RC6 is indeed a filter, only source for a replacement would be pulling one off a scrap board. That being said, I believe pin 11 is a ground connection on these, of which there are three others (all the corner pins of the chip). Assuming all the ground pins are tied together inside the chip, you...
Hopefully the junk iMac board I have is roughly similar to yours. With the motherboard installed, this is the side that's exposed, in the area between the Rage 128 and the external VGA port. Sorry for the crudity of the drawing:
The -10V input to VR2 is generated on the analog board. If you...
The iMac DV has an EL2386 triple op-amp (U5) on board like the aforementioned Molar Mac. Presumably the Rage 128 drives the pre-amp IC on the CRT neck board directly, and U5 buffers the Rage 128's outputs to drive the external monitor. The -5V for U5 is generated by VR2 (79L05) on the flip side...
That’s the gist of it, although it’s a good idea to add a little bit of fresh solder to the joint as well to guarantee that it’s solid.
It is good that the power switch can be ruled out, but pressing the power switch is not the same as shorting out the connector. The exact details are a little...
The 400V rated capacitor after the bridge rectifier often appears to be bulging, and it is in fact normal. It's a plastic disc on the top that gives the capacitor that appearance; it does not need to be replaced.
This also seems to be normal, both supplies read about half the nominal voltage on...
Most likely a similar situation as what was found in this thread, the gist of it being that cracked solder joints on the power supply board (mostly around the connector going to the motherboard) result in loss of -12V to the video/audio op-amps, which causes the lack of sound and the...
In principle I think you should be able to do that with the CC too. Don't be angry with me if it blows up though ;)
That is, unless the root problem isn't with the computer power supply on the analog board. I'm not sure whether a fault on the monitor-side B+ supply/deflection circuitry will...
Does that error show up when you format/access a disk with the stock floppy drive, and has the motherboard in the Color Classic been recapped? If you see the same error with the stock drive, there may be capacitor-related damage near the motherboard's edge connector (which carries all the...
Based on its location I'm assuming C102 is the decoupling cap for one/both of the 74LS245s on the flip side of the board. Most likely 0.1uF, 10V or more, 0603 case size, exact value really isn't critical. It being missing might be enough to cause minor system instability but it's definitely not...
As far as I'm aware, it's safe to power up the analog board without any of the computer-side parts (LB, drives) loading it. You'll hear the protection circuit ticking without a load. That said, you should definitely keep the CRT anode cap and the yoke connected; if it comes to a point where you...
Are the +5.6/7.5V from chip IP7? If so, I get the same 7.5V on my working analog board (I have 2V instead of 5.6V on pin 3, but that's due to the lower line voltage here in the US).
Could be that there's a problem with the feedback circuit on yours, or there's a short on one of the power supply...
If the reset line was stuck low and the power supply was functioning normally, you'd hear the fan running, but the screen would be blank/displaying the initial state of the VRAM (checkerboard, jailbars, etc). No audio either. Typical EGRET issues definitely won't cause instability on the power...
An effective method I’ve found helps with EGRET issues is to put a healthy amount of flux on the pins and touch them up with a soldering iron. If the solder doesn’t take to the pins due to corrosion, you can flood all the pins with solder and remove any bridges later with solder wick (look up...
157S0166 appears to be the transformer for the DC-DC circuit. Reading a DC short between the pins of the transformer is to be expected.
Is the clicking noise coming from around that part of the board, or from the charger/power brick?
The power supplies in these older systems inherently create some amount of acoustic noise sometimes. If you still have the stock fan in the Quadra and the noise is audible over it, that could indicate a problem with the power supply (but if you've upgraded the fan to a quiet modern one, the...
As a matter of principle, you should be fine replacing film safety caps with ceramic safety ones. Quick search on Mouser says that the Murata DE2 series includes the 2200/4700pF typically used for the Y caps on these analog boards, so you should be good there. Their stability with regards to...