Well, it looks like the only 7486s I have on hand are LS. What with buying bulk parts I'll probably never use and waiting for the slow boat from China, it'll probably be more cost-effective just to buy the module on Arcade Shopper. Thanks for your help, guys!
-- Jim On Mon, May 7, 2018 at 11:04 AM, Francesco Messineo < [email protected]> wrote: > On Mon, May 7, 2018 at 4:42 PM, Diggy Dude <[email protected]> > wrote: > > To make sure I understand: > > > > Clean all pads and leads with flux.Will a flux pen suffice, or should > liquid > > flux be used? > > no, flux residue after soldering has to be removed. I use water-based > flux, so I clean the boards with water and bake them to remove the > water > > > > > What specific 74HC and SRAM devices do you use? > > I use AS6C6264SCN memories, though they aren't guaranteed to have > standby current lower than 4 uA, but I measure every module to be > sure it meets this requirement. It's the only part that can be found > new at this time. I have used batoches of several other SRAMs when > I've found a good deal on ebay for example. > I do all glue logic with a single 74HC86. > > > > > On Mon, May 7, 2018 at 2:45 AM, Francesco Messineo > > <[email protected]> wrote: > >> > >> On Mon, May 7, 2018 at 9:08 AM, Diggy Dude <[email protected]> > >> wrote: > >> > Thanks, Fugu! > >> > > >> > So the modern solution is a single SRAM and capacitor on a SOIC-to-DIP > >> > breakout? What's the RAM chip they're using? > >> > >> and a logic chip (there're a few different approaches here) to combine > >> the separate chip selects to a couple of addresses and a single select > >> signal. My own version of the circuit uses the fewest ports possible > >> (at least if nobody comes up with a different approach I couldn't > >> think of). > >> The RAM chip must be a CMOS static ram, 8kx8 and with low power > >> standby (not all have this feature). The original 8k modules were > >> specified for 4 uA max standby current, that allows the standby > >> battery to keep the RAM content for over a month. Usually the suitable > >> chips have L or LL in the part number, but you better check the > >> datasheet for the fine details. Most of the suitable RAM chips have a > >> measured standby current of 0.1 uA (often less) at 3.3V if the chip > >> select are driven with the correct voltages. At these current levels, > >> cleaning the soldering flux is a must. I've measured up to 15 uA of > >> standby current on badly cleaned modules. YMMV. > >> Glue logic *must* be 74HC family, it has a suitable current draw at > >> 3.3V standby and suitable speed. In one case I've used 74AHC and it > >> worked well too. > >> > >> > > >> > -- Jim > >> > > >> > On Sun, May 6, 2018 at 10:29 PM, Fugu ME100 <[email protected]> > wrote: > >> >> > >> >> You could try > >> >> > >> >> https://www.arcadeshopper.com/wp/?page_id=11#!/8k-RAM- > module-for-Model-100/p/104430801/category=28313042 > >> >> > >> >> They have the M100 modules if you want to buy. > >> >> > >> >> If you want to build your own there are PCBs on OSH Park for surface > >> >> mount > >> >> and DIP versions. > >> >> > >> >> No need for any pillaging :) > >> >> > >> >> From: M100 <[email protected]> on behalf of Diggy > Dude > >> >> <[email protected]> > >> >> Reply-To: <[email protected]> > >> >> Date: Sunday, May 6, 2018 at 8:13 PM > >> >> To: <[email protected]> > >> >> Subject: [M100] 8K RAM module > >> >> > >> >> Anyone know where I can get an additional 8K for my 24K M100 without > >> >> pillaging another M100? Let's face it: if I got another M100, I'd be > >> >> inclined to leave it intact. > >> > > >> > > > > > >
