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Old 22nd Oct 2018, 6:03 pm   #1
bigfathairyvika
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Default Yamaha R-3 Receiver/Amp

Hi All,

This receiver came in with the quote "I think its the speaker relay is faulty, should be a quick fix".

On turn on , nothing, no display , except the power supply voltages appeared ok.

A quick trace through found TR124 of the protection circuit faulty, a replacement fitted and still no display , but after a few seconds the speaker relay clicked over.

After a lot of prodding about and testing transistors etc. I've found that if you switch it on, leave it for a couple of minutes then power cycle, the display works and all works fine.
But switching off and leaving to for an hour or so and the problem reoccurs.

Checking the supply voltages, 6v, + - 12v, +- ~39v and all show ok, with no change when it springs to life.

So, has anyone fixed this type of fault on an R-3 before?

My suspicions are with the processor chip possibly not "booting up".


Mark
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Old 22nd Oct 2018, 7:29 pm   #2
orbanp1
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Default Re: Yamaha R-3 Receiver/Amp

Hi Mark,

You could try finding the problem with a hair dryer and freeze spray.
That should help to narrow it down that which part is heat sensitive.

Regards, Peter
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Old 22nd Oct 2018, 7:54 pm   #3
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Default Re: Yamaha R-3 Receiver/Amp

Have you checked for dry solder joints? - especially at points where there may be any physical or heat stress to the PCB...
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Old 22nd Oct 2018, 8:37 pm   #4
bigfathairyvika
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Default Re: Yamaha R-3 Receiver/Amp

Just ran out of freeze spray this afternoon so awaiting some more.

I havent tried warming it up from cold yet though. Will try hair dryer tomorrow. If it works first time then I'll be on the right path.

Checked for dry joints and resoldered any part which go hot or may flex.
No amount of flexing and tapping solves fault.

Mark
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Old 22nd Oct 2018, 9:15 pm   #5
percival007
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Default Re: Yamaha R-3 Receiver/Amp

Is it this one..................

https://www.hifiengine.com/manual_li...maha/r-3.shtml

If so, I don't think TR124 is in the Protection Circuit. It's part of the RHC O/P Stage.
Are you sure you still haven't a fault here?

James.
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Old 22nd Oct 2018, 10:38 pm   #6
bigfathairyvika
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Default Re: Yamaha R-3 Receiver/Amp

Yes it is that one.
I think I explained it wrong.
Should have been TR124 was faulty causing the amp to go into protection mode and stop the relay circuit from switching in the speakers.
Basically replacing that transistor with a suitable replacement resulted in the relay switching on. But it could have just been coincidental, as I did re-solder a few other joints whilst the iron was hot.



Mark
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Old 22nd Oct 2018, 10:44 pm   #7
bigfathairyvika
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Default Re: Yamaha R-3 Receiver/Amp

Just a thought, there is another thread on here which mentions the same sort of fault but was never mentioned if it was resolved as it concentrated on another fault.
The fault was also mentioned in the "offers" advert on here!

So, a common fault or I have the same unit on my bench!
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Old 23rd Oct 2018, 8:09 am   #8
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Default Re: Yamaha R-3 Receiver/Amp

Is the Crystal for the Micro OK?

Although you say the +6V is OK, have you 'scoped the Supplies?
It's old enough for the Electrolytics to be failing. Some supplies near the Micro not quite smooth enough?

James.
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Old 23rd Oct 2018, 5:48 pm   #9
bigfathairyvika
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Default Re: Yamaha R-3 Receiver/Amp

Good point.
All lines are smooth with hardly any noise, until it does start working. Then the 6v line goes a bit noisy, probably generated by the processor chip itself.

Symptoms have changed, it now works if left on for around a minute.

I scoped the crystal and the resonator, the crystal oscillates immediately, the resonator doesn't until the display starts working.
The resonator drives the main chip for the display etc, the crystal is for the PLL. ( which is controlled by the main chip )

btw: the "main chip" as I call it is the Sanyo Tuning Controller chip.

So.. I re soldered all the joints on the chip and resonator components.

I'll leave it off overnight and see if it starts up first time tomorrow.
If not I'll try replacing the resonator, although the nearest I have is 455khz.

Thanks for the reminders, why I didn't scope the oscillators to start with I don't know.

Mark
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Old 23rd Oct 2018, 7:32 pm   #10
stevehertz
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Default Re: Yamaha R-3 Receiver/Amp

Just keep on resoldering any joint that looks even vaguely poor...
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Old 23rd Oct 2018, 8:49 pm   #11
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Default Re: Yamaha R-3 Receiver/Amp

No reset on the CPU, check C162


Kevin
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Old 28th Oct 2018, 11:09 am   #12
bigfathairyvika
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Default Re: Yamaha R-3 Receiver/Amp

Kevin!
C162 appeared ok, but with a few ohms more internal resistance so I replaced it anyway.

Now it boots on in approximately five seconds which I would think is perfectly acceptable as the protection circuit takes longer!

Many thanks to all.
I can now work on the damage they did to the rear connectors!

Mark
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