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Epson scanner Perfection 1650

Discussion in 'Troubleshooting and Repair' started by Hardisk, Aug 27, 2010.

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  1. Hardisk

    Hardisk

    6
    0
    Aug 27, 2010
    Hi
    I've just discovered this interesting Forum,. looking for schematic of my poor scanner Epson Perfection 1650..

    Owing to a short circuit in the inverter transformer (I've already fixed the inverter circuit, replacing the shortened transformer), I've found two exploded components on the mainboard i.e. : SMD transistor Q7 and capacitor (smd) C3. I don't know the type or the value of these components, besides the burned transistor has caused a 'black hole' and I cannot easily identify its wiring connections. I think it's a general purpose NPN power transistor, but it may be also a darlington.
    Is it possible finding the S.M. or a list of the electronic components?
    Regards
    Donald
    PS
    The scanner works, but light is off, because no supply voltage reaches inverter circuit

    :)
     

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  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    OK, Q7 -- definitely a transistor, but it has also clearly died in a spectacular manner. I can't even see the pads any more. You'll have to clean up the board (isopropyl alcohol on a cotton bud would probably do the trick).

    Why do you think the transistor is bipolar, and why NPN? A mosfet is also a possibility.

    The board looks like it's multi-layer so you will have almost no chance of visually tracing the circuit.

    The best bet would be to find someone with the same model and get them to photograph the same section of board. Even then, the surface mount capacitor will likely not have any markings, and the transistor will have a code on it rather than a part number. I would also not totally discount the possibility of another component in that burnt area.

    Good photograph by the way :)
     
  3. Hardisk

    Hardisk

    6
    0
    Aug 27, 2010
    success! (I Hope)

    Hi
    Thanks
    Obviously, I've cleaned any part of the board and, following the circuit, I've found that the output(emitter) of Q7 is directly connected to inverter power supply (Q7 is a regulator tranistor) Collector ( heathsink) is connected to 24V and the base to a couple of resistors, so this transistor is N channel. I've tried to install a BD137 and my scanner began working again. Q7 is (according to my opinion) a general' half' power transistor NPN , working as regulator, in order to decrease 24Vdc to 12 V dc for inverter power supply.
    At this point I've to clean only inverter board and reassembling this ..experimental circuit . I've also to put Bd137 in another place ,with a new heathsink.(owing to mainboard damage)
    C3 capacitor is still 'unknown' , but it's no much important...

    Regards
    Donald

    :)
     
  4. Hardisk

    Hardisk

    6
    0
    Aug 27, 2010
    Last news...

    Hi
    Bd 137 went into 'over-heathing' and burned (three times)

    I've noted that output voltage (on emitter) was 21V instead of 24V, so I've increased base control positive voltage, in order to obtain an output voltage of 24V, and BD137 doesn't burn and my scanner is perfectly working. Now I've to clean the scanner from... ash and dust and reassemblig it.
    Regards
    Donald
    P.S. Without schematic it is very difficult to fix a device
    :)
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    It's great that it's working, I just wonder why you figured that the voltage on the emitter should be 24 volts?

    I would be wondering *why* the base drive was insufficient (could be due to the failure of whatever is driving the transistor, or due to a higher than expected load).

    And how did you increase the base drive?
     
  6. Hardisk

    Hardisk

    6
    0
    Aug 27, 2010
    OK

    Hi
    My scanner is working and it's cool!
    I've read (somewhere online) that the voltage supply for the inverter is 24V DC, and the emitter of Q7 is directly connected to the positive pin of the inverter.P.S...!!!
    Owing to (I suppose) the different transistor type, the driving voltage of base was, instead, less than 21 V! and Q7 was working badly, so I've tried to connect a 10 Kohm trimmer , in series with a 1 Kohm resistor between base and collector. Acting on this trimmer,I've regulated the emitter output voltage, until 24 V DC exactly. At this point Q7 stopped overheathing. In this case, I've found that the best value of the resistor is 3900 ohm, besides I've also replaced bd137 with other types (I've tried also with a Bu508) Now I'm testing the device, before reassembling it, to be sure of a good (and long) working(Do you know Murphy's law ??)
    Regard
    Donald:)
     
  7. Hardisk

    Hardisk

    6
    0
    Aug 27, 2010
    Last news:

    In order to be sure, I've replaced the inverter with another more powerful, and added a suitable regulable switch power supply for this inverter. Now I am able to increase or decrease the light too. This is, for me, a very useful tool!
    I've tested any function and all is right.
    Epson Smart Panel isn't fully working, under Windows 7 (OCR , negatives and slides are missing) so I've installed Vuescan.
    Regards
    Donald
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    vuescan is a great tool (or at least it was the last time I used it)
     
  9. Tesla

    Tesla

    165
    2
    May 10, 2010
    If your old scanner won't work under native Win7, try Windows XP Mode (the new Virtual PC). It supports USB devices now.

    I got XP-Mode working so I could install the old XP driver package ... but when I connected the scanner, the XP Scanner Wizard saw it, installed the proper driver, and I just used the built-in XP scanning app.
     
  10. Hardisk

    Hardisk

    6
    0
    Aug 27, 2010
    Hi
    Windows drivers are perfectly working(without using compatibility mode) , but there are some functions of SmartPanel missing, however I've tried also in this way, but without any success. The fault is caused by Epson scan software , while drivers are right!
    Third parts softwares (like Vuescan) recognize my scanner and unable these missig functions (OCR... u.s.w.) In any case my scanner is fully working, by means of Vuescan!
    Regards
    Donald

    P.S.
    I'd several difficulties installing the drivers of my old HP4400C under Windows7 (Now all is OK, after several trials and tricks) )
    On the contrary.. HP 4400c official drivers for W7 don't exist, but HP (XP) software is fully working in compatibility way with XP SP3

    :)
     
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