Engl Powerball II: what are these "mods"? Why can't I bias it?

[Andree88]

Hi, I've bought a used Engl Powerball II. It's fully working except two things:

 

1) The first "problem" I heard is that channel 3 (lead 1) and channel 4 (lead 2) have the same tone and the same gain. I've red (and heard online, even on Engl site) that channel 4 has more gain than channel 3 and is tonally different but in mine channel 3 and 4 has same sound and gain (if I put gain pot to max it's same gain on both). Why? Maybe last owner done something?

 

I though was "bad tubes" issue, so I replaced the stock Engl pretubes with TAD and JJ (that I used on my old amp, so I know they are good) and bought a new quartet of JJ 6L6 (replacing the quartet of TAD) to see if was a tube problem. But I had a second problem.

 

2) I cannot bias the 4 JJ as I want. Done some research online and I saw where I have to put the multimeter to test the current. I got a low value (108 mA on tube socket). So 108/4 = 27 mA each tube. I wanted 6L6 at least 32 mA each but I cannot go higher with bias pot. It stops at 108. Is it right to measure 108 and then divide per 4 (final tubes) in order to obtain the mA of each tube (approssimatively) or am I doing something wrong?

I measure in 6L6 socket, like in the image below.

 

I only have a multimeter, not bias probe or anything else. I can bias amps, done a lot with Marshall, Fender etc (except Mesa), but I cannot understand why JJ can't go more than 108 mA (even stock TADs were going to 130+ mA with pot). Am I doing something wrong or I have to change bias pot to bias my JJ 32mA each? Or am I counting this wrong?

 

I saw another thing inside amp, maybe a "mod"? Why are these resistors etc. here? It seems that they are added after. I though.. is it a "mod" to reduce "gain" on channel 3 and 4 or what?

The last owner said that he didn't change anything.. bah. I see thing changed, Here are the images.

RED circles is where I put my multimeter (ground, socket of tube and bias pot). YELLOW circles are the "mods" I saw.

 

[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"Engl Powerball II","data-attachmentid":32567855}[/ATTACH]

 

And here the "mods" I see.

 

[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"20190731-135914.jpg","data-attachmentid":32567856}[/ATTACH][ATTACH=JSON]{"data-align":"none","data-size":"full","title":"20190731-135919.jpg","data-attachmentid":32567857}[/ATTACH]

[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"20190731-135925.jpg","data-attachmentid":32567858}[/ATTACH]

[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"20190801-184704.jpg","data-attachmentid":32567859}[/ATTACH]

 

 

If anyone has an idea of what are these resistors etc and what maybe they do can please say it to me?

For the bias problem too

Thanks! Sorry for mistakes, I'm italian!

 

[onelife]

When you adjust the bias are you actually measuring current flow or are you determining current flow by measuring the voltage drop across a given resistance? Do you measure each tube individually or is their just one adjustment for the quartet?

Your amp definitely looks like it was modified or experienced a makeshift repair so it is difficult to diagnose without being in the same room and getting an up close look.

[Hodettocico]

Ciao Andrea. Anche io ho una pb2 e anche nel mio caso il ch3 mi sembra uguale al ch4 .

La mia non ha subito modifiche, né riparazioni

Hi Andrea. I also have a pb2 [PowerBall II] and in my case ch 3 seems to me the same as ch 4.

Mine has not been modified or repaired

 

[William shredder]

Dont know if you figured this out but I've had a pb2 for about a year and it's the same way,I changed a few preamp tubes and it gave ch3 just a small amount more low end than ch 4 but the tone is the same and ch 4 does not have more gain.