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1000PX - not booting

Dennis Spanogle (Mr. Kurlewin K1000.net) All Messages By This Member #44 All good suggestions. As previously mentioned too much load could be bad caps on mother board or other load not on Power Supply. If you have not done so, I would check the traces and solder joints on the Power Supply.? If corroded, the normal load will pull down the voltage.? Sometimes the solder joints corrosion is really hard to see - re-solder if in doubt.?? The relay is closed by the processor after the boot, so if it does not boot, the relay will probably not close.? toggle quoted message Show quoted text ------ Original Message ------ From: "Frank D via groups.io" <rhythm4_4@...> To: [email protected] Sent: 1/25/2021 9:47:06 PM Subject: Re: [K1000-K1200] 1000PX - not booting OK, I went back in... The 4.3vdc readings at the power supply are present when the PS is connected to the motherboard. If I pull the Molex connector from J4, 5vdc is present at the same pins. Seems that the power supply works correctly when not connected. Looking at the PS schematic from k1000.net, I can not see any reference to pins 9 and 10. The rest of it is a bit hard to read. I also found a small AC voltage present at pin 9.? 4.3 v is reaching the CPU at pin 14. Here's what I have at the connector: Pin# - VDC disconnected - VDC connected 1.???????? gnd???????????? gnd 2.???????? gnd???????????? gnd 3.???????? +5 ???????????? +4.3 4.???????? +12 ??????????? +12 5.???????? -12 ??????????? -12 6.???????? -0.5 ??????????? 0 7.???????? +5 ???????????? +5? (backup) 8.???????? +5 ???????????? +4.3 9.???????? +1.9 (2.2vac)?? +1.2 (1.5vac) 10.??????? +5 ???????????? +4.3 If anyone can interpret this or give any suggestions, I would truly appreciate it. Many thanks! P.S. I'm also curious about the relay which Nicole mentioned. Seems like its function is to prevent a pop on the outputs during power-up. In any case, I do not hear it click. Is that a clue?? ;-) -- peace, Frank Dickinson 90 East Productions
mjkirk12 All Messages By This Member #43 The +5V supplies that you measure at +4.3V when connected is a problem.? K1000 won't likely boot. Digital logic of this era needs at least +4.75 V to operate properly. Some component is dropping this voltage under load - either on power supply itself or on main board. But not enough to blow a fuse from excessive current (short circuit) This low voltage would prevent boot.? I would closely inspect the power supply capacitors on +5V. Some ideas: 1)??If you have a bench power supply with +5,?output (sufficient current > 3 amps? ), you could substitute for the K1000 supply +5V. Must make sure to tie supply grounds together.? 2) Use a triple bench supply (+5, +12 and -12V)? or maybe an old PC power supply with these output voltages? 3) Test the? K1000 power supply with a?resistive load (power resistor 10 ohms -> 500mA current, 2.5 Watts) on the +5V supply to see if voltage drops to 4.3V If voltage drops, then power supply is problem (capacitors are first to check). The relay is as you describe- protects from output 'pop' on power up until K1000 is fully booted. Good luck.
