Ekco T161

[Heatercathodeshort]

That is the T.C.C. VISCONOL..J.

[anthonys radios]

Sometimes the CRT developed a cathode/heater leak/short circuit and the heater transformer was added to correct this, if so, you may find it is wired to supply only 2 volts to the CRT heater, rather than 2 volts plus 20% boost (I think it was 20%).
I never replace wax or any other component unless it is faulty, as the originality is lost, do you need to simply change these as a matter of course ? as many even if a bit leaky will not have much if any effect (those that bridge cathode resistors for example)

The best way to clean the implosion screen is with Duraglit, and this is absolutely ideal for cleaning around EHT areas. Duraglit is a waddinding material now sold under the Brasso brand, it dries very very quickly to dust make sure you get the wadding ! other cleaners can result in EHT crack over, or even fire.

If you have a Variac transformer I would fire it up with this, keep your head out of the way, wear safety glasses, electrolyics can explode, covering you and the cabinet with foil and electrolyte, will not happen often, but my, it make you ears ring when it does
I think in this set the side escutcheon was held with a metal screw, into an insulated nut assembly, in the later sets they used a plastic screw into a metal nut.
The capacitors used for aerial socket isolation were to BS 415, dont replace with anything else.
If I recall correctly, the CRT used an in electrostaticly inclined plane gun assembly, so you need to check the Ion trap magnet on the CRT neck, near the base, is in the correct position or you may (when you fire it up) get no picture or a distorted picture, best note its position exactly before you disturb it.

[anthonys radios]

Memory may be wrong ref ion trap needed on this CRT as your pictures does not show one. it's a long time ago !

[Electricdreams]

Right, too late, I've replaced all the waxies. Done the potentiometer, sorted out the fuse. Cleaned up the EHT Perspex, realigned the CRT. Built a Lamp Limiter...

Is there anything else before I power up without the CRT to check the valve heater is working and the electrolytic isn't getting hot..?

[Electricdreams]

Right I'm going to put the chassis in the set and wire up the mains plug, I'll do it with the crt.

Should anything go wrong I can discharge the EHT by wrapping a wire around the screwdriver connected to the earth on the mains socket right?

[Electricdreams]

The visconol is o/c

[Electricdreams]

Right the lamp limiter lit very brightly. Any ideas?


I need a cup of tea...

[anthonys radios]

Best to avoid short circuiting electrolytic and high voltage capacitors if you can
When a capacitor such as these are subjected to a short cicuit to discharge it, it can mean that a very large, even damaging surge current flows in the capacitor.
Always best to discharge by placing a medium value (10K to 100K perhaps) resistor across the terminals.
In high voltage systems, this has to be done carefully by a suitably insulated probe, with a metal tip connected to a resistor, grounded by a fly lead, earth the fly lead first of course !
Part of the job of the Metrosil was to safely chischarge the EHT over time.

[anthonys radios]

Make another cup of tea!
How long did you leave it on, did any valve heaters glow, did all the heaters glow, ( darken room will make it easier to see)
Was there any sign of the 405 line whistle from the line Output Stage,
(a 10,125Hz whistle)
Did the lamp brightness reduce if you waited a miniute or so, any smells, fissles or pops.
More tea needed at this stage !

[Electricdreams]

Oh I didn't leave it on longer than 2 seconds. Should I leave it on longer...?

[anthonys radios]

Perhaps, but take great care, try say 30 seconds, put your finger in your ears, and your big toe on the mains socket switch !

[Electricdreams]

Hmm I'll do that after dinner :S

[anthonys radios]

I would do it next week ! the nerveswill have settled by then

[Hunts smoothing bomb]

yes you need to leave it on for a few minutes to get any result, The lamp will light brightly, and as the valve heaters slowly warm their resistance will rise therefore warming further(as the voltage across the string rises) and the lamp will fall slowly in brightness, I would use three lamp holders in parallel for the limiter as you could then use an assortment of wattages to make what ever value you like. You will need to start with a 100w lamp and work up to about 200-300w to get enough voltage dropped across the set to work.

Good thread this, well done so far and keep it up!!

Cheers

[KeithsTV]

I don't know if there are separate tappings on the dropper resistor for the heaters and HT but if there are you could disconnect the HT tapping and power up the heater chain only and check this works, then connect the HT tap and take it from there.

I did this with my TV22 and it showed up a faulty thermistor in the heater chain.

Keith

[Electricdreams]

Ok, here's something new.

I left the lamp limiter on, it glows brightly. Then very slowly dims.. brightens once more then slowly dims a little. At this point all the valves lights up apart from the U24 and 20P1, 20L1 and 20F2.

I'm a little confused I thought they were on a chain?

The CRT glows as well. I gave it a few more moments but nothing else happens.

Your thoughts?

[Lloyd 1985]

Hi
this sounds like maybe there's a short somewhere in the chain, maybe a cap connected between chassis and a valve heater, if they go then this sort of thing happens. the one valve that won't light will be the eht rectifier, that'll only light when the line output stage is running.

regards,
Lloyd.

[Electricdreams]

I checked again, I couldn't find any shorts the caps looks ok but I'll get about replacing them.

I found a wire that wasn't soldered on properly. So I soldered it and tried again. The lamp only glows. All the valves are lit apart from U24 and 20P1

I made a mistake with 20L1 and 20F2, they are glowing just not brightly.

I felt like leaving it on to let it warm up but not even a line whistle can be heard.

Time for lunch

[anthonys radios]

The Mazda 20P1 is the Line output valve I recall, it's a long time ago.
If the heater is definately not on, then there will be no EHT, no picture, no line whistle and the EHT rectifier U25 (three wires solder in) will have no heater supply.
It may be the 20P1 is soft,(ie lost it's vacuum) rather than o/c heater, especially if all other valves are alight.
Does it look a bit milky white inside the glass ?

[Electricdreams]

Well I've cheated a little bit and plugged the set into the mains direct. All the Valves light up even the 20P1 but not the U25.

Is 20P1 vaccumed? As the base is cracked.