[tomb]

Quote:

Originally Posted by pddjsteve /img/forum/go_quote.gif Hmm. After listening to it for a while, I've discovered the right channel seems to have a little less gain than the left. There also seems to be some "bleeding" between the channels. All the voltages measure fine, I've gone over all the solder joints again under a magnifying glass. I read about Yen's problem with the tube socket... is that where I should be looking next? This is more a small nagging annoyance than anything else... it sounds awesome, just a little teeny bit louder in one ear than the other

Typically, that's a pot tracking problem, or perhaps some un-matched resistors on the output.

 

[pddjsteve]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Typically, that's a pot tracking problem, or perhaps some un-matched resistors on the output.

Hmm. I'll check the output resistors when I get home tonight, but I think they were pretty close to one another (they're 150 ohm 1% vishay dale). I did go through and measure all my other pairs of resistors, and they were within an ohm or two of each other. I'm using 80ohm DT770s, so I also might just jumper the output resistors to eliminate them as the culprit.

If that looks ok, I think I'll switch out the pot. I'm using a 50k RK27 right now, would something like this ratshack pot be a decent temporary replacement? I've also got a few panasonic evj and alps rk097, but they're all 10k.

 

[tomb]

From what you describe, that's not the problem. If you are already using the RK27, and you've checked all the resistors, then that's not it.

You may have a bad tube - perhaps the grid or plates on one side are not up to snuff. Change the tube out, re-bias, and see if that's it. BTW, have you checked the bias lately? Sometimes that can change as the tube gets broken in and could cause some channel imbalance. Of course, the high gain of the SOHA will exacerbate this problem.

 

[sphinxllama]

Hello,

I bought a SOHA Kit

Already working on it and it went pretty good until now.

And now I have a problem and need some help from you guys. Here it comes:
I had to desolder the LM78L12 Regulator and the LM79L12 Regulator. Now my question is if they are easy to break? Because they got pretty hot when I desoldered them. Does it matter. Would it be better to buy new ones? (I hope I can find a shop who carries them).

I also did not do a very good job when I desoldered the parts. Have a look:

Do I have to worry about connection problems when I solder the new part in that damaged possition? What can I do?

greets
kim

P.S. hope it is OK that I post my problem in this thread seemed right to me.

 

[gates_2]

can someone confirm that I have my CCS configured correctly?

http://img297.imageshack.us/my.php?i...1010090eg3.jpg
thanks

 

[FallenAngel]

sphinxllama : You're alright, use the same regs, they'll be fine, but personally I would prefer to use 7815 and 7915 regulators in TO220 package, if they're already out of the board, might as well

gates_2 : You should be good as well, I just can't read your resistor values.

 

[gates_2]

ahh- solved the problem

I think I soldered the pot in wrong.... Was shorting to ground....

Getting reasonable values now... lets try it out

 

[sphinxllama]

@FallenAngel

thanks a lot for your quick answer!
I think I will use the same regs. Otherwise I would have to desolder the CCS and buy the TO220 in 12V. Hope that is right. But I heared there are some Buffers from Steinchen on its way for the soha that use 15V.

greets kim


Edit: Oh I see in your sig that you already have them in your soha. Where can I get them from?

 

[FallenAngel]

Quote:

Originally Posted by sphinxllama /img/forum/go_quote.gif @FallenAngel thanks a lot for your quick answer! I think I will use the same regs. Otherwise I would have to desolder the CCS and buy the TO220 in 12V. Hope that is right. But I heared there are some Buffers from Steinchen on its way for the soha that use 15V. greets kim Edit: Oh I see in your sig that you already have them in your soha. Where can I get them from?

Yes, Steinchen's buffers will need 15V regs, and no you don't need to change the CCS for the JisBos.

I don't have them in my SOHA yet, I've built all the buffers I've seen for the SOHA and unfortunately couldn't get even one working yet

 

[pddjsteve]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif From what you describe, that's not the problem. If you are already using the RK27, and you've checked all the resistors, then that's not it. You may have a bad tube - perhaps the grid or plates on one side are not up to snuff. Change the tube out, re-bias, and see if that's it. BTW, have you checked the bias lately? Sometimes that can change as the tube gets broken in and could cause some channel imbalance. Of course, the high gain of the SOHA will exacerbate this problem.

Well, this is not fun.

The bias is ok. Jumpered the output resistors. Switched the pot out. Switched tubes. Still doing it.

When the balance is centered, I get more output from the left channel.

When I put the balance all the way right, I can't hear anything from the left.

When I put balance all the way left, I hear from both left and right, but at the same volume, as if balance was center and there was no channel difference????

I'm about to just give up and solder the 2nd board.

 

[tomb]

Quote:

Originally Posted by pddjsteve /img/forum/go_quote.gif Well, this is not fun. The bias is ok. Jumpered the output resistors. Switched the pot out. Switched tubes. Still doing it. When the balance is centered, I get more output from the left channel. When I put the balance all the way right, I can't hear anything from the left. When I put balance all the way left, I hear from both left and right, but at the same volume, as if balance was center and there was no channel difference???? I'm about to just give up and solder the 2nd board.

I'm confused - how are you adjusting balance, period?

Can you post some photos of the board? Maybe some of us can spot a problem. Honestly, this is the first problem of this type I've heard about with the SOHA boards.

 

[pddjsteve]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif I'm confused - how are you adjusting balance, period? Can you post some photos of the board? Maybe some of us can spot a problem. Honestly, this is the first problem of this type I've heard about with the SOHA boards.

Sorry, adjusting balance on my source. Should have mentioned that. Yeah, lemme put the ALPS pot back in and then I'll snap some pics.

 

[tomb]

Quote:

Originally Posted by sphinxllama /img/forum/go_quote.gif Hello, I bought a SOHA Kit Already working on it and it went pretty good until now. And now I have a problem and need some help from you guys. Here it comes: I had to desolder the LM78L12 Regulator and the LM79L12 Regulator. Now my question is if they are easy to break? Because they got pretty hot when I desoldered them. Does it matter. Would it be better to buy new ones? (I hope I can find a shop who carries them). I also did not do a very good job when I desoldered the parts. Have a look: Do I have to worry about connection problems when I solder the new part in that damaged possition? What can I do? greets kim P.S. hope it is OK that I post my problem in this thread seemed right to me.

Sure about this? It looks to me like your photo is showing the CCS positions, not the opamp voltage regulators. Could you be confusing these?

 

[pddjsteve]

Ah, the joy of finishing the SOHA in the middle of the night a couple nights ago - I found the problem. My own stupidity. This was the first time I've used the Neutrik locking 1/4" jack, and I freaking soldered it like a 1/8" jack because I wasn't thinking. It wasn't the SOHA, it was me.

On the other hand, I now know more about the circuit/board than before, so it isn't a complete loss

Thanks for the help, though.

 

[gates_2]

so.. problem not solved... With the pot out, i get 70 plate, and then like 51, 56 on the 2 +40 check points.....

No matter how much i turn the trimpot either way, neither of these values change

The second I connect the pot.... I get plate voltage at +60 and both +40 voltages, or If I turn the pot all the way one way, I get plate voltage at one +40 and a lower voltage at the other....

Ended up breaking a RK27 pot trying to desolder it from my pimeta to try on the soha... GAH

any ideas... With teh pot wiper all the way one way, I get a short between input left and ground... Confused.....