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Author Topic: Two Test Equipment questions.....  (Read 925 times)
N4UE
Member

Posts: 291




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« on: February 28, 2009, 02:33:08 PM »

Hi,
#1. I have been searching the WWW for a Manual for a recently acquired Exact Electronics Inc. Model 528 Sweep / Function generator. Big ZIPPO. I'm not looking to bum one. I am willing to pay good money for the Manual, but it appears Exact no longer exists.
I have searched EVERY Manual site I could find, and I have come close, but NO Model 528....
Any suggestions?Huh?

#2. I have a Tek Model 7623A 'scope that's driving me nuts! One day, I turned it on and heard a very low 'click', like a fuse blowing. I have NO trace or even a 'power' light.
I have been working on this thing for ...TOO...long.
I have a fan, but it's pretty weak. I have found:

A blown fuse.
A blown resistor on the P/S.
One of the power-on micro-switches was broken 'Normally Closed' instead of "Normally Open".

I have a Manual by Tek called 'Troubleshootig your Oscilloscope". This was pretty useless, it just pointed me to the P/S. I also have the Op / Service Manual. The voltages look OK. Yes, I removed the plug-ins and same thing.

I have asked for help on the "Test Equipment Digest" on QRZ, and NO replies.
I have had this scope for over 20 years and I REALLY hate to scrap it......

thanks!

ron
N4UE
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KI4VEO
Member

Posts: 166




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« Reply #1 on: March 01, 2009, 11:01:31 AM »

As Claude Raines said in Casablanca, "Round up the usual suspects."

The power supply is usually the first suspect - bad electrolytics.  They dry out, change value, short, open (did I miss anything?

You need a resettable breaker to substitute in place of the fuse (unless you have a pile of glass fuses to sacrifice to the Gods).  You also need a 120 volt variac to gently bring up the patient...and a troubleshooting "game plan".

With no AC power applied***
Disconnect the supply leads from the circuitry and check the power supply by itself.  Check voltage rails with an ohmmeter.

I am sure your troubleshooting book covers the basics.  I learned troubleshooting skills while going to the Air Force electronics school at Keesler AFB.  The same principles hold true today.  Isolate, then divide and conquer.

Most equipment can be repaired using a schematic, an ohmmeter, and a "game plan"
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