On 04/09/2016 01:21 PM, Seth Morabito wrote:
> I'm fairly surprised that the 7805 regulators died, and that they
> present this symptom (no horizontal scan) upon their death. I'm sure
> there are other marginal components that will need to be replaced,
> so the restoration is not yet complete un
Well, since it was such an easy job, I took a chance and replaced the
two suspicious 7805 voltage regulators. The terminal works just fine
now!
http://imgur.com/a/wharu
I'm fairly surprised that the 7805 regulators died, and that they
present this symptom (no horizontal scan) upon their death.
Try renewing the thermal compound.
Also, look for any really hot components on the 5V
lines. Tantalums don't always smoke.
A lot of older circuits also used a shunt resistor across
the regulator to share part of the load. These were usually
the square wire wound resisters. These often fail because
> On Apr 8, 2016, at 11:59, Seth Morabito wrote:
> One more observation: Two of the three +5V regulators cut out
> when their input voltage exceeds about 11.5V. The input voltage
> comes from a 9.4VAC winding on the primary transformer. Input ripple
> is VERY low, maybe 200mV. So, I suspect those
* On Fri, Apr 08, 2016 at 02:33:25PM -0400, Mouse
wrote:
> > Today, for whatever reason, my Variac was turned down to 110V, and I
> > didn't notice. I turned on the ADM 3a, and... it's fine. [...]
>
> Fascinating!
>
> I have trouble imagining what sort of fault could cause those symptoms.
> I
> Today, for whatever reason, my Variac was turned down to 110V, and I
> didn't notice. I turned on the ADM 3a, and... it's fine. [...]
Fascinating!
I have trouble imagining what sort of fault could cause those symptoms.
I would have agreed with whoever (tony, I think) said that if you have
HV t
OK, I made a very interesting discovery today.
When I'm working on a project on my workbench, I normally have it
plugged into a Variac. This ADM 3a is no exception. I bring up voltage
slowly on any unknown old electronics, and then let it sit at our
normal wall voltage - which currently reads 121V
>
> This particular 3a has no horizontal scan. None at all. I just get a
> vertical line down the center of the screen. First thing I checked was
> the horizontal deflector on the yoke, which seems secure.
I am going to assume this is a conventional design, I would be very
surprised if not. In wh
>
> I've been on a tear trying to resurrect old projects here, and next on
> the list is an ADM 3a.
>
> This particular 3a has no horizontal scan. None at all. I just get a
> vertical line down the center of the screen. First thing I checked was
> the horizontal deflector on the yoke, which seems s
* On Thu, Apr 07, 2016 at 11:34:52PM -0500, Eric Christopherson
wrote:
>
> Is this the same one that was showing all exclamation points on every
> other line?
Nope, this is a different one. I got this one "as-is" in a known non-working
state.
-Seth
On Thu, Apr 07, 2016, Seth Morabito wrote:
>
> Hey folks,
>
> I've been on a tear trying to resurrect old projects here, and next on
> the list is an ADM 3a.
>
> This particular 3a has no horizontal scan. None at all. I just get a
> vertical line down the center of the screen. First thing I chec
Hey folks,
I've been on a tear trying to resurrect old projects here, and next on
the list is an ADM 3a.
This particular 3a has no horizontal scan. None at all. I just get a
vertical line down the center of the screen. First thing I checked was
the horizontal deflector on the yoke, which seems s
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