Recent content by MacinPosh

I finally got some time to replace R1 and U1. Unfortunately it doesn't seem to have made an improvement  :( Are there any other common problem components I can look into?

Thanks lisa2  I’ll replace these and report back asap. 

Thanks again for the ideas. I've had the card out a few times to inspect it and always made sure everything was connected back up, but i'll check again. Going on the assumption that as BU406 is hot, maybe something in the Horizontal drive circuit is failing, i.e. Row A of the schematic. I'm...

A very good point, although I went through and recapped it when I first got it in 2018. I don't think they'd wear out that quickly?

I recently brought my Lisa 2/5 back out of the cupboard to have a tinker during lockdown. Unfortunately after a few minutes the contrast goes very dark and the image starts to shrink on the right hand side. I haven't dared to leave it on long enough for something to go bang... The BU406 is...

I haven't found any shorts around the ROM pins, and the same issue happened to two different ROM chips, so I don't think the ROM is the issue. As I mentioned in my previous post, the ROM now only boots to death chimes and B&W Stripes in my other working machine

I was in the process of cleaning and recapping an SE/30 logic board which had been subjected to a battery leakage.  I've checked and rerouted all the rotted traces (totalling about 15) between the RAM, ROM, VROM and GLU but when I was satisfied enough to attempt a boot, pin 63 on the ROM burnt...

Following up on this after a long time.  After a lot of head scratching and component swapping, I went back to basics and discovered that the problem was in fact with two capacitors on the Hard Drive's analog board that had gone short circuit. (Shown in the RED box in the photos, compared to...

Unfortunately I don't think that's the correct schematic for the board. The component is from the small daughter board connected to the Astec Power Supply AA11770

Inspecting the Profile power supply board, I noticed a very burnt resistor that had cracked into two pieces. I'm having trouble identifying its value. Can anyone help me out? It looks like Brown-Grey-Orange-Grey-Brown? Thanks 

I recently acquired a 5MB ProFile drive in an unknown condition for use with my Lisa.   I promptly replaced the power supply caps in hope that the drive would be operational. Powering the system on resulted in a high pitched whine but nothing else, but when I disconnected the internal data...

I've finally got round to looking at these Pluses, and interestingly/unfortunately the analog boards are working fine as they boot up the logic board borrowed from a working plus just fine.  Larry Pina suggests the 5v regulator or the TSM chip is to blame for logic board related flupping. I've...

These are all great suggestions. I'll order up and replace parts sequentially and post my results ASAP Thanks 

Good afternoon all, I have acquired two Mac Plus units of which neither want to boot. I've started with the usual logic and analog board cleaning and recapping to no avail. The most promising combination of boards only achieves a white horizontal line accompanied by noise from the speaker, as...

Hi Everyone, I recently acquired a Mac Plus with a temperamental analog board which would only display a picture briefly whilst being tapped on the left side. I tracked this problem to a failing flyback which I have replaced, but I now get horizontal scan lines across the display which I...