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Old 19th Dec 2019, 9:19 pm   #21
FERNSEH
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Default Re: Newbie to Televisions working on GEC BT320

Circuit diagram of the IF, video and audio board.

DFWB.
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Old 20th Dec 2019, 10:27 am   #22
Heatercathodeshort
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Default Re: Newbie to Televisions working on GEC BT320

From your picture the black line looks more like a telegraph wire. You will probably find it is oscillation in the frame output valve N379. The Mullard equivalent is I believe a PL84.
The scan coils will require a slight adjustment to square up the picture.
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Old 20th Dec 2019, 11:58 am   #23
NickG0HIK
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Default Re: Newbie to Televisions working on GEC BT320

Quote:
Originally Posted by Heatercathodeshort View Post
From your picture the black line looks more like a telegraph wire. You will probably find it is oscillation in the frame output valve N379. The Mullard equivalent is I believe a PL84.
The scan coils will require a slight adjustment to square up the picture.
Thanks for the info, I have a new PL84 and I'll check the components around that valve too.

It still didn't stop my enjoyment of Hancock last night though
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Old 20th Dec 2019, 12:00 pm   #24
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Default Re: Newbie to Televisions working on GEC BT320

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Originally Posted by FERNSEH View Post
Circuit diagram of the IF, video and audio board.

DFWB.
Thanks for that, I have two circuits for this set, both have the correct components, or so it seem's, but the numbering is incorrect on both of them.

I guess with such a long production run of this model, it went through various changes.
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Old 20th Dec 2019, 2:28 pm   #25
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Default Re: Newbie to Televisions working on GEC BT320

Quote:
Originally Posted by Heatercathodeshort View Post
From your picture the black line looks more like a telegraph wire. You will probably find it is oscillation in the frame output valve N379. The Mullard equivalent is I believe a PL84.
The scan coils will require a slight adjustment to square up the picture.
I had already changed most of the caps around there, so I changed a few resistors, that I thought were acceptable being around 50% high, it did not cure the line, but the picture has improved.
A replacement PL84, has cured it though.
It must have been self oscillating, I've not come across that before.
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Old 20th Dec 2019, 2:34 pm   #26
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Default Re: Newbie to Televisions working on GEC BT320

The tuner would cause a blank screen if the knob was touched and I wanted to check for Hunts capacitors in there.

I pulled off the cover and a little roller fell out, I cant see where it goes.
The tuner does not give the reassuring clunk as it's turn now.

I can see a Hunts capacitor, but I'm now nervous removing the biscuit assembly.
If I release the springs on each end of the spindle will the assembly just drop out?

I still have what I pressume is Video on Audio, A loud raspy buzz. There is also not a great deal of audio.

I thought the set had not been touched as there was no evidence of any replacements, but while replace them myself, it appears quite a few of the slugs are cracked, so the alignment could be way out.

I've only ran it up on a variac so far, and watch the H.T. on a voltmeter as I wind it up.
I would imagine the H.T. would rise to over 300v if it's just "Plugged in" the caps are all rated to 400v, so that not a problem, but the supply cap is a 275v component, Am I worrying needlessly ?

Nick
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Old 20th Dec 2019, 7:41 pm   #27
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Default Re: Newbie to Televisions working on GEC BT320

The attachment shows the channel indexing spring and roller on the side of a similar tuner fitted in the Ferguson 454T.
That 275volt capacitor, is it an AC rating?

DFWB.
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Old 20th Dec 2019, 8:17 pm   #28
NickG0HIK
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Default Re: Newbie to Televisions working on GEC BT320

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Originally Posted by FERNSEH View Post
The attachment shows the channel indexing spring and roller on the side of a similar tuner fitted in the Ferguson 454T.
That 275volt capacitor, is it an AC rating?

DFWB.
Thanks for that, tuner striped and reassembled now.

I found the intermittent was caused by the I.F. coax centre had come adrift.

As the markings had come off the channel selector, I have made a note of the biscuits, it looks to be a standard universal. 1,9,2,10,3,5,11,8,5.

The Supply cap says 275 v DC & 275 DC surge.
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