Gary, I have the 27CM4.pdf if you want to give it a try, it uses LA7837 but I think the pinout is the same. I can "beam" it to you if you want. Jim Myers Since 1972 Telrad Electronic Services Co. Fort Wayne, IN 46815 jr.myers@xxxxxxxxxxx 260-432-4486 Fax and Voice Fax is always on ----- Original Message ----- From: "Gary McCartney" <number63@xxxxxxxxxxxxx> To: <techassist@xxxxxxxxxxxxx> Sent: Monday, October 07, 2002 2:19 PM Subject: [TechAssist] JVC TV model AV27CM3- top half of screen stretched with foldover [SECOND POST] I still haven't solved this set. Measured B+ to vertical chip. I get 28.7V with 1.5 V p-p of ripple. Replaced D534 rectifier and C534 filter cap but no change in ripple. Also measured output of 12 V regulator I changed earlier. Measured 11.94V, with no noticable ripple. Scoped input pulse to vert. chip at pin 2 and got nice clean square wave at 8V p-p and very high duty cycle, maybe 95%. I don't have waveforms or schematic in print to verify my measurements to be correct. Scoped vertical output waveform on pin 12 and get 55V p-p pulse with a blip in the slope which doesn't look normal. I drew a picture of this and posted it for you to view: http://www.number63.ca/waveform.jpg Also replaced yoke. I found one in my stock which appears to be the exact same yoke only out of a Philips set and the connectors were a bit different. I switched the connectors from the JVC yoke and tried it. No change in problem. If anyone is interested, here are the yoke numbers (from the stickers on the yokes). Sorry I don't have record of the Philips TV model. Original JVC yoke: CE20240-AOA Philips yoke: 362075-7 Changed a few more small caps and resistors in the vertical section. Problem has not improved. Any help appreciated. Gary McCartney McCartney Electronics 7134 Fife Rd, RR 7 Guelph Ontario Canada N1H 6J4 Fax: (519)821-1530 email: number63 (at) inetsonic.com My original message: This is a 27" JVC tV model AV27CM3. No Sams listed but there is one for model AV27CM4, # 3379. The vertical linearity is off all the way from the bottom but once it hits the center of the screen, it starts stretching so bad that there is about 3" of foldover. Working without a schematic. I have replaced: IC421, LA7838 IC422, 12V regulator ZD425, 75V 1W C425 C426 C430 C421 C536 C530 I removed D421 and checked it but I don't know what it is. marking on it is 3N. It looks like a glass 1W zener but symbol on board shows it as a regular diode. Checks ok anyways. Does anyone have a schematic of the vertical circuit plus hopefully waveforms? Thanks for any help. -- Gary McCartney McCartney Electronics 7134 Fife Rd, RR 7 Guelph Ontario Canada N1H 6J4 Fax: (519)821-1530 email: number63 (at) inetsonic.com ------------------------------------------ To REMOVE your email address, click here: http://www.tech-assist.org/unsubb.html To CHANGE your email address, click here: http://www.techassist.net/forms/change.html ------------------------------------------ ***NEW*** Tips Added Instantly!!!*** Submit Repair Tips here: http://www.tech-assist.org/secure/tip/ ------------------------------------------ To REMOVE your email address, click here: http://www.tech-assist.org/unsubb.html To CHANGE your email address, click here: http://www.techassist.net/forms/change.html ------------------------------------------ ***NEW*** Tips Added Instantly!!!*** Submit Repair Tips here: http://www.tech-assist.org/secure/tip/