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Problem with RCA STAV-3970 a/v receiver


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07-01-16, 05:06 PM   #1 (permalink)  
Problem with RCA STAV-3970 a/v receiver

I need the service manual or help to repair the RCA stav-3970 audio video receiver, puts POWER OFF flashing 5 times after turning on and turns off. Sorry my English is not good. If someone can help me i thank you very much.

 
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07-01-16, 05:13 PM   #2 (permalink)  
The unit was unplugged for more of the one hour and then connect it without speakers or audio in. The problem continues. Please help.

 
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07-01-16, 07:37 PM   #3 (permalink)  
Welcome to the forums.

You may be in bind there. Are you able to buy parts.... if needed ?

The five flashes signifies an overload/protection condition. More than likely the audio output stages have shorted keeping the unit in protection mode. There are two IC amp modules that power all the speakers.

This is truly a miracle receiver. It's advertised as a 5.1 receiver with five amplifiers. It only has three small power amp stages. Two for the front speakers and a center channel amp.

STK-411 (single channel 100w amp) IC
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STK-410 (dual channel 100w amp) IC
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I haven't found any available schematics or service manual. For a tech it would be easy to fix. I'm not sure how you want to approach this as you're going to need a meter and a soldering iron at the very least.


~ Pete ~

 
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07-01-16, 10:05 PM   #4 (permalink)  
Are you sure that 5 flashes is an overload/protection condition, where did you find that. Thank you.

 
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07-01-16, 10:08 PM   #5 (permalink)  
Some failure could be for low AC voltage?

 
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07-02-16, 10:28 AM   #6 (permalink)  
If your going to attempt to fix this yourself, you are going to need a multimeter and soldering iron . Plus know how to use them.


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07-02-16, 10:57 AM   #7 (permalink)  
Are you sure that 5 flashes is an overload/protection condition, where did you find that.
I remember it from years ago. You are not going to find much of any published service information on that unit. It may be a good idea to locate a servicer for it.


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07-02-16, 04:30 PM   #8 (permalink)  
I don't specifically know your model but they are actually made by Pioneer for RadioShack/RCA

I had the somewhat high-end model (At the time around 2001) the STAV-3990 which was basically a rebadged VSX-D710S
I bought it on sale with their infamous service plan which I needed as the unit was almost always broken.

If you can find the equivalent Pioneer model number you can probably find a service manual for it

 
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07-02-16, 04:36 PM   #9 (permalink)  
OK it looks like the Pioneer model is VSX-D510
So Here is the service manual for the Pioneer version there may or may not be differences in the two units so you will have to be careful and always disconnect power when working on the unit

 
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07-04-16, 06:43 AM   #10 (permalink)  
Thank you all for responding, the service manual is the one I need. I appreciate any help in repairing of the unit. Thanks again.

 
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07-04-16, 11:38 AM   #11 (permalink)  
In looking at the Pioneer versus the RCA unit..... there are differences. I see differences in the amp stages.


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07-05-16, 03:22 PM   #12 (permalink)  
I checked with the multimeter the protection that senses the micro, the fault is not overload, is for DC. I check DC voltages and are symmetrical. When I turn on the unit on each power output no DC voltage but when the unit is turned off automatically appear about 2-3 volt. Why could this be. Thanks to all.

 
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07-05-16, 10:36 PM   #13 (permalink)  
I'm not following you.

The protection circuit monitors the voltage on the speaker terminals which is the same thing as the audio amp output stages. When that circuit sees a DC voltage it goes into protection mode which is usually a relay opening and disconnecting the speakers from the amps.

More than likely you have a shorted audio output like I previously mentioned. You need to isolate them to determine if they are the cause of the fault.


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07-06-16, 07:08 AM   #14 (permalink)  
Thanks for responding, first the the relay of the speakers never closes because the receiver when turn on enters in protection mode. As I said check the power output and had not DC voltage in the few seconds that the receiver is on. Could not be the transistors of the DC protection circuit?.
Thanks to all.

 
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07-06-16, 08:31 AM   #15 (permalink)  
The normal part/parts that go bad on an amp/stereo is the audio output ICs. Forget your meter for now. Unsolder and remove the ICs. Turn on the power. If unit stays on, using your meter check the pins where the ICs solder for the proper voltage readings. If everything checks ok, replace ICs. If the unit still goes off. There is a different cause of the problem OR the IC/ICs took some parts with them when they went bad. This is where the real trouble shooting begins . Let us know what you find after removing the ICs.


