DM500 BSBE1-702A no lock

[bobzombie]

Today , i bought a DM500-S but when i connect it , i saw the tuner is faulty. ( i read most of the posts in this section )
here is the situation: From the whole 100 frequency of hotbird, only FIRST 3 freq. has signal: 10719, 10722, 10758
On other satellites too, only freq. lower than 10760 has signal.

DM500-s More look like a clone.
Tuner: BSBE1-702A
No lock & No sync. SNR and AGC are ok.
Tuner output 13v/18v both ok even with LNB connected.
Power supply is ok. ( i change it with psu of a working dreambox,
and dish, lnb, cable are all ok. i test the dream in 2 other house with 2 different sets of Dish & Lnb, Tried 3 different images gemini and enigma , connected the earth link, Lnb setting in the menu is ok too, i tried with & without Diseqc switch ) still no signal lock.

without opening the box , i can see that the power supply voltage is about 12.30 volt and stable , even when the box is up and running.
And the Lnb output 13/18 volts are ok too. Then only thing i found is that when i was testing the Lnb output voltage a very lill short happened ( very fast less than 0.5 seconds) and the Lnb output changed to 5 volts and didn't back again until i disconnect and connect the power again OR i check & unchecked the "Inv:" in the manual scan menu.

my problem is that i live in a fcked up place and here there is no dreambox so if i send it back to the seller, then i cann't find another dreambox , maybe i should wait months.
If some one had same problem and figured it out to fix it, then i'll keep the box and open it, then i can check Q70,71,72,571, C4, C6, pin5 30volt, ... but if i understand correctly , i guess cause i have 13/18 Volts , then my problem is not Q72 or Pin5 30 Volts

[weirdo]

Hi bob,
Are you 100% sure it's not the PS?
Not sure if you already read this post but there's some good tips

[gw1]

You've ruled out the power supply and LNB (using a separate working dreambox) so your faulty tuner diagnosis is probably correct.

Perhaps the receiver's 22kHz system is broken. As an experiment you could try a non-universal LNB, say one with 11300 MHz local oscillator. It will only be able to receive higher frequencies of course but might be worth a try.

I realise in your country it's hard to find a local supplier who can support you, but since the receiver is new my recommendation is you do not remove its cover - return it to the supplier! The clones which have tuner modules soldered to the motherboard are designed to be thrown out, not serviced.

The failure rate for clones seems to be high from those I've talked to - quite a few receivers are DOA or have short lives. Those who buy from China in bulk usually have to fund their customer warranty out of their own pocket, writing off the returns. That's why when buying clones it's important to use an established seller who is likely to honor his warranty promises.

good luck

[bobzombie]

ok, finally i opened the box, it more looks like an original DM500.
(The main board says Version 7.0 - 2004.)

From this post here by z80 :

oh alright, here you go......

My tuner is exactly like this with 28 pins but it's a 702A , and the pic is 703A

does some one has the schematic of 702A ? (or maybe it's like 703A) ?
Also i don't have 30 Volt on pin 5.
Also i removed C4 and test and replaced C4 and test , still no 30Volts and no signal lock.

[slang]

703 and 702 schematics are absolutely the same.
if you doesn't get 30 volts, there must be a faulty component among those soldered on the pcb that is under the tuner: maybe an electrolytic capacitor, the diode or, better, the 5 pins ic: it is an LT1930 from Linear.
Do you find correct voltages on the other tuner pins?
let me know if you resolve.
Slang

[bobzombie]

well , finally with the help of this great forum and it's professional and helpful users , i could repair my DM500.
The problem was LT1930 inside the tuner 702A , and cause i couldn't find this IC to replace it , i had to do just like "Phillip James" in this sticky :


I used 2 * 9Volts battery in series and they gave me 18 Volts and connect the 18 to pin 5 of tuner and the negative head of batteries to GND and now i have signal Lock & Sync & picture.
i'll add one more battery to generate totally 27 Volts .
My friend which is an electronics pro, he said the pin 5 of tuner need very low Ampere , so the battery will last long, but he will use a resistor for limiting the ampere .

then he disconnected the power of dream , and checked and find out that some element in tuner is using battery power even when dreambox is totally off. So he will use a relay powered by main 12 Volts from wall plug pack to disconnect the battery from tuner when dreambox is completely off. i hope all these won't make further problem for the box.