Frank D All Messages By This Member #42 OK, I went back in... The 4.3vdc readings at the power supply are present when the PS is connected to the motherboard. If I pull the Molex connector from J4, 5vdc is present at the same pins. Seems that the power supply works correctly when not connected. Looking at the PS schematic from k1000.net, I can not see any reference to pins 9 and 10. The rest of it is a bit hard to read. I also found a small AC voltage present at pin 9.? 4.3 v is reaching the CPU at pin 14. Here's what I have at the connector: Pin# - VDC disconnected - VDC connected 1.???????? gnd???????????? gnd 2.???????? gnd???????????? gnd 3.???????? +5 ???????????? +4.3 4.???????? +12 ??????????? +12 5.???????? -12 ??????????? -12 6.???????? -0.5 ??????????? 0 7.???????? +5 ???????????? +5? (backup) 8.???????? +5 ???????????? +4.3 9.???????? +1.9 (2.2vac)?? +1.2 (1.5vac) 10.??????? +5 ???????????? +4.3 If anyone can interpret this or give any suggestions, I would truly appreciate it. Many thanks! P.S. I'm also curious about the relay which Nicole mentioned. Seems like its function is to prevent a pop on the outputs during power-up. In any case, I do not hear it click. Is that a clue?? ;-) -- peace, Frank Dickinson 90 East Productions
Frank D All Messages By This Member #41 Thanks so much for the tips! Will get back into it tomorrow. I no longer have a 'scope, but can perform the other tests. -- peace, Frank Dickinson 90 East Productions
mjkirk12 All Messages By This Member #40 Scanning the schematics, the DC supply voltages are:? +12V,? -12V,? +5V and +5V backup (present with power off) I don't see a 4.3V supply that you measured - unless this is the +5V backup voltage (low battery ?) If 4.3V is the +12V supply, then you may focus on that part of the power supply (regulator, capacitors, etc) Also, see that the RESET signal is low for normal operation.? It will go high briefly at power up. At the CPU, it is inverted as RESET* - should be active high in normal operation. POWER_OK* should be low? (0V) in normal operation. if you have a oscilloscope or logic probe, check clock input,? address and data pins on the CPU - are they active? If yes, then the CPU is attempting to run code - which is a good sign.
Dennis Spanogle (Mr. Kurlewin K1000.net) All Messages By This Member #39 Check every electrolytic capacitor with a magnifying glass.? These units are very old and some of the caps go bad and, if so, they usually leak.? The leak corrodes the traces and or contacts under or around the cap.? Repair is sometimes possible. Good luck Dennis toggle quoted message Show quoted text ------ Original Message ------ From: "Joey Mastrili via groups.io" <jmastrili@...> To: [email protected] Sent: 1/20/2021 6:16:12 AM Subject: Re: [K1000-K1200] 1000PX - not booting I have a K1000 with exactly the same symptoms as your 1000PX. ? I?did everything that?you mentioned (following the tips in K1000.net)?and still got?solid blocks on the display. ? I replaced the OS chips and the synth was?able to do?some (but?not all) of?the diagnostics functions,?but it still does not?boot. Joey On Wednesday, January 20, 2021, 7:01 PM, Nicole Massey <nyyki@...> wrote: Sounds like the relay. Give it a decent (but not excessive pop) on its cover and see what happens. The tap will work for a while, but if this is it and you still have it open it's good to replace it. See K1000.net for suggested part replacement. Sent from my HAL 9000 in transit to Jupiter -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Frank D via groups.io Sent: Wednesday, January 20, 2021 12:27 AM To: [email protected] Subject: [K1000-K1200] 1000PX - not booting Belated Happy New Year! Finally spent a bit of time on my non-functioning 1000PX. Here's where I am so far... The unit comes on, but does not boot. All I see is black blocks on the upper row of display. Tried hard reset and test mode. Nada... Checked solder joints on bottom of power supply board where transformer connects. All looks good (I remember fixing these a while ago). Backup battery had been replaced at that time also. Showed a solid 3v on meter. Re-flowed the solder, all is tight, no cracks, voltages are present. Power transformer secondaries give me 16-32 and 7-14 volts. Power supply is working. DC voltages to motherboard are + and -12v, 4.3v and 5v. Seems like pretty standard values. Went through and exercised any socketed ICs in their sockets. I don't have a chip puller, so didn't pull them all the way out to clean pins. No change, so I put it back together... Looking for any info or suggestions from the group. Many thanks! -- peace, Frank Dickinson 90 East Productions Our "lockdown" videos <>