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07-06-16, 11:28 AM   #16 (permalink)  
OK I do that, thanks. Moreover, the only component that heats up a little is the 5.6V regulator 78M56A in the power supplay assy, but this DC voltage is present. I don't know.

 
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07-11-16, 10:03 AM   #17 (permalink)  
OK, I unsolder and remove the audio output IC PAC010A. Then, the unit stay ON. The problem is this CI, it is two audio amplifier (Front Right and Front Left) and now i want operate the unit in 5.1 function so that the other audio amplifier IC PAC011A operate and can use the unit only with three audio amplifier (Surround Right, Surround Left and Center channel). For this case the unit stay ON but not operates the output relays and I not have sound in the output.
This that i want could be possible, what can i do? Thank you to all.
p.d. I have to do at less it work a part because in my country do not sell this circuit or similar.

 
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07-11-16, 10:26 AM   #18 (permalink)  
I do not have the diagrams so can not help you on that.


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07-11-16, 03:20 PM   #19 (permalink)  
Here's the link again for the manual... PIONEER VSX-D510 Service Manual

Are you saying that you cannot get the replacement audio amp IC ?


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07-13-16, 12:00 AM   #20 (permalink)  
For simplicity try shorting the contacts on the output relays for the surround speakers.


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07-13-16, 11:08 AM   #21 (permalink)  
That unit has front left, front right and center channel amps.
The surround outputs are RCA line level only


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07-13-16, 08:27 PM   #22 (permalink)  
I have to go back and look at the schematic. According to the RCA owners manual..... there are three speaker outputs. I've outlined them in red below.



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07-13-16, 09:18 PM   #23 (permalink)  
OK, I see the problem .The RCA and Pioneer are not the same unit. The model I down loaded was the Pioneer. Check out the pics of the rear panel from the pioneer manual you posted right above me earlier. Totally different amps and rear panel. We need the part number off the amp ICs to see if either manual would even work for this unit.


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07-14-16, 08:56 AM   #24 (permalink)  
Thank you all for responding;
CircuitBreaker: thanks to you I could find the pioneer equivalent service manual of my equipment.
PJmax: thank to you for being the first in respond my question, for show me the similars STK circuits and for help me in the repair.
craftsman_50: thank to you for helping me and guide me in the repair. You were very successful in the comments.
I commented that i achieved work the equipment in 5.1 function with three operating channel, for that i connect the damaged CI again but without the power supply pins and output pins. When the unit turns on it operates the output relays and there is sound on in the 3 channels (right and left surround and center), of course the two front channels no have sound. For now i use the equipment to amplify three channels of audio from the PC until appears PAC010A integrated circuit.
As I said thank to you all.

 
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07-14-16, 09:23 AM   #25 (permalink)  
Your very welcome. You also did some very awesome trouble shooting on your own. Re installing the IC leaving the shorted pins unsoldered to activate the relays normally showed great intelligent thinking on your part !


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09-11-17, 09:24 AM   #26 (permalink)  
repair the RCA STAV-3970 a / v receiver

Hello everyone, a long time ago no greetings, but I bought the integrated circuit PAC010A, can give me some suggestion for its installation. Thank you

 
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09-11-17, 12:14 PM   #27 (permalink)  
The PAC010A is a 22 pin dual audio amp IC chip. You'd need to unsolder the old one out of the board first. You can buy a small hand operated vacuum pump or use solder wick to remove the old solder.

This is a very basic desolderer from amazon.
WEmake-WM-SP4-Solder-Sucker-desoldering


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09-16-17, 09:34 AM   #28 (permalink)  
Thank you PJmax, something more about manipulating the component and protection of this one so as not to damage it at the moment of the installation. Again thank you

 
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09-16-17, 09:48 AM   #29 (permalink)  
I use a Variac. That is a variable AC control like a big dimmer. I bring the voltage up slowly and watch for excessive current draw. An expensive item to have kicking around.


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09-16-17, 10:10 AM   #30 (permalink)  
Ok, thank you PJmax, I do not have it but I appreciate the suggestion

 
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