Laney guitar amp, pre amp is dead

stevekendal · 12th August 2010, 12:05 AM

My trusty Laney DP150 bass guitar amp died a while ago and I've been using the power amp section with a graphic EQ pedal since then.

Tonight I decided to give it another go and theres still no signal thru the front end, but in addition there is a squealing noise when either the pre or post gain knobs are turned down. Also, the pre amp overload LED is on all the time so that might be a clue? I'm fine with valve amps, but this one has me guessing. If anyone here is able to assist, I can forward the schematic (by e mail) as supplied to me by Laney, but it wont let me copy it onto here.

Cheers, Steve.

stevekendal · 12th August 2010, 11:35 AM

Bumping this before itvanishes altogether! No tech heads out there?

burbeck · 12th August 2010, 01:10 PM

hi steve
email me for more info and advise

regards
bob

stevekendal · 13th August 2010, 04:17 PM

e mail sent

Enzo · 13th August 2010, 10:58 PM

First check the preamp power supplies. I forget on those, but it will likely be either +/-12VDC or +/-15. A missing or very low voltage can fool the system into thinking it is clipping, and can cause symptoms as you decribe.

stevekendal · 13th August 2010, 11:15 PM

Thanks for that tip but no, the voltages are well up.

burbeck · 18th August 2010, 07:29 PM

did not get email steve

12th August 2010, 12:05 AM	#1
stevekendal diyAudio Member Join Date: Mar 2010	Laney guitar amp, pre amp is dead My trusty Laney DP150 bass guitar amp died a while ago and I've been using the power amp section with a graphic EQ pedal since then. Tonight I decided to give it another go and theres still no signal thru the front end, but in addition there is a squealing noise when either the pre or post gain knobs are turned down. Also, the pre amp overload LED is on all the time so that might be a clue? I'm fine with valve amps, but this one has me guessing. If anyone here is able to assist, I can forward the schematic (by e mail) as supplied to me by Laney, but it wont let me copy it onto here. Cheers, Steve.

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12th August 2010, 11:35 AM	#2
stevekendal diyAudio Member Join Date: Mar 2010	Bumping this before itvanishes altogether! No tech heads out there?

12th August 2010, 01:10 PM	#3
burbeck diyAudio Member Join Date: Aug 2004 Location: Ratae Coritanorum	hi steve email me for more info and advise regards bob

13th August 2010, 04:17 PM	#4
stevekendal diyAudio Member Join Date: Mar 2010	e mail sent

13th August 2010, 10:58 PM	#5
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	First check the preamp power supplies. I forget on those, but it will likely be either +/-12VDC or +/-15. A missing or very low voltage can fool the system into thinking it is clipping, and can cause symptoms as you decribe.

13th August 2010, 11:15 PM	#6
stevekendal diyAudio Member Join Date: Mar 2010	Thanks for that tip but no, the voltages are well up.

18th August 2010, 07:29 PM	#7
burbeck diyAudio Member Join Date: Aug 2004 Location: Ratae Coritanorum	did not get email steve

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