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can someone please advise on a problem with my Luxman tuner?
can someone please advise on a problem with my Luxman tuner?
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Old 15th September 2020, 07:12 PM   #1
zachengland is offline zachengland  United States
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Join Date: Aug 2020
Location: Salt Lake City
Default can someone please advise on a problem with my Luxman tuner?

I have owned a Luxman T110 for about ten years and have had no problems with it until now. It worked fine yesterday afternoon and when I turned it on this morning the panel lamps did not light up. I had not listened to it at this point--I just unplugged it and checked the internal fuses. We had a bad windstorm here last week and our power grid has been unstable since then. One of the .75a internal fuses was blown. I replaced the fuse, powered it up and the panel lights worked again. However, I cannot tune in any station. If I take the muting off and set it to mono I can get some audible reception, but the signal meter does not budge. I use an outdoor antenna and the other stereo receivers in my house get perfectly clear reception. I verified the path of the antenna wiring and tried a smaller indoor antenna in various configurations with very little change and still no visible movement of the signal meter. I should add that I live in the middle of a large metro area and have a clear line of sight from my house to the peak with most of our broadcast antennae. The signals or antenna aren't the issue. The attenuator and de-emphasis controls make little difference. I see no obvious shorting or charring inside the chassis. I downloaded the service manual (attached) and did not find anything that was useful to me there. I lack the equipment to do the alignment procedure.

Can someone please point me in the right direction of what to look for? It seems that troubleshooting info for these tuners is a bit scant online.

Edit: Forgot to attach the doc. This is the site I got it from:

Luxman manuals | Hifi Manuals Free: page 3

Last edited by zachengland; 15th September 2020 at 07:21 PM.
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Old 15th September 2020, 07:39 PM   #2
MarcelvdG is online now MarcelvdG  Netherlands
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Do you get the audible mono reception at the correct frequency? That is, does a station at, for example, 88.7 MHz indeed sound most audible when you tune to 88.7MHz?

Was there any lightning during the storm? If so, it might have blown up the LNA.
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Old 15th September 2020, 07:43 PM   #3
zachengland is offline zachengland  United States
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Join Date: Aug 2020
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Yes, the audible reception does come at the correct point on the dial.

There was not lightning. It was a bad wind storm a week ago today that uprooted many trees and took out lots of lines. I have seen no evidence of a surge but we have had periodic brownouts or short blackouts as they work to fix various parts of the grid and remove debris. I stopped unplugging things because I thought we were out of it but this morning the clock on my microwave was flashing.

On an unrelated note the 50 foot pine tree that used to stand next to my house is still blocking my street.

Last edited by zachengland; 15th September 2020 at 07:53 PM. Reason: spelling is hard
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Old 15th September 2020, 08:05 PM   #4
MarcelvdG is online now MarcelvdG  Netherlands
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It sounds like the LNA or an IF stage is broken down, resulting in a much too small gain. However, it's strange that the attenuator makes little difference. If the gain were indeed too small, activating the attenuator should make the reception even worse.

What kind of measuring equipment do you have?
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Old 15th September 2020, 08:13 PM   #5
zachengland is offline zachengland  United States
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I tried it again and you are right. When the attenuator is set on "in" there is no audible reception. When it is set to "out" there is some.

The only measuring equipment I have is a typical multimeter.

Last edited by zachengland; 15th September 2020 at 08:43 PM.
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Old 15th September 2020, 09:00 PM   #6
MarcelvdG is online now MarcelvdG  Netherlands
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I saw some DC bias voltages annotated in the schematics, with a multimeter you can at least check those. I guess the values apply with no input signal, but I haven't read the documentation carefully yet.

In general, when measuring anything in the RF and LO sections of an FM tuner, don't bend any inductors as that will detune them.

By the way, do you have or can you borrow one of those miniature FM transmitters people use to play their MP3 players over their car radio?
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Old 16th September 2020, 08:32 AM   #7
lcsaszar is offline lcsaszar  Hungary
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In any case it is not a misalignment. Resist the temptation to adjust the screws. A storm could not misadjust them.
I had a Luxman T112L and it consisted of an FM tuner block (the FS116J12 block on your diagram) that can be repaired only at a special service shop. It had a dual-gate MOSFET if I recall correctly (3SK45 in your case). I still have the schematics somewhere. Those devices are very sensitive to electrostatic discharge. If they lost input sensitivity, signal can still be mixed down, but it sends much lower to the IF stage.
An option would be to desolder the FM tuner front-end block, open it, desolder the Q101 dual-gate MOSFET and replace it with something similar, like 3N140. Success is not guaranteed, though. There is a shorting wire around the legs, that should be removed only after having the device soldered in.
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Old 16th September 2020, 12:05 PM   #8
zachengland is offline zachengland  United States
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I am starting to feel like this repair is not in my wheelhouse...
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Old 16th September 2020, 02:12 PM   #9
zachengland is offline zachengland  United States
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Folks, I am very grateful for you taking the time to respond so thoughtfully. Since this does not look like it is a simple repair I am going to set it aside for now and get back to my tube amp project. I have ordered a Dynaco FM5 to replace this tuner and am hoping it is fit for purpose. I still would like to fix the Luxman as it is a fairly nice piece of kit, but it can wait. I will revive this thread again in the future.

Again, thank you.
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