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SOHA II Builders Thread - Page 84

post #1246 of 1686
Oh that is what R3P is for. I probably should use 5W 22-33R instead.
post #1247 of 1686

Need some help with my build

please help!

I have built up my board, the power supply checked out ok - everything looked good there. I strapped in J1 and J2 but wasn't able to read anything across R10L or R10R. Found out that my problem was because I had put Q6(L and R) and Q7(L and R) all in backwards. I ordered new parts, pulled all the Q6 and Q7s out and replaced them all. Powered everything back up again and was able to get the left side to work. I dialed in the current, no problems. Somehow I'm still not able to read anything across R10R. Next I tried replacing all of Q5, Q6, Q7, Q8 on the right side but i'm still not seeing anything across R10R however i am reading -15V with respect to GND at either side of R10R.

I did double check all of the resistances for R9-R15 all look ok,

Anyone have an idea of what could be wrong?
post #1248 of 1686

more info

OK here is a little more info:

So, it turns out that on the base of Q5R I am getting -8.6v but on the base of Q5L (the working side) I am getting +6V. In both Q5(L and R) the collector is correctly at +15V. R15R and R16R are the correct parts, and measuring proper resistances.

I double checked and I used the correct parts, Q5(L and R) both BC550Cs.

Not sure if this helps... but I am stumped.
post #1249 of 1686
Thread Starter 
Please measure all of the pins on the opamps. Let's see what they are saying.
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 #1250 of 1686
Attachment 27974

Here are my op amp voltages as looking at them from the top down. (Click on image to view)
LL
post #1251 of 1686
Thread Starter 
Are these voltages measured from the bottom of the board or the top?? In either case they are almost all bad voltages. But as soon as you tell where you took the measurments we can start to debug the problem.
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 #1252 of 1686
These voltages were measured from the top with one probe on the board GND and the other probing each leg of the opamp where they exit the housing of the part.
post #1253 of 1686

A little problem with setup on the PS

Having a little problem getting any kind of readout on PB+ test point. I have hooked up everything except the jumpers and am getting a reading of 18.6 volts on the screws holding the yellow and black wires coming into the board. My led on the tubes light up fine so i know some power is getting to the board. However when i measure the PB+ the DMM goes crazy with no steady reading. None of the other test points measure anything. i have not installed pins into the test points, would this help. Also i have installed 100v 100uf caps in C8P, C9P, C11P and C12P and its a little crowded on the board. I see the original parts list show 22uf for C11 and C12, does this matter. Any help would be appreciated, thanks
post #1254 of 1686
Quote:
Originally Posted by tuna320 View Post
Having a little problem getting any kind of readout on PB+ test point. I have hooked up everything except the jumpers and am getting a reading of 18.6 volts on the screws holding the yellow and black wires coming into the board. My led on the tubes light up fine so i know some power is getting to the board. However when i measure the PB+ the DMM goes crazy with no steady reading. None of the other test points measure anything. i have not installed pins into the test points, would this help. Also i have installed 100v 100uf caps in C8P, C9P, C11P and C12P and its a little crowded on the board. I see the original parts list show 22uf for C11 and C12, does this matter. Any help would be appreciated, thanks
The parts list on the webpage is way off I follow the schematic and excel BoM.
post #1255 of 1686
Thanks Eokboy, they both ponit to 100uf for those caps, so i guess thats not the problem.
post #1256 of 1686
Hey there,
I have a small problem with my soha II which only appeared recently. I start the amp and after a few minutes of music listening, i hear the click of the relay and the music stops for a few seconds. The same behaviour happens 2 or 3 times during the first 30 minutes of use but not afterward

I have quickly checked with the meter and nothing seems to be out of range (the amp is working flawlessly except for those random "pause").
What should i check?
post #1257 of 1686
Quote:
Originally Posted by FairyTales View Post
Hey there,
I have a small problem with my soha II which only appeared recently. I start the amp and after a few minutes of music listening, i hear the click of the relay and the music stops for a few seconds. The same behaviour happens 2 or 3 times during the first 30 minutes of use but not afterward

I have quickly checked with the meter and nothing seems to be out of range (the amp is working flawlessly except for those random "pause").
What should i check?
Normal behavior IMO, all tube amps need to warm up 30 minutes for the tubes to settle.
post #1258 of 1686
Quote:
Originally Posted by tuna320 View Post
Having a little problem getting any kind of readout on PB+ test point. I have hooked up everything except the jumpers and am getting a reading of 18.6 volts on the screws holding the yellow and black wires coming into the board. My led on the tubes light up fine so i know some power is getting to the board. However when i measure the PB+ the DMM goes crazy with no steady reading. None of the other test points measure anything. i have not installed pins into the test points, would this help. Also i have installed 100v 100uf caps in C8P, C9P, C11P and C12P and its a little crowded on the board. I see the original parts list show 22uf for C11 and C12, does this matter. Any help would be appreciated, thanks
Are you sure your heatsinks are isolated?
post #1259 of 1686
Quote:
Originally Posted by regal View Post
Normal behavior IMO, all tube amps need to warm up 30 minutes for the tubes to settle.
The only problem is that behaviour only appeared recently, and it also happens after the 30 minutes, it's completely random, yesterday for example it did happen more than 2 hours after powering on the amp.

Could the relay be toasted?
post #1260 of 1686
Quote:
Originally Posted by FairyTales View Post
The only problem is that behaviour only appeared recently, and it also happens after the 30 minutes, it's completely random, yesterday for example it did happen more than 2 hours after powering on the amp.

Could the relay be toasted?
Try running with your B+ 10V's lower than what its set at now.
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