Sounds possible, thank you!! For the same reason and to get used to the new desoldering tool I'll first remove and test the 2 decoders M3 and M4 (40138).
Mauro Il 04.12.2018 09:24 Francesco Messineo ha scritto: > On Mon, Dec 3, 2018 at 11:00 PM Mauro Pintus wrote: > >> Checking some signals with the oscilloscope it looks like it is looping after a fix time without completing the boot. Francesco Messineo (another user of this list) wrote me in this days to offer some help and he suspect I damaged the RAM. Thank you again Francesco. I bought a desoldering iron and I hope in the next few days I'll find the time to try removing all RAM modules and fit one at a time in the first socket (hoping one module is still alive). > > I actually suggested the RAM could be damaged when he opened SW3 (the > RAM backup power) with SW5 (the main power switch) closed is that some > logic and the RAM have Vb as Vdd rail and almost the rest of the > system has Vdd derived from Vp (via the dual output inverter). Now, if > you look at the schematic, SW3 removes both Vb and Vp, but, on Vb > there's only a few bypass capacitors to ground plus 1 uF electrolytic, > so it might discharge quickly, while on Vp there's at least one 470uF > capacitor plus another 470uF on the output of the inverter on Vdd side > (yes, also much more logic powering from it, but stil...). > What might happen in this case is that the Vb got quickly to 0V with > still some inputs of the chips powered from it have something like +5V > applied; in this case, the protection diodes on the input start > conducting and some of them might get shorted or degraded from this > current. It happened a few times on logic that I designed that had a > backup power for CMOS RAM, I had to make sure that all inputs to the > RAM were either following Vbackup or already switched to logic 0 > before removing the backup power. > So in this situation I would examine all the logic powered directly > from Vb and that includes the RAMs. Usually a quick test with a > multimeter (with all circuits powered off) from each input pin to Vdd > pin of the chips can show if there's some damaged input protection > diode. > > HTH > Frank IZ8DWF > >> Sent from my iPad On 03/dic/2018, at 19:06, Jan Vanden Bossche wrote: Mauro, What do you need to repair your M-10? Greetings from the TyRannoSaurus Jan-80 ________________________________ From: Mauro Pintus To: m...@bitchin100.com [3] Sent: Saturday, 1 December 2018, 16:12 Subject: Re: [M100] Olivetti M-10's for a new home Thank you Jeff, really appreciated. Now I keep my finger crossed :) Have a nice day Mauro On Dec 1, 2018, at 3:59 PM, Jeffrey Birt wrote: Mauro, You have a need for them, so you should have them if the original person does not speak up. Fixing your machine is a better use. I have no specific need, just thought it would be neat to have a machine with AZERTY keyboard. Jeff_Birt From: M100 On Behalf Of Mauro Pintus Sent: Saturday, December 1, 2018 7:50 AM To: m...@bitchin100.com [5] Subject: Re: [M100] Olivetti M-10's for a new home I was soo exited I didn't see the other answer from Jeffrey, I'm sorry... Hope we can find an agreement, I'm really interested but I don't want bother anyone. Mauro On Con OpenStar hai Giga, SMS e i minuti che vuoi da 4,99€ al mese, per sempre. Cambi gratis quando e come vuoi e in più hai 10€ di credito omaggio e 6 mesi di INFINTY! http://tisca.li/myopen
