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Amstrad DRX100 and new Tuner

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pj::
#1
Hi all,

I have an Amstrad DRX100 that "displays no signal received". I have been told that I need a new tuner. Can any techy out there shed some light on where I can get a new tuner from and more importantly how it is fitted?

Thanks
Morgan
 

rolfw

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#2
[updated:LAST EDITED ON 11-Jun-02 AT 10:50 PM (GMT)]If you go to http://www.satcure.co.uk I seem to remember that there is a bit of information on where to get the tuner and how to replace it. Beware, it is not the easiest of jobs.

Rolf

PS. I notice from an earlier post that you are using the box to see Hotbird, it will show no signal if you are on hotbird and not tuned to one of the working transponders.
 
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pj::
#3
Thanks for the info Rolf. I have 2 Amstrad boxes 1 that works fine and the other with the signal message. I thought that the tuner would be quite easy to fit just a couple of screws, similar to fitting a modem. Do you know what the tuner looks like. Is it the unit that the satellite aerial goes into??

Cheers
 

lee32uk

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#4
Hi morgan
The link for Satcure is below.

http://www.satcure.com/digirep.htm


Lee
 
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pj::
#5
Thanks for the info Lee. I had a look at the link but you have to pay £7 to download the book for the information. I'm not prepared to do that just yet, I'll see if I can get any further info from this forum!!!...lol

Cheers
 

rolfw

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#6
Here's a picture of the tuner, from the satcure site, you can send it to them and get an exchange unit. But as I stated earlier, it is not for the inexperienced, the main board is too easily damaged, for the extra £25 I would be inclined to send it away for repair and perhaps the fan added.

Rolf
 
G

groundsman

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#7
The £7 must be a relatively new thing because when I had the same problem about a year ago the replacement instructions were available on the site. Luckily I saved them. E-mail me if you want them as they are too big to attach here. Three pages in Zip form approx. 400kb.
 

easysat

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#8
The tuner is the rectangular metal box with the F connector sticking out the back of the Digibox. It is possible to remove it if you have a good quality soldering iron and either a desoldering tool or some desoldering braid and a bit of patience. If you haven't got this equipment, you'll have to pay a repairer to to the job for you.

The difficult part is getting the solder off the two metal lugs at either end of the tuner as you need to heat a lot of tin plate to the temperature at which solder melts. The lugs have been twisted after the tuner is inserted in the board and it is difficult to remove all the solder and straighten the lugs so that they can pass through the board again.

If you know someone with some expertise in electronics, you can repair the tuner for the price of a ­£1-50 kit from Grandata. It consists of a couple of surface mount capacitor chips which will generally get the tuner working again. Alternatively I can explain which capacitors to change and what values to try if anyone wants to have a go themselves (but I'm off on holiday to France tomorrow :-) .)
 

rolfw

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#9
Can the capacitors be replaced with the tuner in situ Easysat?

Rolf
 
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#10
Hi Easysat,

I have the capacitors but don't have a clue on how to fit them onto the tuner. I would appreciate it if you could possibly shed some light on this when you get back from France.

Cheers
Morgan
 
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#11
When you come back,would you please tell me or mail me the capacitors & values that have to be replaced in the amstrad tuner, it would be very appreciated.

nick673@hotmail.com

tnx
 

easysat

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#12
[updated:LAST EDITED ON 04-Jul-02 AT 07:36 AM (GMT)]If you buy the kit from Grandata, they come with a photocopied diagram with brief instructions showing which capacitors to replace. They're assuming you've already got a certain amount of repair expertise to tackle a tuner.

First you need to remove the rectangular metal cover from the tuner on the side where the components are. It clips on and can be eased off with a wide blade screwdriver but go gently as you don't want to bend the metal tabs too much. The component side can be identified by the fact that the metal cover has a couple of holes in for tweaking coils during the factory set-up and you can see the components through the holes. The solder side is covered with a cover with no big holes in it (from memory).

As for Rolf's question, it is difficult to unclip the tuner cover without first removing the tuner from the main board as there are some other components mounted right next to the tuner. It may be possible to unsolder these components first but I haven't tried it myself. You will also need to be fairly dexterous to unsolder the tiny capacitors if the tuner is still on the board. I found it much easier to change the capacitors on the tuner once it was off the board and on the bench so that I could use a magnifying glass. Also it is much easier to test the tuner on its own and I wanted to test the tuner before putting it back on the board. (If you're going to try doing the repair with the tuner in place, make a note of which component was where and the correct orientation before removing anything else).

OK, the next step is to identify the 16 pin quadrature downconvertor IC. It is made by Zarlink (which used to be Mitel Semiconductor and before that GEC Plessey Semiconductors). It will have SL1710 marked on it and either Mitel or GPS depending on its age. It is in the same section as the big round metal can marked R2663 (a 478MHz SAW resonator from Epcos, which used to be called Siemens-Mashushita, hence the S+M marking!!).

