[Amps] Dentron ML2500 and 3.5MHz

[ADRIAN REES]

Hi all
I have two Dentron ML2500 Linears (pair of 8875's).
 
The rig is an ICOM 756PROII.
 
When using one of the linears on 3.5MHz the ICOM will NOT tune into the Linear. (The Dentrons don't have any input tuning, and the ICOM always goes into auto tune, to match the input of the Linear). 
 
When using exactly the same setup (Cables, rig etc) but with the other Dentron I don't get this problem.
 
When using the "faulty" linear the ICOM goes into auto tune and tries to tune the amp. By manually adjusting the linear, I can fudge it such that the ICOM drives the linear to about 250 W before the ICOM goes into auto tune and shuts itself down.
 
The two amps appear to have exactly the same design and components in them, yet I get the above anonmaly.
 
(Both test scenarios where firing into a dummy load).
 
I have tried a manual ATU between the ICOM and the "faulty" Linear, but to no success.
 
Any suggestions ?
 
de mw1lcr