[Heatercathodeshort]

I am at the present time bringing back to life a Beau Decca 131 projection receiver dating from around 1951 for the museum at Dulwich.

It has been a bit drawn out due to the passing of Gerry with all the changes that inevitably take place. I would add that the museum is in good shape and open to visitors [by appointment of course] and it can only get better.

The Power supply, a very heavy mains isolated affair with a mains transformer to supply the valve heaters and approximately 350v for the H.T. line, has been overhauled with new electrolytics and should be OK.

The main IF and time base chassis has been completely overhauled [therapy needed] and looks good. Only an actual powering up will prove this to be true.

The receiver was produced for Decca by Plessey as were all Decca television receivers prior to the 'DM' model numbers. [Decca Manufacture]

I thought you might like to see the 25kv EHT unit manufactured by the Philips company in the Netherlands. All post war projection receivers in this country employed a folded version of the SCHMIDT optical system manufactured by Philips together with the two and a half inch projection tube [MW6-2] and the 25kv EHT unit.

The sealed oil filled unit contains the ringing coil and three special quality EY51 rectifiers in a tripler arrangement. They are not replaceable but have a very long life. An EBC33 connected as a blocking oscillator provides the drive to the EL38 in a similar arrangement to a line output stage. A feedback winding in association with the two strapped diodes in the EBC33 provides a degree of stabilization.

The unit is mounted on the right side of the cabinet looking in from the back and is self contained other than it's HT and heater supplies that are drawn from the main chassis.

This example was very rusty and required removal of the sealed ringing choke to allow a 'deep clean' and de rust. This took a while this morning as you can imagine but access is very good and it only took a short time to replace the 60 year old black tar capacitors. They actually read almost useable but these units tended to suffer from poor regulation [No PD500s back then..] and everything needs to be 100% for satisfactory operation so no chances were taken.

On completion the unit was connected to my Griffin power supply set for 350v HT and 6.3v heaters. It soon warmed up and the whine of the blocking oscillator could be clearly heard. Soon that nice EHT rustle you used to experience just before the picture appeared on those early colour receivers was sensed and 25KV was registered on my stand by EHT meter. Success!

Now...I wonder if the main chassis will behave itself when it comes to powering up?

If all goes well I hope to do this next Friday and will take some more pictures so that you can see the beautiful beast in full glory..

I'll keep you posted. Regards, John.