10-02-2019, 10:25 PM
The 5U4 and 5Z4 are somewhat different both in rating and internal construction and basing. Look at these data sheets.
For the 5U4:
https://frank.pocnet.net/sheets/137/5/5U4G.pdf
For the 5Z4:
https://frank.pocnet.net/sheets/127/5/5Z4.pdf
For the 5U4:
https://frank.pocnet.net/sheets/137/5/5U4G.pdf
For the 5Z4:
https://frank.pocnet.net/sheets/127/5/5Z4.pdf