ANRITSU MS610A need help!

[5065AGuru]

I picked up an MS610A for a dedicated use to monitor a signal.
Unit worked OK with the exception of the display being a little fuzzy. Seemed like the signal was wiggling back and forth a tiny bit. Took the cover off and with the help of a downloaded MS610B manual found one of the local oscillator signals wiggling also. Could not ID the cause so I buttoned it back up. With the settings I needed for my signal it was usable and I lived with it. Then (later) the CRT went blank. Planning to dive in and troubleshoot but looking in the manual it shows the schematic and how the CRT interfaces with the CRT drive circuit board but give no voltages! Anyone worked in this circuit before? Is there a better manual out there somewhere? I guess I could check the filament to see if it's open.

Cheers,

Corby

[orbanp]

Hi Corby,

Nice SA!

I also did find the 610B manual, but curious how close the "A" version of the SA to the "B" version is?

I could not find the part number of the CRT in the part list, but that would be a way to find the operating voltages to the CRT, by looking up the datasheet of the CRT.
Possibly you could identify the CRT from the actual unit and go from there.

Also, a first step would be to check the supply voltages, if they in spec, and without ripple.

Good luck, Peter

[5065AGuru]

Peter,

The only difference I can see between the A and B is that the B has DC-DC convertors that allow operation of off DC.

The CRT is listed as a Matsushita 150CUB39.

No data available that I can find.

I did find a 1.5Meg 2W HV 5% resistor that has a crack running around the middle. It's reading high also.
Need to find a replacement. Probably put three 1W ones in series.

The unit has a display again but the display is not clear. (did try focus and astigmatism) When a CW signal is displayed it looks like it has LF FM on it as the trace width is about 1/8" wide. The first and 2nd L.O. have an SMA monitor jack on the rear. Guess I'll hook another spec-A up and see if one of the L.O.s is not stable.

Cheers,

Corby

[orbanp]

Hi Corby,

Looks like you are well on your way to fix that SA!

Have you seen the following thread?
He seemed to have a similar problem on a 610B SA:
http://www.antiqueradios.com/forums/viewtopic.php?t=233304&view=next

Regards, Peter

[5065AGuru]

Peter,

You are the man!
His symptoms look the same as mine. I've replaced the cracked R24 and pulled C23 and C24 prior to finding replacements. Also considering replaceing the four 3.3uf 100V caps in the voltage multiplier.
Once the caps are  in I'll fire it up and see what happens!
That reference to the Antique radio forum was just the ticket.

Cheers,

Corby

[5065AGuru]

Replaced the C23 and C24. Also replaced the cracked 1.5Meg resistor.
The caps did the job and the trace is sharp now.
Again thanks for the help!

Cheers,

Corby

[orbanp]

Hi Corby,

Congrats on the successful repair!

If you do not have an ESR-meter, get one, or better, build one for yourself!
I am sure it would have found your problem (the faulty caps) in no time.
I built one about 15 years ago, it is one of the most useful test equipment that I have!

Regards, Peter