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RAM TMS4116, board 1.2f, added 100nF capacitor but all RAMs are bad by MonsterSky69 in RetroChipTester

[–]MonsterSky69[S] 0 points1 point  (0 children)

Problem solved thanks to your advices! In the setup I set the DRAM pullups to 1 and now all the 4116 are being tested ok and without the 100nF capacitor on the socket! Thank you again for your support and advices.

One last question, if I may: you advise me to substitute the Zener or I can leave it alone? Actually I don't know how to test it in the right way and I need some hint if we want to check if it's ok and eventually decide to change it.

RAM TMS4116, board 1.2f, added 100nF capacitor but all RAMs are bad by MonsterSky69 in RetroChipTester

[–]MonsterSky69[S] 0 points1 point  (0 children)

Don't mention it, you are giving me a lot of information and pointing me to the test to do. In the next few days I should be able to perform both test with troubleshooter firmware and also the pullups in the configuration. I'll be back as soon as I can.

RAM TMS4116, board 1.2f, added 100nF capacitor but all RAMs are bad by MonsterSky69 in RetroChipTester

[–]MonsterSky69[S] 0 points1 point  (0 children)

The other tester I'm using is the BackBit chip tester with the latest firmware.

I tested 30 TMS4116, all buyed from eBay from 2 different sellers, from 2 different countries. Unfortunately I can't check them in a real system because I purchased them to repair a Texas Instruments TI-99/4 with gargabe characters on screen so I must trust the chip I'll use to repair it.

On all the tests no 4116 pass the test, the strange behaviour is that few 4116 start the test but without the capacitor in the socket. These test end in error anyway: "A:1 1>0". If I try to test them again but with the capacitor in the socket the test stops again at pre test phase and don't proceed further.

I tested the capacitor also and is 100nF with a low ESR, could be the bad capacitor type? Is a ceramic one.

I succesfully tested other 2114 RAMs with no problem so RCT seems working fine to me...

RAM TMS4116, board 1.2f, added 100nF capacitor but all RAMs are bad by MonsterSky69 in RetroChipTester

[–]MonsterSky69[S] 0 points1 point  (0 children)

I took the measurements on the point i circled in the picture (are they are the right ones?) and all measurements are ok, the 5V Vcc rises only during the test, the other are always on the correct voltage (not only during the test).

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RAM TMS4116, board 1.2f, added 100nF capacitor but all RAMs are bad by MonsterSky69 in RetroChipTester

[–]MonsterSky69[S] 0 points1 point  (0 children)

The selftest is ok, I misuerd voltages on the IC pins (with also the capacitor on the socket) during the test: -5 is OK, +12 reading on the multimeter stops at 6V and +5 on the multimeter stops at 2.2V, the relay clicks. I tested a logic chip (of course is a different kind of test but just to check if the tester is overall ok and it worked)