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SOHA II Builders Thread - Page 43

post #631 of 1688
they'll operate at either voltage depending on how your wire them - they wont be happy with the wrong voltage.
post #632 of 1688
Quote:
Originally Posted by adamus View Post
they'll operate at either voltage depending on how your wire them - they wont be happy with the wrong voltage.
I understand they can run at either voltage. The confusion is, the tube documentation says run them at 6.3V parallel.
The documentation for the Soha is leading me to think if I strap it to 6.3V they will be in series.

Is there a jumper I am overlooking that will change the series/parallel configuration of the tubes?
post #633 of 1688
Quote:
Originally Posted by Zippy View Post
I understand they can run at either voltage. The confusion is, the tube documentation says run them at 6.3V parallel.
The documentation for the Soha is leading me to think if I strap it to 6.3V they will be in series.

Is there a jumper I am overlooking that will change the series/parallel configuration of the tubes?
I think they are describing how the tubes will be used in a circuit. If your circuit provides 6.3V, then you put the tube heaters in parallel so they both get 6.3V. If your circuit supplies 12.6V, then you put the tube heaters in series to so they both get 6.3V still. That's my interpretation (although there's a strong likelihood I'm mistaken).
post #634 of 1688
Quote:
Originally Posted by Zippy View Post
I understand they can run at either voltage. The confusion is, the tube documentation says run them at 6.3V parallel.
The documentation for the Soha is leading me to think if I strap it to 6.3V they will be in series.

Is there a jumper I am overlooking that will change the series/parallel configuration of the tubes?
There is only one jumper block- Use the silk screen indicators from the PCB - 6.3V position is toward the front of the board, 12.6 toward the rear.

The SOHA II Headphone Amplifier
post #635 of 1688
Thanks guys, I understand whats going on now. Looks like the backward wording threw me for a loop.

While I'm at it. Does the center jumper position have any function?
post #636 of 1688
Quote:
Originally Posted by Zippy View Post
While I'm at it. Does the center jumper position have any function?
Yes, please see the schematic page I linked to, under the box 'Heater Wiring Jumpers' - you'll see all the "J1" jumpers have connections. You need two jumpers taking up four of the pins...
post #637 of 1688
Hi folks,
Another new guy here building the Soha. I've been following this thread from the start and finally decided to build but, I have a bit of a hangup with the epsilon circuit. The relay isn't kicking on.

I think my problem is in the left channel. I have set my voltage across R10(R&L) at 200mV but when I check the voltage to ground I'm getting my full 15V at R10L.

Any ideas on how to hunt down the culprit of the problem would be appreciated.

Edit: For clarification, from ground to the input of R10L is 15V. Ground to the input side of R10R is 220mV.
post #638 of 1688
Thread Starter 
Quote:
Originally Posted by Zippy View Post
This is my first build with tubes and I'm having a bit of confusion I hope you guys can help clear up.

I have finished stuffing a Soha II board and ready to start testing but I'm a bit confused about the heater jumper. I have a pair of 5963 tubes and according to this spec sheet I found
http://scottbecker.net/tube/sheets/127/5/5963.pdf
I can run them in 12.6V series or 6.3V parallel.

The Cavalli Audio site says
"The 2 x 3 onboard header can be jumpered to select 12.6V parallel or 6.3V series operation."

What do I strap the heater at? I think I'm overlooking something obvious here as those are backward from each other and the 5963 would be unusable.

Use the 12.6V setting for 5963.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #639 of 1688
Quote:
Originally Posted by rnickl View Post
Hi folks,
Another new guy here building the Soha.

...

Any ideas on how to hunt down the culprit of the problem would be appreciated.

Edit: For clarification, from ground to the input of R10L is 15V. Ground to the input side of R10R is 220mV.


Welcome, sorry to hear you're having an issue. The Epsilon is not kicking in to protect the output from 15VDC. 15V positive, corrrect?

More experienced folk will need to chime in here - but looking at the schematic of the buffers, my general troubleshooting process would lead me to look (after checking for solder bridges and shorts) at the BC550's, BD139 and servo opamp. What's the output of the opa134 (pin 6?) Please note that I'm just guessing to give you some direction...
post #640 of 1688
What Wiatrob said. And what's the voltage at the base of Q5L and Q6L?
post #641 of 1688
I have double checked for any shorts, bridges or bad joints and all looks good.

I'm reading 7.2V at the base of the BC550C (Q5), 14.95V at the base of the BD139 (Q6) and -15V at the OP134 output.

I appreciate the help guys.
post #642 of 1688
Hmmm... I think you have a problem with Q5L (collector/emitter junction shorted) or Q6L (collector/base junction shorted), look at the schematics.

With the SOHA turn off, check with your DMM if you have continuity or very low resistance from Q5 or Q6 collector to Q6 base. If so, unsolder and remove either Q5 or Q6 from the board and check again. Depending wich transistor you have removed from the board you will find the culprit.
post #643 of 1688
Quote:
Originally Posted by wolf18t View Post
Hmmm... I think you have a problem with Q5L (collector/emitter junction shorted) or Q6L (collector/base junction shorted), look at the schematics.

With the SOHA turn off, check with your DMM if you have continuity or very low resistance from Q5 or Q6 collector to Q6 base. If so, unsolder and remove either Q5 or Q6 from the board and check again. Depending wich transistor you have removed from the board you will find the culprit.
Thanks for the input. My first instinct was a problem with Q5 and after seeing no obvious problems with solder joints I tried to swap it out. It obviously didn't help.

I didn't ohm out the collector emitter junction so the problem may very well be with Q6. I don't have the board with me so I'll have to check that out tomorrow morning.
post #644 of 1688
Well this problem has got me chasing my tail.

I took some measurements and found I was short between pins 1 and 2 (collector and emitter) of Q6 so I pulled it out. To make a long story short I currently have Q5, Q6, C1 and the OP amp off the board yet I still read a short (0 ohms) between pads 1 & 2 at the Q6 location. I did wick and clean up all the empty locations to make sure I didn’t have any bridging.

I guess my next step is to pull R9/R10 to isolate Q6 location further from the circuit. Any other ideas from you guys?
post #645 of 1688
Quote:
Originally Posted by rnickl View Post
Well this problem has got me chasing my tail.

I took some measurements and found I was short between pins 1 and 2 (collector and emitter) of Q6 so I pulled it out. To make a long story short I currently have Q5, Q6, C1 and the OP amp off the board yet I still read a short (0 ohms) between pads 1 & 2 at the Q6 location. I did wick and clean up all the empty locations to make sure I didn’t have any bridging.

I guess my next step is to pull R9/R10 to isolate Q6 location further from the circuit. Any other ideas from you guys?
So you have Q5 and Q6 removed, but you measure a short on pin 1 and 2 of Q6? Granted, I'm not an expert compared to many here, but looking at the schematic, it seems to me you should read ~820ohms from R9. I don't see anyway you could be getting a direct path between those pins. What do you measure across R9? I think you're on the right track to pull R9 and test it. Don't pull R10 yet, I don't see how it is causing this.
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