I think I'll love this! This is one of the lines of units I've worked lots on, and have only had about 70% success fixing them. Indeed, I always open devices I don't know the state of. I also check for shorts on the mains, and a reasonable resistance to check for fuse worky-work.
I'm not an electronics engineer but I would have thought that initially switching it on with a sine wave input and a dummy load of 4 or 8 ohms and a scope first would have been useful. Most things like this work until the smoke gets out, then they stop working, so obviously it is the smoke that makes them work....... Then, leaving the sine wave input running, if it didn't appear at the output, working along from the input with the scope probes, looking for where the sine way stops or is corrupted would have isolated where the fault would be instead of fannying around checking supply voltages, and the input sensitivity switch would have been easy to bridge out so as to eliminate it as a possible source of the issue with the amp. The fault/protect lights can be because the amp can't see a load on the speaker outputs, as you unplugged the Speakons.. But what do I know? I wanted the last bit of the video to be so the amp now works fine and can be returned to the customer with a bill. Always mistrust Silly-con components first that's why they are silly. Diodes, and their cousins transistors, and voltage regulators, rectifiers. However although I watch these videos avidly, I know nothing about fault finding, or electronics, so I bow humbly to your greatness as I know I am not worthy. So keep up the good work and I may learn a bit about this stuff....
@@LearnElectronicsRepair Yes, I got that from your dialog, however, I’m referring to physical placement on the board. From observing the rust stains on the switch it looks as though you rotated the switch 180 % when you soldered back on the board. May not mean anything if the contacts are symmetrical end to end. Anyway, just an observation. I just started watching your videos and have been enjoying your laidback, like we are in the same room with you, conversation. Thanks for sharing your adventures. 😊
@@billstoner5559 Oh I see what you mean. It's a DPDT wired as a SPDT so it should not make any difference, and the multimeter tells me it's OK (if you don't try to switch it to the other position) but well spotted
Love your channel Richard great work As someone else has mention they usually power up in protect mode and the come out after 2-10 seconds Also i have had amplifiers that wont come out of protect mode due to low input voltage caused by the series current limit lamp. Also the main board seems to get its ground from the bolts mounting it to the chassis as their is no ground wire from the psu... So i assume all those mounting bolts need to be fitted to test the amplifer?
@@AnnaVannieuwenhuyse Agreed I can try this with a load but what I do know is that before I looked at that 1.4V/0.775V switch I had power on, signal LEDs and no audio output. Afterwards I have power on/signal and fault LEDs on and no audio output. I had no load attached in either cases. So I changed something for sure when 'fixing' that switch but can't so far work out what it is. All I seem to have achieved so far is to prove what is *not* wrong with it, and reverese engineered enough to work out what those 4 MOSFET + 78M24 do and the rather unusual topology of the output stage. I'm quite tenacious though so for sure I will be looking into this further. I consider it something of a challenge now
@@AnnaVannieuwenhuyse It says so on the first page of the data sheet. But it's not clear as to whether having no speakers connected actually trips the fault light, or whether the amplifier simply tolerates it.
Richard it is a common fault in the crown amps.... plus the fault lights should come on and after 2 - to - 4 seconds they go out.. there where you have the 4 fets and the one regulator in a row in that block you need to check every component usually there is the fault.... also you best connect a dummyload those amps do not like it when there is no load on the outputs
Hi Dutch. I think I showed that I tested the four FETS plus the regulator and also the diodes nearby and they were OK but given what you say I could go back and test them out of circuit, however as I reverse engineered that section and worked out two of them regulate the +/-15V from VL+ and VL-, the 78M24 regulates the +24V and the other two control the fans I can't see how the problem could be there because all those voltage rails are present and correct. I can of course attach a load but what I can't quite figure out is why the fault behaviour changed after finding the problem, with the 1.4V/0.75V switch and I didn't have a load attached either before or afterwards
The Black-Orange-Orange-Silver-Red resistors are coded that way because these are high precision resistors. They have three digits for their signifier, and in such case, you'd need a x0.001 multiplier which *does not exist*. Orange-Orange-Black would not work as a digits code, because you cannot get 0R33 with any multiplier -- at most 3R3. To sum that up, they had to make it weird like that because they had high precision resistors, which is commendable on their behalf for design care.
Seen it. Unfortunately mine does not have the same fault, I showed that I tested the diodes and mosfets in that area and they are OK, plus I reveresed engineered that part of the PCB and all the voltages are present and correct
Thanks!
Thank You!
I think I'll love this! This is one of the lines of units I've worked lots on, and have only had about 70% success fixing them.
Indeed, I always open devices I don't know the state of. I also check for shorts on the mains, and a reasonable resistance to check for fuse worky-work.
As with flux, schematics are not overrated.
