BC109 to BC550

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13-Mar-2018 04:11 PM

QuadOAP

QuadOAP

Posts: 12

On a recent refurbish of my friends 33/303 Amps, I noted that all the BC109 transistors were being replaced by BC550c transistors. Is this worthwhile doing, I refurbished my own Amps a few years back and this was not in the revision. 

I had a fault 2 years ago which turned out to be one of the BC109s, so I replaced all the BC109s at that time. (got a batch deal)

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13-Mar-2018 11:46 PM

EJP

EJP

Posts: 1484

As a general rule, BC107=BC547, BC108=BC548, BC109=BC549, where BC54x is better in each case (more gain). We started using BC550 a few years ago as it is slightly lower noise than BC549. I don't know that I would rush out and replace a dozen BC549s with BC550, but you should use the latter in any repairs.
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