Orange Tiny Terrors gutted and rebuilt

[Njall_L]

Wow! Where have the last two months gone? I guess it is time for some update on the project.

- PCB tracing and schematic drawing is completed, more on that further below.
- Some components have been ordered but we are still making some final decisions.
- We are currently working on the parts layout within the chassis.

The most noticeable update is that we have painted the housings on the transformers. The color of choice is RAL2003 and it matches the orange on the outside of the chassis very well. This has taken way to much time to paint but we guess it will be well worth it in the end.

IMG_0469.jpeg

Now, regarding the schematics

We have different versions of the PCB, mine is ORA-PC211-1 but Hermannbjorginv's is a ORA-PC211-4. They are very similar but there are some key differences worth highlighting.

- The mains transformer on the PC211-1 has output voltage of 250V and 180V for running the amp in 7W or 15W mode. The transformer on the PC211-4 is however 238V and 173V on the output.
- The PC211-4 has a Hum Balane adjust on the 6,3V line to the heaters but the PC211-1 does not. I think this is is because the PC211-4 has +/-5.0% tolerances on all 1/2W resistors but the PC211-1 has +/-1.0% on those same resistors. Therefor the adjustment is needed on the PC211-4 but not the PC211-1.

1.png

- The value of R23 is lower on PC211-4, 470k ohm compared to 1M ohm on the PC211-1.
- C8 and R19 are "swapped" on the different PCB's. I have no idea why this might be, but it is that way.

2.png

When comparing my tracing I did of the amps to other schematics found online there is one thing that stands out from every schematic I can find. I trace that the tone pot and capacitor come before the volume pots in the circuit but all schematics I find show the tone pot and capacitor after the volume. This however does not seem to be the case. Can anyone share some input on what is the correct since I would like to get second opinion. See image below of my tracing compared to a schematic found here: http://www.prowessamplifiers.com/schema ... error.html

3.png