nevertheless it has no incidence on your problem : if every voltages around V1 are correct , have a look also on K3  : one set of contacts are used to mute the receiver and can affect the agc line and the « s « meter

Envoyé de mon iPad





Georges Ricaud
 

Bonjour Thierri
A priori ton 51S-1 date de 1972  (s/n 8198 - 8925)
73
Georges F6CER

Envoyé de mon iPad

Le 20 déc. 2020 à 13:48, thierri.delvaux <thierri.delvaux@...> a écrit :


Salut GEORGE, 

JE POSSÈDE UN VÉNÉRABLE RÉCEPTEUR 51S1,NUMÉRO DE SÉRIE 8261 (CR/ANAMOSA).
Ce qui m'intéresse c'est de connaitre la date de fabrication .???
Merci pour ton retour.
73,sqro.
Thierri. 
On5td.




Envoyé depuis mon appareil Galaxy


-------- Message d'origine --------
De : "Georges Ricaud via groups.io" <f6cer@...>
Date : 19/12/20 17:21 (GMT+01:00)
À : CCAE-Collins@groups.io
Objet : Re: [CCAECollins] kwm2 signal low

As stated by Roger , the AGC resistors value can be very different and depends on whenyour ´KWM2 has been manufactured , nevertheless it has no incidence on your problem : if every voltages around V1 are correct , have a look also on K3  : one set of contacts are used to mute the receiver and can affect the agc line and the « s « meter

Envoyé de mon iPad




<20201220_132359.jpg>
<20201220_132424.jpg>


electronicavalvulas@...
 

Well, I'm still working on the kwm2, I found a manual by sections of the 9th edition, leave the kwm2 off for a few hours, when turning it on, notice that for a few minutes, the problem is intermittent, although it seems that when it takes a few degrees of temperature, the problem it stays fixed. I have exchanged v7 6dc6, for another one, according to the manual, it is the rf amplifier for tx and rx, when removing this tube, there is no difference in the receiver, I also tried a new 6bz6 without result, so I think that the problem is close to v7, the values ​​in the socket are correct, except for pin 1, which is 2.4 megohm, instead of 3.6megohm.


thierri.delvaux
 

Merci GEORGES,

JE TE  SOUHAITE DE JOYEUSE FÊTES  DE NOËL. 
😊🤗

AU PLAISIR.
AMITIÉS  QRO.
THIERRI.


Envoyé depuis mon appareil Galaxy


-------- Message d'origine --------
De : "Georges Ricaud via groups.io" <f6cer@...>
Date : 20/12/20 15:04 (GMT+01:00)
À : CCAE-Collins@groups.io
Objet : Re: [CCAECollins] kwm2 signal low

Bonjour Thierri
A priori ton 51S-1 date de 1972  (s/n 8198 - 8925)
73
Georges F6CER

Envoyé de mon iPad

Le 20 déc. 2020 à 13:48, thierri.delvaux <thierri.delvaux@...> a écrit :


Salut GEORGE, 

JE POSSÈDE UN VÉNÉRABLE RÉCEPTEUR 51S1,NUMÉRO DE SÉRIE 8261 (CR/ANAMOSA).
Ce qui m'intéresse c'est de connaitre la date de fabrication .???
Merci pour ton retour.
73,sqro.
Thierri. 
On5td.




Envoyé depuis mon appareil Galaxy


-------- Message d'origine --------
De : "Georges Ricaud via groups.io" <f6cer@...>
Date : 19/12/20 17:21 (GMT+01:00)
À : CCAE-Collins@groups.io
Objet : Re: [CCAECollins] kwm2 signal low

As stated by Roger , the AGC resistors value can be very different and depends on whenyour ´KWM2 has been manufactured , nevertheless it has no incidence on your problem : if every voltages around V1 are correct , have a look also on K3  : one set of contacts are used to mute the receiver and can affect the agc line and the « s « meter

Envoyé de mon iPad




<20201220_132359.jpg>
<20201220_132424.jpg>


electronicavalvulas@...
 

