Wondering if anyone knows for sure where the LNB voltage is developed in the Prof?
The Prof7500 I have has never output any LNB voltage for as long as I can remember.
I have always had it slaved so it's never really been a problem, just curious
the other day I took the cover off, took some measurements with a meter and looked up
some IC datasheets in the area of the power supply.
I am assuming for now that the LNB Voltage is developed in the Tuner Can, which I have not removed to see what's inside (yet).
Anyway, here are some pics and some of what I have found on my own so far.
http://db.tt/ISRDAzED
http://db.tt/qGco4q8n
http://db.tt/ip7ZQbVe
here is a datasheet for U5 and U6, which is a bucking sw regulator.
http://db.tt/o3TccUOi
U5 is used to convert the 7.5VDC in from the wallwart to 5VDC rail, I'm not sure yet what U6's purpose is yet, though mine seems to measure somewhere ~ 1 VDC at the output. Which doesn't ring any bells with me. Wonder if anyone has ever poked around inside their known working Prof if they know what that voltage coming from U6 is for?
The resistors 28 and R30 are in the feedback and configure the output voltage of U5, while the resistors R39 and R40 configure the output voltage of U6. When I do the math as per the datasheet with respect to U6, the values work out to ~ 1.6 VDC.
This IC is another regulator that just generates the 3.3V rail.
http://db.tt/ISRDAzED
I have not found any IC that would act as a "Boost" sw regulator. So thinking it must be in the tuner can?
Is that LNB Voltage developed in the STB6100 tuner IC?
The STV0900 demod?
Or (hoping) None of the above?
The Prof7500 I have has never output any LNB voltage for as long as I can remember.
I have always had it slaved so it's never really been a problem, just curious
the other day I took the cover off, took some measurements with a meter and looked up
some IC datasheets in the area of the power supply.
I am assuming for now that the LNB Voltage is developed in the Tuner Can, which I have not removed to see what's inside (yet).
Anyway, here are some pics and some of what I have found on my own so far.
http://db.tt/ISRDAzED
http://db.tt/qGco4q8n
http://db.tt/ip7ZQbVe
here is a datasheet for U5 and U6, which is a bucking sw regulator.
http://db.tt/o3TccUOi
U5 is used to convert the 7.5VDC in from the wallwart to 5VDC rail, I'm not sure yet what U6's purpose is yet, though mine seems to measure somewhere ~ 1 VDC at the output. Which doesn't ring any bells with me. Wonder if anyone has ever poked around inside their known working Prof if they know what that voltage coming from U6 is for?
The resistors 28 and R30 are in the feedback and configure the output voltage of U5, while the resistors R39 and R40 configure the output voltage of U6. When I do the math as per the datasheet with respect to U6, the values work out to ~ 1.6 VDC.
This IC is another regulator that just generates the 3.3V rail.
http://db.tt/ISRDAzED
I have not found any IC that would act as a "Boost" sw regulator. So thinking it must be in the tuner can?
Is that LNB Voltage developed in the STB6100 tuner IC?
The STV0900 demod?
Or (hoping) None of the above?