Frank D All Messages By This Member #38 Thanks, Nicole! Will give it a try and report back... -- peace, Frank Dickinson 90 East Productions
Joey Mastrili All Messages By This Member #37 I have a K1000 with exactly the same symptoms as your 1000PX. ? I?did everything that?you mentioned (following the tips in K1000.net)?and still got?solid blocks on the display. ? I replaced the OS chips and the synth was?able to do?some (but?not all) of?the diagnostics functions,?but it still does not?boot. Joey toggle quoted message Show quoted text On Wednesday, January 20, 2021, 7:01 PM, Nicole Massey <nyyki@...> wrote: Sounds like the relay. Give it a decent (but not excessive pop) on its cover and see what happens. The tap will work for a while, but if this is it and you still have it open it's good to replace it. See K1000.net for suggested part replacement. Sent from my HAL 9000 in transit to Jupiter -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Frank D via groups.io Sent: Wednesday, January 20, 2021 12:27 AM To: [email protected] Subject: [K1000-K1200] 1000PX - not booting Belated Happy New Year! Finally spent a bit of time on my non-functioning 1000PX. Here's where I am so far... The unit comes on, but does not boot. All I see is black blocks on the upper row of display. Tried hard reset and test mode. Nada... Checked solder joints on bottom of power supply board where transformer connects. All looks good (I remember fixing these a while ago). Backup battery had been replaced at that time also. Showed a solid 3v on meter. Re-flowed the solder, all is tight, no cracks, voltages are present. Power transformer secondaries give me 16-32 and 7-14 volts. Power supply is working. DC voltages to motherboard are + and -12v, 4.3v and 5v. Seems like pretty standard values. Went through and exercised any socketed ICs in their sockets. I don't have a chip puller, so didn't pull them all the way out to clean pins. No change, so I put it back together... Looking for any info or suggestions from the group. Many thanks! -- peace, Frank Dickinson 90 East Productions Our "lockdown" videos <>
Nicole Massey All Messages By This Member #36 Sounds like the relay. Give it a decent (but not excessive pop) on its cover and see what happens. The tap will work for a while, but if this is it and you still have it open it's good to replace it. See K1000.net for suggested part replacement. Sent from my HAL 9000 in transit to Jupiter toggle quoted message Show quoted text -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Frank D via groups.io Sent: Wednesday, January 20, 2021 12:27 AM To: [email protected] Subject: [K1000-K1200] 1000PX - not booting Belated Happy New Year! Finally spent a bit of time on my non-functioning 1000PX. Here's where I am so far... The unit comes on, but does not boot. All I see is black blocks on the upper row of display. Tried hard reset and test mode. Nada... Checked solder joints on bottom of power supply board where transformer connects. All looks good (I remember fixing these a while ago). Backup battery had been replaced at that time also. Showed a solid 3v on meter. Re-flowed the solder, all is tight, no cracks, voltages are present. Power transformer secondaries give me 16-32 and 7-14 volts. Power supply is working. DC voltages to motherboard are + and -12v, 4.3v and 5v. Seems like pretty standard values. Went through and exercised any socketed ICs in their sockets. I don't have a chip puller, so didn't pull them all the way out to clean pins. No change, so I put it back together... Looking for any info or suggestions from the group. Many thanks! -- peace, Frank Dickinson 90 East Productions Our "lockdown" videos <>
Frank D All Messages By This Member #35 Belated Happy New Year! Finally spent a bit of time on my non-functioning 1000PX. Here's where I am so far... The unit comes on, but does not boot. All I see is black blocks on the upper row of display. Tried hard reset and test mode. Nada... Checked solder joints on bottom of power supply board where transformer connects. All looks good (I remember fixing these a while ago). Backup battery had been replaced at that time also. Showed a solid 3v on meter. Re-flowed the solder, all is tight, no cracks, voltages are present. Power transformer secondaries give me 16-32 and 7-14 volts. Power supply is working. DC voltages to motherboard are + and -12v, 4.3v and 5v. Seems like pretty standard values. Went through and exercised any socketed ICs in their sockets. I don't have a chip puller, so didn't pull them all the way out to clean pins. No change, so I put it back together... Looking for any info or suggestions from the group. Many thanks! -- peace, Frank Dickinson 90 East Productions

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