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View Full Version : 24VDC on 3rd pin of LNBP, EVEN transponders only



govideo
01-28-2004, 04:39 AM
OK, I've done a lot of reading so here goes:

GXCEBOT:
Good power supply: 3VDC, 5VDC, 24VDC, & 30VDC where it's supposed to be
30VDC coming off of pin 8 from paralex cable
24VDC on 3rd pin of LNBP (about an inch away at the trace pinhole per Greek)
24VDC on 1st pin of Tuner (LNBIN), didn't believe reading so went here too per Greek
Only gets EVEN transponders
LNBP voltage does not vary from 24VDC when changing from odd/even transponders

Does this mean I have bad LNBPs?

I read somewhere that 24VDC on pin 8 of the paralex cable was average, but mine is putting out 30.14VDC. Should I back down the juice if 24VDC will do the job?

chazbell
01-28-2004, 10:19 AM
Govideo - Your voltages are fine. Pinouts should read:

Pin 10, 7, 4, 1 - 0.0v as this is ground
Pin 9 - 24v
Pin 8 - 30v
Pin 6 - 5v
pin 5 - 12v
Pin 3 & 2 - 3V

If you have anything but 13v and 18v on pin 3 of the LNBP chip you probably have a failure of the LNBP. If it does not switch between these voltages also means it is probably dead. 24V on this pin means that it's inputs and output are shorted, so yes it is cooked. Remove power ASAP as you could possibly fry other things down the line. i.e. tuner module or possibly your LNB as well. LNBP chips are on the way to you, let me know how the repair goes!

chazbell





OK, I've done a lot of reading so here goes:

GXCEBOT:
Good power supply: 3VDC, 5VDC, 24VDC, & 30VDC where it's supposed to be
30VDC coming off of pin 8 from paralex cable
24VDC on 3rd pin of LNBP (about an inch away at the trace pinhole per Greek)
24VDC on 1st pin of Tuner (LNBIN), didn't believe reading so went here too per Greek
Only gets EVEN transponders
LNBP voltage does not vary from 24VDC when changing from odd/even transponders

Does this mean I have bad LNBPs?

I read somewhere that 24VDC on pin 8 of the paralex cable was average, but mine is putting out 30.14VDC. Should I back down the juice if 24VDC will do the job?

GREEK
01-29-2004, 03:15 AM
I too agree with Chaz. I suspect you may have tested pin 2 of the chip and got 24v, MAKE SURE you are reall on pin 3. Its only about 7/8" long and its a thicker trace like 1 and 2. I dont think Ive ever seen 24v on pin3, but 1 and 2 should have them. When referencing the board, dont test pins on the parlex, thats not a good idea really. The mainboards have tiny white letter ing on them, move towards the board and test the capacitors on the right side, you should have 30 on C256 and C259. Make sure your seeing the right voltatges there, they should be 3.3, 5, 12, 24, 30, or very close to it. There is a very rare occurance that the supply would increase power to whatever line, very rare. It should be 13 or 18 volts for pin3, if its 24 something is REALLY screwed up, check both chips. It would make sense if you were right, anything above 18v would still operate the tuner and stick it on evens, 13v is for odds. I wouldn't juice this up with the tuners on there, if you have signal at all those tuners still most likely work, dont blow them. Be careful putting the chips on and off, I think thats your problem. If BOTH tuners do this, my guess is your supply is shot, or heavy trace damge and the lines are mixing, but probably the supply is fuked up if the 24v reading is true. Make sure you diagnose this before applying chips, you'll blow them too if 24v is indeed the reading........

govideo
01-30-2004, 06:17 AM
Chaz and Greek, I appreciate your willingness to help and your quick responses to my post. Thank you.

All of the voltages are proper: 30v, 24v, 12v, 5v, and 3v. I too had a hard time believing the 24v reading from pin 3 off of the LNBP (really 1/8" down from C235) so I took another reading off of pin 1 at the LNB. It too read 24v. I'm tempted to agree with Chaz that the 24v is passing through pin 3 from pins 1 & 2 unmolested.

I noticed on the schematics that the LNBP has a cap on pins 6 and 8. I wonder if that has anything to do with the wrong voltage.

I have some shop time lined up to install the new LNBP chips when they arrive. If the new chips do the same as the old, I'll be back looking for a root cause. Either way, I'll post again for everyone's benefit.