It is likely that the display filament power supply circuitry in your Boom has failed. Many units suffer from this after some years. The display itself is also wearing out, but if it goes all dark or starts to fade from the outside edges towards the center, and sometimes recovers after a few minutes of being powered-off, it's the filament supply with 95% chance. A VFD is basically an electron tube, albeit a pretty complex one. In operation, it needs the filament (the six thin wires close to the front side of the display) to emit electrons, so it needs to be heated. This happens at a low voltage and a rather high power. The filament is fed +5 Volts on the left side and between 2 and 3 Volts on the right, creating a voltage drop between 2 and 3 volts. The higher this voltage drop is, the more electrons are emitted (and the brighter the filament wires are glowing). Besides the filament glowing brighter, the display's pixels will also become brighter. In 9 out of 10 cases, the failure is in supply for the the right side of the filament. Instead of keeping a voltage around 2.5V, it ramps up to 5.5V so it's even higher than the left side. This stops electron emission gradually or completely. VFD experts at Noritake (the manufacturer of the displays used in the Squeezebox range) call this "filament starvation". A Boom in operation has some hidden SMD parts behind the display that get red-hot. I am pretty sure that the failure point can be found somewhere in that area, however, it is practically impossible to find suitable replacement components because the SMD markings don't tell exactly enough what each component is for. While I could not find a way to repair the root cause yet, I found a workaround that turned out to work fine for many people who sent me their Boom for a display replacement. The fix is this:
22025 I am using three run-of-the-mill diodes, each of which has a known voltage drop of around 0.7V. Three of them in series make a total voltage drop of about 2.1V. I am using them to pull down the voltage on the filament's right side. Diodes are needed because current must not flow from GND towards the filament pins. GND can be found in each of the screwholes so that is an ideal point to solder (as long as you leave enough room for the screw). The diodes can be packed together closely, shrink-wrapped, and hidden on the backside of the board. This little trick ensures that voltages on the right will never exceed ~3V as 2.1V are always subtracted by the diodes. So even if the gone-crazy Boom circuitry is sending +5.5V in, we will make 3.4 out of it which is in the acceptable boundaries. 2.9 Volts are still fine, actually we should just stay below ~4 Volts on the right to ensure a voltage drop big enough for the whole thing to work. The fix works for all brightness levels also. I found that an intact Boom is regulating the right side of the filament with different voltages, depending on the selected brightness. It does not make much difference though if we use diodes to make kind of a fixed voltage out of it. So you might give this a try, because this will help you a lot more than a new display that would also stay dark if the power supply circuit is broken :D +-------------------------------------------------------------------+ |Filename: 2015-08-11 18.51.49 _MG_9826.jpg | |Download: http://forums.slimdevices.com/attachment.php?attachmentid=22025| +-------------------------------------------------------------------+ 5x Squeezebox Classic SB3 2.5x Squeezebox Boom 1x Transporter 1.5x Controller ------------------------------------------------------------------------ JoeMuc2009's Profile: http://forums.slimdevices.com/member.php?userid=23131 View this thread: http://forums.slimdevices.com/showthread.php?t=106381 _______________________________________________ Boom mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/boom