Well, I have measured the voltages in v1, and on pin 6 I get 0.030v, according to the manual there must be -1.6v, on pin 3 I have 4.6v, in the manual it says 2.6v, the other pins seem correct, it could be the avc


electronicavalvulas@...
 

Hello again, first of all I hope you have a good year 2021, and a very good radio. well, I decided to buy a whole kit of valves, green letter, including the final ones, I have placed them, but the equipment seems to remain the same, the sensitivity has improved, -125dbm, but the smeter seems not to measure correctly. I have checked the k4 relay and the resistance between contacts is correct, I have measured the voltages in v1, and they are the following, 1- 284v, 2- 176v, 3- 2.9v, 4- 0v, 5- 0v, 6- -0.089v. 7- 0.43v 8- 33.3v. 9- 0.47v. As you can see, the voltage on pin6 is quite out of parameters. Can you think of where to look? I think the failure is quite close. Thanks for the help


DAVID KNEPPER
 

With the 100 Khz calibrator turned on, what reading do you get on the S-meter. Do this on 80 meters and then each band.

David Knepper, W3ST/W3CRA
Secretary, Collins Radio Association
www/collinsradio.us

On 01/16/2021 2:16 PM electronicavalvulas@gmail.com wrote:


Hello again, first of all I hope you have a good year 2021, and a very good radio. well, I decided to buy a whole kit of valves, green letter, including the final ones, I have placed them, but the equipment seems to remain the same, the sensitivity has improved, -125dbm, but the smeter seems not to measure correctly. I have checked the k4 relay and the resistance between contacts is correct, I have measured the voltages in v1, and they are the following, 1- 284v, 2- 176v, 3- 2.9v, 4- 0v, 5- 0v, 6- -0.089v. 7- 0.43v 8- 33.3v. 9- 0.47v. As you can see, the voltage on pin6 is quite out of parameters. Can you think of where to look? I think the failure is quite close. Thanks for the help


electronicavalvulas@...
 

Thanks for answering, I did the tests in 80 meters and the rest of the bands, I barely get the smeter to move, if I close the rf gain, the maximum I get is a signal of 5, when I turn on the equipment, if the smeter goes all the way to the right, but then down to abnormal levels. , R74, R78 and R158 are fine. I have thought of verifying the resistance of the smeter, but this data does not appear anywhere.


ernst.schroeder@...
 

Hello,
tried to think about causes of your problem:
- can you verify that the Ext VFO jumper is plugged into J17 ?
- can you verify that there is a short piece of shielded wire plugged between J22 and J23 ?
- if that's not the case, can you verify that there is a short circuit between J22 and J23 ? (Just measure resistance between them, with M-2 switched off, Should be near zero)
- Do you have a signal generator? Even a primitive one will do. Set it to 455 kHz and a few 100 millivolts, Feed it into J27 (Q Mult). Do you hear anything, does the S-meter react?

So far for the first steps in signal tracing and injection (David W3ST already had that in mind when he answered)

Ah, BTW, do you happen to have a name, or call sign perhaps?

Best 73
Ernst DJ7HS
https://www.qsl.net/dj7hs/


electronicavalvulas@...
 

Hello, I have made the checks that you have told me, the j17 connector is in place, the bridge is made at the factory, even though I did the test at the time with a double rca cable, I have a Marconi 2955A
To radio tester, I have tried in Q MULTI 455khz / 100mV. giving a signal the smeter of 4, if I raise the signal a little more, there is hardly any response from the smeter. it's like if there was a cap. the smeter has a resistance of 220ohm, I have tried another smeter from another piece of equipment and the behavior is the same. as a curious fact, the resistive values ​​in the valves are fine, but not the voltages.

EA5IMJ, Manuel


Georges Ricaud
 

Hello
Just in case , have a look at C87 (100pF mica) I have had problems with leakage in that cap disturbing the AGC and sensivity

Envoyé de mon iPad