Hi Rich,
maybe you can help me with that issue
:
I´m wondering, where do you connect the Pot for adjusting the core voltage?
In my point of view (after studying the TI TPS53355 datasheet), I tried to use the
-> "VFB" connector (Pin 1) to adjust the VCore,
(between GND and Vout with a pre-resistor (like in the
schematic link) but there is no change, Vcore doesn´t inc or dec, it´s constant
on 0.608V
.
I´m working with a new release (V 1.09) of the R1 (there is something different (PCB layout, schmeatics) compared with the older ones.
It´s an error in reasoning
?
Maybe you can help
Thx in advance ,
andY
Hi Andy am away from home so cannot look at the board to see exactly what I did, however just checking the picture of the board this is what I remember.
As you can see my board is V1.6 not sure if it's different from V1.09 which actually sounds older which is odd? You are on the right track but the reason why it did not work is because they have fitted a zero ohm resistor (R31) feeding back the Core Voltage to Pin 1 and they have not fitted the resistor to ground (R40) Because the feedback resistor is zero ohms a resistor to ground will have no effect. The reason they have done this is to get the absolute minimum Core voltage which I have measured at 0.61V.
I cannot remember exactly how I fitted the pot, however the zero ohm resistor will have to be removed. It looks like I have 3 wires going to the pot & a series resistor, so I suspect that one end of the pot is connected to ground via the series resistor, the wiper to pin 1 & the other end of the pot to Vout. At a guess the pot is 50K & the series resistor 15K but will confirm connections & valueson Sunday when I am back home.
Rich
Hi Rich!
Thanks a lot for your answer!
That matches with my measurements!
Sorry for the Typo, my PCB is not 1.09!, it´s
Revision 1.9) from 01/09/2016
The problem is, that Bitmain (I guess, to prevent later modification by users!) puts a big hotglue ball on this resistor
(unfortunately its not so comfortable, like on your revision
)
So its hard for me to remove it without damage the PCB
Here you can see, how it looks like:
Resistor Glue protectBtw:
for BM1384 cooling I´ve used
this heatsink on both sides.
It´s a little bit larger than the RPi heatsinks and works fine
But finally, good to know, that I´m on the right track, with the Vcore mod
.
So i´ll try at weekend to remove the zero ohm resistor in any way...
Thx a lot for your help!
BR,
andY