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Hi.

I bought four FST3253 chips to replace broken IC3 and IC4 in QDX (probably
either a spike from the antenna or a self-oscillating PA killed them, and
killed the op-amps... but I replaced the op-amps and they're fine) and
they all behave in a strange way (for example, IC3 gives 5V to one of the
pins connected to L12 -- I don't know which one without desoldering L12).

It seems they are fake, and I can't find any trustworthy shop.

So there are four questions...

1. Do you know of any source of genuine FST3253 that would ship to Poland?

2. If not, maybe Hans could send me a couple of them (I'd like to buy 4 or
maybe even 8 of them, depending on the price, to be safe if they get
killed again) for some fee?

3. If not, is there a pin-compatible replacement that's available?

4. If not, is there any pin-incompatible replacement? I could botch it in
if there's no other option. Maybe HC4052 would work? Did someone
experiment with it in this circuit? Would it be fast enough?

The shop where I bought these fakes has two versions:

- PBOAA (for around $1.52)
- PG5AB (for around $4.37)

Maybe it's their enigmatic way of saying "the cheaper ones are fake and
the more expensive ones are genuine"? Especially as one Chinese offer has
PB0AA on their picture too...

Thanks.

I would try farnell, digikey.?

73 Bojan S53DZ

Shirley Dulcey KE1L <mark@...> wrote:

The SN74CBT3253CDR is a pin-compatible replacement from TI. (The
SN74CBT3253CD, without the R, is the same chip in a tube rather than
tape-and-reel, but it usually costs more.) Hans is now using it in new QCX
and QDX kits; the actual FST3253 in SOIC was discontinued a few years ago.
Distributors have lots of them. For example, there are over 2,800 in stock
at Digi-Key; they cost US$0.71 in quantity one here in the US.

Unless you can't find any distributor that has the chips and will ship them
to Poland, there is no reason to resort to dubious sources from Asia. The
genuine parts are inexpensive.

Thanks Shirley!

In the meantime, I asked the seller what's the difference between PBOAA
and PG5AB and they replied that "PG5AB has less chance to be fake". Wow.
At least they're honest.

I ordered two of them. If they're counterfeit as well then I'll look for
the ones you mentioned (I can't find them locally, but as you say, DigiKey
has them).

Adam via groups.io <qrp-labs@...> wrote:

In the meantime, I asked the seller what's the difference between PBOAA
and PG5AB and they replied that "PG5AB has less chance to be fake". Wow.
At least they're honest.

I ordered two of them. If they're counterfeit as well then I'll look for
the ones you mentioned (I can't find them locally, but as you say, DigiKey
has them).

That was a hit -- they're genuine, QDX is working again.

Andre Thomas <andre1024@...> wrote:

Hi Adan, which one, the "PG5AB" was a hit, or the ones from digikey was a
hit?

PG5AB turned out to be good. PBOAA were fake.

I'm in ZA (ZS6-land) so ordering from digikey is tricky/expensive... I
looked at the ali ones too but not sure if they are any good... of course
mine will not be for a QDX but rather just some experimenting with the
FST3253 on some dead bug constructions :) and maybe to keep one spare for
my QCX+ in case I ever damage it...

I see... I ordered in a local (Polish) shop.

Glad you got it working either way!

Thank you :)

On Donnerstag, 15. Dezember 2022 02:14:51 -03 Andre Thomas wrote:

Hi Adam & Shirley,

Thanks... interestingly I managed to order directly from TI through
their website... 10pcs including shipping (it says 3-5 days but don't
know how they send it yet) for just under $12... needless to say most
of the $12 was for the shipping!

I did not know this was an option before and if it's only to selected
regions but I thought I'd post the info here in case anyone else can
benefit from it.

73, Andre ZS6CO

Hi Andre et all,

even if one buys TI semiconductors from Digikey they might eventually be
shipped directly by TI. Digikey is just the broker in those cases.

73 de Eike KY4PZ / ZP5CGE (former ZP6CGE)

On Wed, Dec 14, 2022 at 2:55 AM Adam via groups.io <qrp-labs=

[email protected]> wrote:

Andre Thomas <andre1024@...> wrote:

Hi Adan, which one, the "PG5AB" was a hit, or the ones from
digikey was a hit?

PG5AB turned out to be good. PBOAA were fake.

I'm in ZA (ZS6-land) so ordering from digikey is
tricky/expensive... I looked at the ali ones too but not sure if
they are any good... of course mine will not be for a QDX but
rather just some experimenting with the FST3253 on some dead bug
constructions :) and maybe to keep one spare for my QCX+ in case
I ever damage it...

I see... I ordered in a local (Polish) shop.

Glad you got it working either way!

Thank you :)