|[AMRadio] A bit of Viking Valiant help|
ne1s at neandertech.com
Sun Aug 28 08:24:51 EDT 2005
I had this problem with my Ranger when I first got it on the air about
20 years ago. I had a 6146B in the socket, and it displayed the same
symptoms. The tube heats up, starts to release gas (I'm trying hard not
to make a joke here!), plate current goes up, and then starts to release
more gas, going into a thermal runaway condition. It is perfectly happy
with 6146's or 6146A's. A "gassy" tube may also be responsible, no
matter which flavor of 6146 it happens to be.
You may also be getting a bit more plate voltage with the solid-state
diodes that with the mercury vapor rectifiers that may be putting you
over the edge, which may be making matters worse (but is probably not
the primary cause).
> Just a wild a-- guess, but I thought that the Valiant used only 6146's, not
> the "B" 6146. It is my understanding that sometimes subbing in the "'B" for
> the early 6146 just doesn't cut the mustard.
> ----- Original Message -----
> From: "John Lawson" <jpl15 at panix.com>
> To: <amradio at mailman.qth.net>
> Sent: Saturday, August 27, 2005 1:56 PM
> Subject: [AMRadio] A bit of Viking Valiant help
>> I'm in the middle of a long, slow project to get my Valiant back in
>>service. I've changed out the bigger power tubes, solid-state replacements
>>for the 866s, and partially re-capped the rig, specifically the RF power
>> After finding (expensively) out that 'W' 6146s just don't work, I
>>replaced the finals with new 'B's and power is now being transferred to
>>the antenna / dummy load.
>> Main bug:
>> On the bands below 20M, however, and getting 'worse' as the frequency
>>gets lower, the rig "runs away" after 15 - 30 seconds - the plate current
>>rises fatser and faster and then needs to be shut down, lest another set
>>of 6146s gets wasted. ;}
>> I have neutralized the transmitter per the manual, seems ok. Bias also
>>set per sepc. LV rectifier tubes have been chacked (on a Weston 686) and
>>seem within spec, though their performance under load is measurable only
>> I left the doorknob cap alone because it's fine electrically and not
>>cracked or discolored.
>> Do the sypmtoms sound familiar to anyone? Before I spend a bunch more
>>hours wearing out the transmit switch, I thought I'd ask those who have a
>>lot more experience than I do with the Valiant.
>> I can add more info/observations as needed, specific caps replaced,
>>AMRadio mailing list
>>Post: mailto:AMRadio at mailman.qth.net
> AMRadio mailing list
> Home: http://mailman.qth.net/mailman/listinfo/amradio
> Help: http://mailman.qth.net/mmfaq.html
> Post: mailto:AMRadio at mailman.qth.net
More information about the AMRadio mailing list
This page last updated 18 Jan 2018.