Sourcing transistors

[Hayden]

Does anyone know what a 1B49AA or a 1B50AA is or where to source them from?
I googled those numbers and nothing they lie next to some output transistors in an amp.

Thanks guys

 

[Enzo]

Don't make it a mystery, WHAT amp? What make and model?

 

[Mark Tillotson]

The part number should be on the transistor, not next to it. Probably some manufacturer's code.

 

[indianajo]

If the emitter goes to the base of the output transistor, don't sweat it. Get a pair (npn,pnp) of the same package style, something of about the same introduction date as the amp, or later. You wan't more power capability, not less. Emitter followers are not critical components, except they handle significant current and power.
In TO220 I keep stock MJE15032/33. In TO225 I keep stock MJE340/350. If these are ancient enough to be germanium (pre 1964), scrap the amp, you can't buy much of anything but rejects.

 

[Hayden]

Thankyou so much!!
It is an EV Q1212 amplifier I think it’s the same as the Dynacord SL2400 looks the same.
Normally you can search for the number and a heap of results come up but not this time.
Thanks heaps
Some photos below of where they are located.

20190511-213231 — imgbb.com
20190511-213414 — imgbb.com
20190512-115110 — imgbb.com

 

[wg_ski]

RCA1B series would be silicon. Never heard of the 49 and 50, though. More than likely complementary pair. Are they TO-220, T0-66, or TO-5? Or something else? Are the outputs 1B05’s? That would tell you something about what voltage you need.

 

[rayma]

Does anyone know what a 1B49AA or a 1B50AA is

They look like Fairchild parts.

 

[wg_ski]

Fairchild, not old RCA. The part # is HUF75542, which is a hexfet equivalent to IRF1407. Its the rail switch in a class H amp.

 

[Hayden]

Yes they do have an F on them assuming the brand fairchild?
It's next to a diode 1649AA
The main ones are a NJW3281G if that's any help to you.

see photo attached

20190512-200841 — imgbb.com

 

[avtech]

Fairchild, not old RCA. The part # is HUF75542, which is a hexfet equivalent to IRF1407. Its the rail switch in a class H amp.

Like this from On-Semi? HUF75542P3 ON Semiconductor / Fairchild | Mouser Australia

 

[wg_ski]

The main ones are a NJW3281G if that's any help to you.

see photo attached

See? picture worth 1000 words. You certainly won’t find vintage RCA house numbered parts in the same amp with any variant of the 3281. And the 75xxx Fairchild part #s are easily recognizable if you’ve used them before. Nothing special, but pretty good bang for the buck. They’re meant for low to medium voltage bus switching, which makes the amp class H or G. The other mystery package is probably the commutation diode.

 

[Hayden]

So would the HUF75542 be a great substitute?
Thanks guys

 

[wg_ski]

It says “75542” right on the package doesn’t it? That is the part #. That code that resembles a vintage RCA house # is some sort of lot/date code. They dropped the “HUF” prefix on the batch of 75344’s I’ve been using, too.

Of course you do want to figure out why it failed.

 

[Hayden]

Thanks!!
Yes they blew due to the top lid of the casing being pushed down shorting out the 2 heat sinks on the right hand side of the amp