Searching for LA7845N solution in EURAS

Axhpblkpt · Joined: 29 Jul 2009 Posts: 10

I might be honest: the vertical deflection ic in this KS3A works very hot, but this week I repaired the crt monitor
of my desktop pc, and I found the vertical ic gets hot after a few minutes.
The monitor is LiteOn with chassis C1770NSL/T, the vertical deflection ic is the Philips TDA4863J, in this chassis
the pcb doesn't have black or smoked area at top or bottom, it seems here nothing overheat,
but after 15 minutes the very small radiator of the TDA4863J is as hot as LA7845N radiator, and all the component are ok in the monitor.

So vtech is right: it's normal for this "modern" crt tv that the vertical ic runs hot.

Probably the LA7845N burns the pcb (KS3A chassis) because there isn't enough space under the tv for air circulation.

I don't know how much hours the KS3A worked everyday, but my low cost LiteOn crt monitor worked 2 hours a day from
2002 to 2011, but this monitor has an high swivel base that allow the air circulates on the bottom of the pcb, this
could be the reason there aren't burnt area in the pcb.

vtech · Joined: 08 May 2006 Posts: 1264 Location: USA

Glad to see that you have finally seen the light Smile

Actually, if you investigate further on the PCB material, you will notice a big difference. Migrating toward the cheaper phenolic types tend to scorch sooner than the epoxy type.
And if you are really, really interested, one of the better thermal softwares in engineering is the PCanalyze

Axhpblkpt · Joined: 29 Jul 2009 Posts: 10

Thank you, vtech.

PCAnalyze is too much for my objective.

I'll reinstall all the components in the KS3A pcb, I'll leave the airbox with the fan to help removing heat, I'll place two wood blocks (one to the left, one to the right) beetwen the table and the tv to increment the air circulation under the tv.

I was using wood blocks under the tv since the first time I mounted the new vertical ic and I discovered it overheated and burnt the board. It probably helped the LA7845N to be still alive after two years of work.

If the first owner of the tv placed the wood blocks probably today there will not be burnt area in the pcb.