Get Problem in Building P3A......

angus0910 · 24th February 2004, 03:42 PM

Hello everyone!
I am getting in trouble about the P3A amplifier PCB... I have tested the prototype. It is work prefectly. However, when I routed the PCB, it is fault. After the error, I have tested all components, they are work. And also, I traced the PCB. It is also no problem...
Does anyone knows the problem??
Also, Would you mind let me see the PCB layout?
Thank you everyone~~~~

pinkmouse · 25th February 2004, 02:58 PM

Hi Angus

The proper PCB layout is the property of Rod Elliot, so even if someone posted it here, we mods would remove it to protect his copyright, sorry.

As for your PCB problem, have you tried building one channel point to point on a peice of perfboard or similar? It is a fairly simple circuit and should work with this method of construction.

Good luck!

JensRasmussen · 25th February 2004, 05:07 PM

Hi,

Maybe you need to check the binout of all your components.

Good luck

\Jens

tiroth · 25th February 2004, 05:19 PM

Especially the diff pair...some manufacturers have swapped pinouts!

angus0910 · 26th February 2004, 01:41 AM

Thank you for the 3 replies~
First of all, I am sorry for i am asking for the PCB layout for the reference because I don't know it has a copy right. I am so sorry about it~
I have already checked all components, they are work perfectly. Apart from this, I can sure the routing is success. That's mean no wrong track. Also, I have checked all transistor B C E. So... I don't know where is the problem come from...
Now, I am starting to route again...

JensRasmussen · 27th February 2004, 05:16 PM

Hi,

If you have layout problems, try dowloading the free version of eagle, it can do 10x8 cm PCBs.

This way you are sure your PCB is ok if you schmatics are 100% ok.

check www.cadsoft.de for download details

\Jens

sam9 · 27th February 2004, 06:06 PM

Random rambling thoughts:

Even with pre-manufactures PCBs mysteries such as you describe can occur. I have at hand an example: four identical PCBs with four sets of identical components inserted. Three work perfectly, one does not. Values of all resistors double (no tripple!) checked, polarity of diodes and caps checked, cap values and ESR tested, all transistors test good (Sencore TF46 used). The bad unit has only one thing systematically different - a different type of solder was used. This may be a red herring but after I take care of some urgent home repairs I'm going to totally de-solder the bad unit, toss the old parts and rebuild it with fresh parts and the same type of solder as the others.

I don't know if I've identified the cause and I certainly don't believe in "magic solders" but suspect a difference in melting points may have interacted with my normal soldering habits in some way to produce bad solder joints.

POINT: Not that I think there is something wrong with your soldering, but rather that it is easy to make errors is some aspect that you don't even think to consider. On more than one ocassion, I have fixed mysteries simply by setting aside the problem unit an building a new one from scratch. Notice I said "fixed" not "solved". Sometimes the big AH HA comes sometimes not. A burden of DIY is that we don't have a defined, repeatable process - thus isolating a fault is especially difficult at times.

ADVICE: Check out a few more possibilities and improbabilities and if you are still lost. Set the unit aside, do something unrealted for a couple of days, the build it all over again with new parts (P3A parts don't add up to much). If the problem repeats, you know it is almost certainly inherent in the circuit somehow. If it doesn't repeat and you really want to find the fault - set the two units side by side and compare it lead by lead, value by value.

angus0910 · 28th February 2004, 04:15 AM

Hi all~~~

I am using another PCB problem to route the PCB. Thank you for advised me to use Eagle! It is a program that I tried before.

I don't know where is the problem come out. The prototype is work. the PCB doesn't work. You know, I have routed another version of PCB. However, It doesn't work too. I can sure the routing is 100% ok~

Let me explain the problem. When I switch on, the voltage across the two 0R33 ohm resistors is about 1.2mV. Of course it can be increased by turnning the VR. I am using 25 turns' VR. The voltage really can be increased slowly. However, When it is over 3.3mV, the voltage increase suddenly over 200mV. That event force me to switch off the power. I can sure, the VR is work~

Thank you everyone and sorry about my bad english explaination.

angus0910 · 28th February 2004, 02:18 PM

I just tested with Speaker, I find some problem, Over heat!!
The MJL21193 and MJL21194 is very hot, over 60C. I don't know where is the problem come out. I checked some points.
1) The voltage across two 0R33 ohm resistors is around 500mV ~ 700mV with 4ohm speaker. If no loading, it is around 5mV
2) The Collector pin voltage of 21193 & 21194 is around -24mV. (my prototype which is normal is around +58mV) If I connected 4 ohm speaker, Collector pin voltage of 21193 is around +300mV, of 21194 is around -300mV.
3) I can sure the VR is setted to 2k ohm.
Thank you for solving my problem.

Kilentra · 28th February 2004, 05:26 PM

Is there a significant DC offset?

