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Old 8th Jan 2016, 6:45 pm   #61
acottrell
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Default Re: Ekco TC267/1

Hi Stephen
Did you mean bypass the choke to give volts to the anode as this is the only supply to the anode and I have no volts there?
Line whistle varies with the control I do have line drive -11volts on control grid of output valve.
Tried a new U191 valve and line output valve. Tried removing top cap no difference.
Thanks
Ade
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Old 8th Jan 2016, 6:51 pm   #62
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Default Re: Ekco TC267/1

Just checked boost cap its not S/C
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Old 8th Jan 2016, 7:01 pm   #63
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Default Re: Ekco TC267/1

Do you have voltage from the output fuse ? yes, when the choke is bypassed it should have volts on the anode.

Have you checked the line linearity coil hasn't slipped down on its former, very common
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Last edited by Freya; 8th Jan 2016 at 7:06 pm.
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Old 8th Jan 2016, 7:11 pm   #64
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Default Re: Ekco TC267/1

I have volts both sides of the fuse and to the 47K resistor no problem just nothing through the coil so 0 volts on the U191 anode. Will have another look tomorrow ( bypass the coil hopefully will come back up ) I am sure this will sort it out. If it does will take your advise and see if I can repair the coil. If this doesn't work will check the line lin coil didn't realise that
Thanks again Guys for your help
Will keep you posted
Ade
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Old 11th Jan 2016, 5:38 pm   #65
acottrell
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Default Re: Ekco TC267/1

Hi Guys
Great news bypassing the choke the set is back to normal operation again no issues. I will try and repair the choke now.
Just one last question I still wanted to replace the CD1 diode what can I replace it with Only reason is after a couple of hours now the contrast still fading a little. Just being a little fussy as I can still quite happily using the set
Thanks again all for your help
Ade

Last edited by acottrell; 11th Jan 2016 at 5:44 pm.
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Old 11th Jan 2016, 5:51 pm   #66
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Default Re: Ekco TC267/1

Good job, the rectifier can be replaced with a 1N4007 and wirewound 10watt resistor around 100 ohms. If the HT is too high then it might need to be increased accordingly.
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Old 11th Jan 2016, 6:08 pm   #67
acottrell
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Default Re: Ekco TC267/1

Thanks Stephen
I did mean the diode in the IF side (CD1 diode inside the first IFT ? )
Many Thanks
Ade
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Old 11th Jan 2016, 6:16 pm   #68
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Default Re: Ekco TC267/1

How much does it change ? slight or dramatic ? no capacitors missed ?
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Old 11th Jan 2016, 6:30 pm   #69
acottrell
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Default Re: Ekco TC267/1

It does go negative all of a sudden Turning down the brightness helps to correct it but then it will go negative again. Playing round with the contrast and brightness I can improve it again for a while till it changes again. Like I say it seems to be fine for a couple of hours. Only caps left are a electrolytic caps sitting on the top side of the chassis. All hunts, Wax, and tuner caps changed nothing missed double checked.
Thanks
Ade
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Old 11th Jan 2016, 6:55 pm   #70
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Default Re: Ekco TC267/1

I tend to use OA81 in this area, there may be others suitable but need to be smallish to fit in the can.
Try monitoring the AGC line for coresponding change.
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Old 11th Jan 2016, 7:31 pm   #71
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Default Re: Ekco TC267/1

Thanks mate I will replace the diode. Not sure how do I monitor the AGC line what voltage checks and where do I need to check?
Thanks
Ade
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Old 20th Jan 2016, 11:14 am   #72
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Default Re: Ekco TC267/1

Hi Guys
Repaired the choke. Melted the wax off it with a hairdryer and was lucky to find the wire broken right at the end onto the lead! easy repair and working fine. Replaced the OA81 diode run the set yesterday for over 3 hours with no issues at all really good clear solid picture
Thanks again for all your help another great set to add to my collection
Ade
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Old 20th Jan 2016, 11:30 am   #73
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Default Re: Ekco TC267/1

Nice one well done.
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Old 31st Jan 2016, 3:40 pm   #74
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Default Re: Ekco TC267/1

Hi Guys
One last thing when I switch off the set I get a bright spot in the middle I the screen which I am worried will burn the tube. If I discharge the EHT soon as I switch of it kills the spot. I have found a what looks like a long thermistor mounted on the tube frame in a sleeve from the EHT to tube wire to earth broken in too. I take it this will be my problem. What can I replace it with. I think its called a metrosil according to the circuit?
Thanks
Ade
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Old 31st Jan 2016, 4:12 pm   #75
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Default Re: Ekco TC267/1

The function of the Metrosil was to stabilise the EHT voltage. The voltage dependent resistor, which what a Metrosil is, was used to maintain a constant load across the EHT supply.
It's unlikely one will ever be found but that doesn't matter because the set will function without it.
In many late 50s and early 60s sets various solutions to discharge the EHT capacitor were tried. The favourite method among manufactures because it involved no extra components was to return the earthy end of the brightness control to the unswitched neutral side of the on-off switch. Definitely unnice but that was one of the cheapo dodges they'd do in those times.
The circuit action was as follows: When the set is switched off the HT will be still present for a second or so before the reservoir capacitor is completely discharged. The control grid of the CRT goes near HT volts because the bottom end of the brightness control is disconnected from the chassis. The CRT conducts hard and discharges the EHT capacitor.
A better method was to employ a special VDR which was connected between the bottom end of the brightness control and chassis.

DFWB.
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Old 1st Feb 2016, 8:22 am   #76
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Default Re: Ekco TC267/1

Thanks for this info very interesting nothing more to do on the set now
Ade
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Old 1st Feb 2016, 10:00 am   #77
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Default Re: Ekco TC267/1

Just to add that the switch off spot will not harm the CRT. J.
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Old 1st Feb 2016, 8:27 pm   #78
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Default Re: Ekco TC267/1

Thanks for that put my mind at rest
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