Hi this is not so difficult, see PDF file setup.pdf if your amp has a build in x-over than you can use both setups. If you your amp has no x-over than you can use the setup wit your x-over. The capacitor is just there to cut off all the low frequencies to the tweeter. That is why the capacitor is lo...

If you don't know how to adjust the bias I should not touch them! These are very sensitive and while you are turning these pots you have to measure the voltage drop over the output emitter resistors of each channel + you have to know the amount of voltage drop over these resistors. I think Jason or ...

Hi and welcome to the phorum. It should be less than 2A on idle any time. after many years it is possible that the bias of your amp is out of balance. with the older models, ZPA, ZX it is possible to adjust the bias but I'm not sure if it's possible to do it with the Zxti. Jason will help you furthe...

could it be wrong spes of the KA339?
the one I used: 512-KA339A (Mouser)
512-2N4401TA

did find the time to continue with this repair. I switched the control board of a working zpa (so I know that the board is 100% ok) with this one. Well... this zpa is now working perfect :D :D :D ! So now I know for sure that the problem is in the control board. What can cause the overload (red) LED...

I'm also a big fan of repair threads. Always loved it. Don't know who is keeping this phorum on the air but for me it would be also a loss if this would be gone one day. There is so much info saved here and some of the threads are so good and funny to read. Maybe we should start a thread "best ...

there is something wrong with the control board but I don't know what exactly yet, need just more time to invest in this project...

depends where you are located...

how is the protection circuit reacting when R47 is 100K ?

He doesn't know his shit

on the control board resistor R47 is a 100K resistor, on the schematics of Jason and my other zpa's it is a 10K resistor. could this be causing the problem? I can't verify it now because I soldered out the board. Could this be the reason that the green LED is not going out when the red LED is on? It...

today I tested the amp with my test speakers and head unit with the risk of damaging my speakers. the amp is playing wonderful and powerful without any distortion in the speakers but the problem with the red overload LED stays the same. It's all the time working. So the most logical explanation (cor...

tested the output BJT's and al the gate resistors. Nothing wrong with them, put them back in and still the same problem...

the voltages were taken without the outputs in the circuit. I measured the 50v between the collector and the + and - of the left channel, so the + of the left channel is the non inverting output and the - (min) the secondary ground potential if I understand correctly. In other words, on both the + a...

Thank you Jason for checking this out. did find some time to continue this project. I pulled out all the output transistors and when I power up the amp the red overload LED is still on. The intensity of the overload LED is going together with the power supply voltage. I use a 10.5v voltage supply so...

until now I couldn't find out why the yellow LED is working for 1- 2 seconds when powering up. But in the end I think this is the normal operation of the amp. I have several other ZPA's in a daily system and when powering them up I have seen never a Yellow LED lighting up. But then I thought, what h...

there are 6 thermistor's with corresponding resistors and diodes. The resistors and diodes are ok.
I've putted a jumper over the 6 thermistors but the problem stays the same.
How does the mute functions works? To me it seems that the thermal LED is somehow connected with the mute function?

think I've spend 6h to desolder and solder in again, with no result. While doing the testing I also saw that after let's say 30 sec the 4 bias LED's are shutting down. So the first thing that happens when you power up is the yellow thermal LED is lichting up for 2 seconds then the red overload LED i...

hope this phorum stays alive...

Holy sh**t! How is that possible? Is that the original RCA connector? Maybe the old one was replaced and the new one was not soldered like it should? Eric you solved the mystery, look first at the most obvious things. This means you have a lot of experience. It reminds me on a situations I think mor...

on this forum everything is explained in the "how to section / capacitor replacement"

the first thing you need to do is replacing these 2 caps. If not they can burn or explode. Do not power your amp again before you haven done this.
The problem wit overload will not dissapear with changing the caps Do you know how to measure the current draw of your amp?

when it goes in protection mode, is it the red LED or the yellow LED that is turned on?
I hope the power supply caps are changed with new ones (the two caps on the right side just under the heat sink)

Hi
the amplifier worked before, after that point did you change something?
can you tell how many speakers are connected to the amp? Is it a subwoofer / full range / component set?
after a few minutes is the amp very hot?

Jason, You said that "fault can potentially drive full rail voltage into a circuit designed for much lower voltages"
Could it be that the overload detection circuit is damaged in the power amp section?