Microtube 100 Transformers

[Yazoo55]

Does anybody know the specs for the two transformers in the Microtube 100 please? I would like to have a go at building one. I'm thinking of doing a single channel version. I've had a look through the available schematics and was unable to spot this.

And another request - if you have any close up photos of the circuit boards, I would find them very helpful. I've found a few on the web but the quality is not very high.


It's always a learning process. I now know what a Pepi switch is - a thermostat to switch off the power if it gets too hot, great name. :)

[Yazoo55]

I went ahead and built this and it works which is always a relief. I used the schematics from this site. I was a bit worried about a note describing a current limiting piggyback board which was retrofitted to the main board. I couldn't work out how this was wired. Fortunately, my build seems perfectly happy without this. I haven't had any blown fuses. I bought a cheap KVM rack off eBay to fit it all in and got the main PCB manufactured in China. I used a couple of back-to-back transformers in place of the custom transformer which supplies the 12AX7 heater and plate voltages. These were quite cheap, again off eBay.

I have attached a picture. I am using it with a clone of the Alembic F2B I built and it gives a very clean sound.

[bunkyloo]

  Totally cool!

[MarshallJMP]

Nice

[rnolan]

Wow nice job  :whoohoo!:

[Aelfad]

So how did you figure out the trasformers' specs?
Anyway, I'm impressed!

[Yazoo55]

Thanks for all the thumbs ups. :)

In the end I guessed the transformers. I knew the tube heaters needed 12 volts and the plate 170 volts. With the back-to-back transformers, the 12 volts was fine but the plate ended up getting around 160 volts which works fine. For the toroidal transformer, the schematic says it should be 52 volts after rectification. I just tried to get as close to that as possible without breaking the bank. I got a 2x18V wired in series. After rectification, this gave me around 50V.

It's great that all the schematics are available on this site. It is a really good resource.