Hi. Im new in the wonderful world of QSC power amp repair.Ive been doing electronics for 35 years and just took on a new gig w/ a local stage sound and lighting company.Ive got plenty of time under my belt working on anything from HDTVs TO power and guitar amps,electrician work,etc etc,so I am qualified. My first challenge is I have about a dozen QSC Powerlight amps mainly 6.0 and 9.0s. Electrically,Im not worried about repairing them. However...HOW THE HELL DO THESE THINGS COME OUT OF THE CASE? 3 hours today. Usually power amps have a top and bottom cover,bingo presto. Im talking about the Powerlight 6.0 here. Its in a "tub". I got the back fan panel and top off,no problem. How do you get the rest of the chassis OUT of the case-i.e.power board,front control board. Does the chassis SLIDE OUT,or does everything have to be undone piece by piece,labeled,and unloaded out of the top? Theres absolutely no forums,videos,etc on this. I found the repair manual but that dont do alot. Right off the bat I DO have a burnt up cap on the power board-a blue ceramic disc cap-directly by the power cord,Im guessing thats a power factor cap.Blown to smithereens so bad i cant even get a value,but I cant even get this board OUT of the case! Its the board that sits VERTICALLY with the power cord on it. Talk about 20 pounds of s*it in a 5 pound bag! If anybody can throw me a bone on disassembly of this thing,youlle be helping me feed me family LOL. Thanks! John K Best Electrical inc. (BTW-amp symptons-plug in,flip switch,trips breaker in service panel)
I used to be an authorized QSC station, but I have been retired a few years.
I don't specifically remember these, but maybe this will help. QSC liked to anchor boards with plastic posts that popped into chassis holes. But there was also a small plastic rod that pushed down into the hollow post to spread the barbs at the other end, They were black, and the rod had a small knob on the end. You turned the knob a quarter turn and then pulled it up, unspreading the end of the post so you could pop it from the chassis hole.
Oh, and likely a number of screws into the heat sink to anchor it to the chassis
There were also some boards with little keyhole shaped holes on the board, and small metal posts stuck up from the chassis. You put the board down on those posts and then it slid a quarter inch or less to seat the posts in the narrow end of the keyhole. Once it was seated there were also a few screws to keep it there.
If I recall, you EITHER had the keyhole thingies OR the plastic posts.
In some amps you had to first remove other things - like maybe fans - to make room for the boards to come out. I remember one that had volume pot shafts that stuck out the front, you had to get clearance for those.
As I recall the Powerlite used SMPS instead of iron transformers and conventional power supply.
I don't specifically remember these, but maybe this will help. QSC liked to anchor boards with plastic posts that popped into chassis holes. But there was also a small plastic rod that pushed down into the hollow post to spread the barbs at the other end, They were black, and the rod had a small knob on the end. You turned the knob a quarter turn and then pulled it up, unspreading the end of the post so you could pop it from the chassis hole.
Oh, and likely a number of screws into the heat sink to anchor it to the chassis
There were also some boards with little keyhole shaped holes on the board, and small metal posts stuck up from the chassis. You put the board down on those posts and then it slid a quarter inch or less to seat the posts in the narrow end of the keyhole. Once it was seated there were also a few screws to keep it there.
If I recall, you EITHER had the keyhole thingies OR the plastic posts.
In some amps you had to first remove other things - like maybe fans - to make room for the boards to come out. I remember one that had volume pot shafts that stuck out the front, you had to get clearance for those.
As I recall the Powerlite used SMPS instead of iron transformers and conventional power supply.
Blue disks right by the power entry can also be MOS surge supressors, instead of a cap. Sits across the power line, takes a AC motor turn off surge or lightning surge on the line and shorts it out, until failure. Have an AC voltage rating, usually about 300 vac or higher on dual voltage rated units, and an energy rating, correlating to the diameter of the device. Usually right after the fuse or breaker, as they fail short. Wimpy ones in PCAT switcher supplies are about .3" diameter, serious ones in Allen Bradley VFD drives are about .75" diameter (and red). Protect switcher mains cap (400 vdc rated) from bursting. ****ese sourced ones are green.
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Thanks for the helpful tips! Im back on that thing tomorrow. Im thinking a complete disassemble going in from the TOP and just stripping it til I hit the bottom of the case to see what Im missing and to get my feet wetter on this model amp. Not alot of info avail ON this amp,usually the cheat sheet is go to You Tube,and theres nothing on disassembly of this amplifier. I printed up the service manual which is very vague.This thing is just assembled to NOT come apart unless youre a qualified QSC service tech it looks like.I cant even get the damn PC board with the bad "cap" off the steel mounting plate-it has slides,but the damn thing will NOT even slide. I do have the schematics-thanks for the tip on the "blue disc". It looks like its in the circuit between the main switch and the smaller internal fuses as the internal fuses tested good,so surge protector sounds correct. For now,Ill forget any idea about "short cuts". Ive done power amps in the past,its been a few years,but if I recall,usually theyre designed so they can be serviced "on the road" with minimul tools in case it breaks down during a gig.Not this thing boy,its gonna fight every step of the way! Thanks!
In the video linked below which is mostly a bunch of unnecessary closeups, towards the end he shows one of the amp modules removed. It doesn't show how it was removed but you may get a few hints from it.
qsc pl6 - Bing video
qsc pl6 - Bing video
Hi. A bit late on the uptake but i just dismantled one of these tonight.
Basically you remove every single screw you can get to. There are 4 main boards. Plus the fuse board which can stay in (down the side of the amp).
I am yet to problem solve, but it's blowing mains fuses (tripping breakers) but not blowing fuses in the amp. It seems like 2x output transistors are short and caused the power supply for that amp board to also go short. I think it's a crowbar circuit but yet to problem solve to that point. i removed the amp boards and then removed the power input to each of the psu boards then found which one was tripping the mains. It corresponded with the apm board that had 2x short transistors.
You unplug any of the un-pluggable cables but not the power switch or mains connector, the top two amp boards have 3 x screws i think and then they have slots where you slide the boards a few mm forwards but first check for rubber feet that have been stuck on to prevent the boards from sliding forwards. These rubber feet being used as safety wedges also need to be removed. 2 screwsare near the front of the boards and there is also one longer screw that attaches in around the centre of each amplifier boards heatsink array from the rear, when working on the power supply boards they slide out in a similar way but as well as the screws at the front there is one allen screw head bolt with a shock absorbing grommet right at the back. The entire back panel with speakons etc. can stay attached to the two amplifier boards, the only other main thing is to remove the power supply cables from their screw down terminals on each amplifier board.
If you experienced similar repairs, perhaps you can throw some tips my way. I'm sure this was too late to help you but it might give others the confidence to tear these down.
The transistors that tested short are acting strange now. I was trying to test them from both above and below but could only see the short from probing one side of the board then it altogether disappeared, i'm going to have a better look tomorrow but one of the power supply boards defiantly needs repairing.
I'm not that good at switch mode so any tips would be handy.
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