v4 2 wires left over please help

beaulieu · Post by **beaulieu** » Thu Nov 29, 2007 5:48 pm

my buddy is doing a ptp conversion on a new 2203. hes telling me there is 2 short wires left over on v4 pins 2 &7 . Can't figure out where they go anybody know?

Gibanez · Post by **Gibanez** » Thu Nov 29, 2007 7:43 pm

heater wires go to 2 & 7 on all output tubes

beaulieu · Post by **beaulieu** » Thu Nov 29, 2007 9:08 pm

Thats what I told him apparently theres 2 small wires coming off those pins that used to go to 2 luds(turrette,posts?)on the ptp board.He said theres nowhere for them to go now .They used to go to the 2 posts right above the hum ballancer i think. Maybee they now go nowhere??

Gibanez · Post by **Gibanez** » Thu Nov 29, 2007 9:34 pm

Here is the layout for a 2203 which shows the heaters on all power
tubes wired to pin 2 & 7. Since the heaters are 6.3 volts AC and the
circuit board is running on DC current I'm wondering what turrets it
could have been wired to? Is there any heater wires attached to that
tube?

http://homepage.mac.com/gaden/.Public/2 ... Layout.pdf

Flames1950 · Post by **Flames1950** » Thu Nov 29, 2007 10:29 pm

Oh crap, the reissues have a hum balance control on the heater circuit instead of a center tap to ground. You'll probably have to find a way to hook a 100-ohm resistor to each of those leads and ground the other end of both resistors to act as a "center tap" reference to ground.

SDM · Post by **SDM** » Fri Nov 30, 2007 6:31 pm

The reissue PT's also have the regular heater center tap still available, it ran as a long green wire to a post (GN11 that went nowhere) next to the white wire to the bias supply post.

So the heater CT is there and if that is grounded out now, the hum balance pot and those two wires that used to run to it (from V4) can go away, be removed.

rockstah · Post by **rockstah** » Fri Nov 30, 2007 6:58 pm

hey Steve, any idea/the thinking of the why they would put a hum balance and have the center tap going nowhere?

Billy Batz · Post by **Billy Batz** » Fri Nov 30, 2007 7:13 pm

Maybe poor quality PTs? Thats he only thing I can think of because the CT is close enough in decent PTs taht you dont need a hum balance. Why add a control that can be vibrated off and most people wont realize and just think marshall makes some shitty noisy amps.

rockstah · Post by **rockstah** » Fri Nov 30, 2007 7:19 pm

so they have a center tap but it doesnt do the job so they tie it off and add a hum balance control?

Billy Batz · Post by **Billy Batz** » Fri Nov 30, 2007 8:15 pm

You got me.