18th Sep 2018, 1:32 pm | #1 |
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Quad FM4
Well it seems I'm not having much luck with radios at the moment.
Perhaps someone can help me with this Quad FM4. I have changed the 220uF and 1000uF capacitors in the power supply can, also the 0.047uF cap across the mains. I have also replaced the back up battery, it was in its own box and there was no sign of leakage anywhere. The radio does work, sort of, tuning is difficult with the tuning frequency jumping around all over the place. I'm not sure where to start looking, when it does lock it sounds very nice, but it doesn't stay lockede for long. I've also replaced C11, 100uF/10V |
18th Sep 2018, 2:02 pm | #2 |
Dekatron
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
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Re: Quad FM4
This any help?https://www.diyaudio.com/forums/anal...-quad-fm4.html
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18th Sep 2018, 2:29 pm | #3 |
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Re: Quad FM4
Thank you, that will certainly help me
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18th Sep 2018, 6:36 pm | #4 |
Nonode
Join Date: Aug 2007
Location: South Bradford, West Yorkshire, UK.
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Re: Quad FM4
I've had the frequency jumping around and an inability to tune over the whole frequency range due to a dry joint on L20 in the local oscillator.
Keith |
19th Sep 2018, 7:54 am | #5 |
Hexode
Join Date: Jun 2011
Location: Glossop, Derbyshire, UK.
Posts: 487
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Re: Quad FM4
I have 3 at the moment with various faults
1: no display radio ok 2 : unable to tune in 12v rail down to 7.5 v 3 : unable to tune 12v rail ok I have been retired for 20 months and still have not had time to look at these ( busy building workshop, extension on house ,garden ) all those roundtoit jobs whilst at work had no time . On the upside I have lost 1 1/2 stone due to hard work ( can I please go back to work for a rest )
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19th Sep 2018, 10:14 pm | #6 | |
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Re: Quad FM4
Quote:
I've done most of what's been suggested in the link that PJL has suggested but it makes no difference. D24 has been replaced by a circuit board which I can't find reference to in the Quad manual. I'll change it to an 1N825 tomorrow. |
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19th Sep 2018, 11:26 pm | #7 |
Nonode
Join Date: Aug 2007
Location: South Bradford, West Yorkshire, UK.
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Re: Quad FM4
L20 is the ground return for the local oscillator varicap tuning voltage as shown on the attachment. From memory it was the ground connection on my tuner that was dry jointed. It's possible that there are other dry jointed components as I've experienced several dry joints in my FM4 and 44.
Keith |
20th Sep 2018, 12:35 am | #8 |
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Re: Quad FM4
Thanks Keith, but on my diagram it's L8 and its not dry jointed.
Mine is the early version, Serial No: 2003 |
20th Sep 2018, 8:11 am | #9 |
Nonode
Join Date: Aug 2007
Location: South Bradford, West Yorkshire, UK.
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Re: Quad FM4
Mine must be a later version. The circuit extract is from the Issue 3 circuit.
Does the tuning vary on manual tuning, preset tuning or both? If it varies on both then it's probably the tuning reference diode. If it occurs on preset tuning only then it could be an issue with the D-A converter. Keith |
20th Sep 2018, 8:34 am | #10 |
Heptode
Join Date: Jun 2017
Location: Southport, Merseyside, UK.
Posts: 646
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Re: Quad FM4
I have had a number of dry joint problems with QUAD equipment over the years.
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20th Sep 2018, 8:39 am | #11 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
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Re: Quad FM4
Quad, although part of the Chinese IAG group, still have their product service function in Huntingdon. Could be worth giving them a call http://www.quad-hifi.co.uk/our-story.php?id=19 .
Craig |
25th Sep 2018, 8:39 am | #12 |
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Re: Quad FM4
Replaced Diodes D21 and D22 with 1N4148's as the original 1S929/921's are not available and so far it's working.
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