Mac Plus Analog: 13007 Good Substitute for BU406 Transistor?

[trag]

Several years ago I bought a small lot of transistors on Ebay that the seller had billed as BU406, but they turned out to be a mixture of Samsung (SEC) 13007F 2 and Motorola F13007. The Samsung also has 722 on the next line and the Motorola has R721.

Are these usable substitutes for the BU406? The seller claimed they were...

I tried looking up the relevant datasheets and comparing them, and it looks like at least the voltage ratings are comparable. But my Transistor Fu is not what it once was, so I figured I'd toss it out here. If I'm ever working on a Plus or earlier again, I may just try substituting in one of the 13007s but I have projects lined up a mile deep before I'm likely to get to that.

Thank you for any humorous or helpful responses.

 

[wally]

Digi-Key lists Fairchild BU406FS-ND TO-220 pkg at 68 cents. Going with an original might be a safer bet.

Larry Pina says avoid ECG379, it can cause left side screen foldback issues in the raster.

ECG specs for the ECG379 read IDENTICAL to Motorola MJE13007.

I don't know for sure that your part numbers correspond to the MJE13007, but it seems likely.

Worthy of special note, comparing with the Motorola BU406 spec sheet:

DC typical betas over the sweet spot collector current range .1 to 1 amp are 50 for the original and only 20 for the MJE13007

Ft(min) is 10 MHz for the original and 4 MHz for the MJE13007

The switching times for the MJE may be ok but it may require more base drive than the circuit currently supplies to achieve them.

Although the typical Vce sat curves look fine, Vce sat max for MJE13007 is 2V, twice that of the BU406. Even when driven hard, it may not turn on as well as the original, perhaps the price paid to achieve the much higher safe operating area high voltage specs.

There is always a wide variation in beta unless the parts are selected. If you do some experiments, select some high and low beta examples from your lots to see if it matters.

 

[trag]

Thanks, Wally. I appreciate it. I'll just throw these in the random parts bin, and not keep them for Plus repair. I have a small supply of actual BU406s which I bought after the 13007 debacle, but I didn't want to down-rate the 13007s if they were usable.

Now if I could just find a supplier which still has the flyback transformers in stock...