This is a follow up to my recent post about the redesigned Beogram Commander remote control board, which now works in both (DC-motor) Beogr...
Saturday, February 21, 2015
Beomaster 8000: Display Repair (IV) - Display Back in Business
After another 24h test of the assembled displays I put them back on PCB#9 of the Beomaster 8000. Before soldering the displays back in, I also exchanged 9R14 and 9R16 with 3.3k and 1.5k resistors:
This reduces the display voltage and allows to reduce the intensity of the SMD LEDs to the original brightness level with R15. One needs to be careful when adjusting trimmer R15, it should not drop the keyboard strobe below 3.2V. Otherwise the keyboard will start getting erratic. More detail about this procedure is posted here.
After the displays were back in and tested o.k. I started remedying the mess Mr. Amateur created with the current limiting resistors and adjacent jumpers. No idea why he needed to mess with these jumpers, too...but he did a great job destroying the solder pads. I soldered bridging jumpers in that bypass the disaster area altogether. I was able to salvage the pads of two jumpers and replaced the jumpers with new wire.
Here are some pictures before:
Much prettier now, I'd say...;-). After this surgery, the displays all showed the same intensity again. All good now in display land. While I listened a bit to the radio, I realized that one of the speaker switches is intermittent on the right channel...so these need to be replaced, too. This is a standard restoration task, it seems they are often corroded.