Re: hobby electronics

"Martin Brown" <'''newspam'''@nonad.co.uk> wrote in message news:v6edtl$cvkh$1@dont-email.me...

On 07/07/2024 00:01, Edward Rawde wrote:

"Martin Brown" <'''newspam'''@nonad.co.uk> wrote in message news:v635o1$24goj$1@dont-email.me...

On 02/07/2024 17:28, john larkin wrote:

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Some of these guys blame surface mount, which seems wrong to me. There
are lots of thru-hole parts and parts kits around.

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Surface mount has rendered modern kit all but impossible for the home user to repair. I cut my teeth mending transistor car
radios
back when chassis earth was chosen randomly by each car manufacturer to be either positive or negative and people blew up their
brand new car radios.
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The other big earner was mending teenage wannabe rock stars amplifiers that had their output transistors fried or a pint of beer
in them.

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Anyone remember SN76013N/023N.
Horrible things, particularly when it must be your fault that the replacements (two for stereo) blew up again a few days after
repair.

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ISTR a remarkable number of 741s or 709s inside them and the odd SE540 in the better ones. 2955/3055 output pairs - before power
FETs took over.

STK devices were fairly common too.
https://www.youtube.com/watch?app=desktop&v=ghyZZSC0Qbw
About 15 years ago a friend asked me to look at a tuner/amplifier which had these in the audio output.
Someone else had cracked the plastic cover off and replaced the short circuit output transistors by wiring to an external pair.
TIP41/42 maybe but I forget exactly. It was working but there was crossover distortion.
Whoever did the repair likely didn't have the Internet.
With the Internet I was able to obtain a replacement device which worked fine and probably wasn't fake.
I wonder if the fakes shown in that video actually work.

When I worked as a designer I came across fake parts a few times.
One reel if devices was SO8 and the devices were marked with the correct number but the manufacturer didn't make that part in SO8.
So it wasn't hard to spot the fake.
Another reel of devices did have the correct part number on the correct package but it was anybody's guess what chip was actually in
the package.

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--
Martin Brown