rabbitgeeks
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Posts
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I fixed my PC3K8 today.😁 I got quite some help from here; I think maybe my experience can help others too. I decide to post how I did it. As I previously updated, I hired an electrician but got nothing useful, except the EPROM thing. After that, as I had no other means to fix it, I decided to check the power supply rail myself. After some measuring here and there, I got my attention on this J301 connector, whose function is to supply power to primary board of PC3K8. Service manual says pin2 should has 5v dc, I only got 4.91v, a 18% off. Last time electrician guy said this amount of difference is ok. But as desperate as I was, I decided to do some experiment. I used a PC standard power supply unit to replace the J301 connector. With some flex wires, I connected Pin1,2,3,4, and 5 to an ATX terminal of PC PSU. Surprisingly, it worked! For the first time in years, my PC3K8 booted up and worked! After some thinking and experiments, I found out that the problem is not actually the insufficient voltage of pin2, electrician guy was right about it. The real problem is pin6, the MUTE pin. As ATX terminal on PC PSU got no MUTE, BRITE, PWRUPRST pins, I left pin6, pin7 and pin8 open without any connection, accidentally solved the problem. Finally, I plugged J301 connector to primary board after removing pin6(MUTE pin), old PC3K8 bootup like a charm. Evern stranger is that after I test a while, I re-connected pin6 of J301, but PC3K8 still worked. Like temporally removing of pin6 "cured" it or something.... So the real cause of my problem is not yet found, but anyway, I got nothing to regret as PC3K8 definitely works now😀. Thanks to you guys giving me all the ideas😸
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Today I hired an electrician to check out my keyboard. He exempts the power supply as the problem, power rail seems well enough(guy even checked if my house power supply is properly grounded). Every voltage reading he got seems to approximate idea values marked on the service manual. At last, he got his suspicion on this EPROM. The service manual says "The PC3x uses a 32 pin EPROM located at U4 to store the boot up information for the CPU." He removed this EPROM and power up to see what will happen. Nothing happened, the symptoms seem identical to the state with EPROM attached. The problem is that I have no way to get a spare EPROM for replacing, so we can't certain if this EPROM is the cause. 😓
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Thank you Jim, I'm gonna do as you say☺️
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Thank you Jose, I can't eye-pick any burnt or swell capacitor, I think It's time to get my multimeter some flexing. I live in a small city located in heartland of China. In China, Kurzweil products are distributed by a subsidiary of Kurzweil's parent company Young Chang. This company's official site is still online, but phone and email are already dead now. Damn Xi Jinping is driving every foreign companies away.
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Thanks your reply YashN. I saw this video, but I don't have a spare display for replacing, and currently I think the problem is most likely on the power supply. I think I will try the display replacing as the last resort, thanks.
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From my previous experiences, most of times, problem like this is nothing more than a loosen connector/dirty pin or something alike. So I wanna open it to see myself first.😁 Thanks ProfD, I'll definitely play the hell out of it!
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You are right JFN, I just wanna to know what happened inside and to try to fix it myself first. Love you profile photo by the way😺
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Yeah, I think my only chance is to fix it myself with help, if failed, seek for a lock general electronics-technician.
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There is no company officially dealing Kurzweil right now in my country... I checked local forums, like everybody complains there is no way to fix Kurzweil and it's broke so frequently😬
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I checked the battery as you pointed out, it indeed depleted. I exchanged it with a new one, but nothing changed. Next step I would try the power supply units. Thanks Jose😄
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I bought my PC3k8 back 2013. For some reason, I stopped using it from 2016 until today. Today I powered it, turned it on, I got what described on title. As my living city has no Kurzweil service facility, I tried to fix it myself. After remove the case, I found out this yellow chip under the display circuit board, which seems has some legs broke off. However, I can't be sure if this is the problem, because I never powered my PC3k8 since 2016 and that chip doesn't look like burnt. I also made sure all the ribbons and connectors are properly connected, still nothing works. Any idea will be sincerely appreciated.😀 Sorry for my cumbersome English.
