45 TSE desired tube current? Acceptable B+?

[Alan Hope]

Reached the checkout stage, and must confess a bit nervous. Read and re-read the checkout/bias sections of the manual, a couple of questions ...

Near the end I do the "slowly adjust pots R12 R23 to raise output tube current to desired."

What is the desired output tube current for 45s?

What is the acceptable range for B+ in a 45 TSE?

[evanc]

The 45 should be biased in the 25 to 30 mA range. I use 28 to 30 mA on 280 volts, and 26 or 27mA if operated at 320 volts.

right out of the manual.....

[Alan Hope]

Ta,
Yeah, found it now. Blush.

One more question. I have breadboarded the amp at present. I have Electraprint OPTs - do I need to ground the outputs from these?

[boywonder]

Originally Posted by Alan Hope

One more question. I have breadboarded the amp at present. I have Electraprint OPTs - do I need to ground the outputs from these?

Grounding the speaker negative assures nothing is floating, and at my house, I sometimes run vintage Polk SDA speakers (with an umbilical between them) that requires the speaker -ve to be grounded.

I'm no expert, but IIRC it's also important to ground the speaker -ve when running gnfb (not the case here, of course)......

[jpjones3318]

There's also a safety issue in that if the primary shorts to the case or the secondary, you'll have full B+ on the case or secondary. Speaker negative and the transformer case (at one of the mounts) should always be connected to earth.

[Nikon1975]

Not in all the OPT. Silk transformers are designed to have the secondary floating. The case should be grounded.

D.

[Alan Hope]

Thanks ...

The Electraprint transformer legend says of the negative output - "this to ground if needed"

Will start with negative ungrounded, case grounded.

[jrobson]

You should ground the grey wire, there is a thread on here where George states that you should ground them.

[Alan Hope]

OK, will do.