Welcome To the Hoffman Amplifiers Forum

September 08, 2025, 01:35:13 pm
guest image
Welcome, Guest. Please login or register.
-User Name
-Password



Hoffman Amps Forum image Author Topic: Troubleshooting Amp with HT Short  (Read 2127 times)

0 Members and 1 Guest are viewing this topic.

Offline Fresh_Start

  • Level 4
  • *****
  • Posts: 2856
  • noob de Lux
Hoffman Amps Forum image
Troubleshooting Amp with HT Short
« on: October 28, 2018, 08:18:58 am »
A Super Reverb I built almost 10 years ago has returned. The Standby switch came loose and rotated to the point where the tab connected to the filter caps touched the chassis. The fuse blew, and the owner put in some odd ceramic fuse he found at Radio Shack.  Apparently he’d blown through the fuses I included with the amp.

I had not included lock washers on the power or standby switches!!!!! :BangHead:
 :w2:
The amp powers up ok. I only have a 2 amp fuse at the moment but I can’t turn the volume above 3 in my small workshop anyway.


Obviously I need to compare voltages with my build notes. Might as well re-bias the power tubes while I’m at it.


Is there anything else I need to pay special attention to?  Any specific parts like maybe filter caps that I should be worried about?


P.S. anyone use Locktite on switches to prevent this possibility?  The amp and I both live in Maine now, so I guess it’s possible the nut came loose due to temperature changes.
« Last Edit: November 09, 2018, 11:43:35 am by Fresh_Start »
Quote from: jjasilli
We have proven once again no plan survives contact with the enemy, or in this case, with the amp.

Quote from: PRR
Plan to be wrong about something.

Offline PRR

  • Level 5
  • *******
  • Posts: 17082
  • Maine USA
Hoffman Amps Forum image
Re: Troubleshooting Amp with HT Short
« Reply #1 on: October 28, 2018, 01:15:14 pm »
Get more fuses. Always start with a Lamp Limiter. Weber has low-Amp circuit breakers which are much more tamper-resistant than fuses; cost more, but may save the amp's life.

I would worry about the rectifiers. However you say it works now? The rects would either be good or no-fooling bad.

Locktite works in Maine. I don't think Locktite alone is enough for a part which can rotate HV into the chassis. Go to NAPA, get "thin gasket paper, small". This is tough stuff and close kin to electrical insulation for large motors. Make a "U" with a 3/8" hole in the middle to cover the sides of the switch. (_I_ would go as far as ShoeGoo-ing this to the chassis; it will stick but can be scraped-out if even needed.)


Offline Fresh_Start

  • Level 4
  • *****
  • Posts: 2856
  • noob de Lux
Hoffman Amps Forum image
Re: Troubleshooting Amp with HT Short
« Reply #2 on: October 28, 2018, 01:41:10 pm »
Thanks PRR - started with limiter bulb initially.  Off to NAPA shortly. 

That stuff sounds good for under the Fender pilot light assembly too.  I recently helped a friend who had a short there and I've certainly had problems with those in the past.
Quote from: jjasilli
We have proven once again no plan survives contact with the enemy, or in this case, with the amp.

Quote from: PRR
Plan to be wrong about something.

 


Choose a link from the
Hoffman Amplifiers parts catalog
Mobile Device
Catalog Link
Yard Sale
Discontinued
Misc. Hardware
What's New Board Building
 Parts
Amp trim
Handles
Lamps
Diodes
Hoffman Turret
 Boards
Channel
Switching
Resistors Fender Eyelet
 Boards
Screws/Nuts
Washers
Jacks/Plugs
Connectors
Misc Eyelet
Boards
Tools
Capacitors Custom Boards
Tubes
Valves
Pots
Knobs
Fuses/Cords Chassis
Tube
Sockets
Switches Wire
Cable


Handy Links
Tube Amp Library
Tube Amp
Schematics library
Design a custom Eyelet or
Turret Board
DIY Layout Creator
File analyzer program
DIY Layout Creator
File library
Transformer Wiring
Diagrams
Hoffmanamps
Facebook page
Hoffman Amplifiers
Discount Program


password