Big doo doo...lots of damage expected as it has not limited the inrush current.
Or too much current has shorted it out.
And it is SMPS, uP...complex.
Sell it after checking the SMPS switching transistors with a meter.
I expect damage there, and the Ferrites may be damaged as well.
Not your skill level at all.
Or too much current has shorted it out.
And it is SMPS, uP...complex.
Sell it after checking the SMPS switching transistors with a meter.
I expect damage there, and the Ferrites may be damaged as well.
Not your skill level at all.
Yes it should. The fact you say it heats up and burns shows it can not be 'short'. If it were 'short' then it could not allow a volt drop across it in response to current flow through it and that is what is happening for it to heat up.
That could be useful because you have to prove to yourself that the thermistor is not short.
Rather than worry over the thermistor I would switch off and unplug the amp and then do some basic static checks looking for 'shorts' on any diodes in the power supply and for any 'shorts' across the rails. Check the power amp output (switching) transistors in the same way. Even if you do find something it doesn't mean its a 'plug and play' repair but at least you have an idea of what might have failed.
Getting hot to the extent of smoking is abnormal.
That points to a larger than rated current passing through it.
Like Mooly says, do a thorough basic inspection before planning any repairs.
Also, you do not know between NTC and PTC, so you are at a basic level in skills, this is complex for the professional repair man.
This circuit is live always if plugged in, very dangerous.
Take extreme care.
That points to a larger than rated current passing through it.
Like Mooly says, do a thorough basic inspection before planning any repairs.
Also, you do not know between NTC and PTC, so you are at a basic level in skills, this is complex for the professional repair man.
This circuit is live always if plugged in, very dangerous.
Take extreme care.
A PTC should start with an initial resistance that gets lower as it heats up. If the PTC is reading as a short, it's not the fault - it's a victim of the fault.
PTC resistance increases with temperature, NTC resistance decreases with temperature.
PC AT SMPS have NTC as protection for inrush current, very common.
In either case, the resistance is staying the same with changes in temperature, which means failed.
Cause of failure, and possible remedy are not a job for the faint hearted, or inexperienced, for this complex unit.
A simple fault should have blown the fuses (are there any?)
PC AT SMPS have NTC as protection for inrush current, very common.
In either case, the resistance is staying the same with changes in temperature, which means failed.
Cause of failure, and possible remedy are not a job for the faint hearted, or inexperienced, for this complex unit.
A simple fault should have blown the fuses (are there any?)
You guys are all great, I've learned quite a bit from this! I was able to locate last night a replacement PTC 6 ohm, soldered it but no change, it gets way hot. I know they are supposed to get hot but not to the point where you can actually smell it. If I didn't mention it before, the amp is totally dead, not even the fan running, no reading at the speaker output, no clicking of relays. I have not checked yet for any shorted components as mentioned above but one reading I noticed, at the point going into RT901 I'm getting a reading of 125V AC, this is as much information as I have now.
Mooly, thanks for the schematic.
NareshBrd, there are no fuses in this beast, only a circuit breaker and that is working.
Would I like to see this amp working, of course but it's not a do or die situation for me whether I get this working or not, nothing lost here. Soon as I took the cover off, I knew this was going to be a different game for me. At this point I'll keep taking advice from you guys. Thanks again!
Mooly, thanks for the schematic.
NareshBrd, there are no fuses in this beast, only a circuit breaker and that is working.
Would I like to see this amp working, of course but it's not a do or die situation for me whether I get this working or not, nothing lost here. Soon as I took the cover off, I knew this was going to be a different game for me. At this point I'll keep taking advice from you guys. Thanks again!
The full service manual is available here (free to register). It is a very complex unit.
https://www.hifiengine.com/manual_library/crown/xls1000.shtml
https://www.hifiengine.com/manual_library/crown/xls1000.shtml
The thermistor itself is behaving perfectly normal. The amplifier is NOT - which is leading you to believe the problem is the thermistor. When they die, they explode or at least crack because they cannot take the heat that is generated. The breaker is obviously cutting things off before that happens. What you have is an over current condition - perhaps shorted IGBTs in the power supply, improper drive for the same, dead secondary rectifiers - dead amplifier hexfets - could be anything. The PTC heats up and drags the supply down enough that it doesn‘t cause a fire before the breaker blows. If the amp were behaving normally, the bypass relay would kick in after a second or two, allowing the amp to operate at high power without the thermistor heating up. The bypass relay will NOT kick in until the power supply has stabilized near its normal DC output and this is never happening due to the fault.
During the initial charge up of the 1800 uF capacitors, the PTC heats way up too, but cools back down when the caps finish charging. Then the relay kicks in because proper operation voltage is detected. Think of it as a very small form factor 2400 watt dim bulb limiter. If you uses DB limiter to power up amps on the bench routinely, the sequence of events becomes familiar.
During the initial charge up of the 1800 uF capacitors, the PTC heats way up too, but cools back down when the caps finish charging. Then the relay kicks in because proper operation voltage is detected. Think of it as a very small form factor 2400 watt dim bulb limiter. If you uses DB limiter to power up amps on the bench routinely, the sequence of events becomes familiar.