- Old plasma screen Y_SUS anomalies - 1 Update
- Kikusui COS6100M Oscilloscope - 3 Updates
| legg <legg@nospam.magma.ca>: Nov 15 10:49AM -0500 On Fri, 12 Nov 2021 13:34:55 -0800 (PST), "ohg...@gmail.com" <ohger1s@gmail.com> wrote: <snip> >> pattern . . . >> RL >The TV will produce an "input" legend at the the top of the screen when it's turned on, and a "no signal" message will appear after about 10 seconds of no signal. The TV's control board most likely has a built in pattern generator that will help isolate a no image complaint to either the main or control board assuming the rest of the boards are working. It's been a long time since I repaired those tanks so my memory isn't great on them - but if the control board has a separate harness that plugs into the power supply, the procedure was to remove the connector from the control to the main and jump two pins on the control board. That would put it in a pattern mode. I'm pretty sure I tossed all the training manuals for those but I'll check next week when I get back to the shop. The small control board actually sending drive signals to YSUS (flat ribbon), ZSUS (10pin bundle) and the bottom Xrow boards (flat ribbon x2) has no direct connection to the power board.I believe it gets some power from the YSUS board. YSUS also seems to supply power to XrowR through an 8pin bundle. The main control board with connex to all the I/O has three harnesses going directly to the power board. It connects to the smaller display control board using a high density shielded cable. I've checked connectors and their insertion/cleanliness. The high density shielded parts are obviously not meant to be fooled with, much. The adhesive on shielding tape holding plugs in place won't last forever. Flat cables from the screen to the 2nd replacement buffer board didn't like the fit. The newer rev socket seemed to stress them - could not avoid some distortion around the alignment shoulders, with less play in their strain loop area. Don't think these cables are up to many more removal or insertion cycles. RL |
| John Keiser <johnkeiser@juno.com>: Nov 14 02:20PM -1000 This old oscilloscope was given to me and I am attempting to restore as a pandemic hobby. I am aware of the HV dangers and take precautions. The screen does display a green blob that can be moved with positioning controls but no trace. I suspect the transformer based power supply. https://imgur.com/FzOaOgp Visually the caps look good. My ESR meter says they are OK. No burnt components. I disconnected all the boards feeding off the PS. TP readings are 15% high. [I had not expected the readings to be high with the regulation.] When I plug in 2 of the boards, the TP readings drop to 50% low. Since the TP voltages drop when either of several boards are plugged in - and I assume that multiple boards would not likely fail - I surmise that something in the PS is unable to handle the expected current. The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily unplug and seem to test OK out of circuit. There are 2 ICs U1212 and U 1211 that seem to be part of the regulation but I don't know how to test these. Am I on the right track? What should I do next? Thank you for any advice. |
| Michael Terrell <terrell.michael.a@gmail.com>: Nov 14 11:39PM -0800 On Sunday, November 14, 2021 at 7:20:46 PM UTC-5, John Keiser wrote: > Am I on the right track? > What should I do next? > Thank you for any advice. It would have helped to have the part numbers. U1211 is a upc4558, a gumdrop dual Op Amp. One half is used for the + 5VDC rail. The other half is in the + 55 VDC rail. U1212 is a TA7199P, which is a dual, tracking voltage regulator. that provide the + and - 12VDC rails. Do you have a working scope to troubleshoot with? Have you tested the bridge rectifiers? Which volatge are you measuring? Manual at: http://bama.edebris.com/download/kikusui/cos6100/COS6100_E.PDF |
| John Keiser <johnkeiser@juno.com>: Nov 15 05:39AM -1000 On 11/14/2021 9:39 PM, Michael Terrell wrote: > U1212 is a TA7199P, which is a dual, tracking voltage regulator. that provide the + and - 12VDC rails. > Do you have a working scope to troubleshoot with? Have you tested the bridge rectifiers? Which volatge are you measuring? > Manual at: http://bama.edebris.com/download/kikusui/cos6100/COS6100_E.PDF Thank you for adding the part numbers to the post. I do not have a scope. I am measuring the +150, +55, +21, +12, +5 and -12 rails. How would you proceed without a scope? |
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