RCA RT2770 Reciever (Home Theater?) Need help!

[infringer]

I have the above mentioned receiver RCA RT2770.

There is a Grey Axial (resistor?) or whatever that is next to the Large transformer on the board the bands are scratched off from someone trying to pull the thing off the board is there anyway that I can figure out its rating so I can find a new one to replace it?

Or does someone have this receiver that could tell me the color of the bands on this (resistor?) This is a tough one folks I wish I knew I would get an accurate reading...

Any help would be helpful I'm really unable to determine I can make out some of the lines as follows:

Red at the bottom and the next is a thicker white line then nothing and at the top it looks to be black...

Marking on the board says R202 by the way which a quick google search turned up 3.3k 1/4 watt but I believe the R202 marking does not note what the rating of the resistor is if I am correct if it does that would solve a ton of learning issues with electronics off the bat.

[budm]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

Any good clear pictures?

[infringer]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

What do you need the full SMPS or the resistor? from what I am finding on ebay its a tuff one to find on my 25th page and cannot find anything to match the bands exactly like those 3 bands that I am able to make out... It is a Grey Metal Oxide type. I was told the unit smoked when it went out the component side of the board this resistor would be the thing that smoked it is fairly clear it is between the transformer and what looks to be a voltage regulator on a heatsink .... I also did find that the power board for this unit is the same model used in other units boy I will tell you what you can find TV power boards or blu ray power boards but finding audio equipment power boards or SMPS is a big good luck with that component level is the only way to go with these things it seems.

I have fixed quite a few TV's but would have to say never had the need to fix audio equipment as mine all still works knock on wood.

Anyhow I could get you pics later but for now it is past sleeping hours already I've been playing with this thing less the 5hours left to make use of that If you could specify what you want and how in depth you would like the pics that would help like full board pics or just area targeted underside top side so on the resistor I may have lost trying to clean stuff up in a hurry but it appears to be a metal oxide type axial as described with the bands I could make out.

Thanks for your reply though budm. As always you seem to be one of the few willing to give it a shot in helping. Does the R220 marker on the board stand for anything by the way or is it just a marking. I wish they would mark stuff on the board that would give representations of what values are needed this would be great for cases like these.

Very few metal oxide resistors I am seeing have white bands on them so I guess that helps kinda if I could at least match the other bands it would be likely I got the right thing.

[budm]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

Pictures of the whole chassis, resistor, area close to the resistor, SMPS board.
I fixed a lot of AUDIO equipment in the 70's~90's (Fisher, McIntosh, Phase Linear, Pioneer, Sansui, Onkyo, SONY, Yamaha, SAE, Carver, Fender amp, Marshall amp, TEAC, AKAI, DUAL, GRUNDIG, TELEFUNKEN, etc) . I still have a lot of old stereo amps and receivers from the 70's that were built like a tank, still use them everyday, they all use good old reliable linear power supply not these easily failed SMPS.
Just fixed the Mixer board yesterday: https://www.badcaps.net/forum/showth...493#post245493

As long as you have good understanding of how components work, it is not too hard to work on any electronics.
1000W that weights less than 50lbs, must be using Class D amp setup.
It sure has funny spec:
Output total: 1000Watts
Power consumption: 90Watts.
http://reviews.cnet.com/home-theater...l#userOpinions

[infringer]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

You bet it isn't quite the same 1kw receivers are kind of a mark up imho but I will say they have there place I have the vizio surround bar with wireless sub and it works like a champ shakes the house as much as I need it to. Working on them pics as we speak btw and thanks again for the reply. I would guess you have been doing this that long that puts your age at roughly high 40's I didnt really get into electronics and hardware until late in the game still very new but have made leaps and bounds of progress. Started off actually in the grey area of hardware hacking and it stirred my interest to go further and start trying to repair stuff have fixed a bunch of stuff so far but I am not no electronics engineer but I am serious about learning serious enough to purchase a decent scope and plenty of meters and slowly learn my way into making these tools useful still I am not 100% on a lot of stuff but the more I look at the more I see that circuits for the most part follow similar concepts on a SMPS the depth is way deeper I know but I'll give it time but I'm always up for pointers. Many folks pay more for vintage audio then I ever thought was possible but you are correct the stuff was built like a tank back then I just picked up an electric can opener for a buck from the 70's thing still worked I said gotta have it lol!

[infringer]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

BudM I hope these will do for pics. I dunno how you would prefer offsite photos or on site so I figured I'd post them on site.

[budm]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

OK, that resistor is part switching noise RC filter to reduce the noise of the rectifier Diode when it switch on and off at very high frequency of this switching power supply, this noise and its harmonics can get into the amplifier section of the audio amplifiers.
Right now the power supply should work without this RC filter, you may want to check that blue cap (value of the cap?) and the resistance leakage, if the cap has resistance reading, that may explain why the resistor burn up.
Check the rectifier also.
Are you getting any B+ from this section?

[momaka]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

Judging by the spot of that resistor in the PSU, it's probably a low-value resistor (most likely 20 Ohms or less). Have you tried measuring the resistance with a multimeter?
Also, check if that blue cap is short circuited.

*EDIT*
I guess budm beat me to it.

