{Collins} Fwd: 75s1 PS Hum



Question?......Have you changed out the triple can 40/40/40uf chassis mounted electrolytic?

I've seen a lot of folks recap their 75S__ receivers but the can cap never gets replaced.  Can cause bad ac hum if defective.

Steve,  N6HK


Sent via the Samsung Galaxy S® 4 mini ™, an AT&T 4G LTE smartphone


-------- Original message --------
From: Gary Follett via Collins <collins@xxxxxxxxxxxxx>
Date:12/10/2017 10:44 (GMT-08:00)
To: Karl Bridges <bridkarl@xxxxxxx>
Cc: Collins Reflector <collins@xxxxxxxxxxxxx>
Subject: Re: {Collins} 75s1 PS Hum

Does the hum vary with volume control?



Sent from my iPad

> On Oct 12, 2017, at 9:57 AM, Karl Bridges via Collins <collins@xxxxxxxxxxxxx> wrote:
>
> I'm fighting the same issue in a non-Collins receiver right now. It's been
> suggested it might be a tube short so start substituting tubes one by one
> going back from the end of the audio chain until the issue resolves. And I
> assume all the PS caps are correctly installed.
>
> On Thu, Oct 12, 2017 at 8:29 AM, George Cortez via Collins <
> collins@xxxxxxxxxxxxx> wrote:
>
>> I continue to work on the 75s1. It has some hum on rx. I replaced all the
>> power supply caps with sprague atoms. The hum persists. Any other ideas?
>> Perhaps some electrolytics down the audio chain?
>> George NE2I
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>
>
>
>
> --
> Karl Bridges
> Dean/University Librarian
> Eli M. Oboler Library
> Idaho State University
> 850 South 9th Avenue
> Pocatello, Idaho 83209-8089
> Phone: (208) 282-4131
> Fax: (208) 282-5847
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