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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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22nd Oct 2018, 6:03 pm | #1 |
Hexode
Join Date: Nov 2009
Location: Cambridge, Cambridgeshire, UK.
Posts: 489
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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 |
22nd Oct 2018, 7:29 pm | #2 |
Heptode
Join Date: Nov 2009
Location: London, Ontario, Canada
Posts: 672
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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 |
22nd Oct 2018, 7:54 pm | #3 |
Octode
Join Date: Mar 2016
Location: Knutsford, Cheshire, UK.
Posts: 1,488
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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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22nd Oct 2018, 8:37 pm | #4 |
Hexode
Join Date: Nov 2009
Location: Cambridge, Cambridgeshire, UK.
Posts: 489
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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 |
22nd Oct 2018, 9:15 pm | #5 |
Heptode
Join Date: May 2005
Location: Oxfordshire, UK.
Posts: 852
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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. |
22nd Oct 2018, 10:38 pm | #6 |
Hexode
Join Date: Nov 2009
Location: Cambridge, Cambridgeshire, UK.
Posts: 489
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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 |
22nd Oct 2018, 10:44 pm | #7 |
Hexode
Join Date: Nov 2009
Location: Cambridge, Cambridgeshire, UK.
Posts: 489
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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! |
23rd Oct 2018, 8:09 am | #8 |
Heptode
Join Date: May 2005
Location: Oxfordshire, UK.
Posts: 852
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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. |
23rd Oct 2018, 5:48 pm | #9 |
Hexode
Join Date: Nov 2009
Location: Cambridge, Cambridgeshire, UK.
Posts: 489
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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 |
23rd Oct 2018, 7:32 pm | #10 |
Dekatron
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 8,809
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Re: Yamaha R-3 Receiver/Amp
Just keep on resoldering any joint that looks even vaguely poor...
__________________
A digital radio is the latest thing, but a vintage wireless is forever.. |
23rd Oct 2018, 8:49 pm | #11 |
Hexode
Join Date: Aug 2014
Location: Featherstone, West Yorkshire, UK.
Posts: 386
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Re: Yamaha R-3 Receiver/Amp
No reset on the CPU, check C162
Kevin |
28th Oct 2018, 11:09 am | #12 |
Hexode
Join Date: Nov 2009
Location: Cambridge, Cambridgeshire, UK.
Posts: 489
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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 |