[Johnson] Viking Thunderbolt

[Steve H]

Well more setbacks - I have threads going on in alot of places asking for 
help.
This one here kinda describes the latest issues:
https://forums.hamisland.net/showthread.php/31592-Johnson-Viking-Thunderbolt/page2

That oil filled cap I described below leaked out, and it was in reality 
accross C117. Still uncertain if its
critical to the mod that makes the amp AB1. It winds up on the output of the 
VR75 tube, and still unsure what
the 75V tube's purpose is.

Steve
KA2PTE

----- Original Message ----- 
From: "Steve H" <teknoskillz at comcast.net>
To: <johnson at mailman.qth.net>
Sent: Thursday, February 11, 2021 8:10 PM
Subject: Re: [Johnson] Viking Thunderbolt


>
> Ok turns out the bias cable connector is NOT keyed, so it can go in 4 
> different ways.
> For sure it was in the wrong position. So I made sure pin 1 (gnd) is 
> marked so its put in
> the right way all the time.
>
> Before I did this fix, the VR75 tube was not lighting up at all, its the 
> 75V regulator.
> Now it lights with the mode switch in TUNE or LINEAR position which I 
> believe is correct,
> as CW  is full duty cycle.
>
> While I was in there saw my 6BY5 has been removed and an octal socket is 
> stuck in there. Opened it up
> and its got 2 diodes tacked in.
>
> http://www.mediafire.com/view/cef1j9tst8u48a5/HPIM0835.JPG/file
>
> I do have a large metal square 0.5uF / 600V cap, stuck accross C120 
> (assuming its not
> defective) which is clearly a mod. Apparently its buffering pin 2 of the 
> VR75 /
> OA3, possibly part of the new AB1 config?
>
> Almost brave enough now to apply plate voltage, only I was warned tubes 
> that have sat a while
> ought to be "de-gettered" on the bench first.
>
>
> --
> Steve Hearns
> KA2PTE
>
>
> ______________________________________________________________
> 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