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Old 4th December 2012, 12:14 AM   #1
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Default Tuners: analogue, synthesized and beyond

Folks, I need your help...

I have recently got seriously into stereo tuners since I found a Luxman TD-377 in good condition (pic attached) and cheap in a 2nd-hand shop: 10 euros. I thought why not? It's a really well-build tuner, has that RDS thing you can read what's playing, has 25khz tuning steps, etc... Once at home, I hooked it to the amplifier and I was astonished by the sound. Then I discovered several FM stations here in the Netherlands airing nice music...

Ok, other than listening CDs and music stream from the Web via an USB D/A audio adapter into the Integrated, now I'm also enjoying FM radio frequencies. Now, the thing is that I found another nice looking tuner for the same price in another 2nd-hand store. The Sansui TU-317. Having knowing that Sansui never did crappy (now vintage) gear, I decided to buy the other tuner, so I now have one digital tuning (Luxman) and one analogue. I want to keep both machines. I'm not a tuner expert but I think the price paid for them was good.

So my questions are:

1. does it worth to change some old components (caps, etc) from the vintage Sansui?
2. changing those few components will affect the so called (infamous) alignment?
3. do digital synthesized tuners suffer misalignment too?
4. any special with regard for antennas or cables?

I'm asking you guys here because there is a lot of confusion over some other forums.

Thanks and regards.
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Old 4th December 2012, 10:25 AM   #2
DF96 is offline DF96  England
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Unless you know about RF circuitry, don't touch the RF/IF circuitry. It is much easier to mess it up than to fix it, unless you have the necessary knowledge and test equipment.

Personally, I only change components to do a repair. However, if you confine yourself to the audio end of the circuit you won't do much harm and you may do some good.

Digital synthesized tuners can suffer misalignment in a similar way to conventional tuners. The synthesizer replaces the local oscillator, but the RF circuits still need to be aligned.

On audio forums you will read some sense and some nonsense about audio. When it comes to RF, you are more likely to read nonsense on an audio forum although there are people on here who know what they are talking about. What do you want to know about antennas and cables?
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Old 4th December 2012, 10:51 AM   #3
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Unless you have a network analyzer, spectrum analyzer and FET probes don't touch the RF part. Messing it up is easy and realigning it next to impossible!

Antennae and RF cables come in a lot of flavors, but for FM reception (87.5 - 108MHz band) usually a 1/4 wave whip or a dipole is all you need. If you want to receive stations that are very weak (RF power that is) look at -for example- Yagi's. These "amplify" the RF signal but are directional. For RF cable use a 75Ohm cable (same stuff as used for TV) things to look for are damping/meter (as low as possible) and screening (as high as possible).
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Old 4th December 2012, 03:09 PM   #4
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Quote:
Originally Posted by Mark.Clappers View Post
Unless you have a network analyzer, spectrum analyzer and FET probes don't touch the RF part. Messing it up is easy and realigning it next to impossible!

Antennae and RF cables come in a lot of flavors, but for FM reception (87.5 - 108MHz band) usually a 1/4 wave whip or a dipole is all you need. If you want to receive stations that are very weak (RF power that is) look at -for example- Yagi's. These "amplify" the RF signal but are directional. For RF cable use a 75Ohm cable (same stuff as used for TV) things to look for are damping/meter (as low as possible) and screening (as high as possible).
Quote:
Originally Posted by DF96 View Post
Unless you know about RF circuitry, don't touch the RF/IF circuitry. It is much easier to mess it up than to fix it, unless you have the necessary knowledge and test equipment.

Personally, I only change components to do a repair. However, if you confine yourself to the audio end of the circuit you won't do much harm and you may do some good.

Digital synthesized tuners can suffer misalignment in a similar way to conventional tuners. The synthesizer replaces the local oscillator, but the RF circuits still need to be aligned.

On audio forums you will read some sense and some nonsense about audio. When it comes to RF, you are more likely to read nonsense on an audio forum although there are people on here who know what they are talking about. What do you want to know about antennas and cables?
Thank you guys for the tips!

