No H Polarized channels on Dreambox 500s

dreamer01
17-10-2009, 18:10
Hi all,
Has anyone encountered the problem of not getting H polarized channels on Dreambox 500s and solved it? V polarized channels ok, other Dreambox work ok on same set-up.
For me it looks like a hardware problem. Already changed the tuner but still the same.:mecry:
Any ideas which components to change?

Much appreciated.

Ferret
18-10-2009, 17:51
Mate this may be obvious but i have to ask.

Have you swapped out the LNB. Loosing either H or V could be sign of LNB failure.

Ferret

dreamer01
19-10-2009, 22:44
Thanks for replying Ferret, I have seen that another member is having same problem as mine and he opened another thread and you asked him for the voltage readings.

The voltage does not change at all remains 12.23v irrespective if V or H. I have checked some voltages and the switching voltage on R710 is 3.23v when on V and 0.65v when on H , seems at this point the 13v/18v is ok up to here (13v/18v cntrl). It's the voltage on U70 pin 3 which is frustrating me, I'm getting 1.16v when on V and 0.85v when on H but the voltage on pin 1 remains the same i.e. 12.23v. Does anyone know what the voltage on pin 3 of U70 should be when on V and when on H cause I'm suspecting that U70 is faulty.

Thx

Ferret
20-10-2009, 09:55
Hi mate

If you have the same voltage 12.23 on h-v on the f connector at the rear this is your problem but you know that.

Have a look at the attached tuner diagram and youll see the LNB voltage control side

Ferret

borsalino
20-10-2009, 22:20
the probleme of No signal horizontal channelle is hard in clone dreambox china
The solution is to replace the piece Q72 Known number Part No.NDS352APCT-ND and Known name Transistor Type P-Channel Logic and It has a standard Voltage-Rated 30 V
Current Rating 900mA
And the replacement piece F70 (amp 0.5)
If it reached a high wire between the two pieces will signale
sorry for my bad english
look the picture
:thum:

digimyth
21-10-2009, 23:45
Good timing?

I just received a 500s clone one week ago to use as a cardsharing server to my pc. Focused on the cardserver part and have that working. Same problem with the horizontal signals but was getting the same problem on the pc so I changed the lnb. No change. Finally working on the pc after switching dvb cards between 2 computers. Also re-aimed dishes and checked cables by switching them around.

Voltage from the dm500 clone is around 12.5 on vertical or horizontal manual transponder scans.

Kinda low, my dvb card puts out 13.5 and 18.5.

So if I cannot get this solved under warranty (I doubt they cover the shipping charge), I need to replace the transistor. Then it looks like you run a wire from the fuse connection to the single leg side on the transistor?

I was also wondering if a better power supply would help?

Ferret
22-10-2009, 00:14
Good timing?

I just received a 500s clone one week ago to use as a cardsharing server to my pc. Focused on the cardserver part and have that working. Same problem with the horizontal signals but was getting the same problem on the pc so I changed the lnb. No change. Finally working on the pc after switching dvb cards between 2 computers. Also re-aimed dishes and checked cables by switching them around.

Voltage from the dm500 clone is around 12.5 on vertical or horizontal manual transponder scans.

Kinda low, my dvb card puts out 13.5 and 18.5.

So if I cannot get this solved under warranty (I doubt they cover the shipping charge), I need to replace the transistor. Then it looks like you run a wire from the fuse connection to the single leg side on the transistor?

I was also wondering if a better power supply would help?

If the transistor has blown then no a better power supply wont make any difference. In you case speak to your dealer mate.

I hope they sort something out for you.

Ferret

dreamer01
22-10-2009, 21:14
In my case it's not the transistor, the 12v I'm getting is coming from the transistor so the transistor Q72 must be ok. It looks like that U70 circuitry is not performing well, but to be sure which component is faulty I need to know the voltage on pin 3 U70 when on V and when on H when the circuit is working correctly.

THX

digimyth
27-10-2009, 03:21
Broke the warranty seals on the dreambox as I was not going to pay to ship it back to China. If nothing else, it works okay as a cardreader and cardserver to the pc.

Rechecked voltage on the coax. Looks like 12.5 and 17.5 tuning to specific channels on vertical/horizontal transponders respectively. However, the voltages do not seem steady (using a digital multimeter). The 12.5 drops to 10V over about 3 seconds, jumps back to 12.5 and cycles like that repeatedly. The 17.5 V seems steadier, but there is a blip on the meter to around 15 volts, also repeats every few seconds.

From Fairchild datasheets, the FDN358P seems to be a better part (1.5 A rating) than the NDS352 suggested by borsalino. There is no way to tell if the correct part was used originally as the Q72 package marking is not useful in Google (A95A with 29 sideways at one end, as seen with a flashlight, magnifying glass, and aging eyes).

Any suggestions?

dreamer01
12-11-2009, 11:02
Reference no H polarized channels with the LNB voltage remaining 12Volts for V and H polarized channels, problem fixed after changing U70..... :)
P.S. Not easy to change U70, need some expertise and special soldering/de-soldering station.

Thx to all who replied to this thread.

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