sansui: Help with TU-555 alignment procedure.

Hello Radiomuseum people,Â

this is my first question in your forum and I imagine thare will be many more in the future. I have been casually interested in electronics for many years but never had much time or cash to pursue it. Now, in my fifties, I get the chance. 

I have so far been mostly restoring and recalibrating test gear: Heathkit IT-28, Huntron Tracker 1000 and others.

Now I find myself taking my first trip into radio land.

I have bought a Sansui TU-555 with which to learn. The set works but the reception is very poor.  

The only thing is that I can't find any official alignment documents! 

I have a schematic but that is all google has managed to offer me.

If anyone here can help in any way towards me a/ getting this set sorted and b/ furthering my limited radio knowledge I will be very grateful.

Thank you for reading.

Apologies if this post is in the wrong place or wrongly formatted.

 

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Poor on AM or FM?

I'd not touch the IF alignment at all. It's unlikely to be at fault.
The screw down capacitors on the main tuning can get out of alignment. Some are for the Local Oscillator (do not touch if the scale pointer is correct, they adjust for the high frequency end of the bands only) and some are for the RF tuning, but only at the high frequency end of the bands.

It will need a good dipole aerial for VHF-FM. Indoor or outdoor depends on the local signal. A room with a window approximately facing the VHF-FM mast direction gives the best indoor results.

The "stick" at the back can be orientated for best MW reception and should not be near any solid metalwork.

 

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Thank you for your response,

the set has trouble receiving AM and FM but FM is the worst. Despite using a good dipole in a variety of different (sometimes precarious) locations I can't get the signal strength meter above 1. Also, all reception goes after 100Mhz. 

I think perhaps I need to study a few books on the subject before thinking about poking around.

But, again, thank you for your helpful input.

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As AM and FM are essentially separate alignments (RF coils, tuning capacitors, IF Transformers etc) and only the power supplies and audio is common, then the first thing to check is the voltages on the supply rails. The next thing then is that no electrolytic capacitors are leaky (lower voltages across them) or dried out (high ESR, need an ESR meter or tack a known good part in parallel). Dried out electrolytic capacitors can affect gain and stability.

I'd never consider alignment unless everything else is perfect, ESPECIALLY if a set is poor on AM and FM.

Failure to operate at higher frequencies is often power supply or decoupling/electrolytic capacitor related on a transistor set, especially if the 88MHz to 95MHz part of the scale is reasonably correct.

It's over fifty years old, so electrolytic capacitors are a likely culprit on a transistor radio that otherwise "goes". Leakage on paper capacitors is really only an issue on valve sets and problems with Silver Mica capacitors are rarely outside of certain USA valve (tube) models with over 50V across the capacitor.

The tin whisker issue (only some Germanium transistors) tends to make a set almost or totally dead. This is probably all Silicon transistors.

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