SD Convertible 100 Board Rebuild

[plexi50]

I couldnt stand it any longer

I pulled the board from the Seymour Duncan Convertible 100 and decided to just make the d*m thing conform to a plain old Marshall long tail PI with a presence pot where the Raw pots now are on the front panel

I removed all the .1 OD caps and put .022 Sozo caps on the board. The output coupling will remain .047 Orange Drops's

I find that using Sozos or Mallorys in the tone path and OD's in the output coupling sound fantastic / A nice mix

I removed the 2 other 9 pin sockets and wired the PI tube from the .047 coupling caps to the bias resistors which will be 220K tommorrow / Surprisingly enough all changes except one were right next to each other as the traces passed each other on the board making it a clean and easy job. The hard part is the eyes. My vision is changing fast now.

The plate coupling 82K/100K is finished. Just have to throw in (2) 1 Meg and (1) 470 Ohm with a 10K to complete the PI tail to presence pots and feedback tap







The amp as it was was loud but thats about all you could say about it. No character whatsoever. The wattage knob on the front panel will control the PI voltage taming the 100 watts. J13 pic 3 is cut in half for the leads to the PI voltage control pot. I expect a whole new toneful and usable amp in a day or so

[woolly]

Nice Job!

[plexi50]

Why did Seymour Duncan build a power supply like this?

The 5U4 is just serving power to the OT from the standby switch to my eyes

Threre is a SS bridge rectifier feeding the amplifer PI and preamp nodes

I have rebuilt the entire amp with the 5U4 feeding a series 33uf/350 VDC caps to stanby and OT CT / 1K resistor (No choke laying around) and then on to the PI and preamp nodes

The B+ is 475 with -36.8 grid VDC / 100 volts less than with the SS rectifier

The whole power supply was ass backwards

If i am missing something here please let me know. This is one screwy amplifier

http://triodeamplification.com/files/SDC-Powers.pdf

 

[dwp]

can the 5U4  handle 4 EL34's? or for how long?

(oops, SS to output tubes still, yes?)

[plexi50]

I dont know how long the 5U4 will last so i really think im going to tie the standy to the SS bridge and (FORGETABOUTIT) remove the 5U4

Were not going to or want any sag from this amp anyway / I think this amp was just some odd marketing experiment

At the time im sure the module thing was a cool and new idea but it in the real world it didnt work to well in this amp

[HotBluePlates]

Were not going to or want any sag from this amp anyway / I think this amp was just some odd marketing experiment

A 5U4GB should power the EL34's just fine. Except that 575v and 100uF of capacitance seems like a lot for a 5U4. The -GB version is rated for 250mA continuous. If you ever see a 5U4 or 5U4GA, know that they are rated for less current than the -GB version.

It makes some sense to me, as the EL34 plates are consuming the most power, and they're being fed by the rectifier tube for a little sag. The preamp and the phase inverter pulls relatively little current, and they obviously did not think supply sag would be beneficial, so they gave those sections their own SS supply.

[plexi50]

The 5U4 PS capacitance is what i am changing again

I am only doing this to see if i can before i snap the board in half and go with a turret board

Waste not want not i say / I will be in a straight jacket before this is finished

Everything is going smooth and all connection modications (Traces) are right near one another so thats a big +

The input tube crap moduel is gone and the input grid is now directly on V1 tube (Channel 1)  V1 (Channel 2)

Grids are 470K now. I am rebuilding each of the moduels again with all the correct values (tube plates  #1 & #6

I have removed the 100K plate resistors that were on the board that the tube plates shared and bussed there connections

Now the tube moduels will have 100K resistors for each plate as normal (What is normal) (Stevie Ray Vaughn)

Channel one is the dirty channel and will have a cathode driven tonestack (EQ)

Clean channel will remain plate driven. I will have a degree in this amp before i am done. I will pass next time

http://s356.photobucket.com/albums/oo5/plexijtm45/?action=view&current=Convertible100.flv