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Boater Sam · 5th Dec 2017, 1:39 pm

Out of interest the UU6 cathode is pin 1. The metallised coating on earlier production is on pin 6 and presumably should be grounded.
Now one of the anodes is right next door on pin 5, I am going to be more careful in future near these valves on a powered up set.
If the set is a later model with no ground on pin 6 because the later valve was originally fitted without metallisation, and then a metallised valve is fitted, there could be a considerable risk that there is 350v AC on the loose to catch the unwary.
Is there any good reason why this valve was originally metallised? Are there any other rectifiers with a coating?
UU6 is not known for having a long life. Neither is the octal version UU4. The UU5 is a better valve, on a B4 base, and UU7 is a higher current version of UU6 again on a M-O base.
UU5 and UU7 take a whopping 2.3 amps heater current, no wonder the solder connections on the heater pins fail.
Mazda did have problems making rectifier valves for many years.

5th Dec 2017, 1:39 pm	#50
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Murphy A188C repair. Out of interest the UU6 cathode is pin 1. The metallised coating on earlier production is on pin 6 and presumably should be grounded. Now one of the anodes is right next door on pin 5, I am going to be more careful in future near these valves on a powered up set. If the set is a later model with no ground on pin 6 because the later valve was originally fitted without metallisation, and then a metallised valve is fitted, there could be a considerable risk that there is 350v AC on the loose to catch the unwary. Is there any good reason why this valve was originally metallised? Are there any other rectifiers with a coating? UU6 is not known for having a long life. Neither is the octal version UU4. The UU5 is a better valve, on a B4 base, and UU7 is a higher current version of UU6 again on a M-O base. UU5 and UU7 take a whopping 2.3 amps heater current, no wonder the solder connections on the heater pins fail. Mazda did have problems making rectifier valves for many years.