Brook 12A Mono blocks

[sunil]

The power supply was built off this schematic. Measurements shown here are to spec in the build. The negative bias voltage is -63v, a little less than the -67v since the mains supply is lower as well.

Does that help.

 

[trobbins]

That schematic states 10V drop across each output transformer primary, and a winding resistance of 160-165 ohm, indicating 61-62mA. With a plate voltage of 330V, that gives 20W idle plate dissipation - is that ok for your 2A3 valves ?

That schematic seems to be missing a CT for the 2A3 heater winding (H-H).

 

[sunil]

The 2A3s are fine. We noticed the missing heater V and have a 1.5v supply.

I'm reworking the power supply from scratch trying to keep with the original. Could somebody take a look at the choke after the first tap. It's helped control the hum by a lot. I'd like to eliminate that as being one of the problems.

We've also seen one of the dual-caps short, so that'll be replaced soon. The PS values I've used is in this link, from post #35.

 

[FullRangeMan]

Hi all,
?What are yours opinions on the Heyboer transformers?

?Someone know what lamination they use? (thick, type, annealed etc)

Heyboer site dont offered much info last time I see it and now seems offline.

Heyboer have gone?

 

[Briney]

Check C3

The schematic you are using has C3 backwards. Positive should go to ground.

 

[sunil]

Thanks Briney, that too was sorted. I read the threads where this warning was sounded out and made sure we got it right.

 

[sunil]

We got this sorted and the amp is singing. Don't want to hijack this thread, so I've posted a pic in the Tubes 'Gallery' page here.

 

[sunil]

Hi, after the first version of the Brook, decided to go the monoblock route.