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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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It is currently 20 Nov 2019, 05:34

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PostPosted: 07 Nov 2019, 14:07 

Joined: 05 Nov 2019, 09:33
Posts: 3
Hello to everyone. I am an electronics technician. I own one of these radios, Model 88CD. This is what I have found to be the cause for the erratic display and general command malfunction(s) with my unit. I disassembled the unit and inspected the front control pc. The lithium coin battery at the top right which is used for memory backup was leaking. I removed it and cleaned the pcb and mounted a socket for new battery but did not install one. I packed it up to see what the results were. The unit malfunctioned just as before within a couple of hours. The problem is the upc is glitched. There is corrupted data. This is more than likely due to the corrosion that was on the pcb caused by the battery. The upc is NLA. So, what I did was reset the upc. I have done this several times with other upc's but I had benefit of a schematic and knew what pin was for reset. I would isolate that pin from the print and energize the circuit and shunt that pin. It corrected the malfunctioning ic every time. This would not be possible even with a schematic, as it is an internal surface mount socket. So, I removed the upc, inspected the pins, turned on the unit, and "plugged in" the ic. The radio chirped and has been functioning flawlessly ever since. This procedure may work for you. I found no cold solder joints, no bad electrolytics, just a leaking battery with a voltage of 1.2 volts. I didn't bother to install a new battery in the socket I put in. I can take a few seconds to set the clock and presets if I unplug it or if the utility fails. I hope this procedure works out for some of you. Please note: I cleaned and "deoxed" the upc's pins when I cleaned the pcb. It still failed. So, it was not a matter of simple oxidation on the pins. The correction was a hard reset as described above. Good Luck.

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