Re: CG551AP - has anyone seen this problem before?


Chuck Harris <cfharris@...>
 

Yep.

There is a handful of mercury wetted relays underneath
a shield. One of the relays is probably sticking shut,
and installing a 50 ohm load all the time. This makes
the voltage output 1/2 what it should be, and trips the
error.

Also, virtually all of the transistors are plugged into
the board. Many have heatsinks. If the cables aren't
dressed properly when you install the boards, they can
push the transistors cockeyed in their sockets and then
can short to the inter board shields.

-Chuck Harris

David C. Partridge wrote:

Oh no, not again!!! Yes apart from not getting errors 56 and 57 ...

Time to dig in yet again. Power board first given previous experience.

David

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David C.
Partridge
Sent: 29 March 2019 14:01
To: TekScopes@groups.io; TekScopes2@groups.io
Subject: Re: [TekScopes] CG551AP - has anyone seen this problem before?

Well I hunted flaky tantalums and found no obvious ones. After re-assembly
and re-seating ROMs on CPU board, I'm now seeing the following error codes:

51, 52, 53, 54, 55 (Both Low SAC and High SAC)
56, 57 (Current mode)
81, 82, 83, 84, 85, 86, 87, 88 (All edge mode errors!)

Which is a step forward in one sense, but about 15 steps backward!

Suggestions most welcome!

Thanks
David


-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David C.
Partridge
Sent: 29 March 2019 12:52
To: TekScopes; TekScopes2@groups.io
Subject: [TekScopes] CG551AP - has anyone seen this problem before?

I turned on my CG551AP yesterday. It flashed up the SELF TEST message in
normal brightness, then the display blanked and the only sign of life was
the LEDs just above the trigger output BNC which were dimly illuminated.

Has anyone seen this behaviour before? If so what was the problem?

I'm guessing a shorted tantalum capacitor :( ...

David










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