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[sevenlayermuddle]

I started to watch a movie the other day, with audio fed through my 5.1 Yamaha AV receiver.   After a few seconds, ‘pop’, the receiver died.

When I got around to investigating with the help of a service manual I “found” online I discovered it has a self diagnosis function.  Diagnostics indicated it had shut itself down due to a self-protective monitor,  having detected a DC offset voltage on one of the speaker outputs.    Sure enough, an ohm-meter confirmed, one of the channel output transistors (right/front for what it matters) is dead short collector-emitter. Wow, that was an easy fix?

No, not really.   The “output transistor” is not like the 3 pin device I grew up with.   It is a 19 pin hybrid IC, containing all output transistors and drivers, for 3 of the 5 driven channels.   Not something that can easily be improvised, by just finding a similar transistor.   And even though the Amp is only 6 years old, the IC seems to be officially obsolete, most suppliers saying no longer available.  It can be ordered from ebay sellers in USA, or China, with weeks’ waiting for delivery, if you trust them.  One UK supplier has stock, but is charging several times the price.

But heck, obsolete , after just 6 years.  Where’s the point in banning carrier bags, and bottle deposits, if a large chunk of electronics becomes junk in such short time?

Still, if I just buy a whole new AV receiver it’ll probably be supplied in bio-degradable plastic-free packaging, with paper-free online documentation, with an option at checkout to donate money to save a tree.  So that’s all right, then?

Fwiw, I have taken a chance, ordered the expensive UK Ebay part.   Installing it will involve fairly major surgery on fragile pcbs with significant risk of outright mortality, but seems worth a punt.  Feel free to wish me luck. 

[roseway]

I wish you luck.  

And also agree with you...

[Weaver]

The problem is that these ‘products’ are just becoming data files, lumps of design IP. When you look at single chip wireless dsl modem routers, the question where’s the x component has the answer equivalent to ‘somewhere around line 148350’.

The problem when you buy a new <insert name of product> is that all the packaging - meaning: the plastic box with PSU, main PCB, LEDs, knobs, switches buttons, all the stuff that surrounds the SoC - is the waste, because you already have all that. What you need is the new SoC that is twice as good and just another very large chip. We need more modularisation but at an internal level, more like PCI or PCMCIA but with the even more massive success level of USB. Perhaps the way would be to start pushing manufacturers to make everything into a box with a very low-cost card-bus interface, so you replace the innards.

Does any one that make any kind of sense? Probably not.

[sevenlayermuddle]

I think I agree, Weaver.

Another recent hobby/indulgence of mine is restoring old 1960s Roberts radios.   The first one came from a local antique shop.  I enjoyed it, so got a couple more off ebay, then got given a couple more by relatives once the word went around.

It’s not just that the technology was different in those days, it’s also that I get the feeling they were designed with a certain amount of passion, as well as logic, and sometimes questionable logic.  Little tweaks that the designer introuduced to the standard circuit conventions of the day, such as an incredibly complicated dual gang potentiometer for the volume control, to “emphasise” the sound at low volumes.   Repairing these things is not easy.  Replacing a transistor might involve removing a daughter board that is secured not by a ribbon plug, but by dozens of individually soldered wire leads.  But somehow it is also a pleasure.

My broken, modern, AV receiver is undoubtably a better amplifier, but I don’t get the sense that the same passion went into its design.  And I don’t get the same feeling of satisfaction as I take it apart.   It feels more like the designers were given a target for performance, reliability and cost,  then choosing off the shelf parts to meet these targets, final assembly details being dictated by cad software.

Apols to any Yamaha design engineers reading this, if I am being unappreciative.   I do concede it is an excellent piece of technology that far outperforms its 1960s predecessors.

[sevenlayermuddle]

Update:  I awoke with a thought - even though it is a generic IC used by lots of manufacturers rather than a Yamaha-specific part, why not try and obtain it through a Yamaha service agent?

