[Heathkit] SB-610 Monitor Scope

[kevin schuchmann]

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