Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: shortfuse on August 17, 2015, 11:01:27 pm

Title: Can I use a polarized cap in a non polar posistion
Post by: shortfuse on August 17, 2015, 11:01:27 pm

Specifically in position C43 & C44 in the Marshall Schematic attached.  They are to the right of the OT on the schematic.
I am re capping the amp and purchased Polarized caps as all others are polarized, the old ones @ C43 & C44 the say non polar on them do I need to get and install non polar caps in these positions?  Or can I utilize the polarize caps?

Title: Re: Can I use a polarized cap in a non polar posistion
Post by: John on August 18, 2015, 09:47:14 am

If it were me, I'd stick with the non polarized. I'm am *guessing* it's got something to do with the signal flow from the OT? But anyway, if they spent the money on 22uf N-P, it must be important.

Title: Re: Can I use a polarized cap in a non polar posistion
Post by: shortfuse on August 18, 2015, 11:23:59 am

10-4 that's what i was thinking as well.  Thank you for the reply

Title: Re: Can I use a polarized cap in a non polar posistion
Post by: sluckey on August 18, 2015, 11:54:23 am

Those caps are part of a voltage doubler circuit that provides a negative vdc to be used for output tube bias. They don't have anything to do with the OT. I would replace them with non polarized electrolytics. You can make a non-polarized 20µF cap by connecting two 40µF polarized caps in series with either positive or negative leads of each cap connected together.

Title: Re: Can I use a polarized cap in a non polar posistion
Post by: shortfuse on August 18, 2015, 12:19:39 pm

Thanks Steve
I found and ordered the size and value in need from Mouser

Title: Re: Can I use a polarized cap in a non polar posistion
Post by: John on August 18, 2015, 08:01:23 pm

Quote from: sluckey on August 18, 2015, 11:54:23 am

Those caps are part of a voltage doubler circuit that provides a negative vdc to be used for output tube bias. They don't have anything to do with the OT. I would replace them with non polarized electrolytics. You can make a non-polarized 20µF cap by connecting two 40µF polarized caps in series with either positive or negative leads of each cap connected together.

Well, at least I had the "it must be important" part right!