[Johnson] Viking I durability?

[Carl]

All the transformers are the same as the V-II and none are capable of much 
abuse. The audio driver one is a dog and there is an excellent series of 
articles in ER June, July, August 1998 for the V-II (applicable to the V-1) 
that cover that and other shortcomings.

Ive also found the oil filled PS cap to be internally leaky on both rigs and 
replaced with a pair of 100uF/450V 'lytics in series with 100K balancing 
resistors. It adds a bit more voltage regulation and very low ripple on the 
scope.
In both cases the oil filled looked fine in place but had signs of 
overheating on the chassis side.

Of course all old paper caps and electrolytics are bad by now. Id also check 
resistor tolerance as various sources were used during the many production 
runs, some are real drifters and others like new.

Leaky 'lytics often take out the 6AL5 bias rectifier as well as the low and 
high B+ rectifiers...that often cooks the transformers. Since I have plenty 
of all types of tubes I do not go SS in the PS plus the extra resulting 
voltages along with higher AC line voltages dont do transformers and tubes 
any good.

Carl
KM1H




----- Original Message ----- 
From: "Brian Burns" <brian at lessonsinlutherie.com>
To: <johnson at mailman.qth.net>
Sent: Saturday, May 25, 2013 11:42 AM
Subject: [Johnson] Viking I durability?


> Hello Carl,
>
>
>
> " OTOH the V-1 didn't age well and survivability percentage is likely 
> lower.
> It was already a throwaway by the time the late 50's SS gear revolution
> hit."
>
>
>
> I've heard that the modulation transformers weren't quite up to the job, 
> but
> otherwise they seem to have a really good reputation for reliability. What
> other issues are there, that might be fixed in a restoration job?
>
>
>
> Thanks,
>
>
>
> Brian
>
>
>
>
>
> ______________________________________________________________
> 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
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 10.0.1432 / Virus Database: 3184/5854 - Release Date: 05/24/13
>