24th February 2004, 03:42 PM	#1
angus0910 diyAudio Member Join Date: Feb 2004 Location: HK	Get Problem in Building P3A...... Hello everyone! I am getting in trouble about the P3A amplifier PCB... I have tested the prototype. It is work prefectly. However, when I routed the PCB, it is fault. After the error, I have tested all components, they are work. And also, I traced the PCB. It is also no problem... Does anyone knows the problem?? Also, Would you mind let me see the PCB layout? Thank you everyone~~~~

25th February 2004, 02:58 PM	#2
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	Hi Angus The proper PCB layout is the property of Rod Elliot, so even if someone posted it here, we mods would remove it to protect his copyright, sorry. As for your PCB problem, have you tried building one channel point to point on a peice of perfboard or similar? It is a fairly simple circuit and should work with this method of construction. Good luck! __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

25th February 2004, 05:07 PM	#3
JensRasmussen diyAudio Member Join Date: Jul 2002 Location: Denmark - Jutland	Pin-out problems? Hi, Maybe you need to check the binout of all your components. Good luck \Jens

27th February 2004, 05:16 PM	#6
JensRasmussen diyAudio Member Join Date: Jul 2002 Location: Denmark - Jutland	Layout problems Hi, If you have layout problems, try dowloading the free version of eagle, it can do 10x8 cm PCBs. This way you are sure your PCB is ok if you schmatics are 100% ok. check www.cadsoft.de for download details \Jens

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25th February 2004, 05:19 PM	#4
tiroth diyAudio Member Join Date: Dec 2001 Location: Pittsburgh, PA, USA	Especially the diff pair...some manufacturers have swapped pinouts!

26th February 2004, 01:41 AM	#5
angus0910 diyAudio Member Join Date: Feb 2004 Location: HK	Thank you for the 3 replies~ First of all, I am sorry for i am asking for the PCB layout for the reference because I don't know it has a copy right. I am so sorry about it~ I have already checked all components, they are work perfectly. Apart from this, I can sure the routing is success. That's mean no wrong track. Also, I have checked all transistor B C E. So... I don't know where is the problem come from... Now, I am starting to route again...

27th February 2004, 06:06 PM	#7
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	Random rambling thoughts: Even with pre-manufactures PCBs mysteries such as you describe can occur. I have at hand an example: four identical PCBs with four sets of identical components inserted. Three work perfectly, one does not. Values of all resistors double (no tripple!) checked, polarity of diodes and caps checked, cap values and ESR tested, all transistors test good (Sencore TF46 used). The bad unit has only one thing systematically different - a different type of solder was used. This may be a red herring but after I take care of some urgent home repairs I'm going to totally de-solder the bad unit, toss the old parts and rebuild it with fresh parts and the same type of solder as the others. I don't know if I've identified the cause and I certainly don't believe in "magic solders" but suspect a difference in melting points may have interacted with my normal soldering habits in some way to produce bad solder joints. POINT: Not that I think there is something wrong with your soldering, but rather that it is easy to make errors is some aspect that you don't even think to consider. On more than one ocassion, I have fixed mysteries simply by setting aside the problem unit an building a new one from scratch. Notice I said "fixed" not "solved". Sometimes the big AH HA comes sometimes not. A burden of DIY is that we don't have a defined, repeatable process - thus isolating a fault is especially difficult at times. ADVICE: Check out a few more possibilities and improbabilities and if you are still lost. Set the unit aside, do something unrealted for a couple of days, the build it all over again with new parts (P3A parts don't add up to much). If the problem repeats, you know it is almost certainly inherent in the circuit somehow. If it doesn't repeat and you really want to find the fault - set the two units side by side and compare it lead by lead, value by value.

28th February 2004, 04:15 AM	#8
angus0910 diyAudio Member Join Date: Feb 2004 Location: HK	Hi all~~~ I am using another PCB problem to route the PCB. Thank you for advised me to use Eagle! It is a program that I tried before. I don't know where is the problem come out. The prototype is work. the PCB doesn't work. You know, I have routed another version of PCB. However, It doesn't work too. I can sure the routing is 100% ok~ Let me explain the problem. When I switch on, the voltage across the two 0R33 ohm resistors is about 1.2mV. Of course it can be increased by turnning the VR. I am using 25 turns' VR. The voltage really can be increased slowly. However, When it is over 3.3mV, the voltage increase suddenly over 200mV. That event force me to switch off the power. I can sure, the VR is work~ Thank you everyone and sorry about my bad english explaination.

28th February 2004, 02:18 PM	#9
angus0910 diyAudio Member Join Date: Feb 2004 Location: HK	I just tested with Speaker, I find some problem, Over heat!! The MJL21193 and MJL21194 is very hot, over 60C. I don't know where is the problem come out. I checked some points. 1) The voltage across two 0R33 ohm resistors is around 500mV ~ 700mV with 4ohm speaker. If no loading, it is around 5mV 2) The Collector pin voltage of 21193 & 21194 is around -24mV. (my prototype which is normal is around +58mV) If I connected 4 ohm speaker, Collector pin voltage of 21193 is around +300mV, of 21194 is around -300mV. 3) I can sure the VR is setted to 2k ohm. Thank you for solving my problem.

28th February 2004, 05:26 PM	#10
Kilentra diyAudio Member Join Date: May 2002 Location: Cambridge, MA, USA	Is there a significant DC offset?

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