DM500S shows Frontend: Unknown ( tuner fault )

**Phillip James** · 15-03-08, 03:45 PM

Gentlemen,

Thanks for all your help, my first DM500S which showed "Frontend:Unknown" is now repaired, I went throught the tricky process of installing a new ALPS tuner and straight away got "Frontend:Satellite", its scanned OK. Subsequently I installed PLI Iolite and all back to normal.

For my second DM500 which lost its +30v for the varicap tuner, it was a bit more tricky........this supply is generated on the underside of the tuner sub board with a 5 pin unknown IC and inductor etc. Discovered a minimum of +14v is adequate for the varicap supply, did a shonk and installed a 9v battery with negative connected to the incoming +12v Dreambox supply giving +21v and this I connected to pin 5 of the tuner (varicap supply).

When powered up the battery supplies 700uA so it should last a while. Later I will replace the battery with a 555 driving a voltage tripler, but for now I have two working DM500's.

Thanks for all you inspiration.

Regards,

**z80** · 15-03-08, 08:19 PM

Originally Posted by Phillip James

For my second DM500 which lost its +30v for the varicap tuner, it was a bit more tricky........this supply is generated on the underside of the tuner sub board with a 5 pin unknown IC and inductor etc.

It's an LT1930 here are the pin designations.

1.sw
2.gnd
3.FB
4.Vin....which is 5volts
5.SHDN-

look here:-

**zorglub!** · 28-04-08, 12:41 AM

Hi Z80
I'm after one BSBE1-703A Alps tuner...
But I live in France...
Does it make a problem...?
If not, pls tell me what would be yr price ( price + shipping costs )
For payment, I'm a registered PAYPAL user ( if not OK, tell me yr choice )
thks and rgds

**caarver** · 03-08-08, 10:32 PM

Firstly thanx to Z80 and Fernbay for their assistance with this.

DM500S 6 months old, suddenly stopped working. Everything seemed OK but lost sync and "unable to switch" error shown on display. SNR dropped to less than 60% from healthy 92% on SelectV here in Bris Vegas.

Following on from this series of threads I decided that being an old techy from wayback it could not be that bad, so in I dived. Checking the diagram from Z80 showed that the 30 Volt supply to the BSBEI-703a was at 0 volts (pin 5). Time to get the soldering station out to access the underbelly. An hour or two later, plenty of solderwick, cursing and swearing and some TLC and out came the Tuner module from the motherboard. Checking with a multimeter the 30V rail was at ground potential (Hm! where is the short), some quick detective work and it showed it was not the tuner, but also not the switching IC. Checked the Diode and inductor all OK and the short was still there. What else could it be, only thing left was a surface mount capacitor marked as C4 with no markings on it. Sure enough it was short circuit and you could also see that the inductor had smoked just a little from the load, but was still in tact (Note these are on the daughter/Sub board mounted under the tuner, so only accessible when the tuner board is removed from the motherboard).

Further detective work and checking circuit diagrams to see if I could work out the capacity. No luck, a quick email to Z80 and Fernbay and in the end whilst waiting for replies I decided to try a 104K ceramic. Seemed to work a beauty once reassembled and has been running for six hours OK.

Fernbay (Thankyou good buddy) came back later this evening having courteously measured one for me and also indicated that it works OK with out. This little beastie appears to be a tantalum (6.8uf) as it is not marked as polarised on the PCB.

As it appears to be working without problem (30V rail sitting at 29V) I will leave for the time being and replace with the 6.8uf if it plays up again. Fernbay indicated these are available from either Wes or Jacar (63Volt).

This is the first surface mount cap I have seen fail, mind you I have been out of the repair game for a few years, however if one goes inside 6 months, there are likely to be others and this maybe the cause of many replacement DM500S units.

So as a little tip, if you have similar problems, check the 30V rail on Pin 5 of the tuner and if it is 0V, turn off the power and measure with an ohm meter and see if the pin is SC to ground. If it is and you feel you have the skills, a good soldering iron, some patience and a bit of solderwick, pull out the tuner board from the motherboard (carefully and take your time, or you will be up for a new motherboard). Once out, desolder C4 and see if the short circuit to ground disappears, if it does replace with the 6.8uf tantalum and put everything back together. Hopefully the switching IC will still be functional, but its seems pretty robust from my experience and should be OK, I suggest that you check the diode and inductor just to be certain before you reassemble.

Good luck and once again major thanx to AUSTECH , Z80 and Fernbay. Collaboration at its best and a very satisfied Motherinlaw and happy techy.

Great work guys.

Caarver

**z80** · 03-08-08, 11:12 PM

Thanks for saying thanks.

You did a fantastic job isolating that component to be the fault.

C4 underneath the Alps tuner unfortunately is on the little daughter board.
A lot of unsoldering to get to a nasty little cap...

**Fernbay** · 04-08-08, 09:05 AM

Originally Posted by z80

Thanks for saying thanks.

You did a fantastic job isolating that component to be the fault.

C4 underneath the Alps tuner unfortunately is on the little daughter board.
A lot of unsoldering to get to a nasty little cap...

Not really... Especially with the plug in tuner module.... No desoldering - it unplugs in two seconds flat

Oh, & with the earlier models, it is possible to hold the board on it's side & lift one end of C4 without unsoldering the tuner module.

Also, I don't think C4 is a tantalum, as neither the cap, or the board has polarity markings. It is either bi-polar, or non-polerised & should be able to be replaced with a 6.8uf greencap from jaycar without any problems. As stated above, it will also run without it.... I wonder, do they really build these things with extra parts for the heck of it?

