I'm trying to determine what cause brand new 4116 chips from Jameco to fail immediately on the intial power up. I had found that after my Rev.0 sat for 8 years, when I powered it up the PSU had died. I had a spare Apple IIe Astec PSU so I installed it. I reseated the CPU and many of the other chips, but not all. I had all good voltages and all good clock signals.
On power up, it beeped on Reset and gave me a Monitor prompt. Running the memory test indicated some bad memory. I reseated all 48K memory wearing a anti-static wrist strap and the Apple plugged into a ground outlet and OFF. Bad memory was still indicated in banks D & E.
I purchased an UNO based memory tester and found all Block C memory tested good, but all Block D & E tested bad, totally bad. I ordered new 4116-15 from Jameco and installed them as described below.
I am no newcomer to adding memory in Apple II's although it has admittedly been many decades since my last time. Any insight into culprits is appreciated.
Methodology used:1. Apple II plugged into grounded outlet with power off for days.
2. Grounded myself sitting in front of Apple and put on my grounded anti-static wristband.
3. Memory was removed from the anti-static chip carriers and placed on a sheet of grounded aluminum rack panel.
4. Memory was loaded into a chip insertion tool and plunged into each socket.
5. the 16K jumper blocks were checked and tested for proper insertion
6. power was applied but the monitor memory test showed some memory failures.
7. powered off the Apple and waited 20 minutes, pulled the D & E 4116 and all but one tested bad (the first chip in bank E, E3 was good all others in D & E...BAD.
8. the first chip in bank C, C3 tested good. I didn't test the remainder of back C as yet.
Any ideas? Thanks in advance.
The only thing I can think of that can damage that many chips is one of the 3 required voltages disappearing for some period of time.
Also to save your own money and the dwindling supply of beautiful ceramic chips from the 70s with metal covers, I suggest you use more common chips until you figure out the problem. One really cheap alternative is the bulgarian made CM8116P, which I have tested myself in my Apple II: https://dsmcz.com/prestashop/en/digital/6654-cm8116-dram-16kb.html
How did you test the chips? In that machine, a chip tester or another machine?
Are you sure it is the chips that are bad and not bad sockets or something? The sockets Apple used back in those days weren't the best.
Wow, that site has some great prices on ICs, thank you for sharing it.
OP, if you are using the system to test the memory, I can recommend the mini 4116 DRAM tester or similar to test the chips on their own.
Initially, I used the Monitor Memory Test command line string for 48K:
C050 C053 C054 C057 N 265:FF N 266<265.BFFEM 266<265.BFFEV 265:0 N 266<265.BFFEM 266<265.BFFEV 34:14(one space)(Return)
The result was a solid white screen that did not alternate to black and only displayed question marks in the 4 lines of text.
about 8 hex memory locations where listed before the test would automatically repeat. (I have a video of this)
At this point the bad memory location addresses were in the lower 2K of memory.
At this point in time I decided it more prudent to buy a 4116 memory testor kit for the Uno and test all of the 24 4116's. I used this testor.
https://bsgelectronics.com/4116-memory-tester-video-and-assembly-instructions
Right off the bat, the top 32K chips in rows D & E tested bad in this tester although some chips had a few cells that tested OK. Most of these chips were original Motorola MCM4116L20, ceramic, gold plated and the remainder were plastic case, tin lead, Mostek MK4116GN-3. The Row D & E chips were installed by the Apple dealer a few months after I bought this 16K Apple II in 1978 and were a mix of these 4116 variants.
Since the chips were tested in the BSG memory tester I think this is fairly definitive regarding the chips but you are right, there could still be some sockets with oxidation. I'll recheck the motherboard.
Wow, the Bulgarian chip is really cheap...so I got what he had. Thanks for the tip.
I wonder if they are any subtle issues using the Astec IIe supply with my Rev. 0 motherboard vs the original that occurs during "turn-on"?
@skate323k137 thanks for the recommendation. I took a look at Kelvin's site . I'm using the BSGelectronics version of the 4116 tester.
When you say your second pawer supply is good how do you know this? Have you monitored all three voltages on a scope at the same time? I'm not saying that's the problem, but whne someone claims "good voltage" raises more questions than answers expecially when chips get damaged. It sounds like a short between one of the rails to ground could be possible. It doesn't have to be with the RAM but I'd check motherboard components (all ICs can caps would me my first look). Check power to ground on all power rails.
One other thing to know about dealing with ICs (and it sounds like you're doing most of things well) the only thing that I'd ask is how are you handling the chips? In general you're not suppose to touch any of the pins and when you do you touch them all (ie hold the chip flat with an open palm). That said, it sound more like the problem is rooted in the II's board. I checked the schematics to see if there's any obvious suspects but nothing stood out on a quick scan.
One other "odd" question is can you check continuitu across your power switch? Maybe also check the grounding in your outlet. Is there anything else connected to the II like a monitor when you're doing the work? These last few are extremely rare, but you're also working on a system plugged into an outlet so power is still a suspect. If I was doing this, I'd have the grounding strap attached to a plate screw on the outlet. When properly wired, the screw is earth ground. I also never work with a supply connected to an mains, I've seen power get around switches too many times.
Jeff d, I sure appreciate all your suggestions.
On spare Astec PSU, all 3 voltages monitored with scope, but only after PSU was turned on with loads on +5 & +12. All 4 voltages were correct on DVM and scope whether view on scope of DVM. However, this spare Astec PSU still had original electrolytics which means turn-on transients could have been bad. I had not checked this. I've since removed this spare Astec from use and will rebuild it, later. In the meantime, I have the original PSU, now repaired and load tested on all four supplies, in addition to another rebuilt Astec.
On a go forward basis I will test using my original silver PSU that has the Power On/Off toggle switch. Power switch was thoroughly cleaned of all gummy gunk, continuity with contacts closed confirmed consistant after cleaning.
There are no shorts on any of these three PSU rails or motherboard rails.
4116 memory chips were handled by cases only and chip pins rested directly on grounded aluminum plate otherwise . Wrist strap and aluminum plate are grounded to screw in earth ground socket of 3 pin 110VAC socket.
Initially I was using a 43" OLED flat screen TV for the display screen (Video RCA input), but also tested using my Apple III monitor, Both worked as expected.
My present issue is getting the residue out of the keyboard keys to correct keys that don't close after cleaning. I just picked up is isohexane based cleaner yesterday to flush those keys that stopped working after cleaning with DeoxIT D5.
New memory has been ordered as well.
One thing I will say after ordering from this website is that after ordering the last 14 chips listed in the link CVT provided, the seller gets a big fat ZERO in communication, no order sale confirmation/shipping info or shipping expectations. I guess time will tell if I get a package from Bulgaria in a month or so.
In the meantime I've ordered more from Jameco, at least they are shipped quickly.
It's not coming from Bulgaria. This site is based in the Czech Republic. They provided a phone number - give them a call.
I stand corrected. The chip was made in Bulgaria, my purchase was through a company in the Czech Republic. I'd received emails from them but they were in my junk folder. So the product should arrive in 7-10 days.
Thank you! I had just been holding tight to hear from them but I found my shipping notification in my spam folder as well.
I did receive the fourteen 8116 memory chips from the company in the Czech Republic as well as 24 4116s from Jameco.
I removed the Astec PSU and replaced it with the repaired original PSU. I suspect the Astec PSU had transient issues even though the output voltages were correct.
I wound up using the Jameco memory to replace the 32KB of bad memory in banks D & E. This time the memory test for memory above 266 showed all good upper memory locations.
This old Apple II Rev 0 is back to its original working state.
Thanks to everyone who offered their wisdom, suggestions and comments.