Kai Robinson Posted November 22, 2020 Author Report Share Posted November 22, 2020 Only $254... Quote Link to post Share on other sites
Trash80toHP_Mini Posted November 23, 2020 Report Share Posted November 23, 2020 LOL! Gotta love the listed prices for new books And that only gets you the paperback version! Click on the 7 used from $25 link to get over the sticker shock. I'm wondering if the selling of "new" books on Amazon angle is a faster, safer path to laundered money than the usual eBay schtick? Quote Link to post Share on other sites
ronan Posted November 23, 2020 Report Share Posted November 23, 2020 Did you have a look here : https://www.abebooks.com/servlet/SearchResults?cm_sp=SearchF-_-topnav-_-Results&ds=20&kn=Macintosh Family Hardware Reference&sts=t ? Quote Link to post Share on other sites
Crutch Posted November 23, 2020 Report Share Posted November 23, 2020 +1. AbeBooks (which is owned by Amazon!) is the place to get such things. Never Amazon proper. Quote Link to post Share on other sites
Trash80toHP_Mini Posted November 23, 2020 Report Share Posted November 23, 2020 Definitely +1 for AbeBooks, looked there first yesterday and search reported the title was sold out. Didn't know Amazon owned them or I'd have been more hesitant to use them in the past. Finally got past my hatred of Amazon, now it's just skin-crawly when I buy from there. This time a couple of Amazon prices are lower: https://www.amazon.com/gp/offer-listing/0201192551/ref=tmm_pap_used_olp_0?ie=UTF8&condition=used Quote Link to post Share on other sites
Kai Robinson Posted November 24, 2020 Author Report Share Posted November 24, 2020 (edited) Okay, it's done... See pics for details! No boot, but a checkerboard again at least... Edited November 24, 2020 by Kai Robinson Quote Link to post Share on other sites
ronan Posted November 24, 2020 Report Share Posted November 24, 2020 Congrats on all the work done ! I'm really impressed ! Good luck for the future of this project Quote Link to post Share on other sites
cheesestraws Posted November 24, 2020 Report Share Posted November 24, 2020 Well done! I'm lagging significantly behind you, I fear... but most of mine is done too, so I will hopefully join you in checkerboard land shortly Quote Link to post Share on other sites
techknight Posted November 24, 2020 Report Share Posted November 24, 2020 Nice! that looks like uninitialized RAM, so the CPU isnt starting up for some reason. Wonder if theres another address/data line that was missed or unconnected. Quote Link to post Share on other sites
Kai Robinson Posted November 24, 2020 Author Report Share Posted November 24, 2020 I just checked the test points for voltages - instead of reading +5v, it's reading +7.5v!!! I think my analog board has potentially killed some chips... Quote Link to post Share on other sites
quorten Posted November 24, 2020 Report Share Posted November 24, 2020 Oops, well... actually I'd vouch the essential chips are still working: GLU and BBU for one. You can double check that the ROM and CPU are okay, and if so, that should actually be good enough for initial oscilloscope debugging. Quote Link to post Share on other sites
quorten Posted November 24, 2020 Report Share Posted November 24, 2020 Easy way to check the CPU is still working in some vein: If you can trigger *HALT + *RESET and it will respond by de-asserting/asserting *AS after a few clock cycles, it should be okay. Quote Link to post Share on other sites
Kai Robinson Posted November 24, 2020 Author Report Share Posted November 24, 2020 I'm thinking my analogue board is potentially in need of repair as well - seeing as the video is very off centre as well as being wonky...voltages are something i'll have to measure....if only i had an extension cable to be able to test this flat on a bench! Anyone make one at all? Quote Link to post Share on other sites
max1zzz Posted November 24, 2020 Report Share Posted November 24, 2020 Very nice! As for extension cables, iirc you can get a normal 20pin ATX extension cable and just use one side of it (I haven't tried this personally though) Quote Link to post Share on other sites
techknight Posted November 24, 2020 Report Share Posted November 24, 2020 3 hours ago, Kai Robinson said: I just checked the test points for voltages - instead of reading +5v, it's reading +7.5v!!! I think my analog board has potentially killed some chips... Yikes! yea that spells death to semiconductors Quote Link to post Share on other sites
