Help me ID some part numbers?

Discussion in 'General Electronics Chat' started by tester272001, Sep 7, 2012.

  1. tester272001

    Thread Starter New Member

    Aug 24, 2012
    I have a PCB (see attched photo). I am interested in what the correct way to read some of the parts. For instance: Q6, D10 or D11, Q8 or and any of the aluminum CAPs. For instance C179 says E4 100C CD. Is that 100uf? If so what is E4 and CD ? I googled that and did not find any good info. The Q6 for instance says FDK 11AD 749 what is the part#? 749 or the 11AD? is FDK the mfg? I was guessing Fairchild but could not find the xref for a 749 or the 11AD (I think the 11AD is a data code?) - someone that has some experience in reading these would be greatly appreciated. I've mostly worked with older repairs like standard electrolytics, etc. Any tips on these caps? Do they ofter go bad? I have a short and I think its Q5, it get pretty HOT and looks like its bulging a but. Ready to start smoking.
  2. WTP Pepper

    New Member

    Aug 1, 2012
    I wouldn't waste my time. These days components are made specifically for a manufacturer for a specific product. The markings are often internal referenced components.

    e.g Vishay may supply all SM components to a DVD manufacturer in the millions. The value may not even be represented, but the DVD maker will know where part X3424532 goes even it is just a simple 100uF capacitor.
    PackratKing likes this.
  3. tester272001

    Thread Starter New Member

    Aug 24, 2012
    wow, I guess I am an old timer. I remember a time when every part has a method to the madness. You could xref anything in NTE ow ECG! the times, they are a changing eh :confused: well thanks for the reply. Your explaination is appreciated. :)
  4. tester272001

    Thread Starter New Member

    Aug 24, 2012
    Reply to my own thread...the 749 and 649 are FTZ749 and FTZ649 respectively. I tried google without the rest, like +749+transistor+smd and that yeilded the match. So, its not impossible to get the data for these. Just a hint for anyonje that might come across this thread in the future. ;)
    Update: the Diodes are read like this: SR24 - SURFACE MOUNT SCHOTTKY BARRIER DIODE
    So I guess this stuff is not impossible like WTP Pepper thinks. How abut CAPS? they have to be standard. I will repost if I find a good guide. There is no way those numbers on the caps are internal to a product ot mfg. caps have always had some industry standard - at least for the last 40 years or so.

    OK another edit for benefit of others: good site on SMT caps:
    And how to read them:

    I must have been zoned out to not have been able to find this stuff yesterday! Hope this helps others.
    Last edited: Sep 8, 2012
  5. praondevou

    AAC Fanatic!

    Jul 9, 2011

    post a clearer picture of it

    where is it?

    EDIT: just saw you found the transistors
  6. absf

    Senior Member

    Dec 29, 2010
    Q5 and Q7 looked like SMD 8-pin SMPS chips. They have corresponding inductors L4 & L5 next to them.

    I guess they are chips like MC34063 or similar. Try to compare their circuit with the datasheet and see if they match.

  7. tester272001

    Thread Starter New Member

    Aug 24, 2012
    Q5 and Q7 are IRF7313 hex power mosfets. I've measured the input b+ voltages and the input is dragged down from 13.5 to like 6.5 volts. Something is badly shorted. I tested all the caps with ESR meter and all read OK. Tested with Ohmeter too and don't show short (but you never know). The coil at the input L537 was shorted. (I bypassed with a couple wire jumpers) It was a dual combined coil SMT device and must have gotten so hot it melted the laminate shorting the input. I am attaching another pic to see if that helps at all. I will take any troubleshooting tips you have on this.
    I get an error adding another pic:"Your submission could not be processed because a security token was missing." - I have no idea what went wrong. I will try to link to an offsite pic.
    Last edited: Sep 9, 2012
  8. tester272001

    Thread Starter New Member

    Aug 24, 2012
    OK I am posting a pic of this board with some things I've checked. The CAPS circled in Yellow all read zero Ohms from either side to ground. I've pulled the caps on the left and checked them they were OK and the short still existed. (I replace Q5 also since it was bulging, perhaps getting ready do smoke).
    If I pull Q4 from the circut the voltage is normal but none of the supplies are up. There are 5V, 3.3V and 1.8V lines. When Q4 is back in circuit the voltage drops from 13VDC to like 3-4 VDC. Definately a short somewhere. I've gone over boths sides of the board with high power magnifying glasses and there are no visible burn marks. The L537 (right at the power plug bottom) I jumped since it was a dual coil package and had melted from the current and shorted. From the looks of the board is it likely an Electrolytic cap or an SMT ceramic one that could fail? Do they ever short to ZERO ohms (ceramic)? Oh and the CAP on the right in RED circle reads shorted but if I reverse the ohm meter it reads a resistance. (from Negateive to ground). I checked all the caps with an ESR meter and they read like zero ohms, which I think is normal for most of these electrolytics. What are some good tips on diagnosing this type of short?
    Last edited: Sep 14, 2012