18Watt.com

Long time lurker, first time poster. I am unable to register for the site but managed to find a generic login for the site on the net. I apologize for using it to post.

I'm about 90% through my 36 watt build (based on Ritchie's 36 watt layout).

I have the GDS Heyboer 36 watt transformer set that I got in a few weeks ago, and my PT is the one seen below (came without color coded wires)





Would someone be so kind as to point me in the right direction? I've read all the 36 watt threads on the board and searched, but don't want to make a mistake on the wiring. I'm used to building pedals and don't want to blow any thing up. lol.

I think the corresponding wiring codes on the schematic (the 36 watt TMB drawing by Mark) to the terminals as I numbered them on the pic would be like this?

1 - gn
2 - Do I cap this one or run to ground?
3 - gn
4 - bk
5 - bk
6 - I would cap this one
7 - rd
8 -rd/yl
9 - rd
10 -yl
11 - tn
12 - I would cap this one

Thank you for any help / guidance!

Would an admin be able to help me create my own user account?

Scott
rottenbologna@gmail.com

2 is grnd for 1 & 3 (6.3vac)
4 is grnd for primary 120vac (4 & 5)
8 is grnd for secondary (7 & 9)
10 is grnd for either 5vac (10 & 11) or 6.3vac (10 & 12)

So would this be correct for wiring?



I would ground #2 to the chassis?

Also, I would just cap off the remaining unused wires?

Thanks again for letting me pick your brain.

Scott

Lug #2 is the center tap for the 6.3V heaters, it is grounded and then you DO NOT use (remove) the two 100 ohm resistors that go from the heater taps to ground.

Thanks!

So, having gone by Ritchie's 36 watt layout, I would be removing these particular ones if I run the spot I labelled #2 off my tranformer directly to ground:



Just out of curiousity, are the 100ohm resistors in question left in place if #2 off the transformer (center tap) is simply capped?

Everything else look about right?

You guys are great, thanks!

Scott

The 100 ohm resistors are used if you have a transformer that DOES NOT have a center tap for the heaters.

The purpose of the 100 ohm resistors is to give a "simulated center tap" to the heater circuit when a transformer does not have a center tap.

If you have a transformer with a center tap on the heaters, such as you have, you should connect the center tap on the transformer to ground and remove the 100 ohm resistors if you have them installed.

Awesome! Thanks for the explaination as well.

I really appreciate you guys taking the time to help a newb builder out.

Scott

If you have a transformer with a center tap on the heaters, such as you have, you should connect the center tap on the transformer to ground and remove the 100 ohm resistors if you have them installed.

Or even better, connect the tap (whether real or virtual) to the cathodes of the power tubes to "elevate" the heater supply and help reduce some background hum/buzz.

Or even better, connect the tap (whether real or virtual) to the cathodes of the power tubes to "elevate" the heater supply and help reduce some background hum/buzz.

I feel like I just read Greek...

I'm gonna see how noisy it ends up being if it doesn't blow up when I finish it. Should I opt to try this modification, do you mind if I ask a few additional questions?

Would that mean tying it to pin 3 on each of the 4 power tubes?

If connecting the tap directly to the power tubes cathodes, does it require you to leave the 100 ohm resistors in place as in the schematic originally?

Scott

See item "E" on this schematic, should be what you are wanting to know about. Terry


http://s938.photobucket.com/albums/ad22 ... ematic.gif

Would that mean tying it to pin 3 on each of the 4 power tubes? If connecting the tap directly to the power tubes cathodes, does it require you to leave the 100 ohm resistors in place as in the schematic originally?

If you're running two push-pull pairs of power tubes, then you would only connect it to pin 3 on one of the pairs.

By this I'm implying that it's generally a smarter idea not to connect all four cathodes (pin 3) together, but to split them into symmetrical pairs, so that if you ever want to run at half power, you can simply pull out one pair of power tubes. Each pair would have its own 150 ohm cathode resistor and bypass cap, just like a regular 18W power stage. Then you connect the heater winding's centre-tap (or junction of the 100 ohm resistors) to the cathode of the pair of tubes you wouldn't pull out.

Thanks again for the additional info / explanation.

Scott

Just a follow up... amp fired right up.

Thanks again for all of your help as well all the other info I gleaned from reading the messageboards. You guys kick ass!




Scott