Hi guys,
I just acquired a Quad FM4, Q02xxxx, fairly late version. Components inside still looks new, way above my expectation of a 30years old tuner!
I made a silly mistake of not having a serious listening test, all I did is just briefly hook up and tested the sound, stereo receiving, and pre-set store 7 stations - all works, without noticing is there background noise or not, I went ahead to replace the following :
- N1 (with 220n 47ohms RIFA PME290)
- C4, C5; 1000u/50v, Panasonic FC
- C6; 220u/50v, Pana FC
- C57; 470u/50V, Pana FC
- C11, C12, C34; 100u/25v, Pana FC
- C62, C37; 2u2/50v, Pana FC
- C56; 22u/50v, Pana FC
- C63; 1u//1u/50v, WIMA MKS
- T9; 7812, ON Semicon with heatsink
- B1; Varta 4.8v 150mAh
After components replacement, I measure the 12VDC, 30VDC rails, all within specs.
Once everything setup, I notice the FM4 is producing high-pitch noise/hiss in the background. The noises are present for all stations, including the "Tune". It raises as I crank-up the volume of my Q34 - Q909 - Harbeth P3ESR.
I tried changing the aerial (essentially a piece of wire with RF connector), doesn't help. I tried removing the earth cable of the IEC power inlet of FM4, hoping it was the ground loop, doesn't help too.
As soon as I come across this thread posted in DADAElectronic (here), there's this guy John from USA experiencing the same exact symptom I'm having! I thought it was the silver light in at the end of the tunnel! I did all I could to desolder, resolder the caps I replaced particularly - C11, C12, C34, C63, C62, C37.
To my horror, the annoying background noise just don't want to go away. I even tried to put back the old caps, doesn't help too. I tried resolder some soldering points of the board randomly, nothing change, no luck.
I was wondering is this background noise already persist when I get hold of the FM4, or was it really due to the change of caps I did?
Aside of the background noise, the Quad FM4 is really a lovely tuner. Matches very well with the rest of my Quad. I'm quite confident to say it sounds very close to my ex-Accuphase T-105, the later of course has added more sweetness that is absence in FM4.
Nonetheless, I really hope someone who's reading this thread could help me out to get rid of the noise.
Thanks in advance!
Best Rgds,
Alvin from Singapore
I just acquired a Quad FM4, Q02xxxx, fairly late version. Components inside still looks new, way above my expectation of a 30years old tuner!
I made a silly mistake of not having a serious listening test, all I did is just briefly hook up and tested the sound, stereo receiving, and pre-set store 7 stations - all works, without noticing is there background noise or not, I went ahead to replace the following :
- N1 (with 220n 47ohms RIFA PME290)
- C4, C5; 1000u/50v, Panasonic FC
- C6; 220u/50v, Pana FC
- C57; 470u/50V, Pana FC
- C11, C12, C34; 100u/25v, Pana FC
- C62, C37; 2u2/50v, Pana FC
- C56; 22u/50v, Pana FC
- C63; 1u//1u/50v, WIMA MKS
- T9; 7812, ON Semicon with heatsink
- B1; Varta 4.8v 150mAh
After components replacement, I measure the 12VDC, 30VDC rails, all within specs.
Once everything setup, I notice the FM4 is producing high-pitch noise/hiss in the background. The noises are present for all stations, including the "Tune". It raises as I crank-up the volume of my Q34 - Q909 - Harbeth P3ESR.
I tried changing the aerial (essentially a piece of wire with RF connector), doesn't help. I tried removing the earth cable of the IEC power inlet of FM4, hoping it was the ground loop, doesn't help too.
As soon as I come across this thread posted in DADAElectronic (here), there's this guy John from USA experiencing the same exact symptom I'm having! I thought it was the silver light in at the end of the tunnel! I did all I could to desolder, resolder the caps I replaced particularly - C11, C12, C34, C63, C62, C37.
To my horror, the annoying background noise just don't want to go away. I even tried to put back the old caps, doesn't help too. I tried resolder some soldering points of the board randomly, nothing change, no luck.
I was wondering is this background noise already persist when I get hold of the FM4, or was it really due to the change of caps I did?
Aside of the background noise, the Quad FM4 is really a lovely tuner. Matches very well with the rest of my Quad. I'm quite confident to say it sounds very close to my ex-Accuphase T-105, the later of course has added more sweetness that is absence in FM4.
Nonetheless, I really hope someone who's reading this thread could help me out to get rid of the noise.
Thanks in advance!
Best Rgds,
Alvin from Singapore
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Hi Mooly,
I do not have proper outdoor Antenna but staying high rised building at 11th floor, with my 75ohm wire attach right beside windows. The reception is very good, I'm getting full dot (FM4 has dot display strength of reception) with some stations. I guess it's not about reception?
There isn't a way to force it into mono...
I do not have proper outdoor Antenna but staying high rised building at 11th floor, with my 75ohm wire attach right beside windows. The reception is very good, I'm getting full dot (FM4 has dot display strength of reception) with some stations. I guess it's not about reception?
