| Electronics > Beginners |
| repairing crt tv, start with recapping |
| (1/11) > >> |
| 2takt:
hi, i have a telefunken palcolor bs 570 dv chassis 619. when i turn on the tv the screen is distorted this will go away after 1hour on(this time will shorten if the tv gets used more frequently). i think the vertical is the issue because the horizontel lines appear right to me. sofar i have cleaned the chassis, tube and case. i have reflowed the neckboard. used deoxit on all connectors. now i want to start with replacing some caps: neckboard, north south modul and the "control and teletext modul". after this i want to recap the mainboard of the chassis including psu and then finaly start with IC swapping. i dont find any datasheet on my caps, can anybody tell me what they are rated or give a number to the next rated cap? i have phoned rubycon germany, 4 distributors nobody could help me. this is the first time ordering caps by myself, i tryed to get into this stuff for 2 years but only ordered packs for specific electronics. my caps and series(i think) is: Rubycon CE W Tosin TSM Samhwa SU or SQ(not shure about that) i have service manual for the tv but there is only the uF rating listed :( if anybody needs pictures just tell me. thanks for helping me :) daniel |
| 2takt:
forgot to mention i have searched the rubycon site for this series no result, also found a list for old caps but they only go back to 1998. mine are from 1990-93 (1m9310). tosin i couldnt find the site, only found toshin but i have read they are taiwan and tosin is japan!? i didnt look up the samhwa cap |
| MosherIV:
Hi. I would advise against replacing capacitors. You might do more harm than good. The need to replace capacitors came along with switch mode power supplies, they have high freq switching meaning they put capacitors through higher ripple currents, wearing them out faster. Old crt tvs would have linear psu with fly back to generat the 30KV needed to accelerate the electrons. Just fault find the bad cap in the vertical or horizontal timing circuits. This may be a ceramic or other non electrolytic cap. Good luck ;) |
| 2takt:
hi mosher dont they go bad on theyre own(electrolytic)? and the tv is somewhere at 30 years old. currently i cant tell you which psu is used on my tv, i will figure this out in the next days. iam currently waiting on my in series esr tester, hope it arrives till friday. thanks i hope i find something. one last question i also ordered this cheap oscilloscop dso 138. the service manual says: the chassis is isolated from line voltage. the isolation point is in the line section. can i measure the chassis without a isolating transformer? |
| vk6zgo:
--- Quote from: MosherIV on August 28, 2019, 05:43:01 pm ---Hi. I would advise against replacing capacitors. You might do more harm than good. The need to replace capacitors came along with switch mode power supplies, they have high freq switching meaning they put capacitors through higher ripple currents, wearing them out faster. Old crt tvs would have linear psu with fly back to generat the 30KV needed to accelerate the electrons. --- End quote --- Not necessarily, SMPS were commonly used in TVs from the mid 1970s. A few TVs sold in EU used a SMPS to supply both operating voltages & EHT, but this was unusual. Most TVs indeed used a transformer variously decribed as a " Horizontal Output" transformer, or an "EHT" transformer, or less commonly (at least in Oz) as a "Flyback" transformer. The electron beam "flyback" during line blanking requires a very fast transition in the current through the yoke, & hence the transformer. A multiple turn secondary produces high peak votages during this transition, which in turn, are rectified to provide CRT tube EHT. --- Quote --- Just fault find the bad cap in the vertical or horizontal timing circuits. This may be a ceramic or other non electrolytic cap. Good luck ;) --- End quote --- OP--- Your fault doesn't sound like it is necessarily a capacitor. I would nominate a dry joint or similar. If it comes good when the TV warms up there are two ways to approach it. (1)While the Fault is on, heat up various likely points on the board with a heat gun. (2) When it is warm, with the fault no longer evident, use "freeze spray" to strategically cool various likely points. (2) Is usually best to pinpoint the problem, as the heatgun can't target a very small area. |
| Navigation |
| Message Index |
| Next page |