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11-04-08, 10:12 PM
| #1 (permalink) | ||
| Senior Member |  How to run your gamma at a cool +3V - with a 'factory' mod Quote:
Yes there is a mod ... ... and no you don't need a resistor or diode or even a volt regulator to drop the 5V supply to the card to 3V ... ... many mods discussed here do the unthinkable ... as was already covered in another post by gw1 ... dropping voltage to the card alone without proper care of the interface electronics can 'break' your smartcard  Quote:
... not exactly true ... If we assume that gamma cards run of +3V - then even though they may indeed operate at +5V and be able to dissipate the 'heat' ... they are not running within their ideal specification that of +3V ... The card reader on the STRONG 4658X as well as many other receivers use a TDA8024 IC card interface ... http://www.nxp.com/acrobat_download/.../TDA8024_3.pdf ... the clever thing about this device is that it already has a +3V mode of operation ... by examining the data sheet (above link) we can see that pin 3 - when strapped to +5v will operate the card interface at 5V - if we GND pin 3 then the card interface will operate at +3V ... If we examine the card reader PCB on the 4658X - then we will see that pin 3 is at +5V - as expected ... to change the mode of operation of the card reader to +3V - we need to tie pin 3 to GND ... WARNING : No we don't just 'tie' pin 3 to GND ... we need to unsolder the pin - 'lift' it so it does not touch any other tracks ... and finaly 'tie' the naked pin 3 to GND ... See picture of completed mod ... If you do indeed make this mod - PLEASE check the voltage of the card reader - by inserting the 'rear' of your gamma - so that no contact is made to its landing pads ... just in case you 'botched' the mod ... you don't want to fry your gamma ... ... by inserting the card ... we trigger the micro contact of the reader socket and enable the 'voltage' to turn-on ... we can then measure between pins C1 and C5 which are clearly marked on the PCB ... GOOD LUCK ... and lets stop all of the 'he' said , 'she' said modify this resistor / add this diode type of mods ... the above IS in effect a FACTORY mod for +3V operation on all card readers utilizing a TDA8024 IC card interface ... so it can be applied to any receiver which uses this chip    | ||
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12-04-08, 08:42 AM
| #6 (permalink) |
| I'am Not a Bloody Joke   iTrader: (10) Join Date: Jan 2008 Location: Australia
Posts: 2,617
Spent time on board: 1 Month, 4 Weeks, 0 Days and 10:39:18
 | Do you need that 100nf cap or should it be close enough Quote from the above PDF For reasons of VCC voltage accuracy, a 100 nF capacitor with an ESR < 100 mW should be tied to CGND near to pin VCC, and a 100 or 220 nF capacitor (220 nF is the best choice) with the same ESR should be tied to CGND near card reader contact C1. What voltage are you getting without the cap and is it stable enough for the card?? Ohh and thanks  nice find
__________________ Please wipe your feet before walking all over me |
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12-04-08, 12:27 PM
| #7 (permalink) | |
| Senior Member | ... most component data sheets cover all aspects of device operation as specifically designed my manufacturers ... the TDA circuit as implemented by various card reader manufacturers may or may not follow specific datasheet guidelines ... reasons for this could be commercial (i.e. save a few $$ on a component you don't 'really' need to insert) ... or from a circuit point of view ... where a designer specifically chooses not to operate the device in a 'published' mode ... ... with regard to the Strong Card reader as used ... which is the basis of this post ... the circuit implemented is perfectly stable and operating within the 'design' parameters of Strong’s Card readers original design ... ... by changing the operation to +3V ... its not really necessary to add additional components specifically for this to function ... … all you have to do is take pin 3 to a GND .. I’ve chosen a good point … the GND side of a SMD cap next to the device … (see photo) .. after the mod .. the power to the card is +3V and stable ... One thing that I don't like about the Strong’s Card reader is the physical mechanism - the landing pads do not retreat and leave 'skid' marks on your card when inserted and removed multiple times ... The JayCar MKII had a 'retractable' landing pad mechanism - this can (I think) be purchased on its own ... and fitted to the Strong (a little skill in soldering and 'pin' manipulation required) ... then you can easily remove your card without causing undue 'wear' on the contacts ... ... perhaps .. my next project with the Strong  Quote:
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13-04-08, 01:08 PM
| #12 (permalink) |
| Member | Ok so you lift pin 3 up on the ic. Solder a piece of wire to the lifted pin. Then you solder the other end of the wire to the gnd. Im having problems deciding which part of that gnd point to solder to. Theres two sides. And they are separated by the board. Which side is the gnd?? Bottom side in relation to the desoldered pin, or the top side in relation to the top of the chip. Or do you solder it so it connects between both points? |
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13-04-08, 01:26 PM
| #14 (permalink) |
| Premium Member | Lift the pin (make sure you get the correct one), and prepare a short piece of wire, stripped and presoldered. Use your ohmmeter to find a suitable earth point...measure between this point and the tuner, or the casing to ensure the point is connected to earth. Solder one end of the wire to the lifted pin, and the other to your selected earth point. |
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13-04-08, 02:44 PM
| #19 (permalink) | |
| Premium Member | Quote:
I'm not sure about the 4653, but if you check for continuity between sc6 and GND, you have done the job... | |
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