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Re: [TenTec] Troubleshooting Century 21 Power Issue

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] Troubleshooting Century 21 Power Issue
From: Gary Follett <dukeshifi@comcast.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sun, 6 Oct 2019 00:01:55 -0500
List-post: <mailto:tentec@contesting.com>
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.



> 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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