hi experts!
i just acquired a HP 54502A scope with one input attenuator missing. When the remaining attenuator is in Ch1 the scope seems to work, however i am not sure whether the ac-square wave signal looks a bit too noisy and the following self-tests fail:
Now, if i swap the attenuator assembly to Ch2 the same self-tests do fail. when i connect the ac-calibration signal to Ch2 i can see the signal but when i decrease the vertical sensitivity starting from 5V/div with the FINE key selected, the displayed amplitude of the signal does not change continuously but only jumps up exactly when i can hear the attenuator's solenoids switching (this takes place between 1.20 and 1.15V/div, 235 and 230mV/div and 47 and 46mV/div).
I am not exactly an expert in electronics so any help with this problem would be greatly appreciated!
Thanks in advance
joerg
i just acquired a HP 54502A scope with one input attenuator missing. When the remaining attenuator is in Ch1 the scope seems to work, however i am not sure whether the ac-square wave signal looks a bit too noisy and the following self-tests fail:
- 'Analog Trigger': (error code 0000 0000 0000 0001)
- 'D/A Converter': (error code 0000 0000 0000 0001)
- 'A/D Converter': (error code 0000 0000 0011 1101)
Now, if i swap the attenuator assembly to Ch2 the same self-tests do fail. when i connect the ac-calibration signal to Ch2 i can see the signal but when i decrease the vertical sensitivity starting from 5V/div with the FINE key selected, the displayed amplitude of the signal does not change continuously but only jumps up exactly when i can hear the attenuator's solenoids switching (this takes place between 1.20 and 1.15V/div, 235 and 230mV/div and 47 and 46mV/div).
I am not exactly an expert in electronics so any help with this problem would be greatly appreciated!
Thanks in advance
joerg
'Analog Trigger': (error code 0000 0000 0000 0001)
The above code just means that there is a problem with the trigger on channel 1. Notice that last digit is a 1. If it was a 2, then the problem would be with channel 2.
'D/A Converter': (error code 0000 0000 0000 0001)
Again, you have a D/A converter problem on channel 1.
'A/D Converter': (error code 0000 0000 0011 1101)
The last digits should all be ones. Yours says 1101 which means that the A/D is bad.
You bought a scope without an attenuator on channel 2. It looks like the AD on channel 1 is bad.
If you move the attenuator to channel 2, you will still get the trigger and DA errors. However, you might try moving the channel 2 AD over to channel 1. On early units the ADs were not soldered in. There were finger contacts under neath the AD. If your channel 2 AD is not soldered in, you could move it to channel 1. You have to be careful because the finger contacts were easy to damage with too much pressure and then the AD pins would loose connection. The screws holding the AD have to be torqued down evenly to about 3 in lbs. If you over tighten the screws you will damage the gold finger contacts and the AD is lost. We got away from the finger contacts and went to soldering the ADs in place. The reliability went went up, but removing the 40 pin ADs is almost impossible. If the AD is soldered in, it is very improbable that you could desolder the AD without damaging the small traces or through hole eyelets. You can try it, but I doubt you will be sucessful. We had to use special tools here at the factory to remove the ADs. (No we do not have those tools any longer.)
You can also check the AD to make sure there are no missing AD codes. Apply a pure low frequency sine wave and carefully observe the sine for small stair steps. The small stair steps would indicate ADs codes are missing. If there are missing AD codes, that would explain why the channel is noisy.
We do not have the parts to support that old of a scope. If you cannot fix it yourself or live with the performance, there is not much more we can do for you. The bottom line is that I hope you did not pay too much for that scope. If the noise on channel 1 is not so bad that it impacks your work, you could still use the scope to just see if signals are present at pins. But I would not use the scope for critical measurements.
I hope this information helps you out.