[Techtoolslist] HP 1650A Logic Analyzer

[Jose Luiz Martins]

Thank you all for the opinions and lessons...

I've changed all output capacitors, some of them was measuring more
than 50% of original value. For instance: 1000uF measuring 1600uF,
470uF - 700uF and so on...

But the PS is continuing clicking and oscillating...

So I've decide to remove the filtering capacitors (4x 470uF 250V) and
now I have the correct voltages. But the voltages decreases a lot when
applying charge on it (back on 1650A mother board).

Tomorrow I'll buy new filtering capacitors and see what happens.

Thank you guys,

JL

On Wed, Mar 6, 2013 at 7:27 PM, John Honniball <coredump at gifford.co.uk> wrote:

> Jose Luiz Martins wrote:

>>

>> The power source clicks and the voltages are not correct. 7V instead

>> of 12V, 4,5V instead of 5V and oscillating.

>

>

> Clicking is a sign of current overload. Oscillation is a sign

> of too low capacitance, i.e. not enough smoothing.

>

>

>> I have not experience in PS repair, but someone told me that the

>> electrolytic capacitors may be dry due the time it was stored (as well

>> as de condition, one it was in Rio de Janeiro, and at summer time, the

>> room temperature may be more them 120F)

>

>

> Yes, that's quite possible. May be best to see if any electrolytics

> have begun to bulge on top. If so, replace then right away.

>

>

>> Could someone confirm that please ?

>

>

> Another possible failure is tantalum capacitors. They fail short

> at any time, and will overload the supply. I had one fail today

> in a Tek scope module (5A22N). It smoked a resistor, too. Worth

> checking, if there are tantalums on the power supply rails on the

> boards of the 1650A.

>

> --

> John Honniball

>

>

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