And Yet Another Ekco TMB272

If I don't turn one up at Gnosall a week on Sunday, Langrex have 607 in stock.

PYE625 said
Hi Marc,

I did see some EY81's on a well known on-line auction site at a fairly moderate cost, if all else fails.

Not sure if I'm allowed to mention the site, but it begins with "e"   

That's well within the rules.

What we don't do anymore is to point out items for sale.. Helping a member find a specific item is another matter, as long as the source is legitimate.

Hi Rich, Andrew & Catho,

Rich, no worries and thanks for looking. 

Andrew, that site you recommended ends in 'Bay' 

Catho, fingers crossed time for Gnosall 

Cheers all, Marc.

Hi Marc,

I'll see if I can bash my way into the cabin, this weekend, and see if I can find anything in there - I do have a few trays of ex-equipment pulls,some of which have lost their markings, but I could try applying some volts to the heaters and get them to glow at the correct brightness then check the current draw, and the voltage across the heater.

Not mega-science, but could help reveal an "E" among the "P" types...

Marion

Cheers Marion,

I've pinched the EY81 from my other TMB in readiness for testing 'TMB the 2nd' although there has been a bit of a delay getting back to this project thanks to a total rewire of my 405/625 distribution system but rest assured I should be back at the bench within the next couple of days.

Marc. 

Hi all,

Progress on the Ekco TMB has been rather slower than I anticipated due to other commitments at the moment, however recapping the waxies and the Hunts is well under way. The removed waxies have all proved to be dead short or O/C which I found very strange as you normally find a few that are serviceable and as for the Hunts virtually every one has detached leads, again I find this very odd too as I've never come across this phenomenon before, the odd one or two yes but never nearly all !The combined 'on off/volume/brightness' control has also been rebuilt (thanks to Andrews replacement switch section) and has been reinstated.  

More to follow as and when I get time.

Marc.

Hi all,

I have finally finished recapping all the waxies and Hunts 'Yippee' and reformed the main smoother can. I have also noticed that the speakers voice coil is seized solid so a temporary speaker has been crock clipped in. So it's now time to shove some volts in.  

Sound came up at about 160v (via the Variac) but by full voltage the CRT only shows screen collapse so I will need to start investigating the frame stage.

Marc.

Good progress Marc....  I bet by tea-time, we'll be seeing a full scan

PYE625 said
Good progress Marc....  I bet by tea-time, we'll be seeing a full scan   

If only Andrew, 

The frame output valve ECL80 checks out fine and a duplicate was tried too. Looking else where I found a 500uf 25v electrolytic was short (C108 on the ERT sheet) so a 470uf 40v was soldered in but still frame collapse ! The height pot seems OK and the surrounding caps are replacements. So I'm now sniffing around the frame TX, it should read approx 430R across the winding's and has a centre tap, the trouble is I'm getting 460R across the winding and 460R at the centre tap....that's not right ! 

Back when I know more.

Marc.

EDIT.... forgot to mention there is continuity from the frame coils back to the frame TX.

Hi Marc,

What is the voltage situation in the frame stage?  T4 looks like an auto transformer and HT is fed via R111 (a Varite).

PYE625 said
Hi Marc,

What is the voltage situation in the frame stage?  T4 looks like an auto transformer and HT is fed via R111 (a Varite).  

I'll grab some voltage readings as soon as I get a chance, could be tomorrow with any luck.

Marc.

I wouldn't mind betting that MR1 is past it's best, but that may cause no frame hold, so one thing at a time lol.

Looking forward to reading how you get on

PS....I was careful not to say WHICH tea-time

Usual trick Marc - if you stick a screwdriver blade on pin 9 of the ECL80, does the scan "open out"?

Cathovisor said
Usual trick Marc - if you stick a screwdriver blade on pin 9 of the ECL80, does the scan "open out"?  

A bit like sticking your finger on the input to an audio amp? Except that the hum is visible, as opposed to audible.

Hi Marc,

did you get some proper LOP valves? - I have an EL81 in the pipe, and possibly an EY81 to follow - Both are NOS, I believe.

Hi Marion,

Yes I'm sorted with the valves thanks to Brian & Catho.

Hi Catho,

The 'usual trick' is actually new to me  but yes I get the idea, I'll try and give it a go a bit later. 

Marc.

marc said

The 'usual trick' is actually new to me  but yes I get the idea, I'll try and give it a go a bit later. 

Long time ago, but if you remember we did that on the TV80 to prove the amp!

Cathovisor said

marc said
The 'usual trick' is actually new to me  but yes I get the idea, I'll try and give it a go a bit later. 

Long time ago, but if you remember we did that on the TV80 to prove the amp!  

And obviously my memory is useless too  Yep I remember now 

Hi all,

Tapping pin 9 of the ECL80 does not open out the frame scan.

Marc.

Hi Marc,

Any HT on the anode of the same valve?

Best not to use a finger for this test

PYE625 said
Hi Marc,

Any HT on the anode of the same valve?

Best not to use a finger for this test   

Hi Andrew,

I have 165v showing which is a little down on spec of 185v