What type of footswitch works to turn on/off digital delay on Harbinger HA 120 PA? tried momentary per manual, didn't work; on/off click footswitch also did not work

This schematic is not available?
you will need to contact the company...

http://harbingerproaudio.com/product/v2115/

probably shorted the integrated amp chip...they are not worth the trouble to fix..buy some good equipment.

That is probably a momentary switch that is dirty and sticking. These onboard effects on guitar amps are usually nothing more than a computer sound card and I've found bad connections going to and from them as well. I do think that switch is dirty and sticking, though.

Not likely a grounding problem. Run a test: Turn on unit with NO sound into the mics and wait 5 minutes... now try the mics. If they start working for a few minutes, then the amp is being overdriven. These small systems can be overheated and a thermal protector shuts them down to protect them. A hidden problem is if the mics are in front of the speakers you MIGHT have ultrasonic (above hearing range) feedback that may be overheating the unit. Put your speakers nearer the audience and mics behind. If problem persists, exercise your warranty.

Yes you can,you will need 2 run ,1\4 in 2 jack 1\4 in imput too the mic\line imput your chaing your signal so you will need too preset vol levels on the 120 too your desired max peak out put buy first putting you output slide too max on your mixer (running a signal from a cd player or other divice into mixer)then turn vol up 2 disered max loudness you want to run sound at then lower the vol using out put from main power slide on your mixer. Its called chaining your componets .better way of hooking up a band on a small system.ywc Rev bob dj 25yrs exp

You need to do some test on the equipment. First check the resistance of each speaker. You may have a bad cable... and yes you can destroy the speakers with too loud a signal... HOWEVER if the system is made to work together this is USUALLY not a problem.

OFTEN Roland has the opposite sense of normally closed contacts versus normally open. Test the switch with any continuity tester or an ohmmeter to see that the contacts work and come out to the switch. ALSO some amps require a TRS type connection (three wire plug) and others do not. From the schematic it appears that the Laney may REQUIRE a normally closed contact. There is also a pull switch involved that you MAY have to change the state of for operation of the pedal.

Here is the scheamtic for your amp:

http://elektrotanya.com/laney_aor100h_sch.jpg/download.html

Scroll down to the link at the page "Get Manual" and click to download. It is a JPG type file.

This is likely a failing switch under the pedal. Either the toggling mechanism is broken in it or if it is a momentary type it probably has "contact bounce" that exceeds the what the de-bounce circuitry can handle.

TRY E-BAY.

It is possible the tweeter prtion of the APS15 has failed. Try a different audio source such as a CD player to verify which part is bad, the speaker or laptop.