Good place to search for obsolete or substitute parts.

[paul8f]

Just wondering where do most people go when searching for discontinued or difficult to find components like old ICs and transistors etc?

I'm hoping there is some sort of master database, that when searched spits out a list of suppliers or recommended substitutes...!   

[TERRA Operative]

Google is that master database.

I have purchased from a number of places to get parts, Sphere, utsource, Ebay (but be cautious), Akihabara, Yahoo Auctions Japan, and a few other Japanese parts companies (Wakamatsu is one that has old parts), etc, etc.

[Kjelt]

Or here on the forum, many people have private collections they rarely use and if for good use are willing to give away or sell for a fair price.

[paul8f]

Cheers! Thanks for the info.

[Brumby]

Octopart is one that seems to show obscure stuff.

[bitseeker]

And sometimes you just have to buy a donor unit to be your parts mule/supplier.

[paul8f]

And sometimes you just have to buy a donor unit to be your parts mule/supplier.

I agree, that's always the other option. (But when you see items for sale as 'For Parts Only' is there a risk that the very component you need is also faulty on that board?)

[wilfred]

If you're lucky you have access to an old electronics store. Like Rockby in Melbourne. But even their old stocks are thinning out.

I swear I once saw a tube of 4004's.

But now I think I must have imagined it. I didn't believe it at the time (~ a year ago) so I went back the next day and couldn't find them. I knew they needed a set of ancilliary chips to function but I thought they looked classy with a gold top and pins.

I did get a pair of MAX038's 6 months ago. I really must do something with them. No, they don't have more.

[paul8f]

Google is that master database.

...You could be right on this one Terra...!

[bitseeker]

(But when you see items for sale as 'For Parts Only' is there a risk that the very component you need is also faulty on that board?)

Yes, that is a risk, and it must be weighed against the asking price and how badly you need the part. Depending on the component you seek, though, even new-old-stock can have risk of failure or dead-on-arrival due to age.

It's all part of the adventure.

[paul8f]

...even new-old-stock can have risk of failure or dead-on-arrival due to age.

...which components are the worst culprits to watch out for? (I'm thinking dried out electrolyte, frayed rubber drive belts, ePROMs after magically erasing or corrupting their memory, stuck relay contacts, RTC/non-volatile mem. batteries leaking)?

I suspect old models advertised as new-in-box carry the same risks!

[bitseeker]

Also carbon resistors drifting way out of spec.

Yes, "new" doesn't mean much for aging items. Time still passes.

[vk6zgo]

Treat semiconductor substitute lists with suspicion unless they contain abridged specifications for each device.

With the other lists, you often have as much chance of success if you just make a guess.
Many BJTs are the original "jelly bean" devices, & can be fairly freely swapped.

Equipment manufacturers like to minimise inventory, & will use the same discrete device in a critical & non critical position.
If you need one for the former position, just steal it from the latter, & replace the one  removed from that position with a "jellybean" part.

Another good trick, is to look at how another manufacturer does something.

If they use a common device, in a very similar circuit layout, there's a pretty good chance it will just "slot into" your circuit.

[bdunham7]

Just wondering where do most people go when searching for discontinued or difficult to find components like old ICs and transistors etc?

I'm hoping there is some sort of master database, that when searched spits out a list of suppliers or recommended substitutes...!   

There's no good single answer.  One thing to do is if you aren't already a specialist or collector of the device you are repairing, seek out those who are.  If it is audio equipment, for example, there's Audiokarma and similar websites.  In general, be prepared to do some work, take some risks and make some mistakes.  And, of course, be aware that any rare or obsolete component with any demand will probably show up as a fake on Aliexpress and eBay.