Digital piano won't power ON

[Tha fios agaibh]

D23 might be shorted. I'd pull it out of circuit and test it again. Pay close attention to its polarity.

 

[Alektron]

" I need Q8 transistor removed from the board, using that same 3 solder ball technique and rapidly walking the soldering iron tiplet between the 3 balls until Q8 leads reach solder release time."

I'm trying to remove Q8 transistor but it won't move. Q8 is so hot that I can barely touch it. Actually the body of the transistor is moving, but the legs are staying in place. I have a feeling that this Q8 transistor is "bye bye", but I can't even remove it now, unless I break it off.

I'm not sure what a 3 solder ball technique is, but I moved the iron rapidly between the 3 legs and nothing really happened, it is just getting hotter and hotter then a hot summer day in July.

 

[bushtech]

Did you put some extra solder on the three legs?

 

[Alektron]

no, should I ?

 

[bushtech]

Yep, makes the old solder flow more easily

 

[bushtech]

From 73 de Edd post #21: you place a dot of rosin flux onto each of the existing solder joints and feed in fresh 60/40 solder, until you achieve a much larger molten solder mass of each, with them being about the size of a 3/16 ths of an inch ball at each joint

 

[Alektron]

Ok, I will add some. Unfortunately this board is two sided with plated thru holes. I'm going to try to ad some solder to the iron, and use a wick, and a sucking pump.

But I'm afraid this Q8 transistor is gone, I see black lines stained on the legs, as if the body moved upwards from the heat. Although I checked it with my DMM in diode test, it's not shorted yet. So let's see...

Beam me up Scotty !

 

[bushtech]

You add the solder to the bottom of the board where the legs stick out

 

[Alektron]

Ok, let's do that I'll be back.

 

[Alektron]

Achtung, Achtung ! Mission Control ! Suspect is down and neutralized, I repeat Q8 Transistor has been removed successfully. Mission accomplished, OVER !

 

[bushtech]

Phew! I suggest you source a new transistor just to be safe. Cheap insurance.

Heat up and wick the holes individually.

Just keep in mind that I am no expert with donkey years of experience so be warned

 

[Alektron]

I didn't use a wick or a suction pump to remove the Q8 transistor, but I will try to use the wick and the pump on cleaning out these holes.

" Just keep in mind that I am no expert with donkey years of experience so be warned "

Expert or no expert, you gave me the right info to ad some solder, and it worked, otherwise I would've brought in my universal Transistor removal tool that works on pretty much everything when it comes to removal. hi hi

 

[Alektron]

73's de Edd >>> " I need Q8 transistor removed from the board, using that same 3 solder ball technique and rapidly walking the soldering iron tiplet between the 3 balls until Q8 leads reach solder release time.

Then the unit needs DC voltage monitoring of a connected CN107 to its mate at the pins 12 and 13, powering up for ONLY the time that is required for a voltage to show up on the meter . . . then power down. "

Ok, Q8 is history now, and next I'm going to reassemble the Main board (after I clean out those 3 holes) , and hook up everything, then turn on the POWER, the 110 V, and let's see what the reading at pin 12 and 13 is going to be.

Aye, aye captain, your wish is my command!

Question (just so I can be in picture ):

What is the reason we removed transistor Q8 from the circuit, and trying to test the unit without Q8 being in circuit at pin 12 and 13?

 

[Alektron]

Checking transistor Q8 with my LCR-T4 ESR, which is a Transistor, Diode, Triode, Capacitance, SCR Inductance tester, making sure Q8 survived this recent and awful surgery... Q8 seems like it's still OK, and going strong...

They always say that drinking is bad for you, but then again, how would you support your circuit board without any cork plugs ? That's only 4 bottles of fine Cabernet Sauvignon

 

[Alektron]

Here is a cartoon where Q8 is ( I mean was ) located on the schematic...

 

[Alektron]

Monsieur 73's de Edd

By looking at the above schematic and contemplating for a while on your decision on removing transistor Q8, was it that you wanted to see if POiNT A (22uF100V capacitor) and POINT L (22uF 100V capacitor) were bad?

I'm just thinking out loud...

 

[Alektron]

73's de Edd >>> " I need Q8 transistor removed from the board, using that same 3 solder ball technique and rapidly walking the soldering iron tiplet between the 3 balls until Q8 leads reach solder release time. "

Q8 transistor is gone, far far far away... from circuit board Kingdom...

73's de Edd >>> "Then the unit needs DC voltage monitoring of a connected CN107 to its mate at the pins 12 and 13, powering up for ONLY the time that is required for a voltage to show up on the meter . . . then power down. "

Alright, here are the readings as per your request. NOTE! I included NEW and OLD readings.

NEW with transistor Q8 removed ...

OLD with Q8 transistor still in place ...

(just for comparison)

 

[Alektron]

Going back to Diode # 23, which is an MA738 diode, or more precisely a Schottky Barrier Diode MA2Q738 (aka) (MA738) by Panasonic. A Silicon Epitaxial Planar type for high frequency rectification. You can read more here, if you'd like:
http://html.alldatasheet.com/html-pdf/101991/PANASONIC/MA738/484/1/MA738.html

After my readings on Diode #23 in Diode Testing Mode on DMM, ( forward and reverse ) I got a 20 mV reading. Could this be in parallel with something else? or I do have to remove it in order to test it properly?

 

[Bluejets]

Usually a good idea to add solder prior to cleaning out the holes also.

 

[Alektron]

" Usually a good idea to add solder prior to cleaning out the holes also. "

I'll do that, I'm learning a very important lesson, that I didn't know before.

Thank you for everyone's input.