daver2
10k Member
Right. So why did you not a while ago?I have also 10,2 VAC on red1 and red2 wires connected on power board...
Dave
Right. So why did you not a while ago?I have also 10,2 VAC on red1 and red2 wires connected on power board...
This is why I asked you to clean up the solder joints.I noticed that it depends on the tip of the multimeter... sometimes it doesn't score and sometimes it does...![]()
10,6 VACSo, now measure from the WHITE wire to the + side of the PCB where C120 was originally fitted (multimeter set to AC volts still).
Dave
So what what do you suggest to do as a first step? change the capacitors indicated in the manual?I suspect that you had a bit of a faulty switch (SW301). This switch works on both secondary windings of the transformer. With one side of the switch working, and the other not, you will get the observed symptom (no -13V rail) and the DAC will not work correctly.
Yes, now I suspect you have some capacitor problems - either in the power supply (high probability) or in the DAC / sample and hold or integrator parts of the logic board. Possible even the monitor electronics.
Glad to see you read the troubleshooting manual! That is what it is there for.
We have already taught you how to use your oscilloscope for this on the last PET. But here it is spelled out for you in the troubleshooting manual.
Glad we didn't wave the white flag in the end...
Dave
If it were possible to open the switch, could I spray contact spray inside?I suspect that you had a bit of a faulty switch (SW301). This switch works on both secondary windings of the transformer. With one side of the switch working, and the other not, you will get the observed symptom (no -13V rail) and the DAC will not work correctly.
No,So what what do you suggest to do as a first step? change the capacitors indicated in the manual?
My gut feeling is to spray a bit of PROPER contact cleaner onto the switch and operate it a few times. Hopefully the cleaner will penetrate into the switch unit and clean/lubricate the switch contacts.If it were possible to open the switch, could I spray contact spray inside?
ok but i can't understand this " CHECK RIPPLE AT T503 ".....
Check the -13V rail again then...I am desperate because now i have again only dot on the screenwhy?
Good investigation.you're right Dave, it's the switch that sometimes works and sometimes it doesn't.... I measured directly on the wires that go to the switch and in a red wire the 10 VAC is still not coming out. It seems that it can be disassembled ... I have to try to remove it and check