Bob,
The open cap will do exactly what you ask. The voltage measured across the
filter cap at the output of a full wave rectifier is about 1.414xRMS. I bet if
you measure the AC voltage applied to the rectifier you will get about 1838VAC.
This is the RMS AC input voltage. The DC voltage measured at the output of the
rectifier (without a filter cap) would be the AVERAGE DC voltage. Where 2600V *
.636 = 1653.6 or 1838VAC * .9 = 1653V.
I think that once you replace that cap you will be in good shape!
-- Buddy
Bob Dodson WB5APD EM84ak wrote:
> Hi Gang;
>
> Here is the story. Turned on my MLA-2500 and plate V. was 1600 volts.
> Found (3) shorted diodes in HV string. Replaced ALL diodes w/new ones.
> Turned it back on. Still 1600 Volts. Checked caps withe VOM and (1)
> looks open. New diodes held and still ck OK. Questions;
>
> 1. Will one open cap in HV string drop HV from normal 2600 to 1600.
>
> 2. Does anyone have an original twist lock cap for this amp 150mf at
> 450vdc they waqnt to sell.
>
> 3. If I can not repair filter bank as original any problem using (6)
> 470mf at 450 vdc instead of 150mf at 450vdc. (going from 25mf to 78mf).
> I always thought more was better. Thinking abt using 470mf at 450vdc
> Nichicon 1.375" X 2.0" with 2 hole cap clamps. Not sure if holes will
> line up with original, but looks like maybe.
>
> Any thoughts on all of this is appreciated. BTW the HV xfmr looks OK
> best I can tell. Running it on 220vac and I ohmed it out. Amp tbl showed
> up at pwr up no load.
>
> Thanks in advance. Before I start spending money on new filter bank
> would appreciate your input.
>
> Bob
> --
>
> 73's
> Robert E. Dodson
> mailto:wb5apd@stc.net
> WB5APD/EM84AK
> "ex-WA4WQC, ex-WV6SKV"
>
> --
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