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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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20th Jul 2017, 1:05 pm | #1 |
Retired Dormant Member
Join Date: Oct 2010
Location: Northampton, East Midlands, UK.
Posts: 16
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Quad FM1 tuner
hi, I am trying to get some life out of my Quad FM1 valve tuner with stereo decoder. I have changed a couple of really ropey looking capacitors in it, and now I can get some very quiet and distorted stations out of it. But this is accompanied by a very loud buzz, not dissimilar to 50Hz mains interference, but at a much lower frequency. I plan to carry on changing capacitors, but wondered whether anyone had any other useful checks I could do, or suggestions. perhaps I am on the wrong track completely.
Thank you in advance, James. |
20th Jul 2017, 1:15 pm | #2 |
Heptode
Join Date: Oct 2007
Location: Southampton, Hampshire, UK.
Posts: 821
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Re: quad fm1 tuner
Randomly changing things is not the way to go and you could cause more harm than good - I know of one chap who changed the capacitors in hs Technics SP10 MK2 turntable "as a precaution" and it didn't work properly afterwards!
Take it to someone who can fault-find it properly and also re-align it for best performance. The results will be worth it. |
20th Jul 2017, 1:20 pm | #3 |
Hexode
Join Date: Jun 2011
Location: Glossop, Derbyshire, UK.
Posts: 487
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Re: quad fm1 tuner
Hi this is the users and cct for the FM1
Dave
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20th Jul 2017, 3:41 pm | #4 |
Nonode
Join Date: Jun 2009
Location: Herefordshire, UK.
Posts: 2,495
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Re: Quad FM1 tuner
For what it is worth: I tried an FM1 quite a few years ago - and found that it just kept drifting in Frequency even after it had warmed up. I puzzled over this for some time and gave up. Essentially it made the tuner unuseable. However since then - and thanks in a large part to this forum - I discovered the real extent to which even post-war paper and some other capacitor types can cause problems due to electrical leakage. This leakage often increases with increasing component temperature, hence they are a possible cause of the frequency drift problem.
I mention this, as looking back with hind-sight I can see that getting that FM1 working as Quad (Acoustical) intended could have been a non-trivial exercise. |