[infringer]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

Ok thanks for the help excellent explanation and label job I'll have to check into this further tomorrow hopefully have about 5 hours to sleep then a nice long hot day at work after my nice hot sleep lol AC pfffft thats old school didn't tesla invent that edison invented the fan and it doesn't kill cats so I think I'll stick with that. heh forgive my geeky humor but it sure has been a warm one lol.

[Home_Command_Center]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

I have the EXACT same problem with mine, but my resistor isn't quite as toasted. I've been posting in a thread on another site in a post from another guy who ALSO had the same problem. my SMPS board even has the EXACT same build date as yours, March 23rd 2007... seems like there should have been a recall... hrrmmm

also, seems most of these have all of the sudden failed this year, interesting.

expiration date anyone?

the thread I've been posting in is here:rca-rt2870-turns-then-back-off

[Home_Command_Center]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

pics of my resistor:

[tom66]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

It sure has funny spec:
Output total: 1000Watts
Power consumption: 90Watts.

Don't you know? These things use a zero-point module to generate the quantum flux. They actually contribute energy back into the grid when you shout into the speaker loud enough.

[budm]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

Lol.

[Wolf_Punch]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

BudM I hope these will do for pics. I dunno how you would prefer offsite photos or on site so I figured I'd post them on site.

Dude, that's like the same resistor that is burnt on mine, though mine still works, oddly.

I can't tell the bands on it eighther because it burnt a little too.

Oh, and another thing? How do I get this stupid subwoofer output to switch on?
I don't have the stupid sub control button and the relay that controls it is switched off

why, oh, why?

[tom66]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

The resistor is a snubber for the diode. Due to poor design, the wrong value has been chosen, which has led to early failure. Increasing the value should be harmless.

[Wolf_Punch]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

I may be a novice but I no what a snubber is.

Anyway I have a whopper 8.2 Ohm resistor on my other RT 2770 (bare in mind it's got a different lay out ). Would that work in place of the burnt one of the other board?

It in the same basic area that the burnt resistor on the other board is right by the 3-pin heat sink mounted diode.

OH, and fyi, my board still works (Well probably not now since the resistor wiggled free of it's soldered terminal) but that slightly burnt resistor haunt's me .

I'm also thinking about upgrading all the 63v 1000uF caps for 100v 1000uF caps (Extra 27 volts of overvoltage cushioning ) along with the 2, 200v 330uF caps, to 250v 330uF caps. I blast my systems constantly, when they work, lol

[tom66]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

8.2 ohms is too low, much too low.
You need about 1~100kohm 3W.

Depends on the output voltage of that PSU and breakdown voltage of diode.

If output is 50V and breakdown is 200V, worst case is 250V across resistor.

So calculate (MaxVoltage^2)/Resistance <= 1.5W (half rating of 3W to limit dissipation)
and that will give you a decent lower bound... Example 47kohm works here.

[Wolf_Punch]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

8.2 ohms is too low, much too low.
You need about 1~100kohm 3W.

Depends on the output voltage of that PSU and breakdown voltage of diode.

If output is 50V and breakdown is 200V, worst case is 250V across resistor.

So calculate (MaxVoltage^2)/Resistance <= 1.5W (half rating of 3W to limit dissipation)
and that will give you a decent lower bound... Example 47kohm works here.

I don't know all these formulas. :S I am a n00b.

Bur, I can tell you that I drive my speakers quite strongly usually, so wouldn't (for the sake of the amp) a high resistance be appropriete?

I was already getting some static noise from the speakers evan on volume level 1 without the sub (I can't get that sub working as I don't have the switch/button to complete the relay circuit thing that is reffered to as "subwoofer control" (that's another story)

Ah... progress... how I hate thee .

Anyway, back to the topic at hand: I guess the stattic was due to the bad resistor (well, it probably is, I mean, It's color coding rings where burnt off,
almost like how the sun bleaches a dead starfish). The capacitor that completes the snubber probably suffered due to burns present on the epoxy close to the end of one of it's leads, most likely caused by resistor leaning on it.

Lol, sorry I talk so much. I'm just a very inquisitive person ^_^.

I already have 2 (sligthy different) RCA RT 2770's so i may as well revamp one of them.

Plz give your honest opinions about each of the ideas I descibed.

I'm not trying to be a pain in the ... but I do like to understand how things work, for mental and physical benifits. I don't wanna set any boards up in flames.

[Wolf_Punch]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

8.2 ohms is too low, much too low.
You need about 1~100kohm 3W.

Depends on the output voltage of that PSU and breakdown voltage of diode.

If output is 50V and breakdown is 200V, worst case is 250V across resistor.

So calculate (MaxVoltage^2)/Resistance <= 1.5W (half rating of 3W to limit dissipation)
and that will give you a decent lower bound... Example 47kohm works here.

Oh and I forgot to mention I live in bahamas and the U.S, though I still am from Guernsey, Channel Islands, U.K

sry for the confusion

[budm]

Re: RCA RT2770 Reciever (Home Theater?) Need help!

There is a small value cap which is in series with the resistor to create RC Snubber circuit to reduce the Diode switching noise, if that cap is shorted or it has low leakage resistance, the resistor will burn up since the current will also flow through the resistor for full cycle.
example:
https://www.badcaps.net/forum/attach...9&d=1354513907