A look inside the 2nd generation of a classic Alesis SR-16 drum machine, which was picked up on eBay for repair. It turned out that the machine suffered from a mysterious corrosive substance, which was found under some of the connectors. How did it get there? In the process of giving the machine its second life we had a chance to compare it with the 1st generation one.
This is a professional wireless system by Shure with rack-mount ULXP4 receiver and ULX1 body-pack transmitter. The receiver did not show an active channel and battery status of the transmitter. A look at the RF spectrum showed that the so-called "tone key" signal was not transmitted. The problem was traced to a cracked soldering joint on one of the pins of a board-to-board connector.
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https://www.youtube.com/watch?v=pQmSV-SRLkU
According to the previous owner, this mixer was diagnosed in a local repair shop as having a power supply failure. I was told that the repair estimate was $500, so the mixer ended up being sold for $50 for parts or repair. I could not resist the temptation. The failure was traced to one 100V 3A schottky diode, which is $0.52 on Digikey. Wonderful mixer for a wonderful price!
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https://www.youtube.com/watch?v=zG43qDlPLbE
The calibrator was picked up in a non-working condition. After replacing a couple of electrolytic capacitors it started working and seems to be in spec. According to date codes on some parts it must have been made around 1983.
Fluke 341A repair: https://youtu.be/mxz3-fGs1Lk
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https://www.youtube.com/watch?v=ctypYMlTWyc
The instrument did not have sound through the speakers. The problem was diagnosed to be in the power supply of the amplifier. A step-down converter chip by Linear Technology has failed. The chip was replaced, and the accordion is back in business.
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https://www.youtube.com/watch?v=nHH8tJpLciM
A sheet of paper was added between the spacer and the overlay film, a few more things were tried as well. It seems that a thicker spacer should help, but I don't have the means to make one at the moment.
Previous video: https://youtu.be/Hcl0KuBE0Ts
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https://www.youtube.com/watch?v=weqgmmNwD9I
This receiver did not stay powered on, but clicked and went off and on repeatedly. The problem seemed to be with some sort of a glue, which was supposed to hold large capacitors in place, but it turned brittle and corrosive. So a diode was damaged and a PCB trace was eaten away by this corrosion. After replacing the diode, restoring the trace, and replacing a capacitor (not a bad one, but just in case), the receiver came back to life.
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https://www.youtube.com/watch?v=66uOFia9TSY
In this episode the project was completed. A few extra features were added such as LCD display and current measurement. Everything was fitted into an enclosure. The temperature inside the enclosure was measured after about 30 minutes of charging Nissan Leaf at 16A.
Part 1: https://youtu.be/JVhBMvj4KuA
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https://www.youtube.com/watch?v=to4eYCJ4ZfM
This active speaker did not power up. The problem turned out to be similar to the one we have seen before in the Mackie Thump TH-12A repair video: broken off pins from power diodes in TO-220 packages that are mounted on the back panel (heat sink).
Mackie Thump TH-12A repair: https://youtu.be/5zkEzjyKNjg
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https://www.youtube.com/watch?v=PTy36zRlHOU
Repairing of Agilent 6612C power supply, which was bought on eBay. It was sold "for parts or repair", and was cheap enough so that I couldn't resist.
Agilent 6612C key features:
Output ratings
Voltage: 0 to 20 V
Current: 0 to 2 A
Programming accuracy at 25°C ±5°C
Voltage: 10 m V
Current 0.05% + 1 mA
Ripple and noise (20 Hz to 20 MHz)
Voltage rms: 0.5 mV
Voltage Peak-to-Peak: 3 mV
Normal mode rms: 1 mA
Service manual: http://cp.literature.agilent.com/litweb/pdf/5962-8200.pdf
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https://www.youtube.com/watch?v=HUSMUtIgP3E