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Hello all

I just got a 7104 for 30 dollars. With all 4 plugins. Including the 1ghz
one.

I need help fixing it. It powers on but the trace is wide and choppy . I
created a video. Please see it and let me know. I will start with
checking the volts on the different rails.





Thx in advance for your help

Hi,

7104 is a very special instrument with a MCP CRT, which is very susceptible
to damage from excessive brightness and static images. You can easily
destroy it if careless, or if the instrument is faulty and generates static
images (like your in case). Given the state of your instrument, I'd turn
the brightness down so that the image is barely visible. Readout on 7104
should be off unless you need it, to avoid MCP burn in. Before attempting
any repair, thoroughly read the documentation on tekWiki, and search for
posts on this group discussing MCP CRT and 7104 in general.

Based on your video, I'd say that something may be wrong with the high
voltage circuit driving the CRT, therefore the focus issue. This CRT
contains a complex internal electrostatic lens that expands the image after
deflection, and is fed by numerous voltages (those black potentiometers
under the clear protective shield on the right side of the instrument). But
I would not touch any of these before I did the following:

- get thorough familiarity with this special instrument from documentation
and group posts
- check each plugin in a known to work mainframe
- check the PSU voltages for ripple and value
- check internal connectors for bad contacts, including plugin slot
connectors
- give knobs and buttons some exercise, patina and corrosion from old age
are a major nuisance for instruments which haven't been used for a while

7104 is worthy of care and attention, don't rush things (touch adjustments)
if unsure, equip and prepare properly before going in.

Best Regards,
Nenad

Thank You for the reply and Tips

Yes the 7104 its worthy from what I have read. I'm def been carefully with the CRT.
I have been doing extensive research and reading on this Unit, SO i'm getting prepare.

I will Try the suggestions you mention, maybe make a better video of the repair attempt and troubleshooting etc.
I will post back with new findings later

Thx Again
Armando