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Dead Yamaha QY20 - can someone help?

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Hello there,

 

my Yamaha QY20 is dead. There is no display action, nothing - except: When it is connected to my stereo amplifier, you can hear a "bump" sound when it is switched on.

 

I started checking some voltages, but I do not have much knowledge with electronics. What I can tell is that the 5 volt regulator is working good. But there are some voltage problems, I think.

Can someone say where the problem might be, depending on the following voltages I measured? I am specially in doubt regarding the voltages on the 74HC14, Max680CSA and 2SB1416:

 

Input Voltage: 12 V

 

SRAM 64K

IC 8 Pin 28: 4,96 V

 

SRAM 1M

IC 4 Pin 32: 4,95 V

 

Yamaha ROM

IC 9 Pin 44: 0,40 V

Pin 23: 4,95 V

 

74HC14

IC 13 Pin 14: 4,96 V

Pin 8: 4,96 V

Pin 1: 4,96 v

 

M62021

IC 1 Pin 3: 4,96 V

 

Max680CSA

IC 12 Pin 8: 1,82 V

Pin 4: 0,25 V

Pin 6: 1,02 V

 

2SB1416:

Pin 1 (Emitter): 11,3 V

Pin 2 (Collector): 0,0 V

Pin 3 (Base): 11,3 V

 

Best regards,

 

Chris

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Regarding the Max680CSA, it generates +-10Volts from a 5V source.

 

What is the voltage between pins 5 (gnd) and 6 (vcc) this should be 5VDC

 

Then measure the voltage between 5 (gnd) and 4 (v-) this should be -10 VDC

 

Then measure the voltage between 5 (gnd) and 8 (v+) this should be +10VDC

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Regarding the PNP transistor 2SB1416, the readings just mean that the transistor was not being asked to conduct at the moment you tested it and does not in itself indicate a fault with that component.

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Regarding the 74HC14 Hex inverting schmitt trigger, across pins 7 (gnd) and 14 (vcc) should be max +7VDC.

 

Depending on how fast the device is working you may not see meaningfull reading on the other pins, it takes a signal in on one pin and drives an output the opposite i.e. if pin 1 is at 5V then pin 2 will be at 0v, if pin 1 is at 0v then pin 2 will be at 5V, there are six of these inverters on the chip and the pins of each pair are 1>2 3>4 5>6 9>8 11>10 and 13>12

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The Max680CSA does not seem to get the supply voltage. I measured between pin 5 (GND) and ...

... pin 4: 0,38 V

... pin 6: 0,60 V

... pin 8; 2,89 V

 

Very strange is that the voltages seem to increase slowly, I also measured decreasing voltages and then increasing again.

 

The 74HC14 shows 4,96 V between pin 7 (GND) and pin 14.

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Probably something on the motherboard went out....it'd probably be cheaper to buy a used one on Ebay.....I bet those don't cost much used.....

 

There's one on Ebay now for a little under $200 including shipping....you might not find one for less than that.....

 

http://www.ebay.com/itm/SEQUENCER-YA...item338d471f1f

 

When I have a motherboard go out in a computer, I salvage what parts I can and get another used computer but I'm not any good at working on electronics....building a computer from parts is not like repairing parts on a circuit board.....I am not very good at soldering.....replacing a motherboard on a computer I could do as it attaches with screws and everything plugs into it, but it's more work than I like to take on (you have to remove about everything and keep good track of where all the cables plug in and where all the screws go).....besides, I like an excuse to buy a used computer....I have fun doing that....

Edited by RockPianoman

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Just reread that you have 5v on chips 4 and 8, this is the same voltage which should be on pin 6 of ic12, it's looking like a track break or bad connection somewhere, no voltage on ic12 means the display will be blank.

Edited by shambler

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It is not only a track break as the device does not produce any audio when pressing the keys. I now spent several (too many) hours on checking and I think I have to accept this device is really dead. I will buy a working one as suggested by RockPianoman.

 

Thanks for your help, everyone!

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You may have lost the vcc voltage to other chips too because of the break. Good luck with your hunt for another QY...btw what are they like?

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Well, I like the Yamaha QY10 and QY20 because of their small size and the possibility to carry them with me. When it comes to sound qualtity there are devices with much better sounds nowadays, but I think the old devices do have a very good sound, somehow special. You can also use the QY sequencers in combination with a MIDI keyboard to have a small and easy setup. Although it looks quite funny to have the small QY20/QY10 connected to my MG124CX mixer ...

