1988 0r 89'? Zenith-Bose Digital tv

[andy]

I saw one of these with a bad teletext IC causing no picture, or OSD. MCM had many of the ICs a few years ago, including this one. I found it by using freeze spray on the ICs on the main board. When frozen, it would work for a while. What's the module number of the main board?

Look for leaking caps and bad soldering, particularly on the IC sockets.

[JCFitz]

Originally Posted by andy

I saw one of these with a bad teletext IC causing no picture, or OSD. MCM had many of the ICs a few years ago, including this one. I found it by using freeze spray on the ICs on the main board. When frozen, it would work for a while. What's the module number of the main board?

Look for leaking caps and bad soldering, particularly on the IC sockets.

Thanks for replying.I remember working on some 9-700 series digital boards in the projection sets that had the awful Nichicon light blue caps leaking all over.(the same caps used in the early 90s Zeniths with the same issue)btw Mitsubishi had this problem thru all the early 90's and so did some Hitachi sets but the only Hitachis with leaking caps I saw where made in 1990.The caps in Mitsubishi and Hitachi were black in color.Electrolytic caps leaking everywhere can wreak havoc.Wonder why some of the capacitors from those years fail like that.Earlier electrolytics just dried up without leaking for the most part.Also in modern equipment they started using surface mount electrolytics and they nearly always leak eventually.Sony had a sound module in early 90's that is so common a failure from the caps leaking and destroying it that it's available everywhere cheap.Mitsubishi PIP modules from 93-94 fail like this but have to be repaired or bypassed.I used to change all the caps but most the PIP didn't work properly anyway from the electrolyte shorting it out.Now most servicers simply bypass it.Far more economical and most people would rather do that since they don't use it or want to spend the money to get PIP working again.Just another quality downfall of the modern tv I guess.I've seen sets only a couple of years old with failed electrolytic caps in the switching power supply.I haven't opened it up yet.Got some schematics I found for it.I have to look for the module no.and get back to you.I know it's not a 9-700.I got a couple of those with all the chips laying around.This one is the earliest digital version with a completely different chip set.

[andy]

Speaking of bad caps, I have a pair of Panasonic AG-1980 editing decks with bad surface mount caps on the time base corrector board (about 30 total). At least these aren't leaking, they're just high ESR. I also just got an early Sony LCD color hand held TV that has lots of leaking SMD caps.

I've seen one or two of those first generation Zenith digital sets. Unfortunately, I don't have any parts for them. A service manual would probably be helpful to you in signal tracing (not that there are many recognizable signals to trace).

Zenith always seemed to forget one or two key features in those sets. I had a projection set for a number of years that had line level audio outputs so you could use an external amp, but it lacked any way to turn off the internal speakers. The last early digital set I worked on had two video inputs, but you could only switch between them via a switch on the rear jack panel. What were they thinking!