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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Repairing a K2000R synthesizer: battery backed memory
Hello all!
I am repairing my K2000R synthesizer. When I turn the unit on, it states it is initializing battery backed memory. But the batteries are fine. Still, I do get a low voltage indication at times. At first this was an intermittent problem. Now it is a consistent headache. I replaced the diode pair that permits the battery to power the memory chip when the power is off. There is also a transistor that I changed which a part of this circuit. It brings the +5V power line up when unit is switched on and cuts off power from the battery. There is a capacitor that permits changing the battery without losing what is in memory. Also there are the memory chips, the battery sensing chip, and the battery pack of three AA 1.5V batteries. Oh yes, there is the cable that attaches the battery pack to the board. I removed the battery pack container and measured the voltage across the external terminals with NEW batteries installed. Even though each battery measured 1.5V separately, I measured 3.7V across the terminals with the three AA batteries inserted. This slowly dropped to 3.3V. Interesting. Particularly when the battery pack is not connected to the board! I then plug in the battery pack into the board and after the battery reading stabilizes (the capacitor is charged), the voltage reads under 2V. I unplug it, and the battery voltage jumps to 4V. I think there is a connection problem here. Otherwise this is not making any sense to me. Any ideas? I am teaching myself how to repair this problem. I appreciate any help! Thank you! Bob Graham |
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Robert Graham Jr. wrote: Hello all! I am repairing my K2000R synthesizer. When I turn the unit on, it states it is initializing battery backed memory. But the batteries are fine. Still, I do get a low voltage indication at times. At first this was an intermittent problem. Now it is a consistent headache. I replaced the diode pair that permits the battery to power the memory chip when the power is off. There is also a transistor that I changed which a part of this circuit. It brings the +5V power line up when unit is switched on and cuts off power from the battery. There is a capacitor that permits changing the battery without losing what is in memory. Also there are the memory chips, the battery sensing chip, and the battery pack of three AA 1.5V batteries. Oh yes, there is the cable that attaches the battery pack to the board. I removed the battery pack container and measured the voltage across the external terminals with NEW batteries installed. Even though each battery measured 1.5V separately, I measured 3.7V across the terminals with the three AA batteries inserted. This slowly dropped to 3.3V. Interesting. Particularly when the battery pack is not connected to the board! I then plug in the battery pack into the board and after the battery reading stabilizes (the capacitor is charged), the voltage reads under 2V. I unplug it, and the battery voltage jumps to 4V. I think there is a connection problem here. Otherwise this is not making any sense to me. Any ideas? I am teaching myself how to repair this problem. I appreciate any help! Thank you! Bob Graham Obviously, something is drawing more current than the batteries can deliver. I would be looking for a shorted or leaky cap somewhere. Do you have a schematic? Your going to have to load shed to find out where the high draw section is somehow. Bob ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
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Hello!
I found out that the problem was a corroded terminal inside the battery pack. Thanks for replying to my problem. Bob Graham "Bob Urz" wrote in message ... Robert Graham Jr. wrote: Hello all! I am repairing my K2000R synthesizer. When I turn the unit on, it states it is initializing battery backed memory. But the batteries are fine. Still, I do get a low voltage indication at times. At first this was an intermittent problem. Now it is a consistent headache. I replaced the diode pair that permits the battery to power the memory chip when the power is off. There is also a transistor that I changed which a part of this circuit. It brings the +5V power line up when unit is switched on and cuts off power from the battery. There is a capacitor that permits changing the battery without losing what is in memory. Also there are the memory chips, the battery sensing chip, and the battery pack of three AA 1.5V batteries. Oh yes, there is the cable that attaches the battery pack to the board. I removed the battery pack container and measured the voltage across the external terminals with NEW batteries installed. Even though each battery measured 1.5V separately, I measured 3.7V across the terminals with the three AA batteries inserted. This slowly dropped to 3.3V. Interesting. Particularly when the battery pack is not connected to the board! I then plug in the battery pack into the board and after the battery reading stabilizes (the capacitor is charged), the voltage reads under 2V. I unplug it, and the battery voltage jumps to 4V. I think there is a connection problem here. Otherwise this is not making any sense to me. Any ideas? I am teaching myself how to repair this problem. I appreciate any help! Thank you! Bob Graham Obviously, something is drawing more current than the batteries can deliver. I would be looking for a shorted or leaky cap somewhere. Do you have a schematic? Your going to have to load shed to find out where the high draw section is somehow. Bob ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
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