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Some additional notes: The Macintosh G3 desktop appears to use the same (or very similar) power supply: https://www.eevblog.com/forum/repair/psu-repair-vintage-macintosh-g3-desktop/ I've done a thorough visual inspection of the board and top side of the components, but I haven't actually...

Hi all, The power supply has unfortunately died in my Macintosh Performa 6400 - it won't start up at all. It is a 150W unit, Apple part #614-0060, Delta model number DPS-150GB B. The PWM controller (TOP200YAI) had failed dead-short across all pins. I'm not sure whether this was the cause of...

Thank you :) It is a little on the dark side, I still have some tinkering with the controls left to do, I think.

Hi all, At last, success! The lack of video was caused by an intermittent connection on the crimp on one end of the white cable between the mainboard and analogue board. I've been going back over all of my own work, and I noticed that the replacement parts that I fitted for CR1 and CR5 were...

Hi all, I've been doing some more testing. C4 tests OK out-of-circuit with an LCR meter (30nF). L3 tests at 10.7uH out-of-circuit - I'm not sure whether this is correct or not, but it seems reasonable. L2 tests at 12.1uH (with slug out) and 44.2uH (with slug in) out-of-circuit - I'm not sure...

That's great! Very nice work indeed. I'm very glad that my tip helped out.

Hi all, I tested R1 out of circuit, and it seemed OK. It looked like it had been running hot, so I replaced with with a 1W part just in case, but no change. When cold, there is 0.4Ohm DC resistance across L3/R1 - does that seem about right? C4 doesn't seem open-circuit or electrically leaky...

No problem 😊 If I recall correctly, RF2 was a 5% tolerance part, but I fitted a 1% tolerance part just in case. As for the lack of a startup bong, based on the gaps in your horizontal line, it looks like you’re getting a checkerboard screen. There could be a problem with your digital board...

I can't imagine sparking ever being a good thing. Did you remember to earth the chassis to the analogue board when you reassembled the unit?

Hi, I had a Mac Classic II (same analogue board) suffering from vertical collapse, even after a full recap. I also replaced a lot of other parts (mostly actives), including the TEA2037 IC. The analogue board had suffered from extremely bad electrolyte leakage. Electrolyte had damaged RF2...

Hi all, I seem to be making some progress! The -12Vdc rail seemed a bit off (-13.6Vdc under load), so I replaced the -12V rectifier CR26 (1N4934) with a 1N4936. I also wanted to double-check my previous work during the analogue board rebuild that I did before it stopped working. I'd already...

Hi all, So, the symptoms seem to be getting worse - the picture has now seemingly rolled fully up to the top of the screen, and is barely visible. It looks like the width and focus are correct, but the vertical deflection is off by the full height of the display. The height control doesn't...

Hi all, I've done some more testing this evening, please see my results below. I've tested T1 (the flyback transformer) in-circuit with a cheap multimeter, the DC impedances are as follows: 8-7: 3.5 Ohm (approx. 3.3 Ohm good) 8-5: 1.5 Ohm (approx. 1.3 Ohm good) 3-4: 0.5 Ohm (approx. 0.1 Ohm...

Thank you, will do :)

Hi all, I seem to be making some progress. The machine is now consistently booting, and displays a somewhat usable image on the screen. However, vertical deflection is still not working properly - the top of the display seems OK, however this ends with a very intense horizontal line and there...

Thank you :) The "ticking" is coming primarily from the large transformer near the speaker. It's audible across most of the board to be honest. I've socketed U1 for testing, I will report back. I'll also keep an eye on U3 and Q12. I'm thinking that the short across the collector and emitter...

I also meant to mention, the part number on the rear of the board is "820-0107-C". I haven't been able to find any service information for this specific analogue board version.

Hi all, I recently got my hands on a Mac Plus 1MB (240V), which has unfortunately died on me. I had previously serviced the board, including touching up all of the solder joints on common problematic areas and replacing the RIFAs. It was working well until about a week ago when I turned it on...

Thank you :) I agree, I'll definitely take extra care when working on this one. Mains earth *seems* to only be used on the power input section (see schematic snippet attached). CP19 and CP38 (XY class) have already been replaced. I'll go ahead and pay close attention to the other components...

Hi all, I have a bit of a weird issue with a Macintosh Classic II that I'm trying to repair. At first, the analogue board was seemingly completely dead, and the digital board was giving a "stripy" screen. The digital board now seems to be working OK, following a recap and a CPU replacement...