Also he said that probably wrong value for capasitor "C7" cause destroying of LT1930 .
C7 is 220u 35 volts and he recommended 100u 35 volts
Also he recommended "C4" as 0.1u just like what gw1 said.

Again thank you all for helping.

[gw1]

Well done! Congratulations for getting it to work.

Another solution, as Phillip James mentioned, is to generate 30V internally from the receiver's 12V input using a voltage tripler. For example:





That way you don't need a battery, or the relay! These are all common parts which you should be able to obtain. AFAIK the tuner only requires about 3mA, so the tripler doesn't need to be efficient - you can substitute other component values to use junk box parts. The only critical thing is the electrolytic capacitor voltage ratings which need to be respected.

The choice of timing values about 1K/1nF is to give a frequency well above the audio range to avoid interference.

If you can't find a 30V zener then you can probably omit it without danger. Due to losses the output without a zener will only be 32-34V, and some tuners are meant to run at 33V anyway I think. I doubt they're fussy about the exact voltage. Because I haven't seen their datasheets though I recommend you use 30V zener if possible.

You can use either multilayer ceramic or electrolytic for the 1uF pump capacitors. If the latter then make sure you get polarity correct (positive on the lead closest to the output).

(For others who are following the discussion, obviously the preferred approach is to replace the faulty parts, but bobzombie lives long way from good parts suppliers.)

[Phillip James]

Well done! Congratulations for getting it to work.

Another solution, as Phillip James mentioned, is to generate 30V internally from the receiver's 12V input using a voltage tripler. For example:





That way you don't need a battery, or the relay! These are all common parts which you should be able to obtain. AFAIK the tuner only requires about 3mA, so the tripler doesn't need to be efficient - you can substitute other component values to use junk box parts. The only critical thing is the electrolytic capacitor voltage ratings which need to be respected.

The choice of timing values about 1K/1nF is to give a frequency well above the audio range to avoid interference.

If you can't find a 30V zener then you can probably omit it without danger. Due to losses the output without a zener will only be 32-34V, and some tuners are meant to run at 33V anyway I think. I doubt they're fussy about the exact voltage. Because I haven't seen their datasheets though I recommend you use 30V zener if possible.

You can use either multilayer ceramic or electrolytic for the 1uF pump capacitors. If the latter then make sure you get polarity correct (positive on the lead closest to the output).

(For others who are following the discussion, obviously the preferred approach is to replace the faulty parts, but bobzombie lives long way from good parts suppliers.)

GW1,

Keep up the good work you have provided an excellent simple solltion to a widespread problem, that pesky DM +30V generator.

Kind regards,

[bobzombie]

Well , i made the lill board thanks to gw1 .
Now i get the 22 ~ 25 volts on pin 5 of tuner .
1 thing that i found is that after i disconnect the power of the box , the lill beast is still generating about 15 volts, and after 5 minutes it reduces to 5 volts and ...

I think after this mod , we should take care only if we want to open the case of dreambox.

[gw1]

I doubt the residual voltage will be a problem; none of it should be flowing back into the digital areas.

You can reduce the decay time by reducing 47uFs to 10uF if you want. You'll get higher output voltage if you use schottky (eg BAT85 or 1N5819) instead of 1N4148. (If you were making a PCB you could replace the four diodes with a pair of .) Low ESR caps or tants for the 1uFs will help too, and it may work better with 0.1uF for those caps. Anyway it was just a quick sketch, I didn't test it on a tuner myself.

[bemol]

Hi,

can you say where you control for 30v on the tuner?.

