This isn't taking a good direction. BPA may be right eventually! I have
spent days analyzing defective Boom boards and to my surprise never
found a single classic voltage regulator. Up to now I thought this
probably indicates a very low tolerance towards other voltages than
specified. But found quite the opposite when I reviewed it today.
There are multiple converters, and that's all I could find that deals
with power rail generation:

*U3*: TI TPS61080: HIGH VOLTAGE DC/DC BOOST CONVERTER WITH 0.5-A/1.3-A
INTEGRATED SWITCH
generates +55V grid voltage for the VFD, takes _up_to_6V_ input, is
not directly connected to +12V rail but fed from U10

*U7*: TI TPS40222: 1.6-A, 1.25-MHz BUCK CONVERTER IN A 3 mm × 3 mm SON
PACKAGE
probably dedicated to creating CPU voltages (1.2 / 3.3V), takes
_up_to_8V_ input, is not directly connected to +12V rail but fed from
U10

*U10*: TI TPS54286: 2-A DUAL NON-SYNCHRONOUS CONVERTER WITH INTEGRATED
HIGH-SIDE MOSFET
probably the main regulator, takes _up_to_30V_input_, is directly
connected to the +12V power jack
half of U10 is creating supply voltage of 3.3V for the majority of
the ICs on the board such as
    
- U12 (Realtek NIC)
- U14 (Xilinx FPGA)
- the obscure U13 (SN0801033) I cannot find any datasheet for
- U26 (Flash EEPROM)
- U25 (DRAM)
- and some more.
  
the other half creates the supply voltage (+5V I think) for U3 and
U7.

Furthermore, directly connected to the input +12V are the digital
amplifier chips:

*U9*: TI TPA3100D2: 20-W STEREO CLASS-D AUDIO POWER AMPLIFIER (for bass
woofers)
*U11*: TI TPA3101D2: 10-W STEREO CLASS-D AUDIO POWER AMPLIFIER (for
tweeters)

U9 and U11 both tolerate input up to 26V.

So yeah, actually I cannot see a reason after all why more than +12V
input should do any harm. All the regulating components which are in the
path of the +12V input rail are capable of taking more than double that.
It seems there is no sensitive component directly attached to the input
jack that would not tolerate a good amount more than +12V.
Certainly one should not generally assume that each low-voltage device
can take an arbitrary amount of more voltage than the label on the box
says but in this case we have a good margin.
I don't have any schematics by the way. Just like everybody else I'm
condemned to reverse engineering, and not particularly good at it.
Please don't take my word for granted.



PN me if your Boom / Classic / Transporter display has issues!

LMS 7.9.0 on Windows Server 2012
1x Squezeebox Classic SB2
7x Squeezebox Classic SB3 (one waiting for repair)
7x Squeezebox Boom (two waiting for repair)
1x Transporter
2x Controller (one waiting for repair)
3x Touch (two waiting for repair)
1x Radio
------------------------------------------------------------------------
JoeMuc2009's Profile: http://forums.slimdevices.com/member.php?userid=23131
View this thread: http://forums.slimdevices.com/showthread.php?t=108698

_______________________________________________
Boom mailing list
Boom@lists.slimdevices.com
http://lists.slimdevices.com/mailman/listinfo/boom

Reply via email to