Heya, yes shematics are very help full
I'm not an electronics engineer but I would have thought that initially switching it on with a sine wave input and a dummy load of 4 or 8 ohms and a scope first would have been useful. Most things like this work until the smoke gets out, then they stop working, so obviously it is the smoke that makes them work....... Then, leaving the sine wave input running, if it didn't appear at the output, working along from the input with the scope probes, looking for where the sine way stops or is corrupted would have isolated where the fault would be instead of fannying around checking supply voltages, and the input sensitivity switch would have been easy to bridge out so as to eliminate it as a possible source of the issue with the amp. The fault/protect lights can be because the amp can't see a load on the speaker outputs, as you unplugged the Speakons.. But what do I know? I wanted the last bit of the video to be so the amp now works fine and can be returned to the customer with a bill. Always mistrust Silly-con components first that's why they are silly. Diodes, and their cousins transistors, and voltage regulators, rectifiers. However although I watch these videos avidly, I know nothing about fault finding, or electronics, so I bow humbly to your greatness as I know I am not worthy. So keep up the good work and I may learn a bit about this stuff....
Some wise stuff in there, don't put yourself down !
I assumed the same thing regarding the switch, perhaps the switching back n' forth cleaned the contacts.
I don’t know if it matters, but it looks like when you put that switch back on the pcb, it was backwards from the way it was originally.
It was originally in the 1.4V position bt I didn't show that on video I think. I moved it to the 0.7V position then found i could not move it back
@@LearnElectronicsRepair Yes, I got that from your dialog, however, I’m referring to physical placement on the board. From observing the rust stains on the switch it looks as though you rotated the switch 180 % when you soldered back on the board. May not mean anything if the contacts are symmetrical end to end. Anyway, just an observation. I just started watching your videos and have been enjoying your laidback, like we are in the same room with you, conversation. Thanks for sharing your adventures. 😊
@@billstoner5559 Oh I see what you mean. It's a DPDT wired as a SPDT so it should not make any difference, and the multimeter tells me it's OK (if you don't try to switch it to the other position) but well spotted
Love your channel Richard great work As someone else has mention they usually power up in protect mode and the come out after 2-10 seconds
Also i have had amplifiers that wont come out of protect mode due to low input voltage caused by the series current limit lamp. Also the main board seems to get its ground from the bolts mounting it to the chassis as their is no ground wire from the psu... So i assume all those mounting bolts need to be fitted to test the amplifer?
Seen that a few times.
Can you find the data sheet on the protect IC? See which legs are the inputs and chase back from there?
Try the Crown CT-800 schematics. Probably not a match, but the protection circuitry may be similar.
Manual says 'Protection against shorts, no-load, on/off thumps and radio-frequency interference . Are speaker 8R load resistors needed'?
Does the manual ask that question? I've never noticed that.
@@AnnaVannieuwenhuyse Agreed I can try this with a load but what I do know is that before I looked at that 1.4V/0.775V switch I had power on, signal LEDs and no audio output. Afterwards I have power on/signal and fault LEDs on and no audio output. I had no load attached in either cases. So I changed something for sure when 'fixing' that switch but can't so far work out what it is. All I seem to have achieved so far is to prove what is *not* wrong with it, and reverese engineered enough to work out what those 4 MOSFET + 78M24 do and the rather unusual topology of the output stage. I'm quite tenacious though so for sure I will be looking into this further. I consider it something of a challenge now
@@AnnaVannieuwenhuyse It says so on the first page of the data sheet. But it's not clear as to whether having no speakers connected actually trips the fault light, or whether the amplifier simply tolerates it.
Richard it is a common fault in the crown amps.... plus the fault lights should come on and after 2 - to - 4 seconds they go out.. there where you have the 4 fets and the one regulator in a row in that block you need to check every component usually there is the fault.... also you best connect a dummyload those amps do not like it when there is no load on the outputs
Hi Dutch. I think I showed that I tested the four FETS plus the regulator and also the diodes nearby and they were OK but given what you say I could go back and test them out of circuit, however as I reverse engineered that section and worked out two of them regulate the +/-15V from VL+ and VL-, the 78M24 regulates the +24V and the other two control the fans I can't see how the problem could be there because all those voltage rails are present and correct. I can of course attach a load but what I can't quite figure out is why the fault behaviour changed after finding the problem, with the 1.4V/0.75V switch and I didn't have a load attached either before or afterwards
Those fault lights can take from 4 to 10 seconds to go off when powered up.
The Black-Orange-Orange-Silver-Red resistors are coded that way because these are high precision resistors. They have three digits for their signifier, and in such case, you'd need a x0.001 multiplier which *does not exist*. Orange-Orange-Black would not work as a digits code, because you cannot get 0R33 with any multiplier -- at most 3R3.
To sum that up, they had to make it weird like that because they had high precision resistors, which is commendable on their behalf for design care.
Thanks for the info. Yeah it was a bit weird IMHO and I expect a lot of people will be interested in seeing it
Great channel. Might wanna work on the Spanish accent.... 🙂
Are you shure that the switches are ok?
The one that looked iffy tested OK. I will be honest I didn't test the other one but can do
See TH-cam video from TKF Electronics “how to repair power amplifier crown XLi 800 fault red light on”
Seen it. Unfortunately mine does not have the same fault, I showed that I tested the diodes and mosfets in that area and they are OK, plus I reveresed engineered that part of the PCB and all the voltages are present and correct
@@LearnElectronicsRepair yep. I thought you tested all the diodes. Wishful thinking.
Its a long wasted time again 😂😂😂
Really?
How it's wasted time?
Just sent you a e-mail with the schematic for a very similar amp @LearnElectronicsRepair