Got it working! When I went to try and desolder the EPROM the first pin I tried I found that solder was also sucked out of the castellation next to the pin! I then desoldered all the castellations, checked the clearance between EPROM pins, castellations and trace gaps under magnification to make sure no junk had gotten in there and it now works.
I'm not sure why the castellations were filled with solder. Maybe someone was trying to fix a connection issue that was really the result of the PCB sitting to far down in the socket? With them cleared out the socket contacts fit and align much better too. Measuring the length of the protruding pins it seems the cardboard shim must be about 2.5mm thick to allow the pins to not touch the socket bottom. I'll remake my shim to tomorrow to match. Thanks everyone Jeff Birt -----Original Message----- From: M100 <m100-boun...@lists.bitchin100.com> On Behalf Of Brian K. White Sent: Saturday, December 19, 2020 8:14 PM To: m...@bitchin100.com Subject: Re: [M100] SuperROM SR is available, but it's still always possible there were revisions over time. The datasheet for the socket doesn't show the shape or dimensions of the contacts: https://github.com/bkw777/pcb2molex8878/blob/master/references/015299282_sd_corrected.pdf The datasheet for the carrier shows the shape and dimensions of the installed chip legs, but that is several solid mm of vertical length. When measuring a socket with calipers, I get a measurement of 3.9mm from the socket floor to the center of the curved part of the contact, the point that actually makes the contact. And if the PCB is 1.6mm, that gives an elevation of 3.1mm from the socket floor to the bottom of the pcb. However, in actual testing, many many times with several different sockets and machines, while designing this pcb carrier: https://github.com/bkw777/pcb2molex8878 I arrived at the following, from: https://github.com/bkw777/pcb2molex8878/blob/master/Carrier/pcb2molex8878.scad " // 1.6mm pcb pcb_elev = 2.2; // bottom of pcb above socket floor. Min 1.9 - Max 2.4 " So the bottom of the pcb is 2.2mm from the floor of the socket, with notes that say you could go as low as 1.9mm or as high as 2.4mm. It's true it's a tight window, simply because a DIP installed on the official carrier provides a huge tall straight flat smooth side of a chip leg, rounded away from the socket contact at both top & bottom, and the socket has a comparatively sharp contact point that is free to slide along and land anywhere along that several mm of chip leg. The chip provides all the slop to make the combined system reliable. But with a pcb, you're having to get two narrow things exactly lined up, with the added stress that you don't DARE err in one direction and let it go too deep since that results in damage. Maybe it would be worth it to make a little block or 3d printed tool that fills the socket and compresses the contacts, which would let you extract a trapped board like that safely. -- bkw On 12/19/20 8:13 PM, Jeffrey Birt wrote: > Thanks for the pictures. I did see where it had something glued to the > bottom. This one also had all the pins flattened over. No doubt because > the cardboard was missing. > > I tried to shim it up 2mm to 2.5mm but if it is high enough to not get > stuck in the socket it pops right out. The electrical connection even > when it is ‘stuck’ in the socket is also poor. I can wiggle it and get > it work well enough for the SR menu to pop up but when I try to select > any one of the 4 programs it locks up. > > I’m really surprised that the PCB and a cardboard shim was all there was > too it. > > Has this ROM been dumped? I may go ahead and pull it off the PCB to try > and dump it to at least confirm the EEPROM itself it good. > > Thanks for your help. > > Jeff Birt > > *From:* M100 <m100-boun...@lists.bitchin100.com> *On Behalf Of *Greg Swallow > *Sent:* Saturday, December 19, 2020 6:56 PM > *To:* Jeffrey Birt <m...@bitchin100.com> > *Subject:* Re: [M100] SuperROM > > Jeff, > > The SR should've had a shim/cardboard attached to it's underside. I'll > try and micrometer one and give you a thickness. > > GregS <>< > > Dec 19, 2020 5:47:48 PM Jeffrey Birt <bir...@soigeneris.com > <mailto:bir...@soigeneris.com>>: > > SuperROM – > > Working on an M100 now that came with a SuperROM that had stuck in > the socket and the socket managed getting it out. Socket replaced, > but I am confused as to how the SuperROM (SR) was ever intended to > fit properly. > > The SR gets stuck as while the Pin1/28 side is held up from the > bottom of the socket by the pin 1 tab on the SR PCB, the opposite > end drops down so far that the PCB falls below the bend of the > contacts. This lets the contacts spring out over the top of the PCB > and thus it is stuck. > > If I shim up the SR enough to prevent it getting stuck then it pops > out very easily. It seems to be a very poor design. Perhaps there is > some part of this one that is missing? I could not find any images > on the web that clearly showed the SR board to compare to though. > > The contact is also really poor, sometimes it will make contact in > the socket and sometimes not. It may be that the PCB was damaged > when it was wrestled out. > > Lastly, has this ROM been dumped? If not, I’ll pull it off the PCB > and read it. > > Thanks, > > Jeff Birt > -- bkw
