Sylvia Else wrote: =============> <https://www.dropbox.com/s/rddddzpkwqo44sc/TransformerWiring.jpg?dl=0> > > Shows how the power transformer is directly wired to two separate > boards. Not sure how, or why, they'd want to do that.--------------------------------------------------- That power tranny is a regular E-Core with no magnetic shielding or even a copper flux shorting strap. Surprising it does not cause some trembling of the trace - being so close to the CRT like that. ..... Phil
Some oscilloscope pictures
Started by ●August 22, 2021
Reply by ●August 23, 20212021-08-23
Reply by ●August 23, 20212021-08-23
On Mon, 23 Aug 2021 07:43:10 +0100, Tom Gardner <spamjunk@blueyonder.co.uk> wrote:>On 23/08/21 03:30, Sylvia Else wrote: >> Another oddity is the two leads covered in yellow insulation. They are only >> connected at one end, and are marked on the schematic as "wired capacitors" >> across the resistors that lead to the tube X axis plates. No doubt they do >> produce some capacitance, but I can't imagine it's much. Anyone know what the >> purpose would be? > >It is a gimmick capacitor, often made with a couple of wires >twisted together to make a ~1pF fiddlable capacitor. > >Quite a lot of old Tektronix equipment relied on parasitic >stray capacitance and inductance of circuit tracks. They had >the decency to include the caps on the schematics, and to >indicate they couldn't be seen on the boards.They also discovered "hook", the terrible time-domain behavior of FR4 as a capacitor. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
Reply by ●August 23, 20212021-08-23
On Mon, 23 Aug 2021 01:10:12 -0700 (PDT), Phil Allison <pallison49@gmail.com> wrote:>Sylvia Else wrote: >============= >> <https://www.dropbox.com/s/rddddzpkwqo44sc/TransformerWiring.jpg?dl=0> >> >> Shows how the power transformer is directly wired to two separate >> boards. Not sure how, or why, they'd want to do that. > >--------------------------------------------------- >That power tranny is a regular E-Core with no magnetic shielding or even a copper flux shorting strap. > >Surprising it does not cause some trembling of the trace - being so close to the CRT like that. > > >..... PhilWe did one NMR gradient amp with two power transformers, where proper placement and phasing made the fields cancel where it mattered. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
Reply by ●August 23, 20212021-08-23
On Mon, 23 Aug 2021 12:30:08 +1000, Sylvia Else <sylvia@email.invalid> wrote:><https://www.dropbox.com/s/rddddzpkwqo44sc/TransformerWiring.jpg?dl=0> > >Shows how the power transformer is directly wired to two separate >boards. Not sure how, or why, they'd want to do that. > ><https://www.dropbox.com/s/nlzx6f0w5deomb1/SolderThroughHere.jpg?dl=0> > >Shows the hole through which the transistor has to be soldered. Note the >two resistors in plastic tubing that have one end soldered to this >board, and the other end soldered to a board at the back of the tube. >Also a wire directly soldered to the board that also goes there. > ><https://www.dropbox.com/s/degb7topima7yle/TransistorLeads.jpg?dl=0> > >Shows the formed leads for the transistors. Fortunately, I now have a 3D >printer and have been able to make a template for bending the leads. Not >sure whether the white stand-offs have any useful thermal properties. >They have to withstand about 170 volts. > >Another oddity is the two leads covered in yellow insulation. They are >only connected at one end, and are marked on the schematic as "wired >capacitors" across the resistors that lead to the tube X axis plates. No >doubt they do produce some capacitance, but I can't imagine it's much. >Anyone know what the purpose would be? > >Sylvia.It is impressive how much stuff is inside an old analog scope. A cheap 100 MHz 4-channel digital scope is mostly air inside. Multi-channel traces never worked well in analog scopes. They shared the tube with alternate traces, or chopped. Digital scopes often share ADCs, which costs sample rate when additional channels are enabled. For dual trace, it's better to use 2 and 3, instead of the obvious 1 and 2. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
Reply by ●August 23, 20212021-08-23
On 23/08/21 16:05, jlarkin@highlandsniptechnology.com wrote:> On Mon, 23 Aug 2021 07:43:10 +0100, Tom Gardner > <spamjunk@blueyonder.co.uk> wrote: > >> On 23/08/21 03:30, Sylvia Else wrote: >>> Another oddity is the two leads covered in yellow insulation. They are only >>> connected at one end, and are marked on the schematic as "wired capacitors" >>> across the resistors that lead to the tube X axis plates. No doubt they do >>> produce some capacitance, but I can't imagine it's much. Anyone know what the >>> purpose would be? >> >> It is a gimmick capacitor, often made with a couple of wires >> twisted together to make a ~1pF fiddlable capacitor. >> >> Quite a lot of old Tektronix equipment relied on parasitic >> stray capacitance and inductance of circuit tracks. They had >> the decency to include the caps on the schematics, and to >> indicate they couldn't be seen on the boards. > > They also discovered "hook", the terrible time-domain behavior of FR4 > as a capacitor.Indeed, but they also used the "tricks" where that wasn't important, e.g. time-domain calibrators where the (nuvistor's) output is a sinewave.
