Ekco T370

Hi Frank, MR1 reads 150k in the right direction with a DVM on ohms, open circuit in reverse. MR1 is one of the few components that can still be reached with the crt in place.

I like the horseshoe design Marc, a neat idea.  

Those older style horseshoe shaped LOPTX's didn't disintegrate like the later ones.

I would imagine that a horse shoe LOPT cover would be easy enough to make with a piece of acrylic laid over a former and a heat gun.

Some thing else you could make to compliment your 'tuner cover' manufacturing Andrew.

Marc.  

The method of heating and bending over a former works great for making the horseshoe housing. It pays to slightly over bend to create a better grip on the lamination block, I have used black polyurethane sealant to glue the block into position but I'm sure using the liquid solvent glue and strips of acrylic would work just as well.

The couple I tried were made using a heat gun on low, you do get some slight discolouration on clear acrylic and maybe a few bubbles. The former was just a thick-ish glass tumbler from the cupboard.

Back again, well today I have been servicing the tuner. First picture is of the FM/TV changeover switch on the chassis. The tuner itself is in good condition, just needing a clean and replacement of a wax capacitor. The 2uf 350v next to it reformed and is good. The only thing still bugging me is the missing screening cover for the tuner.

C22 and 97 are both parts of a small dual can electrolytic, 16+16 uf 275v and were reading about 3uf each. They would not reform, so I re-stuffed the can with a couple of modern replacements. 

I have re-fitted the LOPT and it all goes together ok with it's screening can (removed for photo's)

Looks like it's just come off the Ekco production line.

Hi Andrew,

As Franks suggests that chassis looks almost like new, excellent !

Marc.

Thanks chaps,

This afternoon I have refitted the tube (a job I'm never too keen on), after cleaning it and previously testing for emission using a bench psu for the heater and an avo as per Chris's suggestion in my Ekco TMB post. See first picture.

Next is the chassis all ready to receive the tube. It went back in without issue and we are ready for the big switch on.

I set the tuner for ch1, connected the aerial and switch on. Valves start to glow and HT rises. I can hear the test card music from the two speakers. Line whistle starts and there is life. EHT comes up very slowly and the picture balloons badly. I replaced the U26 EHT rectifier and try again. This time, a bright picture is the result. Some adjustment of the hold and height controls result in a sensible picture.

As ever Andrew, an excellent and detailed log of a quality repair, always a pleasure to follow. Looks like you're on the homeward stretch now.

This Ekco is coming on a treat, great stuff ! 

Marc.

Again, excellent stuff, Andrew. Your descriptions of the work that you put into these restorations are excellent and are "appetising", making me more and more attracted to this era of set! However, I seem to have a bit too much to do without another project in my program. What I like is that you embrace both sides of the work to be done - some can be classed as restoration and the some as repair and there is a definite need for both types.  Keep up the good work.

Thankyou gents, the positive comments are very encouraging and I really enjoy working on sets like this. The forum makes it even more worthwhile.  

Ok, the set is working, but is not without issues.

Firstly, there is sound on vision that cannot be tuned out and the vision is poor. This could be due to some of the IF coils have been messed with (not by me) and one core is broken and stuck in the former. They are mainly of the short hexagonal cores in the former's. I will need to see to this later as there is a more urgent problem.

Although I had a bright picture initially, EHT is falling and the picture is now ballooning quite badly upon increasing the brightness. I don't like the look of this.... overwind springs to mind. 

I will be looking into this later today 

Check the U26 heater wiring, socket and possibly a resistor in the valve base. Common fault.

trying to type on a phone while on a bus is not easy, apologies for typos.

nuvistor said
Check the U26 heater wiring, socket and possibly a resistor in the valve base. Common fault.

Ta Frank,

I think the clue is in the fact that by replacing the EHT rectifier when I first tried the set temporarily cleared the fault.

I'll check out the base and wiring this evening.

I have a feeling that if your overwind is wax covered then its probably in need of a day or two on a low voltage supply to dry it out. It has the classic symptoms I have seen so many times with a wax or pitch covered lopt.

If you use this method you should expect to see enough heat generated to slightly melt the wax, if you look very closely you may see the water particles bubble and spit out from time to time.

freya said
I have a feeling that if your overwind is wax covered then its probably in need of a day or two on a low voltage supply to dry it out. It has the classic symptoms I have seen so many times with a wax or pitch covered lopt.

If you use this method you should expect to see enough heat generated to slightly melt the wax, if you look very closely you may see the water particles bubble and spit out from time to time.  

I think you could be right there. I have checked the heater connections and all is ok plus the fact the set is better tonight with only slight ballooning with full brightness. I have even re-fitted the old U26 and it seems fine. I will leave the overwind with a few volts across it overnight and dry it out a bit.

To be able to correct the IF response, I need a suitable ferrite core for one of the IF transformers. Unfortunately, I have nothing the correct size. It needs to have a hexagonal hole so as to be reached from one side only ( trimmer passing through the top core).

Here is a link to the wanted section...

https://www.radios-tv.co.uk/forum/sales-wants/wanted-ferrite-dust-cores/#p4637

Frank is very kindly sending me a couple of cores and I am certain they will fit just fine. 

After a 24 hour period of warming the LOPT overwind with around 25vdc at 165mA flowing through it, I am pleased to report there is now plenty of stable EHT even at maximum beam current. The tip from Freya above certainly worked out good.

Oh and by the way, I wouldn't recommend reaching under the EHT rectifier base for a paintbrush with the set switched on. It has a metal cap sitting nicely at EHT, just waiting to sting the back of your hand.

I dare not type the words I uttered.  

Hi Andrew,

That sounds like great news about the overwind, excellent !

What was that you said about that metal cap ? F what ? 

Marc.