tag:blogger.com,1999:blog-31955893.post1660554457492836766..comments2024-01-16T18:45:41.582+00:00Comments on The "Speaky" HF SSB transceiver and other homebrew projects: 5LO38I CRT testRicardo - CT2GQVhttp://www.blogger.com/profile/10682005152577217807noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-31955893.post-55238094413043307162018-02-08T23:31:21.611+00:002018-02-08T23:31:21.611+00:00Well since my intention was to just test the CRT i...Well since my intention was to just test the CRT i did not have the time and knowledge to test the focus issue. Just tried the circuit for 10 minutes, wrote some notes about it in paper and disassembled it. I am now studying your links attached and trying to decide for an oscilloscope circuit with solid state components that i will soon start. But there is a lack of complete projects for this CRT except danyk's tube oscilloscope that i try to avoid.<br /> However about the focus issue before cutting the B+ 200V supply i decided to turn off the separate AC transformer feeding the filament. And what i saw was that the dot before vanishing became really sharp and correct for 4-5 seconds (before the filament cooled down and stop emmiting electrons). So this clue maby makes me think that there is a slight possibility that the filament is overdriven with 6.2V RMS (that is the exact voltage i measured on pins 1-11) and we could try lower filament voltages like 4 or 5 vols rms. A friend of mine that is more involved with tubes suggested that i could use DC supply for filament which would be more handy than trying removing transformer winding from the 6.3V transformer or putting power resistor in series with filament since dc allows us to use regulators or even a power diode to drop voltage by 1volt easily.<br />i am looking forward to see your updated design and maby an oscilloscope project by you.<br />be well Ricardo!dimitris Khttps://www.blogger.com/profile/07161876328904899584noreply@blogger.comtag:blogger.com,1999:blog-31955893.post-41673372839106574912018-02-08T19:20:43.899+00:002018-02-08T19:20:43.899+00:00Hello Dimitris,
Thank you for the comment.
I upda...Hello Dimitris,<br /><br />Thank you for the comment.<br />I updated the design, got better (not perfect) results this time regarding the focus.<br />Hope shortly to create a new post with the info.<br /><br />RegardsRicardo - CT2GQVhttps://www.blogger.com/profile/10682005152577217807noreply@blogger.comtag:blogger.com,1999:blog-31955893.post-14081746444541708882018-02-08T15:08:02.624+00:002018-02-08T15:08:02.624+00:00Hi sir. Im into the crt tubes and DIY oscilloscope...Hi sir. Im into the crt tubes and DIY oscilloscopes lately and i (DE JAVU!!!) have bought an 5Lo38i 2 months ago that i never really tested.<br />I used your test circuit and guess what. It was a long long time ago that a project i did worked straight with and no problems. Well it worked at once and guess what. Mine dot as well was a bit large and focus pot did almost nothing to fix. Anyway im very happy, i now know my CRT works and it will be used in the future for a DIY oscilloscope.<br />Be well!!dimitris Khttps://www.blogger.com/profile/07161876328904899584noreply@blogger.com