Stuck on a 6G15 build.

[Esquirefreak]

So... I've run into trouble with a new reverb unit build. At the DC end of the rectifier diodes I'm only getting 170VDC.

I've built the reverb using Tubeswell's hum loop blocker schematic, but I'm using a Hammond 261D6 PT (250VAC CT).

I just now noticed that his schematic says 240-0-240, which would make that 440VAC CT, right?

I've got 7.04VAC unloaded filament and there's 270VAC between the secondary HT leads.

× Am I missing something or am I simply using the wrong PT?

× Should I lift the HT CT and ground one of the HT leads (where the CT currently is connected) and then use the original 3-diode string?

Best regards from Sweden.

/Max

[sluckey]

I'm only getting 170VDC.
I'm using a Hammond 261D6 PT (250VAC CT).

250V CT is same as 125-0-125 and 170VDC is all you can get with your rectifier circuit. You can get 350VDC if you rewire those four diodes as a full wave bridge rectifier.

[Esquirefreak]

The previous one I built has a 290WEX PT (237VAC-0) and all voltages were right on spec. One of the HT leads grounded. That's why I thought maybe I could get 250VAC-0 out of this PT by lifting the CT and grounding the end of the coil.

If I were to rewire the diodes for FW rectification, how do I ground the CT? It would bring a lot more clarity to me if I could see it drawn in a schematic...

Sorry for being stupid 

[thetragichero]

if you use a full wave bridge rectifier you would lift the ht center tap (cut the wire and heatshrink it)

[sluckey]

http://sluckeyamps.com/revibe/revibe.pdf

[Esquirefreak]

I'm so glad I have this forum! Thanks a bunch. Will be re-doing the rectifier tomorrow.

Here's the cab I finished today. I tried to make it look like a '61 rather than '63.

I'll update when I've got it up and running!

/Max

[sluckey]

It's very easy to convert your rectifier to a full wave bridge. Just move the PT wires around and ground the negative side of the bridge. Don't use the PT center tap. If you get stuck, post a hi-rez pic of your diodes and we can help.

[tubeswell]

I just now noticed that his schematic says 240-0-240, which would make that 440VAC CT, right?

Yep for a 2-phase rectifier, you use one side of a centre-tapped HT secondary to calculate the B+, i.e.; 240 x 1.414 = 339VDC.


(But that's different to how you rectify a High Tension winding where you don't have a CT, and the others have already picked up on that)

[Esquirefreak]

Up and running!

306VDC at the plate of the 6K6 and dissipating 7.9w at idle. It's early morning here now and I just got back from my graveyard shift. So I'll sound check later today 

/Max

[sluckey]

Nice workmanship!   

[Bieworm]

I finished one too 2 weeks ago... but I had to put in a 6V6GT. With the 6K6GT it was showing blocking distortion...
I built the cabinet to accomodate with my 18W Tremolo TMB 😉

[Esquirefreak]

That's a pretty build, right there!

I moved to a new apartment last month and since I have a spare room, I finally have a space dedicated to amps and guitars. Also, now my cats won't be able to chew up every single cable I have on the floor...