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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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23rd Sep 2022, 11:28 pm | #21 |
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Re: AGA black and white TV
An update: Most of the miniprint capacitors (RIFA) have been replaced especially in the line, frame and audio stages.
I now have pictures and sound but: I did have some frame bounce, adjusting the controls seemed to clear that. i had it on for quite a few hours when the 2K2 ohm resistor between the anode of the PY88 and the G2 of the PL504 sprung open (no picture) I resoldered it and go a full picture but an hour or so later it sprung open again. I'm wondering what to do. Do I need to use special solder? |
24th Sep 2022, 8:03 am | #22 |
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Re: AGA black and white TV
Check the cathode current of the PL504 is within specifications.
In some of these fusible resistors high melting point solder was specified.
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24th Sep 2022, 2:56 pm | #23 |
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Re: AGA black and white TV
The cathode is grounded so cant check the current, where would I get HMP solder or would I be best to bypass the fuse bit altogether?
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30th Sep 2022, 12:40 pm | #24 |
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Re: AGA black and white TV
I have obtained some HMP solder and resoldered the resistor.
The set is running and I’m testing it as we speak |
30th Sep 2022, 12:52 pm | #25 |
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Re: AGA black and white TV
I don’t recommend bypassing the fuse, if it still fails make sure there was no standard solder in the joint before using HMP.
You could put a 1 ohm resistor in the cathode circuit and measure the voltage drop to check the PL504 current. It’s 40 odd years since I dealt with TV’s , other may have more advice.
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30th Sep 2022, 1:24 pm | #26 |
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Re: AGA black and white TV
I removed the resistor from the board, removed the solder, and resoldered the resistor using the new HMP.
I haven't bypassed anything. |
30th Sep 2022, 8:33 pm | #27 |
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Re: AGA black and white TV
Hopefully fixed.
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1st Oct 2022, 9:03 am | #28 |
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Re: AGA black and white TV
That part of it is fixed, it was running for quite a long time, but there are one or two other problems.
Every so often there is frame bounce and sometimes the picture slips vertically so you have the blanking strip in the middle of the screen. I will post up diagrams possibly asap. It seems probable that the cause is around the ECH84 sync separator. |
1st Oct 2022, 9:42 am | #29 |
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Re: AGA black and white TV
The ECH84 may be a noise cancelling sync separator, not often seen in UK sets due to the 625 line Negative modulation transmissions on UHF. The noise cancellation was more important on VHF were noise spikes could affect sync, whereas with the UK 405 line positive modulation VHF system they caused white dots on the picture.
https://worldradiohistory.com/hd2/ID...-Page-0002.pdf
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27th Oct 2022, 10:33 am | #30 |
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Re: AGA black and white TV
An update: I replaced a couple of 220K resistors around the ECH84 together with the valve holder itself and I've now got a very good picture.
However for some reason I've got no sound. |
27th Oct 2022, 10:35 am | #31 |
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Re: AGA black and white TV
Here are some diagrams.
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27th Oct 2022, 10:45 am | #32 | |
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Re: AGA black and white TV
Quote:
Rog |
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27th Oct 2022, 11:08 am | #33 |
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Re: AGA black and white TV
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27th Oct 2022, 12:18 pm | #34 |
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Re: AGA black and white TV
What signal are you feeding the TV, this set uses 5.5Mhz inter carrier sound according to that circuit not 6Mhz as in the UK 625 signal?
I thought the UK voltage was harmonised to 230volts.
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28th Oct 2022, 3:05 pm | #35 |
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Re: AGA black and white TV
The reason for no sound was a broken wire between the O/P TX and the connection tag strip. I soldered the speaker wires direct to the o/p transformer and that solved that!
The TV was working fine until I replaced the back. No after some time the picture goes darker and darker. One thing I noticed is that when the picture is dark, when you switch the set off you get a bright spot in the middle. Any ideas? |
28th Oct 2022, 11:00 pm | #36 |
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Re: AGA black and white TV
Measure the voltages on the crt base, they should change when it it goes darker. Trace the one that’s changing.
OK on the sound fault, I didn’t realise it had been changed to work on the UK system.
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29th Oct 2022, 10:05 am | #37 | ||
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Re: AGA black and white TV
Quote:
UK mains voltage was "harmonised" at 230V but in reality it did not change from 240V just the way it is specified. Some parts of the UK still have a nominal 250V supply. 230 volts -6%, +10%. This gives an allowed voltage range of 216.2 volts to 253.0 volts. ISTR that before harmonisation the supply was specified as 240V ±10% and indeed we still test our equipment to that upper limit of 264V (actually we use 205V to 268V). Modern equipment will tends to be able to accept 230V +/-10% i.e. 207-253V. At my home we are just 50M (as the cable runs) from a sub station and my mains is usually in the range 245 to 248V. Over time as new infrastructure gets replaced I guess the substations will be set for a nominal 230V. Cheers Mike T
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29th Oct 2022, 10:06 am | #38 | ||
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Re: AGA black and white TV
Quote:
BUT, the tolerance has been engineered so that both the UK's old 240V (with its old tolerance) and the European mainland's 230V (With its old tolerance) fit within the new tolerance bounds. So expect 240V from a socket in the UK. The wording has changed, the voltage hasn't. New appliances get 230 written on them but are required to work over a wide enough range to encompass the difference. David
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5th Nov 2022, 12:27 am | #39 |
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Re: AGA black and white TV
An update: I replaced three high value resistors a 470K and two 680K resistors in the line o/p stage which go directly to the CRT grids.
Upon switching on I was rewarded with a very bright picture which gave a normal picture with the brightness turned down. I then fitted the back cover, turned the heating on and left it on. So far so good, its been on for around 6-7 hours. |
5th Nov 2022, 10:51 am | #40 |
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Re: AGA black and white TV
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