On 2020-May-04, at 8:10 PM, Martin Crockett via cctalk wrote: > .. > I noticed there is a capacitor that has vaporized, but I cant determine > what value it is. > > I have the DEC VT-100 maintenance guide but it is very blurry in the > relevant area. > > I cant even read the board designation. > > This is the area of the circuit, I can trace the 2 Zener diodes on the -23V > rail, to one end of the cap, the other end seems to go to ground. The > obvious culprit is C6, but that doesn't match the mud map of the board, as > in C1x. > https://imgur.com/a/tm8mn8b > > This is the capacitor in question. > > It looks like C1x where x is undetermined. > > I think it was a ceramic monolithic capacitor, it seems to be different to > any other caps on the board, i.e. slightly larger and a different colour > blue. When I look at this hires photos on Google images, it is the blue > capacitor circled below > > Does anyone have a VT-100 and mind checking what the value of this > capacitor is please? > Ideally value and voltage or even just the nomenclature written on it, I > can work out the value and voltage from that.
You sure that isn't C14, connected to pin 2 of E24, Vgg PS pin on the non-volatile RAM? (bitsavers schematic pdf pg 15 / "VT100 BASIC VIDEO Sheet 2 of 6" / upper middle of page). See also the board pics on bitsavers. 0.22uF, 50V CER
