Re: Tek 7603 Followed Me Home


Chuck Harris <cfharris@...>
 

I am not sure what you are saying when you say that
C808 tests at 0.0 ohms. Do you perhaps mean 0.0 uf?

Typically, when ripple gets to be that excessive, the
capacitor's internal connection has been etched away
and is open circuit, or the capacitor's electrolyte
has dried up. The capacitance goes to near zero uf.

As a temporary fix, you can get back in business by
paralleling just about anything across the original
capacitor at its terminals. Even as little as 1/10th
the correct value will sometimes be close for the circuitry
to limp along and work. Tektronix was very generous
with its margins.

-Chuck Harris

Robert Hay wrote:

Chuck,

C808 on the -50 v unregulated is the only cap that tests at 0.0 Ohms and is the only
one that doesn't charge up to some value using the cap test position on my Tek DMM916.

I ordered some replacement caps although I am not sure whether to ultimately replace
all the cans in the back section. I may use two 1000ufd 100v caps to replace the
1800 ufd 75 volt C808 on the -50 unreg. In this case the can is connected to the -50
unregulated rather than ground so I need to tie all those loose ends together.

I'll hit up the local electronic surplus tomorrow to see if I can find a replacement
cap for testing while waiting for the ones I ordered.

Bob.

On 9/9/2018 9:57 AM, Chuck Harris wrote:
My guess would be the -50V unregulated supply's
filter capacitor is no longer any good.

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