I have a 300/2 here that when powered up displays an increasing power supply duty cycle, by which I mean is starts out more or less like you’d expect but the square waves keep getting wider and wider until it makes a sort of hissing noise. Is this the feedback signal not making its way back to the control IC?
no limiter
I checked pins 1&2 of the 3525, pin 2 comes up to +5vdc and pin 1 does nothing. Assuming pin 1 is being used for feedback, any idea where it goes?
I checked pins 1&2 of the 3525, pin 2 comes up to +5vdc and pin 1 does nothing. Assuming pin 1 is being used for feedback, any idea where it goes?
Pin 1 is 5v, 2 starts at nothing upon power application but climbs up to around 3.3v and stops when the supply starts hissing at me. I assume pin 2 is the one I’m interested in?
Check the various components between the two CTs on the power transformer. There is also a transistor that drives back to the feedback (pin 1 of the driver board) through one of the diodes.
Pin 2 is generally a reference and should come up quickly as the 3525 receives power. It's generally between 2.5 and 2.8v from my limited notes.
Pin 2 is generally a reference and should come up quickly as the 3525 receives power. It's generally between 2.5 and 2.8v from my limited notes.
Both diodes and the 1-ohm sand resistor check good out of circuit, I followed the trace back from the diodes and it looks like it goes to pin 11 on the driver not pin 1. Output voltage from the power supply is stable at +/-52v, so are the pair of CT’s what it’s using to control duty cycle?
I’m counting the other way- behind the card on the main board there’s a white dot on the right hand side, so I assumed that indicated pin 1.
I don’t see a square pad, but I do have a dot lol.
If going by the numbers in your picture pin 1 has 2.9v and 2 has 2.5 or so.
If going by the numbers in your picture pin 1 has 2.9v and 2 has 2.5 or so.
Post the DC voltage on all pins of U701 on the driver board. Post the exact voltage on pin 1 of the driver board when those pin voltages are taken.
Readings may be a tad ambiguous, I’ll try my best but because certain voltages are changing the longer I leave the remote lead on it might be misleading.
Hope this helps.
For context I took all these measurements as input current was passing through 1.5A (input voltage 13.8), since that’s around the value these typically idle at. If a pin had increasing voltage the longer I kept the remote turned on, it’s noted by an *.
SG3525
1: 0
2: 5.1
3: 350mv*
4: 240mv*
5: 1.6
6: 3.7
7: 1.6
8: 4.9
9: 1.5*
10: 0
11: 2.1*
12: 0
13: 13.1
14: 1.9*
15: 13.1
16: 5.1
Power supply card
1: 1.5*
2: 2.9
3: 0
4: 80mv
5: .9
6: 0
7: 0
8: 0
9: 11.9
10: 350mv
11: 1.5*
12: 2
13: 13.1
14: 1.5*
15: 5
For context I took all these measurements as input current was passing through 1.5A (input voltage 13.8), since that’s around the value these typically idle at. If a pin had increasing voltage the longer I kept the remote turned on, it’s noted by an *.
SG3525
1: 0
2: 5.1
3: 350mv*
4: 240mv*
5: 1.6
6: 3.7
7: 1.6
8: 4.9
9: 1.5*
10: 0
11: 2.1*
12: 0
13: 13.1
14: 1.9*
15: 13.1
16: 5.1
Power supply card
1: 1.5*
2: 2.9
3: 0
4: 80mv
5: .9
6: 0
7: 0
8: 0
9: 11.9
10: 350mv
11: 1.5*
12: 2
13: 13.1
14: 1.5*
15: 5
LM358 voltages as follows, same measurement method as before:
1: 0
2: 150mv
3: 12mv
4: 0
5: 2.9
6: 1.7*
7: 11.9
8: 13.2
1: 0
2: 150mv
3: 12mv
4: 0
5: 2.9
6: 1.7*
7: 11.9
8: 13.2
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