Recent content by wskjinfen

PAL chips can now be completely replaced. When I repaired difficult problems before, I replaced them in this order: ROM, CPU, VIA, SCC, PAL, and 74TTL. Except for IWM, which cannot be repaired, replacement parts are available for others.

I suggest you first check if CR1 is working properly. Touch the blue capacitor connected to the flyback 4-pin connector to see if it gets hot. Use an ammeter to measure the DC current flowing through CR1. The worst-case scenario is that the flyback connector is faulty, which will be very...

Today, while repairing an analog board for a Macintosh Plus, I stumbled upon a phenomenon: when the 12V is overloaded, the 5V voltage rapidly increases until it burns out the logic board. This phenomenon was reproduced on this Mac. My analysis of the possible causes is as follows: The negative...

I was sure that the problem was caused by a broken flyback. I borrowed a mac+ from a friend temporarily, removed the flyback and replaced it, and it worked normally.

I encountered a difficult problem:eek:too bad.My MacPlus flyback transformer is broken. The image is compressed horizontally, and the horizontal output tube current is huge. I've concluded that the coil turns are short-circuited. I've searched many forums and they all suggest replacing the...

The questions you raised are summarized as follows: 1Disk: It is not recommended to use floppy disks and drives anymore. They have been manufactured for decades. The instability caused by aging will be aggravated during use, and it is difficult to find replacement parts. It is recommended to use...

A hard drive was added, and the power supply may be for the hard drive. Is there any sign of modification on the logic board?

Test the PAL chip by swapping it with a working board.

Please make sure that there is no short circuit on the mainboard, and then check the connection wires between the mainboard and the analog board and the fuses on the connection wires.

What does “moaning like sound” mean?

If you find no continuity, the fuse is blown. Be sure to check for other short circuit issues that may have caused the fuse to blow before restoring it.

I speculate that this is likely a problem with the analog circuit, possibly due to a capacitor malfunction in the vertical scanning circuit. Some people also suggest checking if the deflection coil is loose.

I really didn’t expect that this place also leaks electricity. I think this is a design problem. The brightness adjustment voltage is too close to GND.

I don't recommend you to do this. If you dismantle this old device, it will be one less, and it will not work well as a modern monitor, and there is dangerous high voltage. If you can't repair it, it is recommended to sell it to someone who can. If you want to experience the appearance of a...

Hi everyone, thanks for this forum. I have a Macintosh Plus, the analog board (international version, works in 120V mode) is broken, I repaired it, and now I can see the floppy disk symbol when I boot it. The current problem is that the screen brightness is too high when cold start, and returns...