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

[djsheep]

Been having issues burning 27C400 with my Top3000.

I've tried Topall v9.xx which has a 27C400 profile in it and v8.xx which doesn't but have a profile, but I use MX27C4100 instead.

I've had two batches of 20 x 27C400 chips each.
Last batch 9 out of 20 chips burnt fine. 11 not burnable.
Latest batch of 20 chips, none burn, they all just the time out right when it starts with the message "Error at:0000 : (FF)"

Burner reads them after UV erasing as blank just fine.
Burner also reads the data from the 27C400 chips just fine.
Burning however...

Have tried various times of erasing.
Have tried using an external power supply.
Have tried multiple machines.

Ironically enough, the first batch of chips were painted over "refurbished" ones. This new lot are not painted and the real deal.

Just checking if anyone has any leads. I'm going to assume these are bad chips... but wanted to get some thoughts before I return this lot in the off chance they are ok.

I don't have another burner on me, so I can't do anything like that.

Thanks for any advice.

 

[9999 Damage]

Have you tried burning other EPROMs since the badness started? Any chance the Top3000 has detritus or corrosion blocking a pin?

 

[djsheep]

Yep, all other chips burn with zero issues... done 800, 322, 080 recently. Once I hit the 400's though it's all bad news!