S.E.X. > 2A3 Monoblock OPT

[Paul Birkeland]

That is 20 to 35 times more than they need to be rated for; it's a non-issue for these parts.

Pretty much none of the resistors in the original afterglow circuit gets worked particularly hard in terms of voltage.  The power supply bleeder is going to see close to 500V on start-up, so that's a consideration. 

 

[Ken]

I understand but at 1/4W for the R values listed on the parts sheet, 200V is the lowest that I can see on the Mouser site.  Obviously, they do have some with lower V rating but not corresponding to the other specs we need.

 

[Paul Birkeland]

You do not need to hunt for a low voltage rating, as any voltage rating is more than enough for these parts. This is a maximum voltage, nothing bad happens if you run a 500V rated resistor at 1V.

 

[Ken]

I understand; just trying to keep the cost down by not over-spec'ing what I really need.

 

[Ken]

Paul B:  Here are the 270Kohm bleeder resistors that Mouser is showing in carbon film 1/2W.  The max voltage rating offered at these specs is 400V.  I don't understand the difference between the two items listed: one is almost twice the price of the other, at what appears to be the same specs.

https://www.mouser.ca/c/passive-components/resistors/film-resistors/carbon-film-resistors-through-hole/?power%20rating=500%20mW%20%281%2F2%20W%29&resistance=270%20kOhms&voltage%20rating=400%20V

 

[Paul Joppa]

The bleeders dissipate a bit over 0.5 watts. At full rating, inside a tube amp, they will get VERY hot! For reliability, they should be rated for at least three times the actual dissipation - you should use 2-watt resistors. A working voltage of 500v minimum is required, to survive the turn-on transient voltage.  #things_they_don't_tell_you_in_the_specs

The different part numbers indicate how they are packaged, loose individual components, or taped together in reels of 4000 resistors for use in automated insertion machines. See the spec sheet, bottom of the first page.

 

[Paul Birkeland]

Here is the recommended bleeder:
https://www.mouser.ca/ProductDetail/Xicon/294-270K-RC?qs=OFGmc1Cs8YZtYy8epssWyA%3D%3D

 

[Ken]

Paul B:  that resistor shows out of stock at Mouser but I found an equivalent at PartsConnexion for pennies more.

Thanks to both of you for the education