Pentranic CH-250-29

[RichSorr]

I got a buddies 29" Pentranic CH25029 that just has a tiny horizontal line across the center of the screen.

R315 is fried. Any ideas as to what could have caused that and what else I should change?

Also, I'm not sure of the proper value since I can't see the color codes. One schematic I looked at said a 1R .5w 

a parts list I saw said 10k


thanks

[grantspain]

is this the chassis that had the gull wing heat sink on the frame i.c,you got a photo of the chassis?

[RichSorr]

its sitting in my office at work. I'll take a pic tomorrow morning and post it.  its definately got a huge heatsink on it though

[RichSorr]

sorry for the crappy cell phone pics. anyone have any thoughts as to why this burned and what else I should check?

[grantspain]

its possible the frame ic is short which in turn burnt out this resistor
i am pretty sure this is an updated version one that we had in the u.k(can't remember the model number),i had to fix about 100 of these
the fault would start be a small foldover issue at the top of the screen and then progress to frame collapse which in turn progressed to burn up of components
at a good guess i would say you need to replace the resistor,the capacitor next to it,then locate the frame i.c and change that and any caps around and check any diodes

can you tell me the resistor location number so i can look at the schems to establish the likely problems
i can send you a schem showing the parts that i would change

[RichSorr]

the resistor is R315

thanks, appreciate it

[Rickn]

So here is the scoop, R315 is the VCC dropping resistor for the vertical IC the 17" version is 1 ohm .5 watt.

Most likely you have a bad cap... again I am not a fan like a lot of you on cap kits as I  prefer to fix the problem and it ain't broke don't fix it.

Most likely C301 1000uf at 35 volts, but also replace c303- 100uf at 25 volts. Be sure to check R309 3.3 ohm .5 watts as well.

Good luck

Rick Nieman
www.niemandisplays.com

[grantspain]

hey rick,knowing you must have worked on shed loads of these chassis do not think that there may be a shorted tda 1675 as well as what you have suggested?

[Rickn]

No Grant, I can be entirely off base?

I am dealing entirely on symptom, I have an over 90% but hopfully this pays off.

Rick

[RichSorr]

thanks guys. I appreciate it.

I'll give those a shot today when I get into work. Is R315 a 1ohm .5 watt on the 29" version as well?

[RichSorr]

also, if I did want to replace that TDA1675 where could I get one? Mouser says it's obsolete and Digikey and Allied don't carry it. Unfortunately there are only a few approved component vendors I can use through my company.

[RichSorr]

looking at the board again now, looks like R314 took some heat when 315 blew. I guess I'll replace that for good measure, but again can't see what it is. For some reason I can't get the schematic for this thing to load on my computer at work

[Rickn]

Hey Rich e-mail me and I will send you the schematic for this portion of the circuit- the one I have is for the 17" version but it should be about the same in this area or at least very similar.

In the e-mail let me know where you are located and I will see if I can find you a TDA1675.

Rick@niemandisplays.com

[grantspain]

tda 1675a will also work,these are common on hantarex monitors
little diode have them on ebay