[Johnson] Valiant mods........more questions

[Roy Morgan]

At 04:01 PM 2/5/02 -0500, you wrote:
>Hi Roy, I also have a Valiant (1) and a newly acquired Ranger I.

Ron,

Hooray. You have nice radios there.

>   The caps have never been
>upgraded, etc. Sooo\, I'm thinking of modifying it too. Any suggestions?

Yes.  Assuming you plan to run these transmitters on the air, and use them 
at least from time to time:

1) any electrolytics should be replaced.  ESPECIALLY in the bias supply.

2) New electrolytics in any bias supply, and where ever you see a selenium 
rectifier, replace it with a new solly state diode (1N4007's cost only 
pennies.)

3) Take care of the 866's  in the Valiant: plenty of warm up time. Give 
them 20 minutes before applying B+ if they have not been run for a while 
(weeks to months) or tipped on their sides.. Use 3B28's if you have them 
and don't mind not seeing the lovely glow of the 866's.  Use solid state 
replacements if you don't want to mess with any HV rectifier tubes..

4) Valiant modulation: follow available advice: remove the cap across the 
modulation transformer.  Replace any paper coupling caps.. increase the 
values if you want better low end.  Replace any original driver 
transformers.. this is cause for pinched audio it seems. (get a new, bigger 
one from AES for about $14.)  Do not use an amplified D-104, use it straight..

>I'm not too happy with mod reports on the Valiant, either, but, you seem to
>be satisfied with yours.

I have not run mine on the air for a long time..  It should get some 
modifications, like new coupling caps.  I may not change the circuitry for 
a while.

>The mod signal reports I get say I am not as crisp
>as I should be and maybe just a little too mushy.

This is likely the too-small original driver transformer and the cap across 
the modulation transformer.  Also, weak, old filter caps can make it sound 
bad.

See The AM Window and look for mods by Tim, WA1HLR. Don't do them all. but 
just do the minimum to start with..
<http://www.amwindow.org/tech/htm/mods.htm>
Here he says about the Ranger:   " The 10mF 700 Volt capacitor is barely 
adequate for the job and also is a cause of low audio frequency distortion 
due to its capacitive reactance."

My Ranger is going to get a number of mods: its modulation transformer is 
open, the tube sockets have arced, and there are other modes that have to 
come out.  This one is not a collector quality radio, since it has had some 
badly done mods.  I don't know if I will do the all solid state power 
supply, but I might.  I am willing to totally rebuild the audio section on 
it though.  Tim's transformerless driver stage looks good.  I would use 
E34L/6CA7's as modulators not 6550's.  A fan will help keep all this cool.

Roy

- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Work: Voice: 301-975-3254,  Fax: 301-948-6213
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