i agree, all ps's are first check (except i just found a smoking tantalum).
i have a few big rectifiers left over from a 465M fix. if they are a prob i'll be able to hit em pretty easily. i have not even had a volt meter on it yet. i do have a working scope to debug it.
thanks.
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--- In TekScopes@..., "Tom Jobe" <tomjobe@...> wrote:
I didn't notice if you said the low voltages were good or not, but until every low voltage is good, you are wasting your time checking anything else.
Another thing to look for is dead rectifiers. There are a few of them right where the big PS caps are mounted and they are easy to change without taking the scope apart. These are those full wave bridges all in one big rectangular chip.
The Tekscopes Message archive has several methods people have used successfully to change the rectifiers on the 4XX scopes like the 465, 465B, 475, 474A, etc, if you don't have your own method.
tom jobe...
----- Original Message -----
From: pdxareaid
To: TekScopes@...
Sent: Sunday, September 23, 2012 2:04 PM
Subject: [TekScopes] Re: WooHoo! 465B
thanks for the tip. i did not know tantalums smelled.
i'll probably hit big filter caps anyway...i had a bad experience with them in a 465M among other PS components. i have the service manual etc. need to read up and start checking things in and around ps. afraid to leave it on and have failures cascade. quick voltage measurements to start.
i understand failed tants are pretty easy to spot. they fail shorted usually? is that right?
phil
--- In TekScopes@..., "Tom Jobe" <tomjobe@> wrote:
>
> Hi Phil,
> A free 465B is a wonderful thing!
> From my own experiences and reading the Tekscopes group for years, maybe consider starting by checking the resistance to ground at each power supply test point, then go looking for some of those pesky tantalums in the 10uF to 47uF range on the shorted supply(s).
> The tantalums make the bad smells when they die, more so than the electrolytics.
> Maybe someone has a list of expected resistances for the voltage test points on a 465B ?
> tom jobe...
>
>
>
> ----- Original Message -----
> From: pdxareaid
> To: TekScopes@...
> Sent: Sunday, September 23, 2012 1:42 PM
> Subject: [TekScopes] WooHoo! 465B
>
>
>
> I just picked up a 465B off Craigslist. Came with 10x probe.
>
> the ad:
> "Unit was working, then stored for 3 or 4 years. When I turned it on recently, it died. There's a beam, but no sweep. It worked well before that. I was hoping someone would want to fix it and put it to good use. Free."
>
> Nice guy...engineer...just did not want to deal with it.
> He mentioned electrical burning smell when turning on.
>
> I got it home and spent 10 minutes with it...opened it up and turned it on. Burning smell coming from PS section I think. Whole screen glows off and on, no trace to speak of.
> It is in excellent shape otherwise, calibration stickers all over it.
>
> I am thinking PS filter caps to start, then tantalum and electrolytic search after that.
> Phil
>
