50 watt bass project!!!!

stokesdead · Post by **stokesdead** » Fri Jun 01, 2007 7:46 am

So it isn't a problem that my fuse is only rated at 250V and I am measuring 450V across it? I got the fuses at radio shack.

I will check the wiring this afternoon. So you are talking about the 2 resistors in series near the far right side of the board? I believe thier values are 8k2 and 10k. And then you are referring to the 10k resistors where I installed the 16uF preamp caps. Am Iunderstanding this correctly?

10k&8k2 > 10k > 16uF >10k > 16uF > V2.6

I will check this this afternoon.
Thanks Neikeel

~CS

neikeel · Post by **neikeel** » Fri Jun 01, 2007 10:14 am

Yes, there are the two resistors 8k2 and 10k in series (feed to this from choke) other end goes to the 100k and 82k tie point in the PI (plate resistors for V3). This then goes to the 10k->16uF->10k->16uF with V2.6 coming after the first of the 10k resistors in the middle of the board. This link after the second 16uF tehn goes to the 100k plate resistors of V1

stokesdead · Post by **stokesdead** » Fri Jun 01, 2007 10:36 am

Yeah I'll have to check that when I get home. What about the fuse? 250 Volt fuse in a spot of the circuit where the voltage is 455 seems like a problem to me. Is it?
~CS

neikeel · Post by **neikeel** » Fri Jun 01, 2007 10:44 am

The mains fuse will be 120v 3A and the HT fuse is probably ok for voltage, it is the current 500mA that is important (someone chime in if I am off the plot

)

stokesdead · Post by **stokesdead** » Fri Jun 01, 2007 10:49 am

OK just wondering why it would be blowing.

I'll take a look at it tonight.

stokesdead · Post by **stokesdead** » Thu Jun 07, 2007 7:53 pm

Neikeel I believe you got it. I moved the blue wire one turret over and the tone is much better. See picture below...

Still not completely satisfied with the tone. The problem is I have no time to play this thing it is so LOUD. When I get the kids to bed I can work on it but definitely can't test it. If I get home from work fast enough I have like a 10 minute window before Mommy goes to work. Like I said if I am lucky. Hopefully this weekend I will have the time to crank her up for a few hours.

OK I feel like such a dummy but I have to ask...How do I bias?

Thanks guys,
Chris Stokes

stokesdead · Post by **stokesdead** » Fri Jun 08, 2007 7:57 pm

OK problems are still there. The huge woofy bass is gone and the amp sounds pretty good clean at lower volumes. But when cranked is definitely not right. Seems the tone controls have little affect and the presence oscillates when using the bright channel. Maybe ghosting?

Anyway was wondering if anybody could possibly take the amp and check it out on their bench? Not really on a tight time frame here. Thanks for any suggestions guys.

BTW I am in Greenville, S. Carolina.
Thanks,
Chris Stokes

neikeel · Post by **neikeel** » Sun Jun 10, 2007 6:26 am

Hi Chris, good to see some things help.

You need to work logically through your connections from the V1 outputs (valve pin connections to junction of 100k palte resistors and couplers (0.022uFs) to the volume pots, second gain stage to the second gain stages.

You must have a dodgy connection here, I cannot see it.

You really need the eyes and experience of guys like SDM and Flames to move on beyond this stage, my experience of new build fault finding is limited, restos are easier and I seem to have cracked the new build thing myself - as you will do next time