Speccy 48

spodula

In my messing around with hardware, I have managed to nacker a Speccy 48 board. Specifically, i have managed to mess up the power inverter section.

Now, the board appears to be marked (C) 1983 Issue 4S, (Yes, "S")
In the documentation section, there is a Issue 4A, but not a 4S, the layout, and specifically the transistor thats gone to Silicon heaven, doesnt appear to match any of the board layouts in there.

Unfortunately, it appears to be a variant of the power section having an extra Axial capacitor (Labelled C79), a very large TR4 (Labelled C2235A), and TR5 turned 90 degrees.

Does anyone have any information about this board? Specifically what transistor TR5 actually is? Sadly after its little accident, its illegable.

I may be able to get some pictures of it tomorrow if anyone wants them.

Winston

The 4S is the issue 4 board fabbed by Samsung.

It just happens I have an Issue 4S board here, and TR5 is an A733, a bipolar PNP transistor.

Datasheet here: http://www.voti.nl/docs/A733.pdf

I bet any similar PNP transistor would substitute.

gtsamour

Yeah, I've repaired a couple of 4S's before. I used the standard ZTX650 transistor as a tr4, i think it needed to be inverted (in comparison to C2235A) but i don't remember for sure.
I also used a BC213 instead of the classic ZTX213 as tr5, this one had to be installed exactly the same and i think its a direct substitute for A733.

spodula

Thanks! much appreciated.

gtsamour

I checked a 4S board that i fixed in the past. The transistors are exactly as I said previously.