Question about QSC MX1500A 2-Channel Amplifier
Channel ''B'' works fine. Channel ''A'' is out. I have checked virtually every component in channel ''A''. I have test equipment. I have compared resistance and diode meter readings between the good and bad channels I have been an electronics tech for over 30 years. This one has me stumped. The -85V is low at about -55 volts only on the bad channel. I have a schematic, but I can't figure this one out. I have meters, a scope, and also a curve tracer. I have metered all the output transistors - they checked good...someone has replaced 2 of the output transistors previously as they are not the same as the others. Channel ''B'' ' s outputs are all the same like the majority of the parts in channel ''A''. I am hesitant to swap the outputs or the driver boards as I am afraid to damage anything in the good ''B'' channel therefore losing my ability to compare 1 to the other...I have about 10 or 12 hours into this now and I am about to return it to the owner and tell them I can't fix it. any help is greatly appreciated Thanks Bill
It's a log time ago that I repaired those amps., but I give it a shot.
There's a speakerprotection after the finals, what I remember it's a triac (SAC187, or something like that).
You will find it at a small pcb at the back of the amp. Normally it has three legs but the centre is cut away. If it's down you will measure 0 Ohm at the output, also with a switched off amp.
Thats all I can remember, it was about 25 years ago.
Maybe it helps,
Posted on Jan 30, 2009
Hi. i have a peavey cs-800 serial 5A-02115255. when i power on then the fuse blow. anyone here have any ideal what is the problem/?. i do not have a schematic if any one here have could you email it to me at Nam.Nguyen@bnsf.com. thank in advance.
Posted on Dec 16, 2009
I work on these too.
I would replace all the high-watt emitter resistors(in the bad channel) and if you have a REAL transistor tester , check the whole "bad string" of transistors for gain match
Peavey also uses dual series diodes that they wire thru the heatsinks(at least on the guitar amps). Thats a usual suspect.
If you ask peavey tech support nicely..they'll get you a schema if you dont have one
Posted on Jan 27, 2009
a 6ya Technician can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repair professionals here in the US.
click here to Talk to a Technician (only for users in the US for now) and get all the help you need.
Posted on Jan 02, 2017
Tips for a great answer:
Jan 02, 2014 | Peavey SP5 2-Way PA Cabinet (800 Watts, 15...
Jan 03, 2014 | Peavey SP5 2-Way PA Cabinet (800 Watts, 15...
Apr 11, 2012 | Peavey Audio Players & Recorders
Dec 31, 2011 | Peavey SP 5 Speaker PA Passive
Jan 07, 2010 | Peavey AMPLIFIER, 1000 WPC, DDT, 8/4/2...
Aug 20, 2009 | Peavey PV-3800 2-Channel Amplifier
Feb 06, 2009 | QSC MX1500A 2-Channel Amplifier
Jan 12, 2009 | Peavey AMPLIFIER, 1000 WPC, DDT, 8/4/2...
Oct 02, 2012 | QSC MX1500A 2-Channel Amplifier
3,183 people viewed this question
Usually answered in minutes!
Step 2: Please assign your manual to a product: