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NLG Users Repair Logs and Other Ramblings. Request your very own topic. Just ask any site staff. => Channelmaniac's Arcadecomponents' Old School Repair Logs => Topic started by: channelmaniac on March 11, 2021, 11:00:09 PM
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Model: CMS-401 (Roland 401 MIDI Clone)
TIP: Pinout for DB25 port
I could not find any information on this card or the expansion unit that connects to it. It has the same Roland chips on it so here's a reverse engineered pinout from the Roland MPU 401 technical manual's schematic and pinouts and my multimeter.
Pin 1: MIDI OUT Pin 5
Pin 2: MIDI OUT Pin 4
Pin 3: MIDI IN Pin 5
Pin 4: MIDI IN Pin 4
Pin 5: RESET
Pin 6: FSK OUT - to TAPE OUT circuit
Pin 7: FSK IN - to TAPE IN circuit
Pin 8: SYC IN
Pin 9: P21 (SYC IN on U8)
Pin 10: P20 (SYC OUT on U8)
Pin 11: SYC OUT
Pin 12: Metronome Out
Pin 13: NC
Pin 14: Gnd
Pin 15: Gnd
Pin 16: Gnd
Pin 17: Gnd
Pin 18: Gnd
Pin 19: +5v
Pin 20: +5v
Pin 21: +5v
Pin 22: NC
Pin 23: NC
Pin 24: NC
Pin 25: NC
On the MPU401 SYC IN on U1 is connected to P21 on U8 and SYC OUT on U1 is connected to P20 on U8. I'm thinking those 2 just loop together on the DB25 port.
The MIDI ports will connect straight to DIN 5 jacks. The Tape In / Out and Metronome signals will need circuitry connected.
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Model: Alesis MIDIVerb II
Symptom: Dead
AC adapter was open on the 110v side. Replaced AC adapter and unit powered up but had the overload and level LEDs stuck on. Opened the unit and found 4 very hot capacitors. Replaced 1 shorted diode and 4 capacitors. Went ahead and replaced four more diodes in the same circuit area and another 4 capacitors for good measure. Tested.
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Model: Proteus/1 plus Orchestral
Symptom: No audio out. Fails self test with ROM errors.
Ran self tests and it fails with random ROM errors.
Board had attempted repairs done to it and the PCB was charred in a spot where too much hot air was used to remove the main controller IC.
Checked the voltage regulators for the audio amplifier chips and DACs to find that the +12v input to the 7805 was missing. Repaired a broken ribbon cable from the power supply to where it soldered into the main PCB. Audio worked but sounds were distorted. Cleaned and reflowed the main controller IC. That fixed the audio distortion and the ROM errors during self test but instruments were mixed up. Reloaded the factory SYSEX file and tested.
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Model: 360 Systems Professional Midi Bass
Symptom: Hums. Nothing on display
Replaced a shorted 3300uf @ 10v electrolytic capacitor and 2 stressed 1N4002 diodes. Tested.
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Model: Yamaha Motif-Rack
Symptom: No display, locks up, muddy and muffled sounding
Replaced 54 SMT caps and 4 thru-hole caps, reset unit to factory, and tested. Display works, muddy bass was gone, muffled highs were crisp, and lockup issues resolved. Ran unit overnight with zero issues.
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Model: Fender Squire SP-10
Symptom: Buzzing sound
Replaced 2 2200uf power filter caps. Replaced input jack and torn speaker. Tested
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Model: Fender Squire SP-10
Symptom: No input
Replaced bad input jack and torn speaker. Tested.