Where To Find The Power Blinking Fault In Yamaha PSR-3000 Keyboard?
The complaint of this Yamaha PSR-3000 Keyboard was power blink. It causes the LCD Display in the front panel to turn On and Off (the below photo showing when the display was On but after a second it will turn Of f again).
This kind of problem can be due to bad power adapter or the internal circuit board have bad component.
So where to find the power blink fault? The first thing I do was to isolate the problem by checking on the power adapter output. It showed 16 Vdc which means it was good. If you get improper dc output voltage then suspect the power adapter. In some cases, even when you got the good output voltage, this does not mean the power adapter is good. You have to test it with a load to see if the voltage can sustain or not. If can sustain the current draw this means the power adapter is good. If cannot this means the power supply regulation circuit or the secondary filter section have problem.
Since the power adapter was good so I had to open up the casing in order to look at the circuit board. Removing the cover was very easy.
The below photo is showing the low voltage and the main amplifier section. All the e-caps seems to be normal and no bulged e-caps found.
Next I powered On the keyboard and perform voltage testing on the 7812A voltage regulator IC. For a good IC, pin 1 must have 16 vdc (this supply is coming from the external adapter) and should produce 12 volt output at pin 3. Pin 2 is connected to cold ground-see the photo below:
But the defective IC have only 8 to 9 volt output and this is the reason why the LCD display blinks-see the photo below:
The original IC is an insulated type and did not connect to heatsink thus it can gets hot very fast. In my opinion, if I put back the same type it would not long also so I bought the replacement one where it can be attached to the heat sink. This way the IC will run cooler due to the heat can be dissipated fast-see the photo below how I have soldered the 7812 voltage regulator IC.
Once the powered was turned On look at the result below:
Conclusion- Voltage regulator IC (usually 1 ampere) play an important part in supplying the right voltage to the circuit. This means when the main board draws current the output voltage of the IC will maintain the same output voltage. The voltage can drop slightly but not too much otherwise it does not serve the purpose as a regulation device. You need to take note also that voltage regulator IC can breakdown when under full load. If you suspect the IC is bad just direct replace and retest. It is not expensive and you should keep some (variety output voltage such as 7805, 7812 etc) in your compartment. Ok that’s all for today and hope to see you again soon.
This article was prepared for you by Suranga Bandara who owns an Electronics shop in Anuradapura, Sri Lanka.
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Note: You may check out his previous repair article in the below link:
https://www.jestineyong.com/sony-mini-hifi-push-power-protect-problem-solved/
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mahienn
February 18, 2016 at 7:40 am
love u sir
u r a genius
i never miss even a single article of yours
keep it up thanxxxxxxxxxxxxx
Suranga Electronics
February 18, 2016 at 1:55 pm
Ok. Mr, You are welcome !
Thanks..
benny nious
June 3, 2016 at 10:19 pm
Can I send you a youtube video. I'm guessing this is what you are referring to in your article.
David Towers
February 18, 2016 at 11:43 am
I like nice quick fixes - nice article pics etc
Yogesh Panchal
February 18, 2016 at 2:59 pm
Suranga,
Thanks for another good tips.
Anthony
February 18, 2016 at 4:13 pm
Great repair with nice clear photos Suranga, Well done !
Humberto
February 18, 2016 at 8:38 pm
Good repair Suranga and good quality images too. Congratulations
Paris Azis
February 19, 2016 at 12:19 am
Good job, Suranga.
Parasuraman S
February 19, 2016 at 1:29 am
Good and easy repair! Thanks for sharing!
Henrique J. G. Ulbrich
February 19, 2016 at 3:04 am
Good job, Suranga. And thanks for sharing your experience again, as well as the high-quality pictures. Who wishes to know more about linear regulators of the 78XX series can access data sheets at:
https://www.fairchildsemi.com/datasheets/LM/LM7805.pdf or
https://www.sparkfun.com/datasheets/Components/LM7805.pdf
First comment: it's possible that the IC you'd taken out was in good condition; what could be happening was a thermal overload protection feature inherent to the IC design. As there was no heat sink, this thermal overload feature lead to a shutdown, so protecting the IC. If this IC is employed in another low-current task, it will probably perform well. In the present case, you had no choice than use an IC with a thermal tab (the same as mounting tab) and mount it on a heat sink (at least that is the way as I understood it, in an existing heat sink). In these instances, there's a detail that must not be forgotten: the center lead of the IC generally have electrical contact with the thermal (mounting) tab. So, the mounting tab and the heat sink employed must be at the same electric potencial.
Second comment: Is this really a Yamaha design? It’s unbelievable that such a renowned company develop a circuit with a so unacceptable error!
Ashish
February 19, 2016 at 12:38 pm
Awesome diagnosis. Always something to learn from suranga. Would someone chime in and recommend some must have voltage regulators numbers in the spare parts list. 7805, 7812. Any other values people recommend. A nice addition to this website would be a list of must have parts.
Robert Calk
February 20, 2016 at 3:01 am
Good job, Suranga.
dhel costanos
April 21, 2016 at 9:44 am
If you guys problem with low volume input just contact where the parts you replace I just repair today psr-e403.have a good day to all
Reyguel Nious
May 27, 2016 at 9:33 pm
https://youtu.be/pjfJ8_rOKZM
I was wondering if this ( the youtube video) is what you repaired. You may have to copy and paste the link into the address browser to view. I have been having this issue for awhile. I'm praying this is the same thing you were describing in your article. Thanks.
Godwin Thomas
May 15, 2019 at 10:38 pm
When i connect a cable to the line in port of my PasR 3000, a hissing soind occurs which gradually fades out in about 30 minutes.Can anyone explain what the problem is and how to rectify it.
Yemi
September 22, 2020 at 7:48 pm
I have psr 3000 but the sound is not coming out. I have changed the sound ic yet the problem persists. What can I do?
Noelbasada
October 2, 2023 at 12:10 pm
What ic you have to replace?
Noelbasada
October 2, 2023 at 12:14 pm
That problem is in TG1 board try replace ic7 an ic2 in tg1board