• New Sponsor: ShipNerd, Ship Your Gear with Us... for less! Click Here.

Vintage Silvertone 1421 troubleshooting

ChrisCC

Member
Messages
3
I have a vintage Silvertone 1421 (10xl) that I’m trying to get up and running. This is my first time working on an amp so I’m taking it slow.

Schematic: http://schematicheaven.net/bargainbin/silvertone_1421.pdf

I installed a 3-prong power cord and clipped the “death cap” but the amp still has awful 120hz hum. It’s so loud the guitar signal is overpowered. Guitar signal is also flubby and distorted. I’ve swapped the rectifier and preamp tubes with no luck and I've got a NOS 7189 power tube in the mail. As far as I can tell there are no leaky caps or loose solder joints. I poked around in there with a chopstick and couldn't hear any change in the sound. Any help is appreciated!

I'll put up some pics soon when I have time to figure out how.
 
Last edited:

taildragger

Gold Supporting Member
Messages
190
More than likely the Filter Caps need to replaced. If you are inexperienced, do not try this yourself. This can be deadly.
 

ChrisCC

Member
Messages
3
All the filter caps are in a can as far as I can tell. Would it not be as simple as replacing the can and the voltage dropping resistors? (While employing standard safety practices)
 
Messages
6,031
+1 on fresh filter caps. There is also one electrolytic cathode bypass cap that I would replace at the same time.
 

ChrisCC

Member
Messages
3
I can’t find the exact can as the amp has currently (20/10/5uf 450v). I’m assuming it would be fine to use a 20/20/20uf 450v can?
 

jthomas666

Member
Messages
780
Following up on taildragger's post: The filter caps can hold enough of a charge to kill the unwary, long after the amp has been turned off and unplugged. That may be less if an issue if the amp has a bleeder resistor installed. If you don't know how to safely discharge electrolytic caps, search around the web for a video and build yourself a snubber stick... or pass the task on to a tech. If you already know about the potential danger associated with electrolytic caps, then... never mind.
 
Messages
177
Do you have the Hot tied to Pin1/ F1 and the return pin3 to T2 Pin1?
Double check (ohm) your grounds to chassis.
Although 120hz is indicative of bad filter caps.
Not sure if I agree to changing the values. I'd keep the 20, 10, 5. Even if you had to rig three individual caps.
Death caps also provided some line filtering between return and ground in a floating system.
 
Messages
6,031
Chris, if there is room, it is cheaper to use individual caps and leave the original can sitting there...disconnected, of course. I would not hesitate to use a 10 mfd for the input gain stage filter. Depending on the diameter of that can, there are options. There may be a can with four sections..3-20mfds with 1x10mfd...just ignore one section and use a 20mfd for the second stage.no problem there. There is a 4x10mfd in which you could parallel two 10’s for a 20mfd section.
 

rockometeramp

Member
Messages
431
AES used to occasionally carry a 20-10-10 cap can, correct size too, that they made as a replacement for a Supra or Valco amp. I’ve tried numerous times to get them to keep making it, send them enough emails and maybe they’ll keep some in stock. Every Silvertone from ‘63 on has that cap can, and considering they’re still popular, you’d think they could easily sell enough of them to justify making them. I think they want a minimum of 100 made to repro it.

Anyway, there’s enough room inside most Silvertone chassis to fit individual caps, and if you don’t mind drilling out the chassis a little, most have room for the fatter capcan.
 

jthomas666

Member
Messages
780
I realize that several forumites don't like some of Uncle Doug's approaches to amp repair, but I thought it might be helpful to post a link to this amp as it shows using "flying" electrolytic caps to replace a defunct cap can. Check out about 21:00 in. It would be better to install them across several terminal strips, but obviously there's little extra room in this amp.

 




Trending Topics

Top Bottom