Luxman R-1050 trouble

[raveenvijendren]

Hi,

I have a Luxman R-1050 stereo receiver that does not power up.
I would like to know how do you open the casing of this receiver. Any information would be of great help. Thank you very much.

[anatech]

Hi raveenvijendren,
If you turn the unit over onto it's back, you can undo all the large screws. The unit will then slide out the front. Watch you don't damage the from of the wood sleeve as it comes out.

When checking the fuses, if there is a little "puff" of black or silver on the glass it may be okay to replace the fuse. If the glass is blackened or silvered to a large extent, do not replace the fuse! The unit will need service. You will only extend the amount of damage if you try to turn it on again.

Nice unit, really worth fixing.

-Chris

[raveenvijendren]

Thank you Mr. Chris,

The fuse has been blackened to an extent that the fuse wire is not visible. This is the fuse on the primary section of the power transformer that has blown. Other fuses on the power amplifier and tuner section are fine. If this is the case, what sort of trouble am I looking at? A shorted transformer? Shorted filter capacitors?

Thank you very much.

[anatech]

Hi raveenvijendren,
With any luck, a shorted rectifier or filter cap. Shorted outputs could do this also.

Since the fuse has blown in a high energy fault (blackened or silivered), do not try another fuse. You will eventually damage the power transformer doing this.

How ever you get it repaired, this amp is worth the attention of a proffesional. That means a known good technician. Not someone who is cheap and fast.

I just got in a Marantz 240 power amp that a bad technician worked on. The wrong parts were <poorly> installed. Now the owner has to pay for the work all over again - and there are some parts missing too.

So it does not pay to have a TV tech or friend work on good gear.

-Chris

[raveenvijendren]

Thank you Mr. Chris,

The problem turned out to be a shorted rectifier diode. The amplifier section of the receiver works fine. Surprisingly, the potentiometers on this unit work flawlessly, no cracks or pops... although it's thirty years old.
They sure don't make stuff like this anymore.

However, there seems to be some problem with the tuner section. It does not receive stations clearly in both AM and FM, and when switched to stereo mode, the signal to noise ration degrades terribly. What sort of problem am I looking at? RF amplifier troubles, alignment?? Any help would be greatly appreciated. Thank you.

[anatech]

Hi raveenvijendren,
Cool I love a simple problem!

I would check the low voltage power supply for one. Reception depends greatly on where you are and the antenna used. Most units I see could use an alignment (all brands).

The higher noise in stereo is understandable and normal under low signal conditions.

-Chris

[raveenvijendren]

Hi Mr. Chris,

Sorry for the late reply. I would like to know how to perform an alignment on this receiver. What equipment is necessary for this procedure? Thank you.

[Gold_xyz]

This is a kit of am/fm receiver... here you can see how to align
a classic superheterodyne circuit.
http://www.elenco.ws/manuals/amfm-108k.pdf

In this case the schematics would be necessary...
also an oscilloscope and a RF generator.

http://www.antiqueradios.org/gazette/align.htm

bye

[Gold_xyz]

Alignment in few word...

- tuner bandpass : align for center the antenna signal
- local frequency oscillator : align for generate the middle frequency
(455KHz for AM 10.7MHz for FM but it can change from model to model . )
- middle frequency transformer : align for max output.

Alignment of "classic" FM detector is more difficulty.

http://www.dephison.com/luxman/r1050/R-1050.pdf

[raveenvijendren]

Thank you Mr. Gold_xyz,

The information you provided was very helpful. I do have access to an oscilloscope and an RF sweep generator. However, my oscilloscope only has a bandwidth of 20MHz. Is this sufficient to undertake the alignment procedure for the FM stages? (alignment of the AM stages is not very important for me as there are no AM broadcasts anymore in Malaysia). Thank you.