SA-3A (LA-3A Clone) Support Thread

[Jase_Sanderson]

Hello everyone. I've finally got around to building my Sa3a that's been sitting in a box for the better part of a decade. I've got some Sowter transformers for this, but i'm left guessing as what the correct wiring would be for the interstage transformer. Sowters site lists the transformer as

blue - common
pink - 1:
red - :10

but the original schematic and this board it's listed as

5
2.5
.31

I'm guessing 5 is also common (blue) from looking at the original schematic and beep testing to ground, which could mean that 2.5 is pink and .31 is red, but unsure?? Or maybe they've sold me the wrong transformer?? Shrug!

I messured impedance
blue to red 512.96ohm
blue to pink 6.7ohm
pink to red 507.35ohm

Sorry if there's an obvious answer here, I'm terrible at math

Thanks for any help you have here.

 

[ComodoComplex]

Hello everyone. I've finally got around to building my Sa3a that's been sitting in a box for the better part of a decade. I've got some Sowter transformers for this, but i'm left guessing as what the correct wiring would be for the interstage transformer. Sowters site lists the transformer as

blue - common
pink - 1:
red - :10

but the original schematic and this board it's listed as

5
2.5
.31

I'm guessing 5 is also common (blue) from looking at the original schematic and beep testing to ground, which could mean that 2.5 is pink and .31 is red, but unsure?? Or maybe they've sold me the wrong transformer?? Shrug!

I messured impedance
blue to red 512.96ohm
blue to pink 6.7ohm
pink to red 507.35ohm

Sorry if there's an obvious answer here, I'm terrible at math

Thanks for any help you have here.

Pretty sure it's supposed to step-up the signal, so connect pink --> 2.5, blue --> 5, red --> .31

I'm not sure what those numbers mean in the context of the original schematic, but that makes the most sense otherwise.

 

[Jase_Sanderson]

Pretty sure it's supposed to step-up the signal, so connect pink --> 2.5, blue --> 5, red --> .31

I'm not sure what those numbers mean in the context of the original schematic, but that makes the most sense otherwise.

thanks @ComodoComplex

 

[Matthew Jacobs]

Hi everyone been so long since I DIY'ed but lately been getting more time to finish all my projects so happy about that.

Finally had time to work on my SA-3A and I am almost there. But like an idiot I wired the Molex (J6) the wrong way round, inverting pin 2 & 3. Effectively sending that mid bias point (TP1) straight to ground.


R17 (100r) started burning up a little, still reads 100r and compressor works. Before I take everything apart to replace R17, I just wanted to check with someone more knowledgeable than me if there is any other part of the circuit that may have suffered damage?



Any advice and help i much appreciated.

Thanks