Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

PA Systems A forum for discussion of all parts of a sound reinforcement or DJ system: loudspeakers, mixers (desks) etc.

QSC GX5 with fault
QSC GX5 with fault
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 15th May 2019, 08:04 AM   #11
Damo s is offline Damo s  United Kingdom
diyAudio Member
 
Join Date: Oct 2018
Location: Cambridge, UK
Its up for £50. From the posts above it definitely sounds like its way beyond me tbh. I would be concerned that a whole laod of it has been trashed beyond the hopeful quick fix
  Reply With Quote
Old 15th May 2019, 08:20 AM   #12
chris661 is offline chris661  United Kingdom
diyAudio Member
 
chris661's Avatar
 
Join Date: Feb 2008
Location: Sheffield
Well, if you fancy a project you could keep the PSU and heatsink, and install your own amplifier. There are a lot of kits out there.

That's hoping, of course, that the transformer hasn't gone, too.

Chris
__________________
My work: www.grimshawaudio.com
  Reply With Quote
Old 15th May 2019, 08:21 AM   #13
dreamth is offline dreamth  Romania
diyAudio Member
 
Join Date: Nov 2010
I think it's worth the price .Only the transformer is more than 200 pounds...QSC amplifiers are very good and also very interesting to study.They have a very unique topology which is the safest possible among any other topology ever produced for high power amplification to use with a speaker.No matter what happens to the amp it will never damage the speaker.
  Reply With Quote
Old 15th May 2019, 08:57 AM   #14
JMFahey is offline JMFahey  Argentina
diyAudio Member
 
JMFahey's Avatar
 
Join Date: Mar 2009
Location: Buenos Aires - Argentina
Quote:
Originally Posted by Damo s View Post
Ive spotted the above amp for sale very cheap. It has a fault which is that the red clip lights stay on permanently preventing the amp from working. Is this likely to be easy to fix?
Short answer: forget it.
Get *any* working amplifier instead.
__________________
Design/make/service musical stuff in Buenos Aires, Argentina, since 1969.
  Reply With Quote
Old 16th May 2019, 12:31 AM   #15
wg_ski is offline wg_ski  United States
diyAudio Member
 
Join Date: Oct 2007
Quote:
Originally Posted by dreamth View Post
I think it's worth the price .Only the transformer is more than 200 pounds...QSC amplifiers are very good and also very interesting to study.They have a very unique topology which is the safest possible among any other topology ever produced for high power amplification to use with a speaker.No matter what happens to the amp it will never damage the speaker.
Thatís not true of all the QSC designs. The class H versions are DC coupled because you canít do rail switching and make the virtual ground work like on their vintage models. This one is just a stripped down RMX2450. It is DC coupled and has a crowbar and fuse for DC protection. The amplifier is the usual transnova topology with bipolars instead of Lat-FETs and does have the usual inherent overload protections built into the design. But under cost pressure theyíve stripped it down to the minimum they can get away with and have it still drive a pair of speakers. Run 4 ohms off of it and youíre running it within an inch of its life - like running 2 ohms used to be on their old stuff.

The transformer is only a 600 VA unit. That size core only costs $65 from Antek. Would still be useful but not worth any $200 (or pounds). The heat sink is about the size of the one on my old vintage 100 MHz Athlon CPU. The caps may be ok, but I can buy those surplus any day of the week for $3 each. If it turns out the board isnít reworkable that may be where you end up with your inverstment.

I do have a GX5. It works just fine but never sees any hard service. I use it mostly for testing speakers. The hardest t ever gets run at a gig is driving a pair of Selenium D3300ís above 1.2 kHz. Those drivers are only good for 75 watts average power and are 8 ohms.
  Reply With Quote
Old 16th May 2019, 12:36 AM   #16
dreamth is offline dreamth  Romania
diyAudio Member
 
Join Date: Nov 2010
Indeed i didn't see the transformer on the available schematic , I just assumed it's the same with all the others.Sorry about that!
I looked again at the power transistor data and i can't understand why they kept this insane topology for such a low power...I thought it should be a monster with +-125v rails...shame on me!

Last edited by dreamth; 16th May 2019 at 12:41 AM.
  Reply With Quote
Old 16th May 2019, 03:17 AM   #17
wg_ski is offline wg_ski  United States
diyAudio Member
 
Join Date: Oct 2007
They don’t ever come out and say the amp cant put out 500 watts per channel. It can’t, and neither can any other 500 watt per channel amp. What they do claim is that it can put out as much peak power as amps rated at 500 watts per channel. Which is probably true.

But when I put a 500 watt per channel amp into service, I expect to be able to put out 150 to 200 watts of average power per channel without it quitting or otherwise getting upset. Do that with this thing and in a week you’ll have another burnt up amplifier. You can get that much out of an RMX2450 (at 4 ohms, not necessarily at 2) without issues.
  Reply With Quote
Old 16th May 2019, 05:19 AM   #18
dreamth is offline dreamth  Romania
diyAudio Member
 
Join Date: Nov 2010
Due to that huge voltage i suppose they are able to deliver huge instantaneous power though....yet they have 2x 80w transistor in parallel where i would have expected at least 4 x 250w transistors in parallel for stereo operation only.
Now i get the fact that this is a real joke.I never expected this from QSC.I fixed a few USA1310 amps and they were a great value for the money.
  Reply With Quote
Old 16th May 2019, 10:56 AM   #19
Damo s is offline Damo s  United Kingdom
diyAudio Member
 
Join Date: Oct 2018
Location: Cambridge, UK
OK. It sounds like that amp in particular isnt really up to the job, since it would take a beating in my ownership, and not worth my time.
  Reply With Quote

Reply


QSC GX5 with faultHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Fault Rickyeric Solid State 0 3rd March 2015 03:16 PM
Op amp fault? fap Analogue Source 4 6th December 2013 07:48 PM
What is the fault with this amp? analogadikt Tubes / Valves 3 6th April 2011 02:27 AM
Pre amp fault Addolff Parts 4 6th January 2008 01:55 PM
Quad 306 fault steevo Solid State 1 19th May 2007 05:27 PM


New To Site? Need Help?

All times are GMT. The time now is 08:40 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki