[Heathkit] SB-610 Monitor Scope

[manualman@juno.com]

I added an astigmatism control to my HO-10 and HO-13. Can't remember if I
did my SB-610. Got the idea from an old Radio & TV News article on
improving the quality of older oscilloscopes (Eico, Heath, etc.). After
adjustment, along with my focus and intensity front-panel adjustments, my
horizontal trace is smooth from end to end. I also replaced the resistors
that were hanging off the focus and intensity controls.
Pete, WA2CWA

On Sat, 31 May 2003 20:24:00 -0700 kevin schuchmann
<kschuchm@pacbell.net> writes:
> On Saturday 31 May 2003 06:06 pm, Bill Pancake wrote:
> > Hello All...
> >
> > I could really use some suggestions for a solution to a problem 
> I'm having
> > with my Heathkit SB-610 monitor scope. I have just replaced the 3" 
> CRT with
> > an NOS  3RP1A as the old one died of old age.  The new CRT 
> functions just
> > fine and all front panel controls function just fine.
> >
> > The issue is that the CRT's horizontal trace (with no signal 
> input) is very
> > sharp & crisp on the left side of the tube and gets less sharp and 
> somewhat
> > thicker n' fuzzier as it approaches the right side. No adjustment 
> of the
> > intensity or focus controls on the front panel will correct the 
> "fuzzy"
> > right side of the line trace. When monitoring SSB voice signals 
> the display
> > appears normal.
> >
> > Anybody got any ideas on how to make the CRT's trace sharp and 
> even in
> > thickness all the way across the display ??? Thanks & 73, Bill 
> K0JWP 
> > (bpancake@mindspring.com).
> >
> 
> Hi Bill,
>    first off are you sure your 610 really had a 3rp1"A" CRT, I 
> believe the 
> original spec was for a 3rp1 which has the rounded face, the "A" 
> variant has 
> a flat face and can cause you some defocusing as you describe...  
> what you 
> need is a  "astigmatism" control, this was one of the controls on a 
> SB-620 
> which uses a 3rp7 same CRT just different decay time on the 
> phosphor,  it 
> works by varying the voltage on the screen at pin 8.  You could try 
> adding 
> some resistance  or a 1 meg pot in there to adj it, but you may need 
> more 
> voltage than the existing  line supplies, this might be more 
> tinkering than 
> its worth, it might be easier to find a 3rp1. Or maybe some others 
> could 
> comment if they had gotten a 610 with a 3rp1a to start with and 
> maybe we 
> could compare schematics,no use reinventing the wheel if Heath 
> already solved 
> this in later models...
> 
> 73
> Kevin
> WA6FWF

________________________________________________________________
The best thing to hit the internet in years - Juno SpeedBand!
Surf the web up to FIVE TIMES FASTER!
Only $14.95/ month - visit www.juno.com to sign up today!