Metropoulos Forum

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?

heater wires go to 2 & 7 on all output tubes

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??

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

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.

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.

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

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.

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

You got me.