Reply by ●August 23, 20212021-08-23
On 23/08/21 16:12, jlarkin@highlandsniptechnology.com wrote:> On Mon, 23 Aug 2021 12:30:08 +1000, Sylvia Else <sylvia@email.invalid> > wrote: > >> <https://www.dropbox.com/s/rddddzpkwqo44sc/TransformerWiring.jpg?dl=0> >> >> Shows how the power transformer is directly wired to two separate >> boards. Not sure how, or why, they'd want to do that. >> >> <https://www.dropbox.com/s/nlzx6f0w5deomb1/SolderThroughHere.jpg?dl=0> >> >> Shows the hole through which the transistor has to be soldered. Note the >> two resistors in plastic tubing that have one end soldered to this >> board, and the other end soldered to a board at the back of the tube. >> Also a wire directly soldered to the board that also goes there. >> >> <https://www.dropbox.com/s/degb7topima7yle/TransistorLeads.jpg?dl=0> >> >> Shows the formed leads for the transistors. Fortunately, I now have a 3D >> printer and have been able to make a template for bending the leads. Not >> sure whether the white stand-offs have any useful thermal properties. >> They have to withstand about 170 volts. >> >> Another oddity is the two leads covered in yellow insulation. They are >> only connected at one end, and are marked on the schematic as "wired >> capacitors" across the resistors that lead to the tube X axis plates. No >> doubt they do produce some capacitance, but I can't imagine it's much. >> Anyone know what the purpose would be? >> >> Sylvia. > > It is impressive how much stuff is inside an old analog scope. A cheap > 100 MHz 4-channel digital scope is mostly air inside. > > Multi-channel traces never worked well in analog scopes. They shared > the tube with alternate traces, or chopped.I acquired a dual /beam/ analogue storage scope before it hit the dumpster. After replacing the usual PSU electrolytics, it still works as well as analogue storage scopes ever did. Dual beam is particularly useful with a dual channel storage scope, since ALT mode is pretty useless at capturing fast transients, and CHOP is only useful at low speeds. Must sell it sometime.
Reply by ●August 23, 20212021-08-23
On Mon, 23 Aug 2021 16:37:26 +0100, Tom Gardner <spamjunk@blueyonder.co.uk> wrote:>On 23/08/21 16:12, jlarkin@highlandsniptechnology.com wrote: >> On Mon, 23 Aug 2021 12:30:08 +1000, Sylvia Else <sylvia@email.invalid> >> wrote: >> >>> <https://www.dropbox.com/s/rddddzpkwqo44sc/TransformerWiring.jpg?dl=0> >>> >>> Shows how the power transformer is directly wired to two separate >>> boards. Not sure how, or why, they'd want to do that. >>> >>> <https://www.dropbox.com/s/nlzx6f0w5deomb1/SolderThroughHere.jpg?dl=0> >>> >>> Shows the hole through which the transistor has to be soldered. Note the >>> two resistors in plastic tubing that have one end soldered to this >>> board, and the other end soldered to a board at the back of the tube. >>> Also a wire directly soldered to the board that also goes there. >>> >>> <https://www.dropbox.com/s/degb7topima7yle/TransistorLeads.jpg?dl=0> >>> >>> Shows the formed leads for the transistors. Fortunately, I now have a 3D >>> printer and have been able to make a template for bending the leads. Not >>> sure whether the white stand-offs have any useful thermal properties. >>> They have to withstand about 170 volts. >>> >>> Another oddity is the two leads covered in yellow insulation. They are >>> only connected at one end, and are marked on the schematic as "wired >>> capacitors" across the resistors that lead to the tube X axis plates. No >>> doubt they do produce some capacitance, but I can't imagine it's much. >>> Anyone know what the purpose would be? >>> >>> Sylvia. >> >> It is impressive how much stuff is inside an old analog scope. A cheap >> 100 MHz 4-channel digital scope is mostly air inside. >> >> Multi-channel traces never worked well in analog scopes. They shared >> the tube with alternate traces, or chopped. > >I acquired a dual /beam/ analogue storage scope before it >hit the dumpster. After replacing the usual PSU electrolytics, >it still works as well as analogue storage scopes ever did. >The giant Tek with the separate power supply?>Dual beam is particularly useful with a dual channel storage >scope, since ALT mode is pretty useless at capturing fast >transients, and CHOP is only useful at low speeds.Analog storage never worked well. The secondary-emission tubes wore out. The mesh things had low writing rates. All primitive. We have a 7104, the 1 GHz microchannel scope, but we don't use it any more. That display shuts off about once a minute to extend tube life. Nuisance. It's distributed deflection, sort of like these, but ceramic so you can't see inside: https://www.dropbox.com/s/evoq6p2nvzyl6wo/547_crt.JPG?dl=0 https://www.dropbox.com/s/r6c3zkwlqrayt53/519_CRT.JPG?dl=0 -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
Reply by ●August 23, 20212021-08-23
jla...@highlandsniptechnology.com wrote: ====================================> > It is impressive how much stuff is inside an old analog scope.** Only true of expensive ones like Tek and HP.> A cheap 100 MHz 4-channel digital scope is mostly air inside.** DSOs are chock full of SMD, with a SMPS and a flat screen. Not really "scopes " at all. OTOH: My 50Mhz, dual trace is a steel box 90% full of air. Has to be deep enough to accommodate the PDA tube = 14 inches. The front panel has to fit all the controls comfortably = 10 x 7 inches. Easy to carry in one hand and uses only 14 watts of power. No need for a stupid, dust clogging fan. Purchased on the 19/9/1985. Never out of use. ...... Phil
Reply by ●August 23, 20212021-08-23
On Mon, 23 Aug 2021 15:33:47 -0700 (PDT), Phil Allison <pallison49@gmail.com> wrote:> jla...@highlandsniptechnology.com wrote: > >==================================== >> >> It is impressive how much stuff is inside an old analog scope. > >** Only true of expensive ones like Tek and HP. > >> A cheap 100 MHz 4-channel digital scope is mostly air inside. > >** DSOs are chock full of SMD, with a SMPS and a flat screen. > Not really "scopes " at all. > >OTOH: > >My 50Mhz, dual trace is a steel box 90% full of air.20% is full of vacuum!
Reply by ●August 23, 20212021-08-23
