Issues burning 27C400 with Top3000... bad chips?

[Retro Mecano]

Some of these use an 8 pin chip that does a buck/boost convert of the voltage to what is needed by the EPROM. A friend had a TOP2049 that had that chip fail and would do intermittent programming. Check that converter circuit.

Also, look in the window of the chips that do vs. do not work. Any difference you can see with your eyes? My TopMax won't do 27C160 chips that have 8 segments on the chip, but works fine for the ones with 4 segments. I use my TopMax 2 and it does both fine. It's a problem with the algorithms that was fixed on a later revision of software for my TopMax 2 that won't be getting back ported to the final version released for the older programmer I have so I have to just put up with it.

Any thoughts on the GQ4x4 programmer?

I am getting some random trouble burning some eprom, started after a year with 160s, and now almost every 27c010 variants fails at 9%. Already recapped, cleaned the pins etc..

 

[l_oliveira]

Some of these use an 8 pin chip that does a buck/boost convert of the voltage to what is needed by the EPROM. A friend had a TOP2049 that had that chip fail and would do intermittent programming. Check that converter circuit.

Also, look in the window of the chips that do vs. do not work. Any difference you can see with your eyes? My TopMax won't do 27C160 chips that have 8 segments on the chip, but works fine for the ones with 4 segments. I use my TopMax 2 and it does both fine. It's a problem with the algorithms that was fixed on a later revision of software for my TopMax 2 that won't be getting back ported to the final version released for the older programmer I have so I have to just put up with it.

I suggest you check the voltage the programmer supplies the chip on the 5v rail during programming. That is exactly the kind of 27C4096/27C400/27C4000 my programmer would not do (older type with larger die, more segments). I made an extra adapter that boosts 5v to 6.5v on the eprom socket, that solved the problem with programming these chips. It was not algorithm problem it was a physical voltage being too low. As I said before a lot of chips do work fine with normal 5v and the correct VPP at the VPP pin but some don't.

I saw it on the datasheet of one of these chips, it required 6.5v to properly program.