I just had the experience of having my Clarion APX amp go silent after tending to some dirty switches.
After an extensive investigation; signal through crossover, power supplies, lifting pins, checking transistors, I rolled the dice and hacked in a jumper to the (U5) 6 pin, 4N25 opto-coupler, and it worked to allow the amp to function again(!?)
So while I am pleased that things appear to be better, I can only wonder what purpose that portion of the amp serves?
The design is very elegant and not being an esoteric type, I can imagine it’s there to protect something or serve a durability function. It was not on any of my various Clarion APX schematics I have.
Does anyone know what that part does?
Thanks.
After an extensive investigation; signal through crossover, power supplies, lifting pins, checking transistors, I rolled the dice and hacked in a jumper to the (U5) 6 pin, 4N25 opto-coupler, and it worked to allow the amp to function again(!?)
So while I am pleased that things appear to be better, I can only wonder what purpose that portion of the amp serves?
The design is very elegant and not being an esoteric type, I can imagine it’s there to protect something or serve a durability function. It was not on any of my various Clarion APX schematics I have.
Does anyone know what that part does?
Thanks.
Not sure which you have, but the APA amplifiers carry optos for mute and protect circuits. See attached sm.
I doubt that I have any Clarion SMs that you don't but which APX do you have?... Assuming that the SM above didn't answer your questions.
Thanks for that apa schematic, it definitely looks to be of the same origin and drafting style, likely the same designer. That is very helpful.
Perry, it is an APX401.2, I have used a schematic from an earlier APX400.2 that looks pretty much identical.
The IC is likely part of the protect mechanism somehow, there being two of such devices on my APX, and the two that are actually shown in the apa schematic look to be near the incoming power.
Could they be to prevent over voltage, reverse voltage, or over current perhaps?
Perry, it is an APX401.2, I have used a schematic from an earlier APX400.2 that looks pretty much identical.
The IC is likely part of the protect mechanism somehow, there being two of such devices on my APX, and the two that are actually shown in the apa schematic look to be near the incoming power.
Could they be to prevent over voltage, reverse voltage, or over current perhaps?
Perry, I have installed the amp back into the vehicle, for now anyways. I really appreciate your insight just the same. When the temperature (29) inside my garage get a little warmer, I can revisit the opto-coupler.
I did poke around on the 4N25 before and recall seeing 1.281V between either pin 1, or pin 2 and incoming supply ground. Looked like the same as the forward voltage of the internal diode(?) I believe there was virtually nothing when measuring across the other pins for voltage.
I did poke around on the 4N25 before and recall seeing 1.281V between either pin 1, or pin 2 and incoming supply ground. Looked like the same as the forward voltage of the internal diode(?) I believe there was virtually nothing when measuring across the other pins for voltage.
Ok, looking further, I now see the callout for the U5, opto-coupler in the Clarion APX400.2 schematic I have. I was not familiar with the symbols that make up that component in a written schematic. I can’t believe it took me this long to notice that, have been poring over the schematics for days.
The number 1 pin is indeed incoming power for the 4N25 in this application, so while the missing power through the original circuit board is still a mystery, it looks like I have not compromised the function of the opto-coupler or the protection circuit with my jumper hack.
I must say, the amp sounds amazing now after jumping the switches that selected the low-pass feature, low pass frequency range, and inverting/bridge option.
Thanks guys.
The number 1 pin is indeed incoming power for the 4N25 in this application, so while the missing power through the original circuit board is still a mystery, it looks like I have not compromised the function of the opto-coupler or the protection circuit with my jumper hack.
I must say, the amp sounds amazing now after jumping the switches that selected the low-pass feature, low pass frequency range, and inverting/bridge option.
Thanks guys.
I will have a look, I do recall your caution regarding the acidic adhesive that was used on these boards around the large electrolytic parts, that was in another Clarion APX thread from years ago, where you mentioned to get rid of the stuff.
Is quite likely the cause…
Removing the stuff was something I was wiling to do, but didn’t exactly know what would dissolve it and not damage anything else in the process.
Is quite likely the cause…
Removing the stuff was something I was wiling to do, but didn’t exactly know what would dissolve it and not damage anything else in the process.
Yes, that fixative becomes both corrosive and conductive. The only APX photos I have show no fixative of any kind.
I just peel it off (scrape it off if it's so bad it's turned hard). Without photos, I didn't know it was there or I would have told you to remove it.
I just peel it off (scrape it off if it's so bad it's turned hard). Without photos, I didn't know it was there or I would have told you to remove it.
Perry, you had warned me about the adhesive via the older thread. So thanks for that, is now on my list of things to do when it gets warmer out.
https://www.diyaudio.com/community/threads/problem-with-a-clarion-apx-401-4-no-sound.264129/
That older thread is where I learned about the missing power to the 4N25 as well. I wouldn’t have likely figured out that one…
My board looks similar to the picture below, adhesive and all.
https://www.diyaudio.com/community/threads/problem-with-a-clarion-apx-401-4-no-sound.264129/
That older thread is where I learned about the missing power to the 4N25 as well. I wouldn’t have likely figured out that one…
My board looks similar to the picture below, adhesive and all.