A coworker came in last week with a little mini amplifier (a Fender Mini Tonermaster®) that had stopped working. Being the curious sort, I opened it up, and looked at the main board. I immediately saw that D1 was physically blown (top half had blown off, and was rattling around inside the case). I figured this was probably the only issue, and brought it home to replace that diode (a simple 1N4003). After replacing it, however, the amp still didn’t work… which is why it’s nice I had it at home since I have the gear needed to diagnose the problem there. =)
Recent Repairs/Refurbishes
Thought I would throw this into a general email since neither of these require their own write-up.
I recently purchased another Racal-Dana 1992 off eBay as non-working for $60. Having one of these already, I knew not a whole lot could be wrong, and it was most likely the primary oscillator having come loose from the main board (the CPU in the Racal-Dana uses the Counter reference Oscillator for it’s own crystal). Anyway, on receiving it, I saw that indeed, it didn’t work. Opening it up, the oscillator was firmly seated, and I could see the 10Mhz out at the standard output BNC. Looking around the unit, I saw that the IC for the display (in a socket at the back of the display/button board) was unseated slightly. I pushed it back in, and powered up the unit, and it worked! Easiest fix ever. On to eBay it goes!
The second item was a real find. I routinely visit a local computer “thrift” shop for random bits and bobs, and there laying on the bottom of a shelf was an HP 6624a (http://www.home.agilent.com/en/pd-836785-pn-6624A/system-power-supply-40w-4-outputs). Obviously marked HP, so it’s older, but it was only $10! All it had on it was a sticker saying “turned on, display showed information”. Clearly, whomever priced this must have thought it was a UPS, or old Server, or something, because even cheap ones on eBay go for several hundred dollars. Getting the unit home, I powered it up and spot checked the outputs, and they all work great! It’s not the greatest precision power supply I’ve ever seen, but it is 4 sensing outputs, and according to the manual can sink as much current as it generates, so the uses would be pretty high. That said, I don’t need anything this big, nor could I find a place to put it. So, on eBay it goes. I hope to get enough to just buy a Rigol Bench PSU (DP832) that is mV and mA accurate. =)
Update: Sale of the Racal-Dana took 2 days, and was enough to purchase a programmable load (to help test the HP 6624a), and a GPIB to USB adapter (also be good for testing it, as well as normal lab use). So, hooray!
Genie Garage Door remote upgrade
Just a short post: When we bought our house, it came with a 1992 or so, vintage Genie Garage Door opener that used the old dip switch style remote code. I recently found a GIRUD-1T conversion kit at the local Goodwill for $5, and figured I’d convert it, but in the process you want to remove the old controller, or at least clip the antenna.
When I opened the unit, I saw the remote board was only held in by one screw, and had a simple 3 wire header wire hooked to it (more on this in in a moment). Upon opening up the “box” that the GIRUD came in, I noticed the board was the same size, but had screw terminals on it… but it also had the PCB holes for a header. Genie are pragmatic! The conversion kit was literally just the exact same controller that they’d put in an opener, in an enclosure! I took both units, removed the screw terminals from the new on, and move the header over. The only caveat is that the 3 pin connector will go on upside down from the previous board (ground toward the top, vs ground toward the bottom).
After that, it was just screw the new board in, and hook it up. Worked great (new board actually has a relay that audibly clicks when it gets a good remote signal). If curious, the GIRUD board is packaged with a 24VAC adapter that is for power. But, if you look at the board, they’ve just implemented a half-wave rectifier (capacitor and diode) to give DC to the board. Giving it 24VDC is no problem, then.
Of interest to those that are curious, the pin header has a Vcc (Purple), GND (Green), and Trip (Black) connections. When the remote control receiver gets a good signal, and wants to open the door, it grounds the Trip wire, which then tells the controller to open the door. Otherwise, that pin just floats.
Pretty simple project, and avoids the extra wiring and ugly box on the ceiling. Now, I think I’m going to see if I can create some type of code scanner with the old remote and receiver to see JUST how insecure those old openers are. =)