The Marconi's transmitter, with only 3 tubes generating a 250 KW signal was placed into operation in 1987. The band switch used basically the same system as the Continental transmitter, but instead of   moving the switches with a  motor, they were moved by compressed air. Some pistons (9), one for    each band switch, were used to accomplish this task.  Cooling air was fed through air ducts. The transmitter was dependable and ran well, but when it did break down, the failure  was usually major  and always seemed to generate a chain of smaller breakdowns. We always said, that its design was pretty "Machiavellian", because of the difficulty in  removing components to check or change. Changing the PEN or modulator tube could taken easily half an hour, and for the RF final stage even 4 hours, as well as over 5 hour for some capacitors.

The transmitter was the second to last units manufactured by Marconi's in this model series. The last unit went to Sri Lanka and, as we heard, burnt in its first year of service. There are ten later model Marconis installed in the  Morocco station. I understand they, too, are problematic. In our unit, making a frequency change took only a couple of minutes in fully automatic mode. Sometimes we had to retune a little, and few times the automatic system was a disaster. The cooling system used high and low air pressure systems, with water also running through tubes, capacitors, coils and band switch. 

Most of these internal photos, were not taken from the Pals transmitter, instead they were scanned from Marconi's book, due to lack of "real" photos.