Gary, What does the regulated B+ voltage measure on HOT? Might be higher than normal check it out. George Afana Electronics Moreno Valley, CA ----- Original Message ----- From: "Gary McCartney" <gary@xxxxxxxxxxx> To: <techassist@xxxxxxxxxxxxx> Sent: Monday, August 18, 2003 6:58 AM Subject: [TechAssist] Re: JVC TV AV2749S, yoke arcing at CRT neck [UPDATE 2] > I have test run this set now, and after an hour's run, the HOT heatsink > is at 44 deg. C and the regulator heatsink is at 55 deg. C. This is with > either the original 0.0062 uF cap installed, or my 0.0051uF. With the > original cap, the anode HV runs at 30kV zero beam current, and with the > 0.0051 cap installed, the HV runs at 31kV. > > To me it seems 30kV is a bit high for a 27" tube. Is not 28kV more the > morm? The label on the CRT doesn't state the level it should be at. All > it says to not exceed the max. level. > > Can anyone tell me what the actual HV anode voltage should be on this > set, and what I can do to lower it? I will post this question in a new > thread also for those who haven't been following this thread. > > > Thanks for any help. > > > > > Gary McCartney > > McCartney Electronics > Guelph Ontario Canada > Est. 1984 > email: gary (at) number63.ca > > > > > > > My previous update message: > > > > George, I tried a 0.0051 1600V and the picture narrowed by about 3/4" > but the HOT collector waveform went from 1200V p-p (with original caps > installed) to 1250 Vp-p. I have put the original cap back in to run the > set for a while so I can measure the HOT temp. then I'll run it with the > 0.0051uF and measure the temp. > > Is 1200V p-p too high for these JVC's? I think most TVs are 1050 to > 1100V p-p. > > > > > > Gary McCartney > > McCartney Electronics > Guelph Ontario Canada > Est. 1984 > email: gary (at) number63.ca > > > > > George wrote: > > > > Gary, > > > > Try an .005 for the .0062 to start and then you can go from there just keep > > an eye on the HV rise as you reduce the value to make sure that it remains > > within the limit. > > > > George > > Afana Electronics > > Moreno Valley, CA > > > > ----- Original Message ----- > > From: "Gary McCartney" <gary@xxxxxxxxxxx> > > To: <techassist@xxxxxxxxxxxxx> > > Sent: Friday, August 15, 2003 10:47 AM > > Subject: [TechAssist] JVC TV AV2749S, yoke arcing at CRT neck [UPDATE] > > > > > I have this set running now. I applied epoxy to the spot on the glass > > > and covered it with tape. I have a good picture except for one problem. > > > It has too much width, about 1 to 1 1/2 inches too much. The geometry > > > look fine though. The used yoke I installed did not have a JVC number on > > > it and did not have the same connectors, but the yoke itself appeared to > > > be the exact same. I realize that even though it looked exact the > > > winding could be slightly different. > > > Assuming the new yoke is the same as the old, I have removed the 2 blue > > > caps C525 and C524 from the HOT collector to ground. Can anyone identify > > > the valuse of these caps please? > > > > > > C524: labelled PH7001H 1.6KV > > > C525: labelled PH6201H 1.6KV > > > > > > I believe these are 0.007uF and 0.0062uF but I'd like this confirmed if > > > possible. > > > SAMS is having techical problems with their web site else I'd look up > > > the SAMS number for this set. > > > > > > What else can cause too much width in this chassis? Is it safe to change > > > the value of one of these caps enough to narrow the picture up a bit? I > > > am concerned that perhaps the yoke burnt in the first place because of > > > to much current going through it. > > > > > > > > > Thanks for any help. > > > > > > > > > > > > > > > Gary McCartney > > > > > > McCartney Electronics > > > Guelph Ontario Canada > > > Est. 1984 > > > email: gary (at) number63.ca > > > > > > > > > > > > > > > > > > > > > My Original message: > > > > > > > > > I have this JVC TV model AV2749S in the shop and I have found that the > > > yoke is shorted where it wraps around the neck of the CRT, causing a > > > black burn mark on the glass. I took a knife and scraped it off but > > > there is a slight crater in the glass now, maybe 1/64 of an inch or so > > > deep. Is this a weak spot from now on, meaning that this spot will be > > > suseptable to more arcing in the future or worse yet, a crack in the > > > neck? Can I apply some epoxy to the spot to give it insulation, or > > > should this tube be scrapped? I have a used yoke which looks to be in > > > great shape which I can use in the set so I hate to tell the customer it > > > is garbage. > > > > > > > > > Here is a photo of the mentioned spot on the glass: > > > > > > http://www.number63.ca/tube-neck.jpg > > > > > > > > > > > > How I found the bad yoke: > > > > > > The set came in with F902, 1.25 Amp fuse open. I couldn't find any > > > defective parts so I installed a new fuse in case that was the only > > > problem. Pressed power button and saw LED blink and that was all- the > > > fuse was open again. Next, I looked up tips and found one that mentioned > > > the yoke as a possibility, so I pulled the CRT board and the yoke > > > connectors. The LED came on and stayed. Then I reconnected the hor. > > > winding and put a new fuse in. Had to use 1.5A instead of 1.25. I used a > > > variac set at 90VAC and plugged it in. The LED came on and I heard the > > > arcing and saw smoke coming from the yoke/ CRT neck. > > > > > > > > > Thanks for any help. > > > -- > > > > > > > > > > > > > > > > > > > > **************************************************************************** > > * > > > Classifieds! Buy or Sell! > > > http://sell.tech-assist.org > > > The Tech Address Book: > > > http://www.tech-assist.org/secure/tip/contact.htm > > > Add a Repair Tip Here, or Change/Remove your Email Address: > > > http://www.tech-assist.org/secure/tip/main.htm > > > Lost Password: > > > http://www.tech-assist.org and select "Lost your Login Info?". > > > Email Archives: > > > //www.freelists.org/archives/techassist/ > > > > > > > > **************************************************************************** > > * > > > Classifieds! 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Buy or Sell! > http://sell.tech-assist.org > The Tech Address Book: > http://www.tech-assist.org/secure/tip/contact.htm > Add a Repair Tip Here, or Change/Remove your Email Address: > http://www.tech-assist.org/secure/tip/main.htm > Lost Password: > http://www.tech-assist.org and select "Lost your Login Info?". > Email Archives: > //www.freelists.org/archives/techassist/ > ***************************************************************************** Classifieds! Buy or Sell! http://sell.tech-assist.org The Tech Address Book: http://www.tech-assist.org/secure/tip/contact.htm Add a Repair Tip Here, or Change/Remove your Email Address: http://www.tech-assist.org/secure/tip/main.htm Lost Password: http://www.tech-assist.org and select "Lost your Login Info?". Email Archives: //www.freelists.org/archives/techassist/