[Boatanchors] Heathkit SB-610 monitor scope

[Dick KF4NS]

Ron,
I tend to agree with you that the 5408s are a bit of overkill. It is just that I have 10 of them and only 
4 of the 4007s. Why do you not think I should put the resistors in series? Is it because of the low 
current and it is unlikely I would get a surge big enough to matter? By the way, I have a SL10 ( that is 
an Ametherm inrush surge limiter) in the hot power lead. Your comment regarding the flipped xfmr leads 
makes sense so I will likely rewire those leads as shown in the schematic, thanks for the tip.

I don't remember Ray Le Rue.

73, Dick KF4NS
St Petersburg, FL 33714 USA
Keep The Glow!

----- Original Message ----- 
From: "Ron Youvan" <ka4inm at tampabay.rr.com>
To: "Dick KF4NS" <kf4nsradio at verizon.net>
Sent: Monday, November 07, 2011 11:20 AM
Subject: Re: [Boatanchors] Heathkit SB-610 monitor scope


| Dick KF4NS wrote:
|
| > Decided to dig into it again since I had not done much with it since I got it 2002 and replaced all 
the
| > power supply caps. Recent testing showed poor focus and low vertical gain.
|
| > I found the two B+ diodes shorted. Wow, never saw any selenium rectifiers that looked like those two. 
The
| > focus problem should be fixed after replacing the rectifiers and a few resistors. About those diodes, 
I
| > will likely use a couple 1N5408s but the usual thing would be to series a resistor with each anode 
lead
| > which is usually a good idea in power supplies with original seleniums. In this case though I wanted 
to
| > get you input because I noticed that the capacitors are not electrolytic and there shouldn't be the 
usual
| > increase in voltage. What do you think? One chap has a solution online whereby he used 4 1N4007s in
| > series for each replaced diode which I guess he thinks will make up for not using series resistors.
|
|   I think 1N5408s are over kill, use 1N4007s without resistors.
|
|
| > I also observed that the blue and yellow xfmr leads are reversed but don't believe that should be a
| > problem since we are looking at AC here and don't think secondary polarity should be of concern here.
|
|   This can be a problem, the end (start) nearest the core should be kept closest to ground from an
| insulation point, the winding on top (furthest form the core, the finish) can usually tolerate a
| much higher Voltage.
| (in cheap transformers)
|
| > I have a couple options here will take care of the vertical gain situation. Got that covered.
|
|   The deflection sensitivity is a function of the high Voltage, and works in a reverse direction,
| the higher the ultor Voltage the smaller the display.
|   I think Ray Le Rue introduced us 15 or 20 years ago.
| -- 
|    Ron  KA4INM -    Ron  KA4INM - Did you know ...
|                     ... that no-one ever reads these things?