On Sun, 25 Aug 2019 21:38:25 -0700, John Robertson
wrote:

On 2019/08/25 11:24 a.m., wrote:
On Sun, 25 Aug 2019 10:51:23 -0700, Jeff Liebermann
wrote:

On Sat, 24 Aug 2019 20:04:54 -0700 (PDT), Jeff Urban
wrote:

How can you build an electronic circuit without having the schematic ?

I built quite a few Heathkit kits in the distant past that did not
require the use of a schematic. A schematic was provided by Heathkit,
but it was only useful for learning how everything works and for
troubleshooting.

I worked for a Heathkit store in the distant past for a few months.
Most of what I found were the wrong parts in the wrong holes in the
PCB. Occasionally, it was missing, extra, or substituted parts.
Amazingly, I did find one design error. Heathkits spent considerable
time and effort to avoid any assembly instructions or documentation
errors. The unspecified manufacturer of this kit might not have been
able to do as good a job. Methinks it might be worthwhile checking if
there are any addendum, corrections, mods, or changes.

I can usually find someone else's mistakes rather quickly, but have
had less luck finding my own mistakes. Maybe having someone else
check the CRT circuitry for assembly errors might be useful.

Hint: That which is obviously correct, beyond any need of checking,
is usually the problem.
I did have someone check my work and he said it should work. And it
does except for the changing focus. I am now thinking that somehow the
voltages need to be changed. The heater voltage is just below the
lowest voltage given on the spec sheet for the CRT.
Nevertheless I am going to go back and check all the solder joints
with a magnifier. And double check all the component values. The weird
thing to me is that the thing works. It just goes out of focus
gradually from one side of the display to the other.
Thanks,
Eric


Eric, have you tried contacting the kit maker? It may be a problem with
the kit that he/she wasn't aware of - defective component, etc. It happens!

'howchon at hotmail dot com' (from the home page).

John :-#)#
Yes, I did contact him. He has tried to help but so far nothing.
Eric