Gents,
It appears that the transformer is bad. There may be more bad components,
I am not sure. While taking meter readings, my main fuse blew. I changed
it and it blew again.
I desoldered the 2 output connections to the power supply circuit and was
only getting 2VAC from the output of the transformer.
So it appears I need a power supply. If you have one, please let me know
what you want for it shipped to 75077. Thanks!
73's
John - NE5J
Johnathon B. Allread
john.allread@gmail.com
469-336-7763
"The Road to Success is Always Under Construction" - Lily Tomlin
On Sun, Oct 6, 2019 at 9:19 AM Mike Bryce <prosolar@sssnet.com> wrote:
> gary,
>
> that supply is very simple.
>
> if you have 25 V AC from the secondary of the transformer yet no dc on the
> cap, check the bridge rectifier. They have been known to go bad in that
> radio. Most likely one or more of the diodes inside have opened.
> Replacement is the best way to check, they’re not expensive or hard to
> obtain
>
> the over trip circuit uses the voltage drop across a low value resistor
> that when it drops an excessive amount, trips a scr that shuts the PS down.
> It only controls the DC side of the power supply.
>
> when it trips, you would still see both ac from the transformer and dc
> across the filter cap.
>
>
> Mike, WB8VGE
> www.theheathkitshop.com
>
>
>
> > On Oct 6, 2019, at 1:01 AM, Gary Follett <dukeshifi@comcast.net> wrote:
> >
> > Well I have a transformer for the C21 sitting right behind me if you
> find that you need it.
> >
> > With the power switch on, you should see voltage across C1 regardless of
> trip condition, as long as the power switch is OK.
> >
> > You should also see voltage across C2.
> >
> > If not, use an ohmmeter to measure transformer windings and power
> switch. It is not unheard of for that switch to be bad. I may have one of
> those too.
> >
> > Since it is ,not blowing the fuse, likely the diodes in the bridge are
> OK but it would to hurt to test them for open. I doubt you sill find any
> open though. Diodes usually fail shorted.
> >
> > Gary
> >
> > W0DVN
> >
> >> On Oct 5, 2019, at 10:15 PM, Johnathon Allread <john.allread@gmail.com>
> wrote:
> >>
> >> Hello everyone,
> >>
> >> I recently purchased a digital version of a Century 21. Unfortunately,
> >> when I received it, It will not power on. When I turn it off, it very
> >> briefly powers on then off. I have verified 120VAC going to the
> >> transformer from the switch and tried to verify 25VDC from the
> transformer,
> >> but I am not seeing a DC output across the capacitor C1. I did this
> >> quickly, so I will recheck tomorrow. My question is, if there is an
> issue
> >> with the excess current trip shut down circuit, would it have any
> impact on
> >> the unregulated output of the transformer or just affect the regulated
> side
> >> of IC1? I am trying to understand the circuit, but my electronics
> >> knowledge is limited when it comes to ICs and transistors. By the way,
> >> this unit is spotless inside and does not look like it has been worked
> on.
> >> Lastly, If there was an issue with the transformer, where could I
> purchase
> >> a replacement? Thank you!
> >>
> >> 73's
> >>
> >> Johnathon - NE5J
> >>
> >> Johnathon B. Allread
> >> john.allread@gmail.com
> >> 469-336-7763
> >>
> >> "The Road to Success is Always Under Construction" - Lily Tomlin
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