Ah, I should have seen that
I can not get two soldering irons in this small gap so will add a normal 0.6W resistor to the bottom side of the board.
I will not connect it to my amp again until I have output inductors. I actually have some from an old amp lying around, I expect the value of this inductor is not so critical.
I have a similiar experience with burnt zobel resistor.
I remove the 2 adjacent 1000Uf and 10 UF caps to reach it.
I use 2 soldering iron and heat both legs of the caps simultaneously and let it drop out, Then clean the hole with sucker.
I use a 60 w iron to heat one end of the 20 R resistor and wait for the heat to move to the other end and gently push the 20 R off the pad.
You can solder the new 20 R on top of the burnt resistor.
Other wise you can place the zobel cap and resistor off board.
hope this helps
kp93300
hey thanks, that is helpful, I may try and borrow a 60W iron, mine is 45W.
I dont suppose you have a couple of leftover resistors you can spare? Happy to pay, I just dont want to place an order for two resistors, and shipping will cost alot.
thanks Luke.
If your Zobel is open circuit, now, why not add one near the speaker plugs, instead, with bigger resistances and let this board as it is ?
L.E.D. Zeppelin
Don't now who made it and deserve rosen copied picture from some Behringer blog, good weekend.
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A member kindly sent me the two 20 ohm surface mount resistors and they arrived this weekend. I made time this weekend so can finally listen to the amp. I added an L//R Zobel on the output terminals of both channels and plugged it in.Then poof magic smoke, same resistors, no load no signal. Checked and there are no bridges or miswiring. I think its jinxed
Hi again Luke. If you have rumbling with the R23 amend, are you sure it is now shorted, else input pair is floating without R2 10K to ground (measure with DMM that basis leg at input pair have 10.000/10.010 ohm to ground). And if you run isolated screws at VAS devices, be sure there is ground potential at heatsink either via box or with wire (else heatsink can be RF antenna or cap to VSSA module).
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Hi Byrtt, I am not far from a transmitter maybe a 2km direct line on a hill nearby.
There was nothing connected to the amp when I powered it up. Are you suggesting take the blown resistors out again, replace them and then try connecting, this time using a 10k load on input, or maybe rca to my preamp?
There was nothing connected to the amp when I powered it up. Are you suggesting take the blown resistors out again, replace them and then try connecting, this time using a 10k load on input, or maybe rca to my preamp?
Hi Luke
It has to go like this, before powering on:
- check input transistors with universal meter, select to diode measuring
- check VAS transistors with the same meter
- check all resistors values if OK
- replace all broken parts with new ones
- connect VSSA to initial setup (30 Ohm/10 W protection resistors, etc.) like described in installation manual
- turn power on
- use scope on output to see if it's clear
- set the trimmers according manuals instructions
That's about it. Good luck Luke
It has to go like this, before powering on:
- check input transistors with universal meter, select to diode measuring
- check VAS transistors with the same meter
- check all resistors values if OK
- replace all broken parts with new ones
- connect VSSA to initial setup (30 Ohm/10 W protection resistors, etc.) like described in installation manual
- turn power on
- use scope on output to see if it's clear
- set the trimmers according manuals instructions
That's about it. Good luck Luke
Byrtt, what do you mean by if I have rumbling with R23 amend? How should I amend, keep in mind the other channel did not behave this way.
R2 is definitely 10K so no problems there.
I expected my heatsink was grounded via the chassis, the reality is that everything is anodised and there is no continuity test from heatsink to chassis ground. This can easily be fixed. But must I now replace R21 and R22 again.
Hi Luke
It has to go like this, before powering on:
- check input transistors with universal meter, select to diode measuring
- check VAS transistors with the same meter
- check all resistors values if OK
- replace all broken parts with new ones
- connect VSSA to initial setup (30 Ohm/10 W protection resistors, etc.) like described in installation manual
- turn power on
- use scope on output to see if it's clear
- set the trimmers according manuals instructions
That's about it. Good luck Luke
Hi LC, you mean take all these semis out and test them?
Hi Luke, do LC's check and first couple times at power on have input shorted in a way until sure everything stable and calibrated, then connect music.
Other thing is how many SMD 20 ohm spares do you have ?. Alternative is using 10 ohm serial to 100nF between speaker spade and ground, but do only this after ensuring that original R21/22 have infinite resistance or desolder them. Zobel 10ohm/100nF is same as two parallel zobel onboard at 20ohm/47nF. Best be the 10 ohm resistor is 0,5w or more, can be made of 4 times 1/4w (2x10ohm in parallel in series with two more 10ohm in parallel=1w 10ohm). Now when modules run as expected put original SMD zobels at place and take out 10ohm/100nF.
Sounds fine then, but there was a amend in thread that one should short R23 (10ohm). Do this later if you observe hum later when up running.
Yes fix this ground potential at heatsink, if lucky this coursed the oscilation. Measure R21/22, if higher than 20ohm, repair them or do the alternative zobels until everthing runs as expected.
Other thing is how many SMD 20 ohm spares do you have ?. Alternative is using 10 ohm serial to 100nF between speaker spade and ground, but do only this after ensuring that original R21/22 have infinite resistance or desolder them. Zobel 10ohm/100nF is same as two parallel zobel onboard at 20ohm/47nF. Best be the 10 ohm resistor is 0,5w or more, can be made of 4 times 1/4w (2x10ohm in parallel in series with two more 10ohm in parallel=1w 10ohm). Now when modules run as expected put original SMD zobels at place and take out 10ohm/100nF.
Sounds fine then, but there was a amend in thread that one should short R23 (10ohm). Do this later if you observe hum later when up running.
Yes fix this ground potential at heatsink, if lucky this coursed the oscilation. Measure R21/22, if higher than 20ohm, repair them or do the alternative zobels until everthing runs as expected.
Again again, Hi Luke.
Imagine that powering modules on would be safest always with the 22ohm/5w on +/- power rails as in calibration procedure, and then first when zobels stop running hot (oscilation problem cured), connect +/- power rails directly.
About the R23 amend and other small help-info see post #2534 (link:http://www.diyaudio.com/forums/vend...lateral-mosfet-amplifier-254.html#post3653117).
Like to when you report up and running.
Imagine that powering modules on would be safest always with the 22ohm/5w on +/- power rails as in calibration procedure, and then first when zobels stop running hot (oscilation problem cured), connect +/- power rails directly.
About the R23 amend and other small help-info see post #2534 (link:http://www.diyaudio.com/forums/vend...lateral-mosfet-amplifier-254.html#post3653117).
Like to
when you report up and running.
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Thanks Byrtt and LC, I will be more careful next time I power on. I thought it was fixed and after adding the zobel my problems would go away. I also have been thinking about sheilded cable for rca to module, I am using cat 5 for now as thats what I have on hand and its worked well for other projects.
While I'm at it, my zobels are not the ones recommended as I found them in my parts bin. They use a 10 ohm resistor and thicker gauge wire with a bigger diameter. I hope its ok to use these.
Sadly I missed all the updates you have posted Byrtt, I hope this is not why I'm having these problems.
Perhaps it would have been better to start a build thread and capture all these and have updated doco on first post.
While I'm at it, my zobels are not the ones recommended as I found them in my parts bin. They use a 10 ohm resistor and thicker gauge wire with a bigger diameter. I hope its ok to use these.
Sadly I missed all the updates you have posted Byrtt, I hope this is not why I'm having these problems.
Perhaps it would have been better to start a build thread and capture all these and have updated doco on first post.