Agilent U2701A remains in DFU mode (PID=2818)

[ahmetonat]

I am trying to get an Agilent U2701A to run under
-Ubuntu 16.04,
-python 2.7.12,
-pyusb V1.0.2.
-python-usbtmc V0.8

Executing the commands below, I get:

import usbtmc
instr=usbtmc.Instrument(0x0957,0x2818)
print(instr.ask("*IDN?"))
#Traceback (most recent call last):

File "", line 1, in

File "usbtmc/usbtmc.py", line 770, in ask
self.write(message, encoding)
File "usbtmc/usbtmc.py", line 750, in write
self.write_raw(str(message).encode(encoding))
File "usbtmc/usbtmc.py", line 616, in write_raw
self.open()
File "usbtmc/usbtmc.py", line 369, in open
serial = self.device.serial_number
File "/usr/local/lib/python2.7/dist-packages/usb/core.py", line 830, in serial_number
self._serial_number = util.get_string(self, self.iSerialNumber)
File "/usr/local/lib/python2.7/dist-packages/usb/util.py", line 314, in get_string
raise ValueError("The device has no langid")
ValueError: The device has no langid

This initializer does not seem to take the device out of DFU mode, as the PID of the device remains at 2818, and does not change to 2918, shown by lsusb after the above.

However, I can get as far as:

print(usbtmc.list_devices())
[<DEVICE ID 0957:2818 on Bus 001 Address 009>]

I have read and followed the issue: "Agilent U2702A USB scope support"
But that seems to relate to U2702A, and not U2701A. Could it be that:

1. U2702A has a different command sequence to take it out of DFU mode than U2701A?
2. Older firmware version on my scope ignores the code to take it out of DFU mode? (it has sat idle for about 10 years)

It is difficult for me to access a Windows computer, but will do if necessary to get Wireshark report.
Thanks for the answers.

Thanks for any answers.