 

You may search for some videos to have an idea about the QY10 and QY20. Great small machines!

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There's a Y70 buy it now being sold for $119 here. http://www.ebay.com/sch/i.html?_sacat=See-All-Categories&_from=R40&_nkw=YAMAHA+QY20+MUSIC+SEQUENCER&_sop=7

 

Just check it every day and you'll likely find the same unit you have for half that much. Save your old one for spare parts. Units like this are disposable, and never designed to be

repaired. During a warrantee period, the manufacturer just swap the whole board out. They don't even have use qualified techs to do that.

 

You could buy several used ones for the cost of paying a tech to repair one, that is if he can even get the parts for it.

 

Most techs charge $125 diagnostic charges for the first hour minimum. Then they will mark the parts cost up at least 300% add in shipping costs, then add an additional hours time for the repair, so you're looking at $350 minimum for repairing something you can pay $50 used.

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I already bought the QY20 which was recommended in this thread - received it and was really disappointed. The seller stated "100% working". The reality is: no sound on the line jack and I can only hear sound on the headphone jack when I do not plug completely and but leave out the connector approx. 3 to 4 mm. I am in the process for a partial refund for this device. Really frustrating.

 

So, I went back to my dead QY20. Bought the correct battery and soldered it in, removed the Max680 chip and some of the capacitors related to it. Bought the Murata 0509 chip soldered it in, just for fun, without any hope. See pictures for the result.

Edited by Ovations

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Either I am not allowed to add photos because I am too new here or I do not understand how to do it. Anyway, my dead QY20 is back to life and working perfectly. Not I can think about the problem with the one I bought on ebay ......

Edited by Ovations

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Either I am not allowed to add photos because I am too new here or I do not understand how to do it. Anyway' date=' my dead QY20 is back to life and working perfectly. Not I can think about the problem with the one I bought on ebay ......[/quote']

 

Use a hosting site like Photobucket.Simply paste the provided IMG code.

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Here is the picture of the QY20 with the Murata 0509 chip. Two cables from the voltage regulator (24M05) to supply the 5 volts to the Murata chip, one cable to ground (I used the metal case of the power switch after checking that it really is ground) and one cable from the Murata -9 volts to the contrast potentiometer.

 

In case someone requires more details, please do not hesitate to ask :-)

 

And thank you, 1001gear, for the hint with the hosting site. I am not too familiar with forums.

 

QY20_Murata1.jpg

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You should have opened a claim on Ebay.....if you open a claim for a valid reason within 45 days from the date you bought it, Ebay covers you 100 %.....no risk....

 

I had to open a claim the other day because of poor packing....I bought 100 DVD's and they broke open during shipping....

Edited by RockPianoman

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On 5/19/2014 at 3:21 PM, Ovations said:

Here is the picture of the QY20 with the Murata 0509 chip. Two cables from the voltage regulator (24M05) to supply the 5 volts to the Murata chip, one cable to ground (I used the metal case of the power switch after checking that it really is ground) and one cable from the Murata -9 volts to the contrast potentiometer.

 

In case someone requires more details, please do not hesitate to ask 🙂

 

And thank you, 1001gear, for the hint with the hosting site. I am not too familiar with forums.

 

QY20_Murata1.jpg

Hi, can you provide exact details on the murata and the connections you did, I have the same problem. I understand that you removed the max680and the 4 capacitors, but the exact connections are unclear for me as I'm not versed on electronics... thank you in advance.

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On 5/19/2014 at 3:21 PM, Ovations said:

Here is the picture of the QY20 with the Murata 0509 chip. Two cables from the voltage regulator (24M05) to supply the 5 volts to the Murata chip, one cable to ground (I used the metal case of the power switch after checking that it really is ground) and one cable from the Murata -9 volts to the contrast potentiometer.

 

In case someone requires more details, please do not hesitate to ask 🙂

 

And thank you, 1001gear, for the hint with the hosting site. I am not too familiar with forums.

 

QY20_Murata1.jpg

Hi, After sometime I was going to use my QY20 and it happens the same than you.. so I would like to have more detailed info on the Murata and the connections you did, as I'm not versed in electronics, so it's something that I have to be careful.. do you have detailed photos, maybe you can send me information directly, I don't know if it's allowed.. just asking. Thank you.  Josep

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