After a couple of phone calls to trace a service agent, it seems Yamaha do have stock.  It will be shipped from their warehouse in Germany to UK, then onwards to me.  And significantly less than the Ebay price.  I feel slightly happier this way as I am more confident of getting one from the same chip-maker as original which occasionally matters.  The Ebay trader allowed me to cancel as it had not yet dispatched.

A good start to a Thursday. Wonder what'll go wrong to spoil it?   

[Weaver]

You don’t fancy servicing some Quad electrostatics (2003 model) after you’ve done with that? (Warning contains volts and passion.)

[sevenlayermuddle]

 

Thanks Weaver, but I’ll pass.   If (and it’s still an ‘if’) I get the amp working again, priority will be to sit back and take in a few movies with good soundtracks, turned up loud.     Even if they send me to sleep, as most movies do nowadays, I’ll wake up feeling that I’ve earned the snooze.

I spent a few mins googling for quad electrostatic repairs.   Looks like it could be a fun and worthwhile project, if a labour of love, if you can find somebody to take it on.

[vic0239]

Another recent hobby/indulgence of mine is restoring old 1960s Roberts radios.   The first one came from a local antique shop.  I enjoyed it, so got a couple more off ebay, then got given a couple more by relatives once the word went around.

Yes, lovely little radios. I have just one in my collection, but it sounds great. Has a little "Supplied by Harrods" plaque on the inside of the door. Valve too.

[sevenlayermuddle]

Nice.

Is that an improvised stack of 9V batteries to substitute an obsolete an HT battery?  Clever.

I remember playing with a valve portable when I was a young teenage kid.   I should have known better but somehow, whilst probing around inside when it was plugged into mains, balanced on my knees, I took one heck of an electric shock.   Main worry was, Mum and Dad were in the room with me and I desperately wanted not to show my distress, lest they “outlawed” my hobby.   Somehow I got  away with it.

One of my favourite discoveries inside one of the Roberts was a collection of til receipts covering a decade or so from early 70s, all for PP9 batteries.   I guess the owner had been trying to keep an eye on ongoing running costs. I felt compelled to ensure the til receipts were tucked back exactly where I’d found them, when the radio was reassembled.

[vic0239]

Yes, the HT needs 90v and 10 of the PP3s slot together nicely, but require a strong elastic band to stop them flying in all directions! The D cells are for the heater chain. Nice to find something more interesting inside other than spider skeletons. 

[sevenlayermuddle]

So... the new output module, ordered from Yamaha, arrived this morning.   

Installation began immediately and took about three hours allowing for lunch, coffee breaks, and endless time spent looking for tools and small screws that vanish into thin air whenever I put them down.    Happy to say my initial diagnosis seems to be proven correct, and the patient survived the surgery. 

Currently enjoying some soothing music, but I already put it to the test at full volume with a favourite movie scene that involves a train blowing up, derailing and crashing.  Yep it still works, really quite scary effects, even from the other end of the house.

[burakkucat]

Excellent result. Just purrfect. 

[Ronski]

Well done on the repair, its good to hear of something getting repaired these days.

90v batteries, you wouldn't want to stick your tongue across them 

https://www.classicradioshop.info/valve-and-transistor-radio-batteries/

[sevenlayermuddle]

Thought I’d send spoken too soon last evening, when I wandered into the lounge to be confronted with a dreadful cacophony of wailing and screeching.   Some kind of feedback loops, or oscillations in the amplifiers, or maybe the speaker cones were disintegrating? 

Much relieved when better half explained she was watching something called a “Eurovision song contest”, and it was meant to sound just like it did.

[tiffy]

Interesting link, brings back lots of memories from the good old valve days.

I remember an old neighbour who's house did not have electricity, my father fixed her up with a radio which used a glass accumulator, LV battery for the valve heaters and the large 90 volt, dry cell HT battery, took the LV battery to a local shop for re-charging when required, the 90 V. HT battery was quite costly and had to be very carefully conserved.