Re: ADM 3a with no horizontal scan

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

Re: ADM 3a with no horizontal scan

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

Re: ADM 3a with no horizontal scan

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

Re: ADM 3a with no horizontal scan

> 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.

Re: ADM 3a with no horizontal scan

* 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

Re: ADM 3a with no horizontal scan

> 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

Re: ADM 3a with no horizontal scan

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

RE: ADM 3a with no horizontal scan

> > 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

Re: ADM 3a with no horizontal scan

> > 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

Re: ADM 3a with no horizontal scan

* 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

Re: ADM 3a with no horizontal scan

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

ADM 3a with no horizontal scan

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