dm500 problem

[daphney]

i have 2x dm500s with the same fault i get90% sig & agc but when i scan sats no services found , all dish & lnb are ok cause work on other dreams. i have changed tuner on 1 of them but still the same, i have read on here about q70 , 71 , 72 does any1 think this will fix my problem or if not what else do i need to look at.
ps they both flash ok & i have erased flash n/p

thanks in advance for helping

[z80]

yep...sounds like the problem.


earth your LNB cable...read the manual page 8.


unless...they are secondary boxes...to scan they need to be the only boxes on the LNB cable.

[daphney]

ok i have just earthed the lnb cable & it is the same. so what are the values of the q70 71 & 72 or are they all the same?
also do u think i should change all of them or just 1 of them if so what 1
thanks for helping i think dreams mite come back to life soon hopefully

[z80]

ok i have just earthed the lnb cable & it is the same. so what are the values of the q70 71 & 72 or are they all the same?
also do u think i should change all of them or just 1 of them if so what 1
thanks for helping i think dreams mite come back to life soon hopefully

LOL....earthing the cable stops q72 from blowing etc.


once they are blown you need to replace them.


see "Fernbay"...he has them.

[daphney]

ok m8 thanks all this repair procedure is new to me but its great that the info is out there.
thanks again & keeep up the good work

[cobra679]

can someone post a picture of what needs to replaced. Im going to order some off fernbay when he gets back to me via pm. will this defently fix the tuner problem or does the tuner it self needs to be replaced aswell ?

[daphney]

ok i have changed the q72 on both dms 1 still scans no services & the other which is a chinese clone { as i cant change tuner cause wont fit } turns off when u select sat to scan.
any ideas what 2 try next ?
thanks

[daphney]

the update i can scan 1 transponder on the chinese 1 now but no others it appears to be in the middle of the range of transponders if that make any difference
what else can i try ? it would be nice to get 1 box working again

thnx

[z80]

try another power supply....you have tried that ...yes?

(about 12-15 volts DC at 2 amps with positive center connector.)

If it fixes it then you have faulty 470 Uf/25v caps in the switch mode plug pack.

[daphney]

ok i have followed the C4 front end post & changed the c4 cap on the board under the tuner & this has fixed the chinese dream GREAT thnx guys
but the other dream has a different tuner that i have to unsolder the small board which isnt a problem but doesnt look the same this is where tuner came from
h??p://www.kontrolsat.com/catalog/popup_image.php?pID=139

can u tell me what if any thing is different on this please & where i will find c4 cap
thanks again im getting somewhere now thanks to u guys

[daphney]

i have pulled other dream apart & there is no c4 cap on board underneath tuner there is only2 caps & 1 diode which all check ok
now on the main board c726 buzzes on meter both ways so thinkin this mite be the short maybe ?
i have looked at u diagram & is on the lnb power circuit { as this box locks on sat but no services found }
can some1 please tell me what the component value is & if this is likely to be the fault before i start playing with it anymore
thank you

[daphney]

ok forget the above post i had been drinking & stupid..
i now have 15.5v on pin3 of tuner & lnb out when i am on 11585/27500h but on the other box that i repaired with all u guys help i get 18v
does any1 no where i might be losing those few volts to
thanks for all help so far

[daphney]

here is pic of tuner in this box

[z80]

yuk...looks like you have a bit of desoldering to do....


.

[daphney]

i have had the tuner out already & this is the new tuner so any ideas where im losing some power on mainboard as on the underneath of this tuner is only 2caps & a diode which seem to be ok

[z80]

i have had the tuner out already & this is the new tuner so any ideas where im losing some power on mainboard as on the underneath of this tuner is only 2caps & a diode which seem to be ok

measure the sample voltages as above...any irregularities?

[daphney]

i have just compared the 3 pn voltages on the q72 & it seems that i get 12.06v { topleft } when u have front panal facing you 5.74v top right & 12.08 bottom on the 2 working boxes but on broken 12.07v top left 10.98 top right & 0.16 bottom so do you think i have a faulty q72 { again or maybe it blew when i fitted }
ps the tuner wasnt earthed when i fitted q72 but is now

[cwispy]

It sounds like the transistor might be dead. Check it for shorts and possibly lift the transistor and then check the tracks where it was for shorts or extremely low resistance. It may not be that transistor but something else in the circuit causing the high load.

[daphney]

ok i have played abit more & checked alot of voltages on components on both good & bad boxes
i have replaced q72 again & now i getting correct voltages there but the L711 steps the voltage down on good box but on bad it the same both sides can some1 give me correct component info & maybe where i can buy please
ps it looks a bit duff aswell ie wobbly
thnx

[cwispy]

I think you will find that the voltage across that coil is going to depend on what voltage is meant to be presented to the lnb. Are you now getting ~14 and ~18v at the tuner?