Indeed I don't have the knowledge to touch inside tuners, I even don't know which parts I could touch or some other I shouldn't. But I'm really falling in love with these radio machines, specially the analogue one. Other than cool, it looked the company build it with special care and to last, differently from most of today stuff, as we know the story.
I know this Sansui model might not worth to mess up and there's a lot of other much better vintage tuners around, but curiosity to see improvements in such a simple and nice piece of gear is what I trying to understand. The newer digital synth Luxman sounds a bit more full, richer and has less "hisses" than the older analogue Sansui. So I don't know if I'm listening to a misaligned tuner (Sansui) that could deliver a much better sound. An experienced DXer knows where's is the weak part to adjust, improve or replace.

It would be really nice to have a cool vintage tuner sounding "like new", what most people do when they get old Sansuis, Pioneers or Kenwoods integrated amps. Since we have here in Holland a handful of good FM stations I can put all my CDs back to the cabinet for a while and just enjoy the shuffle music and discover new stuff from the stations.

I'm not going to touch it if you guys don't recommend, unless I could find some expert around the Amsterdam area able and willing to do so.

Mark.Clappers, do you know any good tuner expert in the Netherlands?

Thanks again for the reply and regards,

Karl.
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Old 4th December 2012, 03:16 PM   #5
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About antenna and cable: is it enough to have some 5m of the 75 ohms around or is it recommended to to have it to a proper antenna?

Few more important questions:

When around the tuners start to be misaligned and why?

What causes misalignment? Aging components or/and hurting the gear?

Last edited by Karl vd Berg; 4th December 2012 at 03:19 PM.
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Old 4th December 2012, 03:22 PM   #6
DF96 is offline DF96  England
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Quote:
Originally Posted by Mark.Clappers
Unless you have a network analyzer, spectrum analyzer and FET probes don't touch the RF part.
Alignment and most fault tracing does not need analyzers, just a sig gen and DMM and the knowledge of how to use them.

Quote:
Originally Posted by Karl vd Berg
When around the tuners start to be misaligned and why?

What causes misalignment? Aging components or/and hurting the gear?
Yes. Two main methods to upset the alignment is to drop the item (or just general rough handling over a period of time) or to 'tighten up all the loose screws' - yes, people really do that then wonder why their radio has stopped working! (The 'loose screws' being trimmer capacitors or adjustable coil cores.)
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Old 4th December 2012, 04:13 PM   #7
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Hi All,

DF96, in general you are right but if you wat to "tune" the circuit you should at least be able to look at the RF and IF stages without influencing them to much, hence the FET probe. Trust me on this one, I have 8 years experience with TV frontends both digital and analogue combined with DRX39yxZ series of demods for ATV,FM,DVB-T/C,8VSB and ISDB-T (MOPLL and silicon tuner based combined with SAW's and LC bandpass filters for the IF stage & single conversion tuners) and learned it the hard way

You should defenitly use a proper antenna, this can be as simple as a wire 1/4 wavelenght or as complicated as a Yagi. What suites your needs best depends on your receiving conditions.

If you want to learn more about your tuners google "superheterodyne" and be prepared to spend some time reading

I can't help you with a tuner expert in the Netherlands, the people I work with are not into DIY audio..
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Last edited by Mark.Clappers; 4th December 2012 at 04:20 PM.
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Old 6th December 2012, 04:49 PM   #8
rsavas is offline rsavas  Canada
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Choose a tuner based on Silicon Labs Si473x series or the newer Si4770, no adjustments necessary, nothing to drift or age. I have a Si4735 running, it works quite well, I like the RDBS information, I get to learn who are the artists etc.

I am in the process of making a Si4770, so will be able to compare the performance.
Some really nice features all done in a DSP. They have brought this part out to compete with the high end tuners, we shall see. It is a $9.00 part = amazing really

How many people actually have FET probes, >350 MHz BW DSO's, FM mpx SG's? = Very few, I do, but it is of no help to Karl, in this case, wish I could help you out, sorry

Rick
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Old 7th December 2012, 09:02 AM   #9
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Karl,

Spend some time here:-

Tuner Information Center - Vintage Stereo Tuners

Loads of info, particularly for your Sansui. Certainly keep both, in fact get more!
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Old 7th December 2012, 10:48 AM   #10
DF96 is offline DF96  England
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Bear in mind that digital implementations of FM tuners almost always get very poor reviews. This may be because they are added as an afterthought to a digital tuner (e.g. DAB in Europe) and not properly debugged. In principle it ought to be possible to decode wideband FM using digital techniques so I don't know why people seem to do it badly.
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