Where is the first pins?
near the coaxial or the opposite?

best regards

[bemol]

Hi,


I've changed U70 (LT1930) and Q72





so I've always no tuner detected when I reboot dm 500



Tuner is different and I don't know where to connect the electronic setting
( 30 V Pin 5 for alps 702A )

I've checked voltage on tuner

and I' have

pin 1 - 0.001 v
pin 2 - 0.008 v
pin 3 - 4.87 v
no pin - ----
no pin - ----
pin 6 - 0 v
pin 7 - 0 v
pin 8 - 0 v
pin 9 - 3.268 v
pin 10 - 0 v
pin 11 - 5.19 v
pin 12 - 2.359
no pin - ----
no pin - ----
pin 15 - 3.28 v
pin 16 - 3.28 v
pin 17 - 2.69 v
pin 18
to
pin 25 - 3.28 v
pin 26 - 2.64 v
pin 27 - 2.64 v
pin 28 - 3.28 v

If you have an idea ?

[bemol]

Hi

Okay, I solved the failure of the DM500

Some pictures



Best regards

bemol

[beastien]

Is U70 a LT1930 or a LT1930A?

[bemol]

Hi

That is what we read on the lt1930 two different DM500
LTKS or LTSQ

LT 1930 switch at 1.2 Mhz
LT 1930 A switch at 2.2 Mhz

LT 1930 A cost more

Datasheet

 http://www.chinaicmart.com/pdf/?keyword=lt1930

[beastien]

Would they both work?
Which one did you use?

[gw1]

Either regulator version would do.

Bemol, what happened to RN21? Did you break it accidentally during servicing?
RN21 is pullup for ASIX RDY, for EEPROM CS, and for data bus 11, 12, 13, 14.
While broken the ethernet and/or flash memory may have been unreliable.

[bemol]

Either regulator version would do.

Bemol, what happened to RN21? Did you break it accidentally during servicing?
RN21 is pullup for ASIX RDY, for EEPROM CS, and for data bus 11, 12, 13, 14.
While broken the ethernet and/or flash memory may have been unreliable.

Hi

No, when I received this dm500 to repair, I took a first picture, and here we can see this RN 21 is broken

http://rapidshare.com/files/263124117/DSCF2875.jpg.html

Certainly, the first problem was to repair the scan. now I will definitely go up the tuner and test the ethernet port.

No 3.3 V on the RN21 would disrupt U-5, U-15, U-20 and produce a temperature rise of the tuner and destroy

[mmsuranjith]

Hi,


I've changed U70 (LT1930) and Q72





so I've always no tuner detected when I reboot dm 500



Tuner is different and I don't know where to connect the electronic setting
( 30 V Pin 5 for alps 702A )

I've checked voltage on tuner

and I' have

pin 1 - 0.001 v
pin 2 - 0.008 v
pin 3 - 4.87 v
no pin - ----
no pin - ----
pin 6 - 0 v
pin 7 - 0 v
pin 8 - 0 v
pin 9 - 3.268 v
pin 10 - 0 v
pin 11 - 5.19 v
pin 12 - 2.359
no pin - ----
no pin - ----
pin 15 - 3.28 v
pin 16 - 3.28 v
pin 17 - 2.69 v
pin 18
to
pin 25 - 3.28 v
pin 26 - 2.64 v
pin 27 - 2.64 v
pin 28 - 3.28 v

If you have an idea ?

can you tell me how can i find pin 5 for 30v ,pin counting top side or bottom side ?

[mmsuranjith]

well , finally with the help of this great forum and it's professional and helpful users , i could repair my DM500.
The problem was LT1930 inside the tuner 702A , and cause i couldn't find this IC to replace it , i had to do just like "Phillip James" in this sticky :


I used 2 * 9Volts battery in series and they gave me 18 Volts and connect the 18 to pin 5 of tuner and the negative head of batteries to GND and now i have signal Lock & Sync & picture.
i'll add one more battery to generate totally 27 Volts .
My friend which is an electronics pro, he said the pin 5 of tuner need very low Ampere , so the battery will last long, but he will use a resistor for limiting the ampere .

then he disconnected the power of dream , and checked and find out that some element in tuner is using battery power even when dreambox is totally off. So he will use a relay powered by main 12 Volts from wall plug pack to disconnect the battery from tuner when dreambox is completely off. i hope all these won't make further problem for the box.

Also he said that probably wrong value for capasitor "C7" cause destroying of LT1930 .
C7 is 220u 35 volts and he recommended 100u 35 volts
Also he recommended "C4" as 0.1u just like what gw1 said.

Again thank you all for helping.

in my tuner c4,c7 not in there ?