Bottlehead Forum

Bottlehead Kits => S.E.X. Kit => Topic started by: Ebdain on September 04, 2012, 01:05:27 PM

Title: 2.1 build voltage problem
Post by: Ebdain on September 04, 2012, 01:05:27 PM

Finally getting my 2.1 S.E.X. amp finished and working through troubleshooting.  Everything was testing great until I got to the voltage checking on A5/B5 and A6/B6:

A5/B5 - I'm getting 35V instead of 75V
A6/B6 - I'm getting 0.2V instead of 2.5V

All other resistance and voltage checks are coming in within tolerance.  So far, I'm coming up blank on a wiring issue.  Any help or advice would be greatly appreciated.


*edit/update*

I think I found the problem already:  cheap DVMs are useless.  Using a better, auto-ranging, meter I found that what I thought were 1.27k Ohm resistors were actually 120 Ohm resistors.  I'm not sure where the 120 Ohm ones are supposed to go as I can't find any mention of them (help?).  I found the 1.27k ones buried on the bench, so now I'll swap out and see if that gets me where I should be.


*edit/update 2, electric boogaloo*

That was the problem.  The amp is now making sweet, sweet love to my speakers.
Side note:  brushing your thumb across the power switch terminals while the amp is plugged in is really not a good idea.  On the plus side, I'm awake now!

Title: Re: 2.1 build voltage problem
Post by: Noskipallwd on September 04, 2012, 04:32:25 PM

Welcome, happy to hear you got your amp making music. I am hoping to finish mine in the next couple of days. I have the extra 120ohm resistors as well. I think they are a holdover from the previous version, they were used to attenuate lower imp. hphones that had some issues with excess gain.

Cheers,
Shawn

Title: Re: 2.1 build voltage problem
Post by: Grainger49 on September 04, 2012, 10:11:42 PM

This is the second time in a few months someone has been led astray by a cheap meter. 

I take this as proof that those who say, "Any $5 meter will work." are wrong.

Title: Re: 2.1 build voltage problem
Post by: Noskipallwd on September 05, 2012, 07:21:02 PM

Quote from: Grainger49 on September 04, 2012, 10:11:42 PM

This is the second time in a few months someone has been led astray by a cheap meter. 

I take this as proof that those who say, "Any $5 meter will work." are wrong.

I'll second that, my Fluke was the best 200 bucks I ever spent.

Cheers,
Shawn

Title: Re: 2.1 build voltage problem
Post by: Grainger49 on September 06, 2012, 02:37:51 AM

You can find a good used Fluke for under $100.  Poster Paully bought a new one for about $90 a year or two ago.  It is my opinion, as a professional user of meters, you can't beat a Fluke for being all but bullet proof. 

Always buy the rubber guard that goes all around the meter.  I have dropped my meters too many times to remember.