Finished 2204

OnTheFritz · Post by **OnTheFritz** » Tue May 03, 2005 10:08 pm

You experienced guys see any bonehead mistakes in these pics?
Got the 1ohm bias resistors today, and finished her up. Thanks George.

Thanks for any input.

Fritz

Billy Batz · Post by **Billy Batz** » Tue May 03, 2005 10:12 pm

I looked for a few minutes and didnt see anything. Though keep in mind Im the guy that could never find Waldo. Thats a 2204?

OnTheFritz · Post by **OnTheFritz** » Tue May 03, 2005 10:20 pm

Dan,
Yeah, it's a 2204.
One thing I know I did was use the Vishay in the PI instead of the c-film, and used that for the negative feedback. Don't know if it makes much difference, but the leads barely made it.

Dax-The-Ax · Post by **Dax-The-Ax** » Tue May 03, 2005 11:46 pm

A 2204, very nice. Have you fired it up yet? I thought the lug in the middle of the far right diodes went to ground, but i looked it up and i guess it's only on 100 Watters. I wimped out on my 2203 and had George wire it. I couldn't figure out the Input wiring. What all did you replace? Just the board and the Sozo on the presence pot?

Dax

Flames1950 · Post by **Flames1950** » Tue May 03, 2005 11:56 pm

You're missing the 33K slope resistor in the tone stack, between the 500pF treble cap and the (2) .022uF's.
Did you get those 500pF's from George? I like the size of them, it's close to the old sixties-sized caps even if the construction is different.
Overall a nice build. I'm anxious to hear how she fires up; the MV circuit can be pretty touchy about wire placement with oscillation and such.

Billy Batz · Post by **Billy Batz** » Wed May 04, 2005 12:00 am

OnTheFritz wrote:Dan,
Yeah, it's a 2204.
One thing I know I did was use the Vishay in the PI instead of the c-film, and used that for the negative feedback. Don't know if it makes much difference, but the leads barely made it.

I did read it on the thread topic but sometimes Im just a little slow and didnt realize it until looking at the board

OnTheFritz · Post by **OnTheFritz** » Wed May 04, 2005 12:28 am

Flames, you are a steely eyed missle Man! (guess the movie)
That was the extra resistor laying there.

Thanks dude.
Dax, I replaced the board, the pre-sockets, and all the wires except the pinkish-lookin' ones from the vol/tone pots.
Flames, I got everything from George, just ordered the 50 watt MV board.
Thanks for the compliments, I'm anxious to hear the Bitch myself.

Fritz

OnTheFritz · Post by **OnTheFritz** » Thu May 05, 2005 7:14 pm

Compared to a Superlead, I'm getting some bizarre voltages. She's biased @ 35, & 38.(V4,V5)
I know it's a MV, but does anything look out of line to you guys? Flames?

Thanks,
Fritz

Flames1950 · Post by **Flames1950** » Thu May 05, 2005 7:35 pm

I would think the MV's are different but I don't have one to measure the voltages on. For the most part your voltages roughly mirror a 4-hole Lead -- the higher V1 voltages are the only big diff.

OnTheFritz · Post by **OnTheFritz** » Thu May 05, 2005 7:43 pm

Thanks Flames, I was guessing that had something to do w/the MV circuit.
My heaters seem kinda low though, while the plate voltage is about right.

Fritz

OnTheFritz · Post by **OnTheFritz** » Fri May 06, 2005 9:35 pm

Another question.
In this pic, I circled George's notation about the values for 100 vs 50, which I went with on the ptp.
My pc board has a 120k resistor in this spot. Is that for the 6550's?

My other question is about the two 10k's in series.(I drew an arrow pointing to the second one)

My pcb had just the one and a buss wire, so I did my ptp the same way.
What happens with both resistors in place? Would that lower my plate voltage a tad?
Thanks for any and all responses.

Dax-The-Ax · Post by **Dax-The-Ax** » Sat May 07, 2005 12:06 am

With two 10K's, it will lower your voltage giving you less headroom and a bit more dirt. With one, a little more headroom and a little less gain. I experimented with this and it did add a fair amount of compression. I went back to one 10K for a more crunchy tone.

Flames1950 · Post by **Flames1950** » Sat May 07, 2005 12:28 am

The 120K is probably for the 6550's. Most guys found it easier to simply jumper the resistor in line with the bias pot for EL34's instead of changing resistors on the PCB so most of the time that resistor never got touched.
I had my 50-watter with one and two 10K's in the other spot on the board that you're looking at. I put the second one in without thinking when I reworked my PCB, and while it may give a little more crunch due to loss of some headroom overall I thought the amp felt "flat." A single 10K on these is still great crunch but more dynamic feeling as well.

OnTheFritz · Post by **OnTheFritz** » Sat May 07, 2005 12:20 pm

Thanks a lot guys.
You guys know your stuff.

Fritz

Guest · Post by **Guest** » Fri Oct 14, 2005 11:19 pm

Hey Fritz................nice job I'm gonna be attempting one myself over the winter.....got a question for ya though I notice the "grid stoppers" on the el's................did you have to put them there or where they there to begin with?

Just wondering.

Jess