NEC 3FGx - known fix for focus arcing?

[Nadir]

I have an NEC 3FGx (JC1532VMA) that when turned on starts arcing. The
arcing occurs inside the focus sparkgap on the CRT socket. I replaced
VR516 which controls the HV and is known to go open circuit. The
problem still occurs despite several adjustments to the HV. Any help
is appreciated. Thanks.

 

[John Gill]

I would try to measure the focus voltage at the CRT socket.
I think it should be in the range of 3 to 7KV.
I had one that measured almost 20KV and was arching. The flyback
transformer was bad allowing the high-voltage to get to the
focus voltage controls on the flyback.
Try turning the focus control on the flyback and see if the
focus voltage changes at the CRT socket.
John

 

[CJT]

Nadir wrote:

I have an NEC 3FGx (JC1532VMA) that when turned on starts arcing. The
arcing occurs inside the focus sparkgap on the CRT socket. I replaced
VR516 which controls the HV and is known to go open circuit. The
problem still occurs despite several adjustments to the HV. Any help
is appreciated. Thanks.

A monitor that old probably isn't worth the effort. You'll spend more
in time and parts than a new one would cost you.

 

[Mike Tomlinson]

In article <4dde1835.0307201250.1718457f@posting.google.com>, Nadir
<zen_nadir@hotmail.com> writes

I have an NEC 3FGx (JC1532VMA) that when turned on starts arcing. The
arcing occurs inside the focus sparkgap on the CRT socket.

Is it constant or intermittent? If constant, are you sure the tube
hasn't lost its vacuum? Can you see any arcing inside the tube neck?

I replaced
VR516 which controls the HV and is known to go open circuit. The
problem still occurs despite several adjustments to the HV.

If you are sure the tube is OK, check the B+ voltage - if it is too
high, the EHT will go up in sympathy. If so, check PSU. If that's
alright, you could try changing the tube socket.

--
Mike Tomlinson