Need help quick please! P101 bias related

[brianuk]

Sounds like goodstfuff, or should I say it will do.

Good game Shinobi x x x x x x x x if thats what the name is from.

Goodluck with the project

 

[ShinOBIWAN]

Sounds like goodstfuff, or should I say it will do.

Good game Shinobi x x x x x x x x if thats what the name is from.

Goodluck with the project

Yep taken from the very same arcade machine, my personal favourite from the 80's, a top game. Big fan of Starwars too so that's how it figures.

Cheers.

 

[ShinOBIWAN]

Re: Re: Need help quick please! P101 bias related

You probably already have the answer but turn VR1 CW (clockwise) to get minimum resistance. Check with a DMM from the single pin to the 2 joined pins to be sure. BTW, you've got a 20K in your post.... typo? as should be 2K.

I'd be interested how the final bias voltages come up as I didn't get close to the documented values across the 100R test resistor.... a lot of others haven't either. With min resistance on VR1 I was getting 0.68V-0.85V and on the final 2.68V-2.87V. Amp works well without any problems.

Cheers

Sorry missed this one!

Typo with the 20K I did mean 2K 😉

Voltages across the resistors with minimum resistance on VR1 and using the 58VDC supply was 1.84v, after adjustment ~3.87v. Why are your so low? I presume since you are happy that it doesn't really matter.
Measuring across the speaker output reveals 4-5mv.

I have made some changes to the standard component suggestions, I'm using black gate electrolytics and also using Exicon fets after Rods recommendation that they are quite possibly better sounding than Renesas/Hitachi parts.

 

[rabbitz]

Works well with no problems so not an issue. I've seen a few posts around with lower voltages when doing the bias. Good to see someone with a higher value... maybe component choices... who knows.