UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Audio (record players, hi-fi etc)
Register FAQ Forum Rules Calendar Mark Forums Read

Notices

Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

Reply
 
Thread Tools
Old 22nd Feb 2012, 11:04 pm   #1
stevekendal
Hexode
 
stevekendal's Avatar
 
Join Date: Mar 2004
Location: Kendal Cumbria
Posts: 443
Default Growling, howling, shrieking guitar amp

This Aria Loco bass combo 6126B is making plenty of output, but also unwanted noises as follows. With the volume at zero, moving the bass eq produces a growliing noise at full volume. Moving the mid controls makes an equally loud squawking sound and the treble makes a horrendous shriek. Tapping the boards has no effect. Not sure I will be able to find the circuit for this one, so any pointers please before I let my "phantom" fingers loose on it? Steve.
__________________
Knobs and tubes rule ok
stevekendal is offline   Reply With Quote
Old 22nd Feb 2012, 11:36 pm   #2
maninashed
Heptode
 
maninashed's Avatar
 
Join Date: May 2011
Location: Preston, Lancashire UK
Posts: 872
Default Re: Growling, howling, shrieking guitar amp

Hi Steve, not familiar with this amp, some pics would be nice. Its obviously oscillating, and I would say probably something in the pre-amp/tone control area. Im presuming its a valve amp so check coupling capacitors and cathode bypass capacitors.
Bill
__________________
BVWS member
Action is eloquence- Coriolanus
maninashed is online now   Reply With Quote
Old 23rd Feb 2012, 6:55 am   #3
GrimJosef
Octode
 
Join Date: Sep 2007
Location: Oxfordshire
Posts: 1,236
Default Re: Growling, howling, shrieking guitar amp

There's a picture about half way down this page http://www.locobox.com/amps.html showing a Micro Bass amp model 6162B (not 6126B). If this is the amp you mean then it looks from the outside as though it's a transistor unit.

Cheers,

GJ
GrimJosef is offline   Reply With Quote
Old 23rd Feb 2012, 8:12 am   #4
peter_sol
Heptode
 
Join Date: Aug 2003
Location: Welwyn Garden City. Herts.
Posts: 530
Default Re: Growling, howling, shrieking guitar amp

It sounds as if the controls just need a squirt of switch cleaner.
High gain amplifiers often squeal instead of just crackle.
peter_sol is online now   Reply With Quote
Old 23rd Feb 2012, 8:41 pm   #5
stevekendal
Hexode
 
stevekendal's Avatar
 
Join Date: Mar 2004
Location: Kendal Cumbria
Posts: 443
Default Re: Growling, howling, shrieking guitar amp

Yes its a tranny amp and I will try the switch cleaner next time I have a look.
__________________
Knobs and tubes rule ok
stevekendal is offline   Reply With Quote
Reply

Thread Tools



All times are GMT. The time now is 7:13 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at http://www.vintage-radio.net.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Copyright ©2002 - 2014, S&P Technology.