Used wrong powersuply for Keyboard, how to possible repair ?

[Jompot]

Hi people, I'm by no means proficient in things electronic, but have previously have success repairing things by following the advice of people that do know things, and so I'm trying my luck again.

I dug out my old Roland JV30 keyboard from my high school band days, and wanted to hook it up. Unfortunately I used the wrong power-supply that didn't give the required 9V 1000mA but something a little more, the result was the display fluttering a bit for 20 seconds then a dead device. I now found the right power-supply but the keyboard still wont do anything, besides giving a faint hum in the earphones.

With my limited knowledge I assumed there would be a fuse that was blown or something similar, but taking apart the keyboard I cannot locate any fuse looking components, I can't see any obviously fried or burnt elements either- how do I proceed with error checking ?

I have taken some pictures of the circuit board where the power is attached and the schematics from the service manual:

The circuit board


Close up of the area where the power arrives


Element (I think its a zener diode) that I thought looked suspicious


Schematics



Is there by chance anyone that can offer me some advice ?

With hope
Tom from Denmark

 

[KeepItSimpleStupid]

You really have to look at the +5 and +9 V test point with and with SW1 on and SW1 off.

It would help to know if what the characteristics of the wrong power supply was. Polarity and whether or not it was AC or DC.

I'm suspecting D5 or FL-13 (Choke) without any other information.

 

[Jompot]

Forgive my ignorance, but I don't know what it means to look at the +5 and +9 test points with SW1 on and SW1 off ?

The wrong power supply gave DC 18V 1000mA

/Tom

 

[Ian Rogers]

I think the only things that will be blown will be Q16 and or L29... If you haven't got +12v on IC25, this is where I would start!!

 

[KeepItSimpleStupid]

Let's hope you have a voltmeter?

The is going to be real tough. On the upper right side of the schematic, there is something labeled JK1. Find it.
Follow it to the left and find the part labeled SW1. (Switch 1 or the power switch).
Keep following it to the left and locate the +9 and +5 volt items on the schematic.

Locate the component D5 on the circuit board. It may be the one your suspicious about. I can't see the label. D means diode and means the 5th diode.

Measure the voltage across that diode with the power switch on. Right now, don't worry about the polarity of your probes.

---

See if you can locate C80. (might be C60) and measure the voltage across it with the power switch on and off.

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Do you have any idea what the polarity of the wrong supply was. I think the normal supply is barrel nagative.
So, check the voltage across the output of the power packs (disconnected from the KB) with the negative terminal of your meter on the barrel. What do you get?

+9 supply ( - on barrel) (think you will get +9)
18V supply (- on barrel) voltage?

 

[cowboybob]

Made a mess, Doing this post again...

 

[cowboybob]

Once you have your external power supply situation corrected, could you provide the voltage levels at the 3 Test Points (TP) that are shown in the pics below? They would help judge the condition of the voltage regulating components.

 

[debe]

Looking at the circuit the power socket on this unit is positive on the barrel & neg on center pin. So very easy to have a reveverse polarity situation.

 

[KeepItSimpleStupid]

Here is a datasheet on the 1SR35: https://www.google.com/url?sa=t&rct...cL0PMVfkggyJZHA&bvm=bv.59568121,d.cWc&cad=rja

Here is the PLT1R53C **broken link removed**

So, it could have taken out the diode.

 

[Zerotolerance]

Just by looking at the photos alone, the discoloration in the VReg makes me think it is one of your suspect components.