I've buyed this oscilloscope on Ebay and i've discovered that was suffering of some problems (Calibration data checksum error) and some gain problems on one of the two channels.
Great thing of those oscilloscopes is the auto-calibration, with only the aid of BNC cables and a good multimeter is possible to do a complete calibration.
Focusing on the issues, swapping attenuators the fail moved accordly so was evident that the fault was the attenuator, that i've found quickly on ebay for a hundreds of dollars.
Reguarding CRC errors on calibration data, the natural culprit was the Dallas chip DS1235YW-120, that i've dissoldered and replaced on a socket. Ended the operation in few hours i was able to obtain a good calibration and a full working instrument.
In the future i will try to do a backup copy of the firmware that is on two EEPROM
P27010-200 e 1818-4083.
HP 54503-63401 Attenuator
(Failed)
Looking on the net seems that common failure in those attenuators are the following:
1. The 50 Ohm input can be blown open (1Meg ohm input works fine. This is not an obvious failure)
2. The FET DC restore path can be blown out. (only passes AC signals. You will not see this failure on HF signals.)
3. There are mechanical switches in these attenuator modules and sometimes the contacts are intermittent.
Those infos are taken from Ebay, from an auction of watronics that sells spares for this oscilloscopes and has a strong knowledge on those.
Result
No purtroppo, si vede nella foto, credo si sia bruciato qualcosa probabilmente il carico da 50Ohm ma non riesco a capire cosa sia..