Thank you. I bought a soft start board from Nobsound already and a speaker protection
Do i still need to use a CL-12? If so where can i get one? i can't find it. Are these boards ok? (I hope so because i have already bought them!)
1000W Soft-Start Delay Temperature Protection Module for Amplifier Power Board 7921734953406 | eBay
UK Assembled UPC1237 Dual Channel Stereo Speaker Delay Protection Board AC12-24V | eBay
Do i still need to use a CL-12? If so where can i get one? i can't find it. Are these boards ok? (I hope so because i have already bought them!)
1000W Soft-Start Delay Temperature Protection Module for Amplifier Power Board 7921734953406 | eBay
UK Assembled UPC1237 Dual Channel Stereo Speaker Delay Protection Board AC12-24V | eBay
With a soft start board you don’t need the CL-60s. (You can see the equivalent on the board, between the relays) The CL-12 is a misprint I think, it doesn’t exist.
I just stumbled upon this in another thread and thought it very relevant to the previous discussions here over use of thermistors as a means of tying circuitry to ground, and how it is wrong to believe they can provide protection.
Scenario 1.
MOSFET short to ground (V+ or V- short to ground). The PCB trace started burning, the CL-60 was exposed to a very high current at the same time as the PCB trace, it cooked for a (short) while, and then failed. No fire; the PCB trace did not catch fire. CL-60 served dual-purpose (ground lift and safety device)
Scenario 2.
MOSFET short to ground, the PCB trace started burning, there's no CL-60, i.e. the PCB common is wired straight to chassis using nice and thick wire. There's no limit to what that current can do to PCB trace(s). The PCB trace catches fire. Much worse than having the CL-60.
Scenario 3.
A quick blow fuse is used on V+ and V- rails. The fuse will blow, so everything's nice and sweet. I personally hate fuses in that position (DC side of things...) -> they tend to ruin the sound.
MOSFET short to ground (V+ or V- short to ground). The PCB trace started burning, the CL-60 was exposed to a very high current at the same time as the PCB trace, it cooked for a (short) while, and then failed. No fire; the PCB trace did not catch fire. CL-60 served dual-purpose (ground lift and safety device)
Scenario 2.
MOSFET short to ground, the PCB trace started burning, there's no CL-60, i.e. the PCB common is wired straight to chassis using nice and thick wire. There's no limit to what that current can do to PCB trace(s). The PCB trace catches fire. Much worse than having the CL-60.
Scenario 3.
A quick blow fuse is used on V+ and V- rails. The fuse will blow, so everything's nice and sweet. I personally hate fuses in that position (DC side of things...) -> they tend to ruin the sound.
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The CL-60 is in the path between chassis and power ground. How is it involved in your scenarios?
It isn't.
If the PS common was more positive/negative, for whatever reason, than the IEC connector ground potential?
EDIT: I am looking at the photo that shows the burnt trace again.... it is also possible that, for whatever reason, the IEC ground pin was sitting at a high potential.... in which case the CL-60 would, again, blow first - before any of the PCB traces caught fire.
Anyhow, whichever scenario is considered, the CL-60, exposed to a very high current flow, would fail before there's fire. It is NOT intended to be used in this way, but... we don't have fusible resistors / fast fuses on a DC side of things...
EDIT: I am looking at the photo that shows the burnt trace again.... it is also possible that, for whatever reason, the IEC ground pin was sitting at a high potential.... in which case the CL-60 would, again, blow first - before any of the PCB traces caught fire.
Anyhow, whichever scenario is considered, the CL-60, exposed to a very high current flow, would fail before there's fire. It is NOT intended to be used in this way, but... we don't have fusible resistors / fast fuses on a DC side of things...
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SR427 mentioned that the safety thermal fuse was tripping on the power distribution board. I have no idea what other things went wrong there...
Look at the relationship between those points in the circuit. There is NO connection between them except at the CL-60, hence the only thing that can cause a voltage difference is an actual power supply or transformer failure.
The MOSFET shorting out will move the +V and -V closer to ground, not push the ground towards those voltages.
The only scenario that might involve the CL-60 is if you have a diode failure and even then the nature of a split power supply is that all things tend to move towards the center.
I was thinking along those lines myself... but I wasn't really sure how/why would that PCB trace start burning...
Now, this scenario would mean that there's something seriously wrong with the household mains wiring - the mains potential (if the transformer was faulty) was able to hold the chassis at sufficiently high potential vs PS common.... that means that there's no ground wiring in that household.
It seems to me high voltage was fed into the IEC earth. Cl60 or no Cl60 that’s pretty horrific. Even with a solid link there I would expect severe damage.
And the case would have been live etc.
I think this says more about the surge protector than the amp construction.
And the case would have been live etc.
I think this says more about the surge protector than the amp construction.
I agree along with the faulty outlet. If I'm reading all this correctly, the current build with the CL-60 is deemed as satisfactory with all other modifications above and beyond satisfactory for safety.
hi - on the circuit, could P1 and P2 be in either direction? In the illustrated build, they are in reversed direction to the P3 variable resistor. I installed mine all the same way because i guess all i have to do is turn the screw the other way. Is this correct or do i need to desolder?
Yes, they can be installed either way. Correct, CW or CCW doesn't matter. Just set them appropriately. No desoldering necessary.