As far as I know, there is nothing loading that resistor other than the IC.
What is the resistance from pin 3 to pin 1 on each IC?
What is the resistance from pin 3 to pin 1 on each IC?
difficult to measure because of capacitor between. but looks 900k.
Found one damaged mosfet again. Expect now, that the driver is damaged again.
Found one damaged mosfet again. Expect now, that the driver is damaged again.
continue here.
If i conect remote, the amp shortly switch on. Green LED on, relays clicking, then off again. TL494C pin 3 is 5V at that moment. During switch on, rail starts producing, everything seems ok. Then off, no green led or red led is on.
If i conect remote, the amp shortly switch on. Green LED on, relays clicking, then off again. TL494C pin 3 is 5V at that moment. During switch on, rail starts producing, everything seems ok. Then off, no green led or red led is on.
That resistor is connected to Q4 in front of the drive board,that is also connected to Pin5 (VCC) of the drive board.. Before i repared the trace under the board, because that trace was allready burnt. So maybe there is an intermittend short.
Last edited:
No, i dont have. The problem is very strange. Sometimes the resisitor overheat, sometimes not. But anyway, it wont would stay switched on.
Since the problem is intermittent, it could be that when the amp won't stay on, there is a legitimate fault. You could disable the protection but that could result in damage to the amp.
yes, ok. the amp had a few damaged traces which i have repaired. I expect more damagaed traces under the rail caps. The parts in front of the ps drive board i removed allready and checked, but they are all ok. I think to disable the prot, only lift pin 3 of the pwm?
Is it pin 3 or pin 4 going high when the amp goes into protect?
Nevermind, pin 3. There are multiple ways. If pin 1 or 7 are going high on the comparator, lift the diode that's connecting that pin to pin 1 of the 494.
Nevermind, pin 3. There are multiple ways. If pin 1 or 7 are going high on the comparator, lift the diode that's connecting that pin to pin 1 of the 494.
The links to the diagrams at the top of the type 3 page may have something close. I was sort of using the AQ20 as a guide.
So, lifted the Diode on the Powerdrive board for Pin1 of the op. Amp powers up, produce rail. One side Audiofets still inside, all signals ok. Other side without fet, low side signal good, high side with 9V connected i have triangular signal with starts 100V above center.
Connect the source leg of the high-side to ground. If the rectifiers are in the board, realize that the center leg of the high side is at positive rail.
Where exactly i find ground? I have only positive rail and Negative rail. The same on the rectifiers only + and -.
Any ground will work. Try the main ground or just connect your scope ground to the high-side source leg. Do NOT allow it to short to the high-side center leg.
ok, but are you sure, to connect the source leg of high side to ground (Bat -)? It will not short?
If there are no FETs in it, the source pad cannot drive voltage. It's essentially floating. Check the voltage from that pad to ground if you're concerned.
Ok, i connected the source pad to bat -. Still triangle waveform 80V above center. If i connect 9V Batterie to Highside, the Waveform will be 100V above center. That means, DC about 100V, and on that line i have a about 10V Triangle form. Measured on Gate resistor.
What's the resistance between the high-side source and the point where the 9v battery negative connects?
- Status
- Not open for further replies.