There isn't a way to force it into mono...
I'm afraid height alone doesn't guarantee a good signal. Glass bounces signals off it and causes multipath problems and buildings (reinforced concrete etc) absorb a lot of the signal. The signal strength meter isn't a guide either because they are often "customer orientated" and show full strength for totally inadequate levels. That looks better in the shops rather than it showing "poor signal" most of the time.
Sorry if that all sounds very negative but its the way it is I'm afraid. So you need to be 100% sure the tuner is or is not faulty and that means, at least on an easy to try level testing it on an outdoor aerial that is known to deliver a good signal that gives noise free reception on several tuners.
To test it accurately requires an FM stereo generator and RF modulator where a known level can be applied to the aerial input socket and the signal to noise measured.
Have you tried pulling the aerial out a little (to attenuate the signal) and see if that forces it into mono ?
Something like this would be a "minimum" for an outdoor aerial in a primary reception location for noise free stereo reception.
Sorry if that all sounds very negative but its the way it is I'm afraid. So you need to be 100% sure the tuner is or is not faulty and that means, at least on an easy to try level testing it on an outdoor aerial that is known to deliver a good signal that gives noise free reception on several tuners.
To test it accurately requires an FM stereo generator and RF modulator where a known level can be applied to the aerial input socket and the signal to noise measured.
Have you tried pulling the aerial out a little (to attenuate the signal) and see if that forces it into mono ?
Something like this would be a "minimum" for an outdoor aerial in a primary reception location for noise free stereo reception.
Attachments
The 8 led signal strength indicator of the FM4 has an unusually wide range.
It does not go to maximum when you tickle it with a few uV of signal.
I have a 3 element above the roof. I usually get 6 or 7 leds lit.
If i deliberately "test" with an attenuator in the aerial feed, then with 2 leds lit it sounds bad.
With 4 leds lit it is OK, but I would choose never to listen to that weak a signal.
Then you have a strong signal that gets the FM4 way beyond full limiting.
It does not go to maximum when you tickle it with a few uV of signal.
I have a 3 element above the roof. I usually get 6 or 7 leds lit.
If i deliberately "test" with an attenuator in the aerial feed, then with 2 leds lit it sounds bad.
With 4 leds lit it is OK, but I would choose never to listen to that weak a signal.
is that 8 leds lit?
Then you have a strong signal that gets the FM4 way beyond full limiting.
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Not sure if this would help with the diagnosis but how about recording say 30 seconds of it direct into a PC using something like Audacity and then post a .wav or good mp3 file so we can hear it.
What warrjon says is correct although any caps such as electros and large value film and ceramics won't be tuning related directly.
Is it possible there could be some other local interference nearby (SMPS/PC's etc) that you are not aware of such as in a floor above or below.
What warrjon says is correct although any caps such as electros and large value film and ceramics won't be tuning related directly.
Is it possible there could be some other local interference nearby (SMPS/PC's etc) that you are not aware of such as in a floor above or below.
Hi Mooly, okay good idea, I'll try to capture the irritating noise and post asap.
Yes it does sound like smps noise I ever experience with usb dac, but it's more "constant" than smps usb dac noisr where you could hear the noise fluctuating. I tried switching off suspicious equipment uses smps, but doesnt work.
Worst case scenario will really be like what warrjon mentioned, but i hope not...
Yes it does sound like smps noise I ever experience with usb dac, but it's more "constant" than smps usb dac noisr where you could hear the noise fluctuating. I tried switching off suspicious equipment uses smps, but doesnt work.
Worst case scenario will really be like what warrjon mentioned, but i hope not...
IC7 is 3053?
A nice version of pdf schematic can be downloaded here.
http://www.meridian-audio.info/public/quad-fm4-schematic-circuit[4352].pdf
A nice version of pdf schematic can be downloaded here.
http://www.meridian-audio.info/public/quad-fm4-schematic-circuit[4352].pdf
You can't make that assumption though.
FM transmissions are really "line of sight" so if you are 30km from the transmitter then that is quite a long way out. I used to use a 3 element loft mounted aerial for FM and it was OK... just... and that is at a distance of around (guessing) 22 miles from the main transmitter. Transmitter power for FM was 4kW.
What is really important is the "field strength" at any given location. If that is to low then you can never get good reception, no matter how much gain you throw at it. A three element aerial is giving you +5 db of "free" gain, go to a 6 element and that jumps to 8.5db.
Can you try the tuner at another location on another aerial ?
Okay will definitely invest an outdoor aerial.
Here you go the recording I took minutes ago. The first 3sec you could hear the noise loud and clear before the guitar starts to play. When there's music, the noise blend and sometime covered by the loudness of music, but it's still there :-(
https://www.dropbox.com/s/j6v8b1zifnx0nqk/Voice 002.m4a
Here you go the recording I took minutes ago. The first 3sec you could hear the noise loud and clear before the guitar starts to play. When there's music, the noise blend and sometime covered by the loudness of music, but it's still there :-(
https://www.dropbox.com/s/j6v8b1zifnx0nqk/Voice 002.m4a