The first capacitor that you need to change (let's call it 'Cap A' for future reference) is the one connected to pin 13 of the SL1710 and pin 2 of the NEC uPC1688 wideband amp (the four-legged device with C1C marked on it). The existing capacitor is a surface mount size 0603 with a value of about 1pF. The Grandata kit replacement seems to be about 3.9pF (obviously still the same size 0603). Before I had the Grandata kit, I didn't change Cap A, so it is not as critical as Cap B. Now though I change it because it only takes a couple of minutes.

By the way, I used two fine pointed soldering irons to remove the old capacitor, then I clean the pads with some desoldering braid before soldering the new capacitor in place.

The second capacitor (let's call it 'Cap B') that has to be replaced is connected to Cap A and ground (the metal case of the tuner is ground as well if you want to check it). I make a point of saying ground because there is another capacitor which is also connected to Cap A but its other terminal is connected to the resonator and not to ground. Cap B is also a 0603 size and seems to be about 3pF in the original tuner design. The Grandata replacement has a value of about 1.5pF. Before I had the kit, I used 1.8pF and this worked just as well.)

Having done this, the tuner should work again. If you have access to test equipment, you can connect the tuner to a +5V supply and use a spectrum analyser to verify the presence of a clean 479.5MHz oscillation. If the tuner isn't working, I'm afraid you will need to try increasing the values of the other capacitors such as the 22pF connected to Cap A, CapB and the resonator or the 1.8pF between the resonator output and the coil.

For the technically minded, these changes reduce the amount of 480MHz signal that is shunted to ground via Cap B and increases slightly the signal that is fed into the quadrature demodulator via Cap A. Overall this increases the loop gain in the 480MHz oscillator circuit and tends to reduce slightly the signal level going into the resonator. The basic fault in the Amstrad design is that the resonator insertion loss increases with time because the signal level is outside the R2663 specification; eventually the oscillation stops as the insertion loss grows bigger than the loop gain.

Let me know if my instructions aren't clear enough.

NB. The quoted capacitor values have been obtained by measurement using a network analyser. As it is difficult to measure capacitances of a few pF without special test equipment, I don't guarantee that I got it 100% right. But the values I quote worked for me!
 

T_G

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#15
I have got a damaged tuner on my Amstrad 100, a thread on this subject was started, only for the good Easysat to show me the light with this repair manual.
Easysat, can you please give me the web address of Grandata, so I can order the repair kit.

Also, as you seem to have good technical knowledge of the poor Amstrad, do you think it is worth attaching a fan to the outside? The Satcure site seems to think it is quite a must, whereas some think it isn't so critical. What do you think?

Thanks!
 

easysat

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#16
The SAW resonator insertion loss in the tuner degrades faster if it is overloaded and at a high temperature. In theory a fan could help by keeping temperatures lower but I haven't seen any proof in the form of measurements of the temperature reduction in the tuner. I think it is easier to make sure that the box is somewhere where there is a good air circulation, i.e. don't hide the Amstrad in a closed TV cabinet and beware of piling other boxes on top it.

If the Grandata kit fixes the problem, I think you'll probably be OK without a fan. The resonator insertion loss is already degraded but it should stabilise (AFAIK) at this higher value and not increase any further.
 

T_G

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#17
OK, I see.
The receiver is standing on a glass plate, and the gap between the top of the receiver to the next shelf is about 7 - 8 cm. the front and the back of the cabinet are open, and there is a gap to the wall as well. It is not perticulary hot in this room, but I never measured the temperature there.

I suppose that should be ok, but not perfect. Once I fix the tuner, I might get problems with the power unit :D
 

Llew

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#18
I beleive the Panny uses the STi processor, if you know the Jtag pinouts you can connect an interface ('wiggler') to your PC and use the Jkeys program (search for jkeys), although I'm not sure if it supports the 32 meg flash in these S*y boxes.

Only used Jtag in Aston Simba, about to Jtag a Fortec, be interested on how you get on with the S*y box.

Llew
 

easysat

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#19
michael dranfield said:
Question for EasySat ?
Do you know anything about Jtagging the panasonic 31 box ?

Edited by PM to remove email address
I didn't see your message until today.

Unfortunately, I can't help on the panasonic box as I have never found a datasheet for the main processor chip.
 

easysat

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#20
michael dranfield said:
Hi ,
Pace boxes easy to tag,but with pan I need some help, or anyone know anything about OS Link ?
As far as I know, OS link is peculiar to STi chips, as it's a high speed serial interface as used on the original transputer.