The HV supply is in the right-hand-rear of the scope and the HV line runs from there to the front of the scope around again to the side of the CRT. If that cable is arcing, it might sound like it's coming from the left-hand side.
If you still hear the arcing, you could remove the top covers and power the scope in a dark room. That might help show where it's coming from.
Barry - N4BUQ
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My beloved 7704A started arcing internally the other day, At least that's what
it sounded like. It seems to be coming from the LH front side next to the CRT.
Looking at the explosion diagram, this corresponds to the HT section. Also the
display has shrunk by 50% in both directions., so e.g. the readouts are at
25%/75% of height instead of 100%/100%.
Being more than reluctant to enter into an HT section untutored, I am wondering
if there are any hints as to what specifically I should be looking for. Scope
has been working flawlessly for 15 year, and the problem occurs in both A and
B/V and H, so it isn't a plugin.
TIA
EJP
