Thread: Radford STA12
View Single Post
Old 20th Jun 2021, 11:55 pm   #2
GrimJosef
Dekatron
 
Join Date: Sep 2007
Location: Oxfordshire, UK.
Posts: 4,310
Default Re: Radford STA12

I own an STA15 which I repaired quite a few years ago now. I'm afraid the electrolytic capacitors don't age well. They might be reformable, but one of mine (an HT smoother) was essentially open-circuit (I guess completely dried out). The main effect of this was to cause a very low frequency oscillation to start in that channel - something like 2Hz. It's a testament to the very broad bandwidth of the Radford output transformer that this got through it, and I spotted the fault by seeing the woofer cone in my speaker moving slowly in and out !

The other issue is that the insulated stranded wire used to connect the tagboard to the valve pins can be very prone to stiffening, particularly where it's been running warm, close to the valve sockets. It might look OK at a glance, but closer inspection can reveal that almost all the strands have fatigue-cracked and the connection is literally hanging on by a thread or two.

Cheers,

GJ
__________________
http://www.ampregen.com
GrimJosef is offline