|
General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
|
Thread Tools |
19th Aug 2020, 3:17 pm | #41 |
Octode
Join Date: Oct 2007
Location: Exeter, Devon, UK.
Posts: 1,553
|
Re: Question on PPI or Radar displays
PPI radar displays, distorted flyback and Cossor 1039.
Your distorted flyback I suggest is due to capacitance loading on the output stage. In the paraphase pair, the side where the current increases can charge up the stray capacitance on to the CRT easily. But on the other side of the paraphase driver, the current is dropping, and the capacitance is not discharged so easily and the voltage drops more slowly. This can be solved by increasing the current in the whole output stage, which is expensive to do, or as frequently seen for the X output stage, by an extra pentode to discharge the capacitance on that side, so that the rest of the X ouput stage can be made simpler and thus cheaper. Good examples are the Solartron CD1212/CT484, the extra EF91 (V32), and the Tek 535/545 V398 (6CL6). I'll post the circuits is wanted. And as Ed Dinning says, a bit of twin feeder style from the driver anodes to the tube is very common. PPI. The tube usually seen for this is the RCA 3DP1 with the electrode in the centre of the screen. Data sheet on Frank Philipse's tube data site I expect, or else I'll post. A real odd-ball tube. Full size Radar displays use magnetic deflection, and can arrange circular sweep I believe by rotating the deflection coils. I suspect later circuits used a phase change network across both pairs of CRT plates to give a circular trace, and then modulated the brightness. I have used this to compare two frequencies by Lissajous figures. The bright dots are easier to count if the ratio is large. Cossor 1039. You were wondering about the transistron (phantastron) timebase circuit. (SeePuckle for details). The Cossor 1039 MkI uses the ECR30/23D/VCR139 tube which requires a large X sweep voltage, so it uses a second EF91 valve as paraphase for the X output. The 1039 MkII is very different with the very much more sensitive tube DH7-91/3AFP31/24D and has not need for the paraphase driver from the timebase. The spare valve is used as a Sync amplifier to give a better performance. The really interesting one is the MetroVick CT52, which uses a paraphase X output stage, as the tube DG7-5/3ALP1 needs a very large scan voltage. But a cathode follower arrangement to speed up the timebase phantastron and give better triggered performance. If you are not familier with these three circuits, I attach them. The Cossor 1039MkI is thanks to JonEvans The Valve Page. Last edited by WME_bill; 19th Aug 2020 at 3:23 pm. |
19th Aug 2020, 3:41 pm | #42 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,951
|
Re: Question on PPI or Radar displays
Does anyone know what technology the 1950s SAGE displays used? They could display both RADAR plot-data _and_ text annotations.
https://www.ibm.com/ibm/history/ibm1...en/icons/sage/ And they worked with a light-pen too! |
20th Aug 2020, 12:56 am | #43 |
Octode
Join Date: Mar 2020
Location: Blackburn with Darwen, Lancashire, UK.
Posts: 1,566
|
Re: Question on PPI or Radar displays
Hi Bill
Thank you I will look at the diagrams. Perhaps next time I play with these things I will try a transitron time base. Adrian The DG7-5 CRT I use was basically what could I get at the time that was reasonably priced on Ebay |