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Voodoo Amps® Basic Trouble Shooting Guide - Low/No Audio

 

Welcome to Voodoo Amps Basic Trouble Shooting Guide. The information on this page has been accumulated through years of technical experience, trouble shooting and countless live shows. We hope you find this page helpful and that is aids in helping you resolve the problems you are experiencing. 

 

 Basics

Be certain your amp has a properly grounded 3-prong IEC / AC power cable
Do not use a 2-prong AC cheater plug
Be certain you are using a known-to-be-good cables
Plug guitar directly into amp (eliminate all effects, etc from signal chain)
If the problem persists proceed to trouble shooting guide

 

If you are experiencing Low/No Audio, we have compiled a list of possible variables. Some examples are but are not limited to;

Brief Check List:

  • POWER TUBES
  • PREAMP TUBES
  • INSTRUMENT CABLES

New tubes are not infallible and can prematurely become intermittent, fail or short.


1.) SHORTED / FAULTY POWER TUBE(S)

  • Problem - Amp lights up, tubes glow, no audio, weak audio, cracking sounds, volume flucuations, loss of gain/distortion
  • Likely Cause - Faulty/Shorted power tube
  • Solution - Replace all power tubes with a matched set & properly rebias. Replacing just one (1) power tube may result in damage.

If your amp is a Marshall or similar amp the "H.T. Fuse should also be shorted. IE: this is to protect your output transformer from damage. When you replace the power tubes you must also replace the fuse with the proper rating. Do NOT install an incorrect fuse or you will cause damage to your transformer.

Note: clone/kit amps tend to label the "H.T." Fuse as the "B+" Fuse

 

2.) PREAMP TUBES  Faulty tubes are the #1 cause of issues with tube amplifiers

  • New tubes are not infallible and can prematurely become intermittent, fail or short.
  • Problem - No audio, weak audio, cracking sounds, volume flucuations, loss of gain/distortion, etc.
  • Solution - Swap out / replace all preamp tubes with known to be good preamp tubes.
  • You can replace one preamp tube at a time. Simply remove the first preamp tube and replace it with a known to be good tube. If problem persists proceed to the next tube until you find the faulty tube.

 

3.) INSTRUMENT/SPEAKER CABLES

IMPORTANT FACT  Quality instrument & speaker cables will improve your tone while shielding out unwanted noise & hum.

  • Poor quality instrument cables are a common cause for Low/No Audio, unwanted hum, noise, RF signals, etc.
  • Broken grounds on an instrument / speaker cable will cause Low/No Audio, unwanted hum, oscillations, feedback, etc.
  • If you can move your cable against the floor and you can hear it  This is a sign of a faulty or poor quality cable - Upgrade your cables!
  • Do not use a speaker cable in place of an instrument cable.
  • Do not use an instrument cable in place of a speaker cable.

 

Disclaimer:  All information given herein is for educational purposes only. There is no warranty, implied or otherwise, as to the correctness, suitability, or merchantability of the information for any purpose.

Warning  Any and all changes made to electronic equipment must be done by qualified professional service personal. Even an unplugged amplifier contains High Voltages that are easily lethal even to the experienced electronic engineer. Do not remove the cover or chassis from your amplifier without professional assistance.

Voodoo Amps does not provide free tech support via phone or email.

 

 

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