Recent content by alexGS

It was wonderful to fix that error by replacing the memory chip, I really appreciate that advice (a while ago now), thank you :) I hoped it might resolve some of the quirks and allow it to calculate a correct dt/dT rather than “No”. Mind you, probably wouldn’t stop it running dead flat...

Thanks, both of you, for keeping this thread and the good intentions alive :) I look forward to deciding which cells to try next, but it does feel like batteries for old machines are a liability and not worth the trouble and expense… I guess my mistake was leaving it fully inserted in the 540c...

Our stars are sort-of aligned, because meanwhile yesterday here in NZ I realised my 540c battery, made with Eneloop AA cells about six months ago, has stopped working (although the BMS was responding normally, and then reporting a shorted cell). I opened it to find this great disappointment...

I agree with bibilit, faults in battery level sensing sound like hybrid module problems. I’ve fitted replacement hybrids and they have cured such things. I usually have to clip all the pins and remove each pin individually; it’s very difficult to remove a hybrid module intact

With regard to your third example - I had a Portable recently where one of the three 74AC244 latch chips had failed, related to floppy drive function. I swapped it with one of the other two latch chips and immediately had a display similar to that and no chime. Therefore, I wonder if one of...

I haven’t seen this before - a non-backlit Portable where the whole display dims perfectly evenly to black in about 5-10 minutes, then recovers from black to normal when powered off for about the same length of time. In that respect (the recovery), it seems the same as Tunnel Vision, except...

Thanks SuperSVGA - I wasn’t familiar with an electronically-controlled potentiometer. It turned out to be the inverter board faulty, swapping that restored backlight operation. Just coincidence that it failed when I replaced the latch chips

Thanks! :) I got a cheap deal on Eneloop Pro AAs (which I identified as being able to accept a 1A charge rate easily) and swapped that memory chip that I’d ordered. And thanks to jmacz identifying the need for that, it produced a battery pack that actually ‘repaired’ properly with Lind - I was...

Ok, so right now you have the Sad Mac - CD38 error and no chime when you turn on? I think I would apply some flux and hot air to reflow the square power manager chip (near the right-side trackball connector) - also double-check your capacitor replacements in that area.

Thanks, I’m in New Zealand but price isn’t the problem anyway - it takes me hours to do these, especially when there’s a dust bubble and I have to do it again. I ordered some that claimed to be FSTN, but when it turned up it was exactly the same as other films, so produced the usual results...

Further to what I said, the error code ending in CD38 is a Power Manager error, so here’s hoping a reset will fix

Have you tried holding the two buttons on the left side? Should reset the power manager. The process of ‘powering down’ is an important one before installing the RAM card. I hope you had the battery out, power unplugged, AND the battery cover refitted (if you have a 9V battery in there)...

Thanks! Darn, no wonder it can be so difficult finding LCDs for these machines… the number sounded familiar

This is an amazing thread - you’ve been extremely thorough, and generous sharing all your great designs. After such efficiency, it’s almost a relief to know you can have accidents too :) I’ve never worked on a Duo, but I feel prepared now. That LCD type seems familiar - same as 540c?

Sorry I didn’t see this earlier. I’ve fixed a few PB100 logic boards with this exact behaviour and I always start by replacing C22 in the corner - it’s involved with producing the LCD drive voltage. I think you will also have to replace the 8x 3.3uF electrolytic caps on the back of the LCD...