Hello,
Frist of all : please appologise for my english : I'm french...
I wich you a happy new year and hope you've had a happy Christmas.
I have an Audio Precision Portable One + with problems.
- the first issue I've fixed was on the IMD optional card : two NE5534, an OP27 and a ceramic capacitor dead. Now it works fine.
- the second problem is with the filters : see the attached file. As you can see during the self test all the filters (except selctive) are out of use. Heaven if two of them pass the test, I'm quite shure in fact they don't work.
No schematics are available for AP products execpt System one (I also have a Sys one : 222), so I tried to understand how it works, but it's very very difficult. I think filters are on the part enclosed with a red line, but not shure.
I've adressed some of the logical inputs of 74HC4051 and 74HC4052, but I don't understand the way it works. Some of the logical input switche from low to hight when I select filters, but I can't find where is the connection between the output of the filters and the rest of the circuit...
I found strange square signals on the LM339N (botoom of the picture), but I don't know if it's normal or not...
I've changed some relays but it's still the same...
Maybe Duke will be able to help, or anybody who has a Portable one +
Thanks for help !
Emmanuel
Frist of all : please appologise for my english : I'm french...
I wich you a happy new year and hope you've had a happy Christmas.
I have an Audio Precision Portable One + with problems.
- the first issue I've fixed was on the IMD optional card : two NE5534, an OP27 and a ceramic capacitor dead. Now it works fine.
- the second problem is with the filters : see the attached file. As you can see during the self test all the filters (except selctive) are out of use. Heaven if two of them pass the test, I'm quite shure in fact they don't work.
No schematics are available for AP products execpt System one (I also have a Sys one : 222), so I tried to understand how it works, but it's very very difficult. I think filters are on the part enclosed with a red line, but not shure.
I've adressed some of the logical inputs of 74HC4051 and 74HC4052, but I don't understand the way it works. Some of the logical input switche from low to hight when I select filters, but I can't find where is the connection between the output of the filters and the rest of the circuit...
I found strange square signals on the LM339N (botoom of the picture), but I don't know if it's normal or not...
I've changed some relays but it's still the same...
Maybe Duke will be able to help, or anybody who has a Portable one +
Thanks for help !
Emmanuel
Attachments
Troubleshooting things like this without documentation is hard. However you have done some good work. The LM339 is a comparator so its outputs will normally be "high" or "low".
My guess is that its a level shifter to switch the 4051, 4052, which can be uses at "routing" switches. Looking at the test outputs it seems the filters are out of spec, but not dead. If you can plot the actual response of the different filters it would help pinpoint the failure. A guess is that a cap or two are out of tolerance. Its unlikely that a mica caps is bad but the orange caps could easily have drifted. Or one of the cmos switches (40XX) could have failed.
My guess is that its a level shifter to switch the 4051, 4052, which can be uses at "routing" switches. Looking at the test outputs it seems the filters are out of spec, but not dead. If you can plot the actual response of the different filters it would help pinpoint the failure. A guess is that a cap or two are out of tolerance. Its unlikely that a mica caps is bad but the orange caps could easily have drifted. Or one of the cmos switches (40XX) could have failed.
Hello,
I still have problems with my AP portable one +.
I found very strange values on some of the resistors networks, but it's impossible to read the references on them. See picture for location.
If somebody could give me the values of this resistors networks, it would be fine !
Thanks a lot.
Emmanuel
I still have problems with my AP portable one +.
I found very strange values on some of the resistors networks, but it's impossible to read the references on them. See picture for location.
If somebody could give me the values of this resistors networks, it would be fine !
Thanks a lot.
Emmanuel
