B band converter

[jvvh5897]

Trying to do something wierd with a directv Zinwell BBC module--these convert 250-750MHz output from one of the LNBs up to 1650-2150MHz. Inside the snap-together plastic box is a metal box with spring together lids and a few chips and lots of transistors. I see a 74HC4046 PLL chip, an 8 pin chip only marked 1507 and a crystal that looks to be 9.375MHz, on the other side of the board is a 5V regulator, a 3 pin resonator (ceramic I think) marked 400Cm634 and an SOP18 chip TM58PC10SCG--now this last seems to be a flash from what I can find on-line.

Does anybody know more about the chips or the circuits?

I'm guessing that the 4046 PLL chip is for 22 KHz detection but the output in use seems to be the pin 13 Phase II output and that looks to go to the 1507 chip. But the TM58PC10 chip showing up as a flash has me a bit confused--since the box has to pass 950-1450 and 1650-2150 to the output, I kind of figured that the chip would be one of those LNB MOSFET bias supply chips that incorporate the H/V switches and maybe it would switch the 250MHz convert part of circuit on as part of its functions.

[jvvh5897]

Well, a little playing with a meter and I have a few answers, but added a question or two.

Seems the TM58PC10 chip is the controller--pins 17 and 18 are tied together and seem to be open-collector. They drive the mode switching--pull the line to ground and you have the default mode of passing 950-2150MHz, and if allowed to draw no current you get the up-convert side of the board active. How it does that swtching is not simply 22KHz active as some posts I found through google suggest though--bet someone will have to actually tap a receiver control to see what is going on. I think for just a quick fix just cutting the two pins will do to get the up-convert circuit going, I tried to lift the two pins and ended up having the pad lifted off the board and had to do a fix. Board seems to have at least a third layer, but don't think more than 3 total.

On the up-convert side I was guessing that 250MHz got converted to 1650 by mixing with 1400MHz LO. And 9.375MHz times 150 is about 1400MHz (1406.25MHz) and that other chip has 1507 on it--seems resonable to think that it is a divide-by-150 chip. Saddly I only see a really good 1100MHz peak--so that seems to be the LO, even though I can't make that make sense. The Phase II output of the 4046 chip seems to go to an averaging circuit and then to a diode--guess a tuning diode. So we seem to have the basic PLL locked VCO as the LO for a mixer.

[jvvh5897]

Ah! Turns out the LO is 2400MHz and that 1507 chip is div by 256--so, 250MHz ends up at 2150. And that 1100MHz peak--it might be how the receiver tells that the BBC is connected.
divide by 256 might be something like Fujitsu MB506