Ekco TSC30A

[pwdrive]

The Hallicrafters SX28 used a noise limiter based on Lamb's design, it works very well.

Lawrence.

[Geordie McBoyne]

The Racal RA17 has a noise limiter, V21 (CV140/EB91) double-diode.   One section of the valve is the detector and the other performs as a series noise limiter. The noise limiter can be bypassed, the anode and cathode of the valve are simply connected together.

Hi Trevor,
              I've found and posted off to you photo copied circuit diagrams of the Ekco TSC902, the progenitor of the TSC30.   Almost all of the information will apply to the TSC30 and 30A.  The information also applies to vision only models such as the TA701 and TA901.

Geordie McBoyne.

[Murphyv310]

Thanks David.
Not touched the TV today as I've been "in below" a Scottish saying for fixing the car   I've a nice looking PEN46 to play with and I'm hoping to get a start tomorrow or Saturday.

[Murphyv310]

Hi.

I've just received a nice package from David with some diagrams. This has spurred me on to get the back off the set and start some work.
I Intend to re-stuff the 0.1uf EHT smoother today with a 0.1uf 8KV jobbie and hopefully check the HT levels. Thereafter I'll have a go at the shift and centring of the picture.

   
   
   
   

[Brianc]

Great looking innards, Trev. If I were you, I'd fit one of those red/brown Bakelite McMurdo valve top-cap covers to that EHT cap like Decca did on their Beau Decca TV PSU/amp unit. It looks incredibly "accessible" as it is!
Cheers
Brian

[Murphyv310]

Great looking innards, Trev. If I were you, I'd fit one of those red/brown Bakelite McMurdo valve top-cap covers to that EHT cap like Decca did on their Beau Decca TV PSU/amp unit. It looks incredibly "accessible" as it is!
Cheers
Brian

Too right Brian, it's on the list of to do's. I've had a good look around the set and I've found a few marks on the chassis with May 39 showing!! Is this a pre war set reincarnated in 46?

[Murphyv310]

I've a sneaky feeling that some of the chassis's were pressed out prior to the war and were in storage then post war pressed into service. I'll try and photograph the marks and post them up.

[Geordie McBoyne]

Hi Trevor,
              Excellent detective work. You are correct about the chassis metalwork.   It's possible that Ekco were getting prepared for a sales boom 1939, of course it didn't happen. That would leave large stocks of uncompleted chassis assemblies.  I read somewhere that the second transmitter was to be erected in 1940 and the countrywide rollout was to be completed in 1946/7.  

Tomorrow I will take pictures of the pre-war Ekco model TS701, the vision and sound 7" CRT receiver.  The earliest Ekco set to employ this type of chassis was the vision only model TA201.

Geordie McBoyne.

[Murphyv310]

Hi.

I've busy with the set this afternoon.
I decided to find out why we weren't getting full scan. Surprisingly some of the old body tip spot resistors were off value and by quite a bit. I've used some decent 70's resistors in the meantime, eventually I'll try an make something that looks period with modern resistors inside.
The problems were in both output valves cathodes and screen feeds, also the series feed resistors to both T41's were high value.
Here's some pics of the work and screen-shots, My camera focus is not the best though when trying to do pics off a tube.

           

[Geordie McBoyne]

Hi Trevor,
               looking good, it is a pity we have to use modern resistors in old equipment.   Are those old Soviet era resistors still available?      Those resistors have a old fashioned look about them, and they are good.

Pictures of the TS701, the 7" vision and sound receiver. This one was made in 1939.  The circuit design is very similar to the TSC30, the main difference apart from the type of CRT is the valves employed  in certain parts of the circuit.  The HT rectifiers are the Mazda UU5, (UU7 in the later set).
The line output valve is a Mazda AC6/PEN (PEN46). Frame output is a PEN45, (PEN46)  The EHT rectifier is a Mazda U21, (U22). 
The RF pentodes are Mazda SP41 in both sets.

In 1938 Ekco released the vision only receiver, the TA201, this set is also similar to the two sets discussed so far.

From the Valvepage website:    http://www.thevalvepage.com/tvmanu/ekco/ekco.htm

I have never seen any service documentation for the 1937 models although looking at the picture of the TC103 I'd imagine the chassis construction is similar to the TSC902 (TSC30)  The set will not use the SP41, it's likely the RF pentodes were the Mazda AC/SP3.
It also begs the question, what type of CRT?  Electrostatic or Magnetic deflection?  Bear in mind Ekco like Murphy and Ultra was signed up to Ediswan Mazda and in 1937 that firm did not make a magnetic CRT.

Today I found the drawings for the reconstruction of the TSC30 cabinet.

Geordie McBoyne.