https://www.arcadeshopper.com/wp/store/#!/Crystal-Oscillator-32-768-KHz-32-768KHZ-32-768K-Hz-Cylinder-3x8mm-quartz/p/237308514
arcade shopper has the crystals from time to time, or you can get a bag of them on ebay pretty easily. On Fri, Jul 4, 2025 at 9:57 AM Stephen Adolph <[email protected]> wrote: > https://digilander.libero.it/rar2k/TRS80/Images/M100-Pcb.gif > > Do you have a scope? You could check that the timer interrupt input > RST7.5 is toggling every 4msec. > > Timer interrupt TP is generated at M18, which is the RTC chip. It is fed > from 32.768kHz crystal X1. > > Not saying for sure this is the problem but it looks similar to other > machines I have fixed where that crystal was dead. > > > > On Fri, Jul 4, 2025 at 9:06 AM Thomas Morehouse <[email protected]> > wrote: > >> Thanks Steve. Can someone point me to appropriate schematics or >> diagrams, finding a replacement crystal, and how to perform the surgery? >> TM >> >> >> On Fri, Jul 4, 2025 at 9:01 AM Stephen Adolph <[email protected]> >> wrote: >> >>> it is suffering from excessive interrupt-itis. >>> >>> On Fri, Jul 4, 2025 at 8:58 AM Stephen Adolph <[email protected]> >>> wrote: >>> >>>> looks to me like the 32768 hz crystal is dead. >>>> >>>> On Fri, Jul 4, 2025 at 8:56 AM Thomas Morehouse <[email protected]> >>>> wrote: >>>> >>>>> Friday update: >>>>> >>>>> Batteries replaced with fresh AA alkalines yesterday (Thursday). Left >>>>> powered off overnight to recharge backup battery. Powered up this >>>>> morning, >>>>> but no change. See attached screen photo. >>>>> >>>>> The screen clock seems to be working, but date never changes from >>>>> 1/1/1900. >>>>> Top four lines of screen appear normal, but below that, definitely not >>>>> normal. >>>>> >>>>> The "center" screen line consists of constantly changing characters. >>>>> Lowest screen line appears to be reiterations of "Bytes free" - without >>>>> the >>>>> "Byt". >>>>> >>>>> None of the keyboard keys have any effect; when "cursor" is over >>>>> BASIC, hitting Enter changes nothing - screen remains unchanged. >>>>> >>>>> I've done several Cold Starts (CTRL+Pause/Break+Reset) and >>>>> (CTRL+Pause/Break+Power switch), but no apparent change. >>>>> >>>>> Note: when I do a Power On, the screen quickly shows the correct >>>>> original default M100 screen, then immediately changes to the garbled >>>>> screen. >>>>> >>>>> Onward through the fog! >>>>> Thanks. >>>>> Tom M. >>>>> >>>>