**caarver** · 05-08-08, 08:48 PM

Thanx Fernbay, my age is showing and I had not been thinking when I mentioned tantalum, too many years out of the game.

The DM that I have has the solder job, no such luck with the plug and play, but you are correct in that if you know where it is, with a little patience you could remove without desoldering the module from the motherboard.

Hopefully it will still be running this weekend when I go round to see the M/Inlaw.

Too some up it was still a lot of fun and even better that I got a positive outcome. Nice little boxes the Dreams.

For noting, but of probably of interest is a new box built in Canberra that enables streaming of multiple channels from a single transponder via discrete ports associated with a single IP address. Very reliable and well built using commodity parts and a well written kernel url in case anyone is interested and perhaps worth a new thread as it solves a number of streaming issues.
They are still doing development.

Thanx once again for your assistance.

Kind regards

Caarver

**z80** · 05-08-08, 09:46 PM

Originally Posted by Fernbay

.. I wonder, do they really build these things with extra parts for the heck of it?

I have encountered a situation where I questioned what i thought was too much engineering in a piece of gear.

Then there was the one in a hundred events that catered for that event and I had egg on my face.

**cmoore** · 06-08-08, 03:07 AM

Originally Posted by z80

I have twenty alps tuners coming at the end of the week.

OHHH Z80 If only you had asked me!!!!!!!.

I have a couple of hundred in my garage, original 702's though... (Legs are slightly longer) also Phillips versions. I probebly have more DM tuners then they have in China at the moment... maybe I could sell it back to them? that would be ironic.

**weirdo** · 06-08-08, 08:11 AM

Originally Posted by cmoore

OHHH Z80 If only you had asked me!!!!!!!.

I have a couple of hundred in my garage, original 702's though... (Legs are slightly longer) also Phillips versions. I probebly have more DM tuners then they have in China at the moment... maybe I could sell it back to them? that would be ironic.

Or you could hold a really really really cheap garage sale here

**alishankiti** · 08-11-08, 10:42 PM

Originally Posted by z80

$35 is what I think it will end up as.

But you'd better be good at soldering, have a good desoldering station etc.

BSBE1-703A ....damn they were hard to source.

Dear Z80,
I am looking for a tuner replacment for my DM7020 si. The current one is BSBE1-703A. I was wondering if you still have a few of those maybe I can buy one.

Thanks

**Mach III** · 11-11-08, 10:07 AM

Originally Posted by z80

Got the whole machine schematics if you promise not to post all over the net?

You dont know how long I have been searching for these schematics!!
Is it possible for you to send it to me? I will of course not post it on the net.

Regards, Mach III

**JIT** · 17-11-08, 12:47 PM

Originally Posted by z80

Got the whole machine schematics if you promise not to post all over the net?

Z80

Any chance of sending a copy my way. I promise to keep it in a dark place.

Do you also have any spare BSBEI-703A tuners still? I have up set mine. I now get signal, quality, BER's and no SYNC or LOCK. I have it in pieces on the table as I speak.

Cheers

JIT

**melectrics** · 27-01-09, 11:09 PM

I need a BSBEI-703A tuner. Do you have please? how much is it including shipping to Malta?

Thanks.

Mel

**z80** · 28-01-09, 02:36 AM

Sorry guys...I am over importing all that stuff....

crown technologies in china will sell you as many as you want.

They were about $6US last year...plus all the costs to get them here.

Buy at least 50 to make it worthwhile....

Here they are if you want to talk chicken scratchings with them.

Be prepared for the odd "expense" that you didn't bargain for.....LOL

**duz333** · 18-03-09, 08:39 PM

i had the same problem with my clone dm500s with removable tuner. Replaced C4 capacitor with a 6.8uf tanty and it fixed the problem.

great work guys and well done!

**gw1** · 19-03-09, 03:29 AM

It looks like a ceramic. I'm not sure where the 6u8 figure came from - perhaps that was a measurement of other capacitors in parallel?

People thinking about tantalums should know that although they are compact and have good performance they don't last as long as other types and they're very fussy about voltage. If the rail is 30V it would pay to allow plenty of headroom, ie use a 50V type not 35V! If you decide you want a 6u8 50V tant you can find them at amongst other places.

I've not looked at the tuner schematic but substituting a 0u1 ceramic was a sensible guess. Where switchmodes are involved though it pays to check the datasheet to see what's needed to ensure stability. Then again if it's a clone there's no guarantee their circuit took all the necessary precautions. The above clone photo doesn't give me confidence, considering C5 and C7 are missing.

Knowing the fault was the tuner power supply, the Dream's error message "unknown frontend" makes sense: without power the tuner IC wouldn't be detected.

**Phillip James** · 19-03-09, 12:58 PM

Gentlemen,

Great to see you putting in diligent work on this Dreambox tuner stream I started months ago.

Regards,

**Fernbay** · 26-03-09, 09:15 AM

I have found another cap that can cause trouble.
The capacitor is C6. In the pic two posts up, it is the cap at the top left, just behind the hedder pins.

It can sometimes go short circuit. So far I have only seen one do it.
The resulting fault is no remote control operation

**LeroyPatrol** · 26-03-09, 10:55 AM

Originally Posted by Fernbay

I have found another cap that can cause trouble.
The capacitor is C6. In the pic two posts up, it is the cap at the top left, just behind the hedder pins.

It can sometimes go short circuit. So far I have only seen one do it.
The resulting fault is no remote control operation

Sheesh how did you trouble shoot that one? You wouldn't think it would be a cap on the tuner board!

Leroy