With no power applied to the amp...
Measure the resistance from the gate leg of one power supply FET to the gate legs of the other 3 parallel power supply FETs. You should read precisely twice the resistance of the value of the power supply gate resistors. If you read more than ~1 ohm difference, check find the reason for it. Measuring from the leg of the FET confirms that you have a good connection between the FET, the circuit board and the resistor. Do this for each bank of 4 FETs.
With only ground and remote applied to the amp (no B+), measure the DC voltage on the gate of each power supply FET. They should all have ~1/2 of the voltage on the remote terminal.
Measure the resistance from the gate leg of one power supply FET to the gate legs of the other 3 parallel power supply FETs. You should read precisely twice the resistance of the value of the power supply gate resistors. If you read more than ~1 ohm difference, check find the reason for it. Measuring from the leg of the FET confirms that you have a good connection between the FET, the circuit board and the resistor. Do this for each bank of 4 FETs.
With only ground and remote applied to the amp (no B+), measure the DC voltage on the gate of each power supply FET. They should all have ~1/2 of the voltage on the remote terminal.
ok perry checked thoose all seem to be fine but now when i try to power it up the bank of caps behind the power and ground terminals the 330 uf 63 voilts ones all hiss at me and no lights on the amp wondering where i go from here
Does the protection LED light for a couple of seconds when it's first powered up?
If so, does the amp hiss before the protection LED goes off.
It's unlikely the hissing is coming from the caps.
If the power supply caps are not bound together by silicone, twist them to see if any have broken leads.
If so, does the amp hiss before the protection LED goes off.
It's unlikely the hissing is coming from the caps.
If the power supply caps are not bound together by silicone, twist them to see if any have broken leads.
ok well maybe hissing is comming from somewhere else. the power and protection light both come on and my power supply pegs the needle so i dont even keep the amp powerd up dont wanna burn something else up how do i check the srrp15's in it the 2 legged thing that look like fets this problem all started when i solderd one of thoose dual ferrite feed preps back in it sparked a lil and now i have all thoose power supply issues wondering what i might check next
hey man stick a 1-2 ohm resistor (20+ watt) on the B+ wire...it'll be easier to troubleshoot with it powered up...
i never leave home without it ... 😀
i never leave home without it ... 😀
Disconnect the red and black HV wires. Unsolder the end near the rectifiers. Make sure you don't have any solder bridges between the pads after you unsolder the wires.
With the wires unsoldered, does the amp still draw excessive current?
With the wires unsoldered, does the amp still draw excessive current?
hi perry i think i tracked part of the problem down its the power supply fets that are hissing at me i believe the surface mont diode is bad i think its the mmbz5257 its monted on the board right in front of the fets towards the torriod if that is bad could that be the problem making the fets hiss and wondering do i need to order a direct replacement or wondering what is a good cross to that part?
It looks like it's used to clamp spikes over 33 volts. If it opened, I don't think you'd know. If it shorted, it looks it would cause the amp to draw excessive current even without remote voltage applied.
I'm looking at the schematic for a 250M2 but it's likely identical to yours.
I'm looking at the schematic for a 250M2 but it's likely identical to yours.
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