Welcome To the Hoffman Amplifiers Forum

September 08, 2025, 02:55:57 pm
guest image
Welcome, Guest. Please login or register.
-User Name
-Password



Hoffman Amps Forum image Author Topic: Ampeg V-4BH low output  (Read 1738 times)

0 Members and 1 Guest are viewing this topic.

Offline BigE

  • Level 2
  • **
  • Posts: 111
  • Fender guy...
Hoffman Amps Forum image
Ampeg V-4BH low output
« on: March 30, 2015, 08:25:07 am »
I've got an Ampeg V-4bh that suffered a fall from the cab it was sitting on.  Now there is hardly any output our of the mains.  Swapped Tubes and no change.  Chop-sticking doesn't reveal anything.  Can't see anything broken or loose.

Here are my voltages:

V1
1 - 220   6 - 218
2 - 0       7 - 0
3 - 3.7    8 - 1.8

V2
1 - 346    6 - 220
2 - 71     7 - 2.5
3 - 113   8 - 4.5

page 2 schematic:
V1:
1 - 230   6 - 270
2 - 0       7 - 50
3 - 1.7    8 - 102

v2:
1 - 281   6 - 276
2 - 0       7 - 0
3 - 15     8 - 15


Power tube voltages:
3 - 485
5 - -47
8 - 0

voltage at "bias" point in schematic is -48
+- 10v are right on
High voltage drops look OK.

Not sure where to start since I can trace signal all the way through the thing. And you do get output but you have to Max the thing to get any signal out.

Thanks in advance.

Offline shooter

  • Level 5
  • *******
  • Posts: 11018
  • Karma Loves haters
Hoffman Amps Forum image
Re: Ampeg V-4BH low output
« Reply #1 on: March 30, 2015, 08:40:20 am »
usually mechanical hits cause mechanical breaks, I'd still look for that.

Quote
I can trace signal all the way through the thing.
Listening or scoping?  I'd think either would show where the signal gets anemic
Went Class C for efficiency

Offline BigE

  • Level 2
  • **
  • Posts: 111
  • Fender guy...
Hoffman Amps Forum image
Re: Ampeg V-4BH low output
« Reply #2 on: March 30, 2015, 08:45:37 am »
With a listener box i traced the signal.  I figured on the power tubes it would be non existant but it seemed pretty solid.

 


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