Kai Robinson Posted November 24, 2020 Author Report Share Posted November 24, 2020 (edited) Well, most ttl has a bit of leeway, I'm hoping it hasn't taken out the BBU - everything else is expendable... Here's the result of a 20 second power on with a set of 256k simms : Edited November 24, 2020 by Kai Robinson Quote Link to post Share on other sites
360alaska Posted November 24, 2020 Report Share Posted November 24, 2020 In case the problem actually is the board how you ever used one of these: Maybe comparing your board to a stock board with a huntron will yield some clues? Quote Link to post Share on other sites
Kai Robinson Posted November 24, 2020 Author Report Share Posted November 24, 2020 An Oscilloscope is on the way - i do have a logic analyser - but i'll be damned if i can find a DIP64 IC test clip! Quote Link to post Share on other sites
Kai Robinson Posted November 24, 2020 Author Report Share Posted November 24, 2020 Knocked up an adaptor for the SE ROM's - i have a funny feeling mine aren't making proper contact in the sockets, the legs, even cleaned, are tarnished...the ones from the spare board i have...well i tried removing them and the legs stayed in the sockets, so i now have a load of icosaoctaplegic Mask ROM's I have 10 prototype boards in a panel with ENIG and V-Scored edges on the way from PCBWay (Making use of the $100 or so commission i earned from the Amiga stuff i've done in the past) so if anyone wants to test these, i have 9 available. Quote Link to post Share on other sites
quorten Posted November 25, 2020 Report Share Posted November 25, 2020 (edited) Losing legs from a ROM, ouch. The price of those DIP64 IC test clips just keeps going up and up, but they're at least out there... https://www.digikey.com/en/products/detail/3m/923739-64/12091 Another note, I also looked deeper into the Unitron's logic equations and tried coding them up in Verilog mainly to run a simulation that I could compare the BBU's waveforms with. Indeed this was helpful in answering a few last questions, though it did feel a bit like a "distraction" from the BBU. One interesting note, though, I found the Unitron's C3.7M clock is generated by inserting two C16M cycle waits every eight C4M cycles, rather than one C16M cycle wait every four C4M cycles. It could be that the original Macintosh actually used this behavior, but of course there's no need to copy the inferior approach for the BBU. Edited November 25, 2020 by quorten Fix minor error Quote Link to post Share on other sites
cheesestraws Posted November 26, 2020 Report Share Posted November 26, 2020 On 11/24/2020 at 11:24 PM, Kai Robinson said: Knocked up an adaptor for the SE ROM's - i have a funny feeling mine aren't making proper contact in the sockets, the legs, even cleaned, are tarnished...the ones from the spare board i have...well i tried removing them and the legs stayed in the sockets, so i now have a load of icosaoctaplegic Mask ROM's If you want a spare "stock" set I can drop some in the post to you. Quote Link to post Share on other sites
Kai Robinson Posted November 26, 2020 Author Report Share Posted November 26, 2020 @cheesestraws Oooh, i may have to take you up on that - i basically need a whole other SE board, so i have some duplicate customs for testing... Quote Link to post Share on other sites
cheesestraws Posted November 26, 2020 Report Share Posted November 26, 2020 9 minutes ago, Kai Robinson said: i basically need a whole other SE board, so i have some duplicate customs for testing... We can sort this. I'll send you one of my spares. Quote Link to post Share on other sites
Kai Robinson Posted December 3, 2020 Author Report Share Posted December 3, 2020 I have a funny feeling that it's the oscillator, not making good contact in the socket...this weekend i'll desolder the socket and hard solder the oscillator in, see if that makes a difference. Quote Link to post Share on other sites
Kai Robinson Posted December 7, 2020 Author Report Share Posted December 7, 2020 OK - work has been manic (office move of the whole IT store and comms room to new building) and i've yet to have enough time (or space) to sit down and solder anything. I have, however, come up with a few little bits like the ROM adapter, and now, i have this - behold, the PLCC84 breakout adapter! Desolder the BBU socket, solder this in its place, then solder a new socket to that board - voila, signal breakout! @quorten would this be of use to you in your BBU reverse engineering? Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.