[sdiy] How do you source smd parts (for repair)

brianw brianw at audiobanshee.com
Sat Dec 17 03:17:44 CET 2022

I see what you mean. Yes, it's definitely a challenge to find SMD parts if you do not have the official Service Manual from the manufacturer along with their parts list.

In my opinion, there's no way to service SMD parts without some additional knowledge from somewhere. That's either a schematic and parts list - official or community developed - or a basic knowledge of circuits and the ability to reverse-engineer.

One thing you can do is look at the number of pins, and how the part is being used in the circuit, and then make a guess as to what type of device it might be. Then you have to grab the data sheet for the original part, and determine which of the specifications are required (sometimes, the specs can be way over qualified). Finally, you need to select a replacement part that meets the functionality and Absolute Maximum ratings as well as the nominal operating conditions and limits.

Sometimes, even with a schematic from the community and the SMD markings, it's impossible to determine what the original part was.

I was recently working on a synth guitar where the community schematic used vague designations for the transistors, and the markings on the actual SMD transistors were also inconclusive. For some parts it was possible to find a match that fit both pieces of info, but a few parts were complete mysteries. In hindsight, maybe I should just buy a fancy transistor tester, desolder the originals parts (hoping they still work) and scope out the parameters the hard way. You can't really do this with some kinds or parts, though.


On Dec 14, 2022, at 2:04 AM, Jean Bender <lofideadbeat at gmail.com> wrote:
> Well, maybe i was not really good at explaining where i'm bit lost.
> For example, i actually work on an Electro Harmonix pedal, using smd components. Two of them are marked BA132, and i assume they are kind of voltage regulator, but i'm not sure to source them on internet, neither finding replacements parts for them..
> How do you do for easily finding a smd part only from its labelling ?
> Thanks !!
> J.
> Le mer. 14 déc. 2022 à 10:56, Jean Bender <lofideadbeat at gmail.com> a écrit :
>> ok thanks. Never been directly into mouser search engine for that, i gonna check !
>> thanks
>> Le mer. 14 déc. 2022 à 10:42, brianw <brianw at audiobanshee.com> a écrit :
>> Mouser.com
>> For repair, Mouser has a search engine that will allow you to find many replacements, assuming that you understand all the parameters. You might need to consult data sheets to understand the details, but the Mouser search allows you to focus on the parameters that are important to match (or beat).
>> DigiKey is also popular, but in my experience they are always significantly more expensive. I always check, though, when something is difficult to locate.
>> Brian
>> On Dec 14, 2022, at 1:35 AM, Jean Bender via Synth-diy <synth-diy at synth-diy.org> wrote:
>>> > Hi !
>>> > I'm getting more and more into repair, still in a hobbying way, but i'm often in trouble for sourcing them.
>>> > There are a lot of different websites helping to find which part is, but sometimes they don't give the same informations.
>>> > Today i'm mainly working with ........................., but maybe some of you have other ways to do that, or better ideas !
>>> > 
>>> > Thanks for your support !
>>> > J.
>>> > 

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