Riddled TV Repair Forum

law565 · Joined: 22 Apr 2010 Posts: 4

When i turn this tv on i get a quick flash and then it goes dark. The power light stays green but i get nothing. Ive taken it apart to check for bad capacitors and all are ok. There is 1 ceramic fuse in it but i dont know how to tell if they are bad. I would just replace it to rule that out but my local radio shacks do not have the one i need. So is it maybe the fuse, or something else obvious that i can try? Thanks

Google

JTS1957 · Joined: 21 Jan 2009 Posts: 2388 Location: Far, Far Away

Isn't that a tuner in the upper right corner of the Main board? So much for unit being a "monitor."

A fuse is a fuse is a fuse - all test alike = very low resistance (aka has "continuity").

Capacitors can be bad and NOT have a puffed top or oily bottom - I presume this is what you checked for "bad capacitors."

kuhurdler · Joined: 28 Dec 2006 Posts: 2877 Location: Overland Park, KS

that cap in the 2nd picture next to the opto-isolator looks bad to me.

JTS1957 · Joined: 21 Jan 2009 Posts: 2388 Location: Far, Far Away

Which opto? Upper or lower (near sticker)?

law565 · Joined: 22 Apr 2010 Posts: 4

i have only identified bad capacitors by the puffy tops. Ive never noticed the bad ones to have oily bottoms. Is there a way to test them if they look "normal". And yes that is a tuner on the mainboard. Its a tv first but can be used as a monitor.

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JTS1957 · Joined: 21 Jan 2009 Posts: 2388 Location: Far, Far Away

All kinds/prices of meters. Make sure it tests (at least) "value" and "ESR" ("leakage" & "DA" Dielectric absorption are two other tests).

In the "Good old days," Electrolytic capacitors (in no particular order) sometimes exploded, the electrolyte dried out, ESR rose too high or on occasion they shorted. (Drying out and ESR rising will affect capacitor's value).
Today the most common failure is the puffed top lytic.
Within the last decade, IMO, due to greed by the capacitor manufacturers, capacitors were made using substandard materials and quality control inspectors knowingly "passed" as O.K. caps that weren't even meeting their design specs.

Can anyone remember the tainted pet and baby formula stories of the recent past?

End of rant. I'll now fall off my soapbox.

law565 · Joined: 22 Apr 2010 Posts: 4

Ok well i still haven't fixed this tv. The fuse is good, so maybe a bad capacitor, just not noticable. Im not sure. On another note when changing out capacitors i Know i can go up slightly on the voltage for example change a 16v cap with a 25v. Now can that work the same with the uF capacity? Can i use maybe a 1000 uF capcitor in place of an 820uF

kuhurdler · Joined: 28 Dec 2006 Posts: 2877 Location: Overland Park, KS

I wouldn't. That's a ~20% change.

JTS1957 · Joined: 21 Jan 2009 Posts: 2388 Location: Far, Far Away

Depends on the function of the circuit that the capacitor is being used in. In case of power supply 20% is the limit that I'd go.
If you plan on doing this work as more than a hobby, I'd try to stock a good assortment for the items/circuits you'lll be seeing. The more serious you are, the closer you should come to carrying ALL standard values at ALL standard voltages. Cool

law565 · Joined: 22 Apr 2010 Posts: 4

I do have a very wide veriety of capacitors including the correct uF and voltage, The problem is, These new ones are alot fatter that the ones removed from the board and i cant fit them in unless i extend the leads. But then i would have to extend 1 of them about 3", is that acceptable?