Thank you very much, Jeff, this is very useful. Kind regards Pawel
On Monday, 3 May 2021, Jeffrey Birt wrote: > On the power supply connector counting from the left to right with the front > of the machine toward you: > > > > Pin Function > > 3 VEE (-5V) > 4 VB (Battery charge voltage) > > 5 GND > 6 VDD (+5V) > > > > I have attached the relevant section of the schematic that deals with the > contrast adjustment as well. > > > > Jeff Birt > > > > From: M100 <[email protected]> On Behalf Of ExPLIT | Pawel > Radomychelski > Sent: Sunday, May 2, 2021 11:38 AM > To: [email protected] > Subject: Re: [M100] NEC PC-8201(A) Display issues > > > > Thanks for the Info, Jeff. > > > > Sorry for the dumb question, but can you point out on which two points i > should measure +5V and -5V ? > > I think this Info can be also very usefull for other folks having power > issues on NEC. > > > > Thanks > > -- > > Kind regards / > > Mit freundlichen Grüßen > > > > ExPLIT IT Solutions > > Pawel Radomychelski > > > > > > > > -----Original Message----- > > From: Jeffrey Birt <[email protected] > <mailto:jeffrey%20birt%20%[email protected]%3e> > > > Reply-To: [email protected] <mailto:[email protected]> > > To: [email protected] <mailto:[email protected]> > > Subject: Re: [M100] NEC PC-8201(A) Display issues > > Date: Sun, 2 May 2021 11:34:12 -0500 > > > > OK. This sounds like a power supply issue. It is odd that it comes back to > normal with a power cycle though. Take it apart so that you can measure the > power supply voltages. Measure the +5 and -5V when it is working properly and > then when the LCD goes blank. > > > > Jeff Birt > > > > -----Original Message----- > > From: M100 <[email protected] > <mailto:[email protected]> > On Behalf Of ExPLIT | Pawel > Radomychelski > > Sent: Sunday, May 2, 2021 10:53 AM > > To: [email protected] <mailto:[email protected]> > > Subject: Re: [M100] NEC PC-8201(A) Display issues > > > > No, this is not the case, i think. > > Brightness is getting higher and higher until you don't see anything. > > And this happens to different times: after 3, 5 or 10 minutes, sometimes > after 20. > > On some units the lcd is flickering until it shut off. > > > > Pressing a key doesn't activate the lcd back. Only full switch off / switch > on. > > > > On some units the contrast "jog dial" (doesn't know exact name of this part > in English) doesnt work at all. Contrast is always locked to one position. > > > > Kind regards > > > > Pawel > > > > > > On Sunday, 2 May 2021, Jeffrey Birt wrote: > > The unit does have an auto power off if you have not used it for 5 minutes or > so. Is this what you are experiencing? > > > > > > > > Jeff Birt > > > > > > > > From: M100 <[email protected] > <mailto:[email protected]> > On Behalf Of ExPLIT | Pawel > Radomychelski > > Sent: Sunday, May 2, 2021 9:20 AM > > To: [email protected] <mailto:[email protected]> > > Subject: [M100] NEC PC-8201(A) Display issues > > > > > > > > Dear Model T / NEC collegues! > > > > What i noticed holding a couple of NEC PC-8201 and PC-8201A in my hands, that > many have a strange display issues: > > > > > > > > Unit working fine, after some time display is getting blank and i can't see > anything on the LCD. > > > > After switch off/switch on - its fine again. > > > > > > > > I noticed this problem independent prom Power Source (On AA Batteries and 6V > DC Power Supply) > > > > On some units this problem is getting better when replacing old NiCd Battery > with a new one or with 1F / 5,5V Capacitor. > > > > But still not solved completely. > > > > > > > > This is a question on our gurus: Is there a chip (Or couple of chips and/or > other components) on the mainboard which can / need to be replaced? > > > > > > > > I am not so familiar with old electronics, nor i have an oscilograph. > > > > Is it possible for an avarage user with moderate soldering skills and > multimeter to solve such issues ? > > > > > > > > Thanks! > > > > -- > > > > Kind regards / > > > > Mit freundlichen Grüßen > > > > > > > > ExPLIT IT Solutions > > > > Pawel Radomychelski > > > > > > > > > > > > > > > > > > > > -- Kind regards / Mit freundlichen Grüßen ExPLIT IT Soltions Pawel Radomychelski
