Brent, I found the same thing. My 3458A is bright enough and didn't show anything especially glowing on the filaments when viewed through the thermal camera. It was cold just like my blackholatron.
I slapped display and faceplate back together and decided to focus on checking that all the array display I/O Clock signals were present and correct at IC8 and they are. There's a line in the service manual in Figure 3.3, "If the DMA fails, the Display Clock will remain at logic 1 and the Display will be blank." It was at logic 0. I have a new DMA chip in the logic board right now anyways. Since I don't have a replacement VFD I'm a little apprehensive of trying to operate the display directly whilst out of the unit. If I understand it correctly the filaments have +5v, the grid has +40V to help move electrons to the phosphor pads which are at -5V. The decoding IC's are responsible for activating the -5V on the pads. As long as there's no circuit breaks that bring those voltages to their destination and the VFD is still under vacuum then it should work. Know all that information (assuming I understand it correctly) means I should be able to bring the voltage directly to the display and to see if I can light up a phosphor pad. But I'm still apprehensive to do it. Has anyone used any tricks on these displays in the 7071/81? Going back to one of the two original symptoms, all the LED are on solid. Can anyone confirm that during the boot up sequence do all the LED come on together briefly and/or during power down? Thanks Rick On Wed, May 6, 2020 at 8:10 PM Brent Gordon <[email protected]> wrote: > Rick, > > I just tried my thermal camera on my working VFD and did not see > anything. Apparently, the filaments are at a low enough temperature > that not enough IR makes it through the glass. > > Oh well, it was worth the effort. > > Brent > > On 5/5/2020 8:58 PM, Rick Bale wrote: > > Brent that's a great idea since I have one too. > > > > Rick > > > > On Tue, May 5, 2020 at 7:54 PM Brent Gordon <[email protected]> > > wrote: > > > >> Rick, > >> > >> I tried my cell phone camera on a working Keithley 2400 VFD and could > >> not see the filament. I'll try a thermal camera tomorrow. > >> > >> I have very little experience with VFDs. > >> > >> Brent > >> > >> On 5/5/2020 11:53 AM, Rick Bale wrote: > >>> David and Brent, > >>> > >>> I didn't pick up any change in the VFD's surface with the iphone when I > >>> powered it on. So I took it apart completely to see the naked VFD. > The > >>> two getters in the far end corners are still dark black and shiny. > Looks > >>> brand new as opposed to the light grey bad ones I've seen in pictures. > >>> > >>> Since it's apart and disconnected from the unit I'm inclined to power > the > >>> VFD up directly. I need to map out the connections. Have you guys > ever > >>> done this before? > >>> > >>> Rick > >>> > >>> > >>> On Tue, May 5, 2020 at 6:42 AM David C. Partridge < > >>> [email protected]> wrote: > >>> > >>>> It's also worth checking the "getters" in the VFD - are they shiny > >> metallic > >>>> or white? If white your VFD has lost it's V(acuum) > >>>> > >>>> D. > >>>> -----Original Message----- > >>>> From: volt-nuts [mailto:[email protected]] On Behalf > Of > >>>> Rick > >>>> Bale > >>>> Sent: 05 May 2020 03:43 > >>>> To: Brent Gordon > >>>> Cc: Discussion of precise voltage measurement > >>>> Subject: Re: [volt-nuts] Solartron 7081 > >>>> > >>>> Brent, I check that our tomorrow. Thanks > >>>> > >>>> Rick > >>>> > > > _______________________________________________ > volt-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/volt-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/volt-nuts_lists.febo.com and follow the instructions there.
