Start Up Fails When HDD Connected

/df

Well-Known Member
In a related thread, I suggested, not entirely seriously
Some sort of small timer+relay circuit (as small as a circuit with 2 2-pole or 1 4-pole relay can be) could be interposed in the disk power cable to automate [the process of detaching and re-attaching the disk power around boot]. Actually you can get a 4-pole timer-on relay as a single unit, but at RS it's at least as expensive as a second-hand HDR-Fox T2, though if this listing on "an internet auction site" is to be believed that's 10x too much.
Other hack solutions: bypass the on-board supply and fit a 5V+12V brick with a SATA adaptor, wiring its mains cable to the input of the power supply (CN1), or just a scrap 5V/1A brick wired in place of the LDO regulator (U52) o/p (SG Pipeline 2TB: 5V/0.55A, 12V/0.37A), as the 12V supply is not apparently implicated.

Then
I think there is a much easier solution, it seems to me that this is an inrush current problem, I.e. the hard disk is creating too big a current demand on start-up, (or the PSU can't cope as well as it used to), the U52 component can be made to limit this inrush current by adding a bigger value capacitor to the control pin (pin 1), see marked capacitor here :-
View attachment 5579
If so, this looks good in principle but ... If my sums are right the capacitor between pin 1 and ground has to be about 960μF per second of delay to reach 2V (of the steady state 2.9V) at pin 1 (assuming the current into pin 1 stays roughly as specified for 0A output). This could have to be some whacking capacitor, relative to the existing one which from the trace above (appearing vertical with 40ms timebase) must be less than 1μF, and even 5x the output capacitor for 0.5s delay. I suppose one could put 470μF, then 47, then 4.7, etc, across pin 1 and ground in parallel with the existing one to test.

Finally, OP of the original thread said that the resurrection instructions were followed, which would have included re-flashing the box: was that actually done? If some unexpected system management software action (ie, turning off U22) is implicated, could there be a firmware glitch?
...The supply to the HDD is unswitched on the 12V rail but switched on 5V, and the 5V supply turns on when the HDR-FOX comes out of the initial boot phase (indicated by the VFD "Cust FW #.##" turning off).
...
The VFD message is set by the /etc/init.d/S25banner startup script and reset by the settop program, which initiates discovery of the disk, in turn launched by /etc/init.d/S90settop. The documentation on the web for the 7405 power management function is based on a later Linux version (with /sys/power) but I think its statement that SATA is managed by Linux is still valid (some other hardware functions have Nexus APIs).

You can see what happens at startup in a kernel debug log posted in another thread (look for "brcm-pm", and also be aware that the log is from a faulty system where a kernel bug caused the disk not to spin up). This leads to another thought, that it could be useful to run up a problem system with a debug kernel to see if (a) the U22 turn-off still occurs (b) if so, what is logged for that action.
 
OP
Black Hole

Black Hole

May contain traces of nut
Can anyone see anything (on the HDR-FOX PCB) which looks like a power-on reset circuit? It's on page 21 of those circuit diagrams (a Maxim chip), but I haven't spotted anything similar.
 

/df

Well-Known Member
I wonder where the HD-Fox T2 reset button leads? Sadly it's part of the front panel which makes it unclear whether it's handled locally (perhaps generating a short interruption to the power supply) or routed to the main board.

While I had the board, magnifying glass and light together, I found these ICs on the HD-Fox T2 main board:
  • U152, a 10-pin mini d-i-l package next to the main power connector and an inductor, label V59P823;
  • next back from the front, U153, EUP7996 1.5A DDR Termination Regulator;
  • next, by the ribbon connector to the power board (though it seems to have the SPDIF output too), U150, same as U152;
  • close by, U700, SOIC-8, label indistinct;
  • in the next column front to back, U621, U623: 2 x H5PS1G63EFR-S6C 64M x 16-bit DDR2 DRAM (ie 2 x 128Mbyte);
  • next U622, apparently labelled H5PS51G2FFR-S6C (no obvious matching spec), appears similar but must be something other than straightforward RAM (shadow RAM into which ROM is copied for speed?); the 4th location U624 is unpopulated;
  • at the back by the HDMI socket, U1650, NXP TDA9984A HDMI 1.3 transmitter with 1080p upscaler;
  • in the next column front to back, U551, SOIC-8 with indistinct label, similar to this but "0952" instead of "1444" and a slightly different top line;
  • next to the SoC, a BGA package U222 with indistinct label;
  • the SoC, component ID presumably under the heat-sink (and, yes, Wilko imitation Bostik is an effective replacement for the failed sticky pads);
  • at the back, U1600, TDA19977 HDMI1.4 receiver (see here for thea possible rationale for U1600 and U1650 to augment the SoC's limited HDMI support);
  • next to it, U1652 and U1651 are BA00BC0WCP LDO regulators like U52 in the HDR;
  • in the next column front to back, behind the SoC, U1500 is a TSOP-8 or similar, label indistinct, and close by U1501 appears similar;
  • next, U151 is another BA00BC0WCP LDO regulator;
  • close to the TV SCART socket is U1250, STV6412A Audio/video switch matrix;
  • front to back on the far edge, U1532 is another LDO regulator, this time ST LD291501.5A very low drop voltage regulator;
  • U1530 is yet another LDO regulator, RichTek RT9183H Ultra Low Dropout 1.5A Linear Regulator;
  • finally, U1560 is the DVB demodulator Sony CXD2820R.
The story goes that Professor JBS Haldane was asked what characteristic of the mind of the Creator could be discerned from study of nature, and responded "An inordinate fondness for beetles". Asking a similar question about the HD-Fox T2 main board and its designers, we might say "An inordinate fondness for low dropout voltage regulators".
 
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OP
Black Hole

Black Hole

May contain traces of nut
I did a similar exercise, but had not got around to compiling the results.
An inordinate fondness for low dropout voltage regulators
Definitely. I guess it might be possible to use the enable pin as a POR.
 
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