I am at a loss here, I replaced the transistors and diodes on the power input/standby board as was recommended with no change from before for a few weeks. Then, the speaker relays began to intermittently click out and back in randomly very quickly breaking the output sound it didn't matter if the amp was even hooked up to speakers or not. I got fed up an unplugged the power cord for several weeks but, everything else still hooked up to it. Then yesterday I thought I would mess with it a little so, I plugged the ac power cord back into it expecting the amp to come right on like before without having to push the power button. Well, to my surprise the amp didn't come on I pushed the power button and it turned on and sounds great. I went to push the button to turn it off and, the green L/R channel indicator leds blinked the speaker relays clicked but the amp didn't go off but, if I take my finger and just tap the power button the amp will turn off normally. Then I can just give the button a normal push and it comes back on again and plays normally also, I noticed when I plug the power cord in now, I can see the faint red standby led is lit up like it should be till I turn the amp on again. I assume all I need to do is find the component/s that causes the momentary pulse that causes the amp to turn on/off by pushing the power button. Any help troubleshooting to find which component could be causing this on/of switch to have to be quickly tapped to turn the amp off will be greatly appreciated. Here is the old thread link http://www.diyaudio.com/forums/chip-amps/238642-parasound-2125-2-channel-power-amp-problem.html and here is the power/standby schematic. 🙂
I've come to the conclusion that the power on/off button is suppose to be pressed quickly for normal momentary switch operation. I'm not sure what causes the on/off pulse that triggers the actions unless, it could be C-234 10uf 25v. C-236 0.1uf 50v. or, done within the IC chip it's self shown on power/standby schematic but, my speaker relays did not cut in and out all day or night yesterday. 🙂
Did you find solution?
I am too working on my Prasound 2125 with burned one channel due to tosted zeners. I rebuilt burned channel 😉 and having issue with protection. I will be working on protection circuit tonight. Do you have amp schematics as well?
I am too working on my Prasound 2125 with burned one channel due to tosted zeners. I rebuilt burned channel 😉 and having issue with protection. I will be working on protection circuit tonight. Do you have amp schematics as well?
Well, now last night my amp started trying to turn it's self on from the off/standby mode? Funny thing now, if I move the trigger switch on the rear of the amp from manual setting to either 12v. or audio signal position when it is off, the amp comes on and there is nothing plugged into either of those two options anyone have any ideas what might be causing these problems? If I leave the trigger switch set to manual, the amp runs just fine all day and night. It just tries to turn on by it's self sometimes from the standby mode. There is one of these chips on the trigger switch board could it be causing the trigger switch problems. 4N32 pdf, 4N32 description, 4N32 datasheets, 4N32 view ::: ALLDATASHEET ::: Thanks for any ideas! 🙂
r31 D5 r29 D7 and..
Last night I finished my amp 😀 and ran it for an hour or so. Noticed really hot four 2w resistors ( R31, R29 ..) around speaker relays. My unit has 750ohm for the them. The resistors see 35v across and dissipate 1.6w each. they are ( all 4 resistors) ready to smoke. According to schematic, newer version of 2125 amp calls for 1.2kohm and which gives 1w of heat dissipation. I am thinking about putting 5 w 1.2kohm for all 4 resistors ( r31 ,r29 and r's on other channel) to be in safe side.
Last night I finished my amp 😀 and ran it for an hour or so. Noticed really hot four 2w resistors ( R31, R29 ..) around speaker relays. My unit has 750ohm for the them. The resistors see 35v across and dissipate 1.6w each. they are ( all 4 resistors) ready to smoke. According to schematic, newer version of 2125 amp calls for 1.2kohm and which gives 1w of heat dissipation. I am thinking about putting 5 w 1.2kohm for all 4 resistors ( r31 ,r29 and r's on other channel) to be in safe side.
This might help I'm waiting for a new Fluke meter to arrive tomorrow at least I'll have a reason to play with it I guess. 😀
Thanks for schematics. Based on schematics when audio signal is present amp turns on and 12v is present amp turns on if your amp turns on when you toggle trigger switch while it is plugged in, this might be normal behavior. When you unplug amp and move switch to either side and plug it in than amp should stay off unless trigger signals are present. If it turns on still opamp TL072 is probably bad.
Hi,
Hello again. I provided you some suggestion on your problem some time ago.
First every time that you push the standby switch the led light should come up. When you turn on/off the switch what you do it is toggling the flip/flop in U1.
Diode D224 it is in parallel with the LED light. When Q1 it is high that will enable Q217. The collector of the Q2217 will go to ground consequently also will grounded cathode of the diode D224 that will turn off the LED light. That will tell you that the standby circuit it is working OKAY. You should look into why it is does work like it should. The LED light will tell you if the circuit it is working right. Every time that you turn ON/OFF the LED light should follow
the switch. Once the light work OKAY then you can proceed to the next
step.
Hello again. I provided you some suggestion on your problem some time ago.
First every time that you push the standby switch the led light should come up. When you turn on/off the switch what you do it is toggling the flip/flop in U1.
Diode D224 it is in parallel with the LED light. When Q1 it is high that will enable Q217. The collector of the Q2217 will go to ground consequently also will grounded cathode of the diode D224 that will turn off the LED light. That will tell you that the standby circuit it is working OKAY. You should look into why it is does work like it should. The LED light will tell you if the circuit it is working right. Every time that you turn ON/OFF the LED light should follow
the switch. Once the light work OKAY then you can proceed to the next
step.
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