searching replacement to transistor

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  • Haaheim
    Bias matching replacement transistor - Parasound 2250
    by Haaheim
    Hi guys!

    I am currently working on a Parasound 2250 (class AB), which had one defective channel. Components in the signal paths have been replaced, including an output transistor (2SC3519).



    According to the manufacturer, bias is adjusted by measuring 1-3mV across the output resistors. The original ones are completely fine around 1.5mV, but the replacement is not. Initially, I got a couple from eBay, assumed they were fake (they were) and was able to source a replacement locally. This exhibits similar behaviour, being around 0.6-0.8mV on its emitter resistor....
    05-13-2022, 12:45 PM
  • acedogblast
    Guide to transplant MEC1503 EC chip and EEPROM reprogamming for T14s gen 2 and X13 gen 2
    by acedogblast
    This is a guide that I am writing for helping others to replace their MEC1503 EC chip if it breaks (or to get around an inconvenient prompt to the BIOS). This forum has been extremely helpful to me so I would like to contribute to help others. I will tell you right now that this task is very difficult to do. You MUST have experience and tools to do precision micro-soldering, BGA reballing, trace repair, and general laptop repair skills.

    There are some specialty tools needed to do this task. The replacement MEC1503 chips can be acquired from Aliexpress. Do not buy the bare chips as...
    11-02-2024, 05:13 PM
  • reformatt
    Macbook Air M2 A2681 Kernel panics after screen replacement
    by reformatt
    Just had a customer bring in a M2 MBA A2681 that had had a screen replacement in April at another repairer. Since then, she has been getting intermittent kernel panics. It's an aftermarket screen, and of course it fails in diagnostics as the calibration hasn't been done. The error in the panic log is "No device added after powering on the rails".

    It seems the original repairer has swapped the board and the screen to other MAC's, and said that it isn't a screen issue. From what I understand, by doing a quick search on Google, this is in fact a screen issue. The panic relates...
    07-31-2025, 08:37 PM
  • redbaron1007
    Crua CR270C shorted input.
    by redbaron1007
    I've got a Crua CR270C that had a short to ground on the input jack. The input was rated at 12v 4A center pin positive. When I took the board out and powered it with my bench power supply it jumped to 3v and 4A CC and a chip labeled either TM3db2 or TV3db2. I'm not able to find anything online typing in those strings of letters and numbers and searching websites like s-manuals hasn't yielded anything. It is an sot23-6 package type according to my digikey ruler and I was able to work out some of the pinout from voltages on the board and following the traces around. I'm not really sure what a suitable...
    03-12-2025, 02:10 PM
  • the_rem
    Unknown transformer : how to find a good replacement part ?
    by the_rem
    Hello guys,

    I would like a quite old but still good 800 W ATX PSU to be repaired. The problem was an extremely heavy coil whine coming from the small secondary transfomer on the PCB.

    I desoldered it hoping the references on the upper side would allow me to find a adequate replacement part. Sadly the written references drove me nowhere but to the manufacturer (I-MAG). I sent them a message like a bottle in the see asking them to send me a datasheet of the transformer. And... They responded ! I received a kind of datasheet (see attachment) but my competencies do not allow...
    VEF20FB07BW(2025001A)20110927.pdf
    https://drive.google.com
    04-23-2025, 01:48 AM
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