[Johnson] Ranger 1 Turbo Modulator Instability

[Ross Stenberg]

I have seen this before, one of the changes is a cap across the mod transformer secondary or something like that in this area. I think it is mentioned this could be a problem. An oscillation can take place.

Sent from Mail for Windows 10

From: Kenneth Goodwin
Sent: Tuesday, July 17, 2018 5:10 PM
To: johnson at mailman.qth.net
Subject: [Johnson] Ranger 1 Turbo Modulator Instability

With the Ranger's audio setting above 9 o'clock, I get a full peg spike in
the modulator plate current about 1 second after depressing the
push-to-talk. (Turbo Ranger mods by WA1HLR, W3AM, W4PNY) This lasts for 0.25
seconds (stops as soon as it begins).  No spike with Audio at 8 o'clock and
lower where the current spike increases from the 8 to 9 o'clock audio
settings.  I thought it might be the amplified D-104 (T-UG8) but I don't see
any prob with the D-104 when hooked to another rig.  I don't see it when
engaging the phone mode with just the push-to-talk when the mic audio input
into the female mic connector is open, regardless of the Ranger's audio
setting.  See the same modulator plate current spike in the Tune mode
(modulator circuit is engaged but not the finals).  I suspect it is an
interaction between the Ranger and the amplified D-104 or an instability in
the 6550 modulator circuit. I can operationally work around but seeing the
6550's plate current peg for 0.25 seconds is disconcerting.  I need to go
back and see if the power output level circuitry (modification) might be the
source since I have it set to about 20 watts output.  Will try it with full
power and as soon as I get a mic connector, I will try a different Hi-Z
microphone.  Any thoughts on what I should look for to solve the high plate
current spike?  Ken K5RG

 

______________________________________________________________
Johnson mailing list
Home: http://mailman.qth.net/mailman/listinfo/johnson
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Johnson at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html