Tandberg TD20A Reel to Reel Bipolar TTL PROM (U3)
This prom can easily become corrupt especially from power supply issues on the 5v rail.
This is a brand new replacement prom with the exact program data from the original devices. It is a direct replacement and has been programmed. New chips are not programmed and will not work.
The chip reference on the circuit diagram is U3. It is the main controller chip for the logic board. Several types of these were installed in the original board and all function the same.
Common types are TBP28L22N and SN74S471N. This will replace all.
 
The prom is different for 3.75-7.5 ips machines and for 7.5-15 ips machines. Please choose from the selector above your requirement.
 
Brand new, 1 supplied.
Free Postage.