My allen & heath pa 28 mixer afl & pfl indicator always on.but i haven't connect any instrument.I can't get master out from head phone but channel out can get

SOURCE: hi there my allen heath mixer is weired this

If you use analog outputs and inputs try to clear of it really is your mixer and not one of the inputs. If the inputs are good your mainboard could be a bit dusty or you have a loose contact. If you have a mixer with internal interface your audio stream from your computer might be the problem.

SOURCE: I have an allen and

Usually the connector that is board mounted is the problem. I would OPEN the unit as there may just be broken solder at the connector inside. If the connector requires replacement, find one at Digikey.com by searching for "power connector coaxial".

Hint: In the future install one of those little lamp switches that are in a little plastic box with knurled knob sticking out the sides. ONLY break ONE wire from the adapter to avoid getting the connections reversed. Since the wires are smaller than lamp cord, tack solder the wires to the piercing points of the switch .

SOURCE: I would like to buy

Cases are being sold on Ebay, new, from several sources, and if you can't find one specifically listed for your unit, contact the sellers as they custom build them. That is a big unit... expect to pay around $150 to $200 for an ATA type case for it.

Here is an example for a Heath/Allen 420. http://cgi.ebay.com/ATA-CASE-ALLEN-HEATH-ZED-420-ZED-420-ZED420-MIXER-/400127078772?pt=LH_DefaultDomain_0&hash=item5d296eb174

I have bought from them before myself and there are others on Ebay so shop around... You can contact the companies and ask for a specific one and DO compare the size to your unit that they specify as all the companies do not accept returns...

SOURCE: Allen and Heath PA 28 is making pulsating sound,

You haven't given us much information... You obviously have some sort of feedback and saturation in process. First thing is to unplug ANY signals into the unit including any inserts and see if problem goes away. If it does, start adding them back in. If it doesn't go away with only the main outputs then VERIFY that you are using BALANCED interconnects to your amps/speakers AND that the mixer AND all of these amps/speakers are powered from the SAME receptacle or power conditioner module. If the BARE mixer with only headphones has the problem, then you have a power supply in the mixer that is squeging.