My Take on X-BOSOZ

[hayenc]

When mine was not working, I ended up checking the resistance to the heatsinks on the FETs and found two shorts. After cleaning up and replacing the bad FETs, it still did not work. Turns out the zeners also went when the FETs did. So, for lack of other suggestions, I would check the same three things--FET case shorted to heat sink, bad FETs, bad zeners.

Hang in there. The sound when it works is worth it.

 

[jleaman]

When mine was not working, I ended up checking the resistance to the heatsinks on the FETs and found two shorts. After cleaning up and replacing the bad FETs, it still did not work. Turns out the zeners also went when the FETs did. So, for lack of other suggestions, I would check the same three things--FET case shorted to heat sink, bad FETs, bad zeners.

Hang in there. The sound when it works is worth it.

before i powered it up i checked all that.. No shorts on any Fets But only one channel did this. I Am thinking about sending it to Russ / Brian to check out. All the parts are correctly installed 100% I checked before i powered it up.

 

[metalman]

Originally posted by jleaman
I got all my parts and one channel the 4 3 watt resistors got hot and brown after 5 min of being on I don't know what to do.. I think net step give up ?

Don't give up yet! Especially when one channel appears to be working. Your so close, and I ain't given up on helping you yet!

On the channel that is working, measure the voltages across R3 and R8, and use that to calculate the currents across those resistors. They should be more or less equal. Then do the same for the channel that isn't working. The 3W resistors should only burn up if: a) the CCS is incorrectly set to a large current; or b) there is a short somewhere that is allowing current to dump across the resistors independant of the CCS.

Cheers, Terry!

 

[jleaman]

here you go you can see the pictures.

http://jleaman.ath.cx/bos/

Metal man can you email me ? Use the pm button.


Jase

 

[hayenc]

Those are the same resistors that got so hot on my board that they melted the solder when I had shorted zeners. It might be worth double checked the zeners again to really make sure they are not shorted.

 

[jleaman]

Witch ones there are a hand full. i have about 100 9.1v's i can swap all out.

 

[Vigo]

I noticed that on the pics posted by jleaman it said abouth 190 on the fets. On the ones i have i says abouth 400. Can it posibly bee sow that
i have to frong fets or is that only somthing else.

I tested a short test on the in and out and it dident seem bo be shorted to ground.

 

[eapavant]

I think the numbers are Brians notes so he could match them.

 

[BrianDonegan]

I think the numbers are Brians notes so he could match them.

Yup. The FET matching rig I am using reads out to 3 decimal places. The Vgs of the FETs vary between around 4.1V and 4.5V. The three digits on the FETs are the decimal portion of the Vgs. So, 193 means 4.193V (my rig, your results will vary). As long as the numbers are close, you are fine. I keep the variance within .01V per set.

 

[Curly Woods]

Are these boards mounted on standoffs? From the looks of the last photo in your link, that the board is flat against the aluminum plate behind the board. Might be shorting the back side of the board to this mounting surface. Just a thought.

 

[hayenc]

To clarify, the shorted zeners on my setup were the two back to back zeners right next to the hot resistors on the board.

 

[jleaman]

Are these boards mounted on standoffs? From the looks of the last photo in your link, that the board is flat against the aluminum plate behind the board. Might be shorting the back side of the board to this mounting surface. Just a thought.

Look closer to the end of the pictures u will see the boards raised about 1/4 inch.

 

[jleaman]

Any thing else i could check over ?

 

[Russ White]

Jason, what was your voltage drop across the 3W resistors.

 

[jleaman]

Jason, what was your voltage drop across the 3W resistors.

I'll have to do this tonight when i get home and do it fast so they dont burn up.. I did test the fets they seem ok tho.

 

[Curly Woods]

Look closer to the end of the pictures u will see the boards raised about 1/4 inch.

I figured that, but thought I would ask.

 

[jleaman]

I figured that, but thought I would ask.

Never Hurts to ask.

 

[jleaman]

OK Here are the results..

Channel a * slightly browned resistors.

R3 is 2V across it
and across the 3 watt resistors i get 33 & 39V

On the other channel i get the same thing.

Metalman.

What to check now ?

You know not having a construction manual at all to build these kits is a pain fright Russ ? Brian ?

 

[karma]

brown resistors, there not going to last long

 

[Russ White]

Jason, your voltage drops seem a bit high, but I suspect that even if they were normal your preamp would have issues. For one thing the power resistors absolutely need to be raised above the PCB. Did you notice the little notes on the PCB? "Raise R1(R2) and R6(R7) 1/2" above the PCB." When the power resistors get too hot they increase in resistance which will increase the voltage drop accross them.

Also a note, This kit was never intended for absolute beginners, people who are not comfortable with projects like this simply should not attempt the project. Also this is not a commercial endeavor, but a community driven DIY project. Brian and I are always glad to help be we don't expect to be the sole providers of building instructions. This is not a "product" but rather a community "project". The PCB is straight forward and the parts well labeled. If you need help beyond that you should post.

For those with questions, it is only natural so please don't hesitate to post if you can't find an answer. And post early, before you make a critical mistake. If you are in over your head, stop, ask, understand, and then continue.

Now that said, a manual is planned(and actually a lot of the prep done), but Brian and I have real jobs to do outside of DIY audio, so don't expect it to happen immediately.

Cheers!
Russ