help help!can i fix this box????301 010

[gunther]

I was fixing to read the keys read them then I moved the board I had it on top of the box then I seen a flash then I look at the fuse it was blown I put another fuse in and they all blow can I fix this or did I mess it up no return able??

You had the board out, and sitting on top of the metal case? Is that what you are saying here?

[skinerd]

Damn........
it is probably recoverable but it is going to take some doing, if the fuse continually blows probably the power supply is shorted. The 301 uses a ST Viper100 SMPS primary IC.
A new chip for switch mode power supplies.

[gunther]

yes!!

Good luck...

Not to be mean here or anything.. but NEVER EVER do that. You can not set a circuit board on a conducting surface. Anymore than you can stick a paper clip in a wall outlet.

You probably shorted out the switching transistor in the power supply. The problem with that is that transistors only have a couple of failure modes... They either become totaly open, or they become totaly shorted.

If it became totaly shorted then it applied full line current to areas that where never supposed to see that much voltage.

I wouldn't waste my time with it either way. Probably more caost effective to get a new IRD.

[JT]

Skinerd could probably fix it. He's really talented that way. I can get the basics done with lock install etc., but Skinerd is the guy to listen to on this one.

[skinerd]

I just checked out a 301-013, my 010 is unavailable at the moment, the power supply is simpler than the older RCA 420's and 430's, but relies heavily on the Viper100, which is a combination switching transtistor with built in oscillator circuit. I'll check my 010 when I get it back, maybe tomorrow.
Being it relies on the Viper100, maybe it and a diode or two are shot.

[skinerd]

Ok, just checked a 301-010, it uses a IR840 switch in the power supply, similiar to the dtv 430's. but not exact, with a lot more support circuitry.
If you want to tackle the repair I can give some giudance if you are familiar with the use of a multimeter, and know how to check diodes. I won't give a class in electronics tho I don't have time.

[skinerd]

bare with me Im goin to find out were to get a mutimeter and how to use it ~you use it to check diodes yes~??


Don't know how to use a meter? This is not a good place to learn, you can cause damage by shorting things out if you are now careful, some components are small and close together.
And the high voltage side has up to 160 Volts DC, and is capable of causing a small fireworks show right there in your receiver.

[skinerd]

The power supply on a 301-010 is several components intergrated to the board, and takes up about 30% of the board,it is not a seperate board like some older receivers or the 501/508's are.

Basically how it works is that it takes the 120VAC input and rectifies it to DC then feeds that DC to the chopper which makes pulsating DC for the transformer. It uses some flameproof resistors so they won't catch fire if the chopper, IR840, shorts out. This was a relative common problem with the old dtv 420 and 430 type receivers.

Want to know how it works?? Do a google search for switch mode power supply info, there are some pretty good instructions and info out there. A switch mode power supply is used because it requires the least components for many output voltages, and is more economical to apply. These types of power supplies are found in almost every type of comsumer electronic product made.

[skinerd]

I can be a lot of work, depending on what went......I got pretty good on 420/430 type receiver power supplies, these are not a whole lot diferent.