Pioneer elite vsx-51 shutting off as soon as I power

[freakaftr8]

Hey all first time poster and audio forums.

I'm usually in the TV and video section helping people repair their TVs. I'm very fluent electronics but I thought I'd run this across somebody's brain maybe I can pick it. My Pioneer Elite receiver was running great the other day and then it just shut off. I was listening to a couple songs And went into the other room when I heard the stereo shut off. Long story short.

Hit the power button I get a click the blue light glows around power button and the HDMI light comes on at the same time and then immediately clicks back off. I can never get it to stay on longer than a split second just hang up then click on it click back off. I have tried all the reset procedures I have found on the internet with regarding the key code combination to no avail. Also I have already remove the cover and started probing circuits and checking a few fets here and there.

I have tried disconnecting everything except for just an hour in coming to the digital main board can have also tried disconnecting the ribbon cable powering the amplifier module. I have not yet told the amplifier module out to check to see if any fets or shorte.

Has anyone seen this before or have any ideas as to what to look for? It almost seems like it's going into an immediate overprotection or a trip circuit because it releases completely back to standby right after you power it up

[tech2014]

Re: Pioneer elite vsx-51 shutting off as soon as I power

I would check the output transistors section for shorts.

[freakaftr8]

Re: Pioneer elite vsx-51 shutting off as soon as I power

On the amp module?

[tech2014]

Re: Pioneer elite vsx-51 shutting off as soon as I power

yup

[freakaftr8]

Re: Pioneer elite vsx-51 shutting off as soon as I power

Ok thanks! I'll check tonight and repost. This short if in the amp module must be a direct short before the circuit turn on the amplifier pre-outs as isn't there a system check when you first power of the unit up where it takes a few seconds before it releases power to the module?

[tibimakai]

Re: Pioneer elite vsx-51 shutting off as soon as I power

Hi freak, I'm here as well.
I'm into Onkyos mostly, but I have repaired Harman Kardons, Pioneers, Yamahas as well. TV business is very slow.
Test all the final transistors for short, if you find any, just cut those legs and try booting up again. You may have to clear the error code.
I also have a Pioneer 1122k, that does not want to turn on. Sometimes, I manage to reset it and it shows Starting up, but it is stuck there.

[freakaftr8]

Re: Pioneer elite vsx-51 shutting off as soon as I power

Good to know. I'm psyched to getting back to it tonight! Thanks guys!

[freakaftr8]

Re: Pioneer elite vsx-51 shutting off as soon as I power

Well I removed the amplifier assembly and no shorted mosfets. As a matter of fact I left the amp out of circuit and problem still persists. I seriously doubt that the primary board is the cause. It's hot all the time it seems. The secondary board at the bottom with all the relays and big filter capacitors that has 4 relays on it. I'm suspect thee could be a problem here. This is after the main transformer. Noticed a square rectifier diode on here along with what looks like a bridge rectifier.

[freakaftr8]

Re: Pioneer elite vsx-51 shutting off as soon as I power

Oddly enough I just walked into my other room and it looks like my Pioneer VSX 1021 K is the exact same Innards. Maybe a lol part swapping is in order?? Got these two units at the same time.

[freakaftr8]

Re: Pioneer elite vsx-51 shutting off as soon as I power

Ok since these are the same units - the HDMI port on the front of the Elite Series tried swapping the digital main board and I still have the same problem. However the digital main board from the problem receiver works in the good receiver input out perfect sound. So now I'm more or less thinking this is something to do with a standby problem. However I should note that if you do not have all the snap and connectors connected to the digital main board it will do the same thing as my symptoms click on click off immediately. So this could be a number of issues now within the power supply section

[freakaftr8]

Re: Pioneer elite vsx-51 shutting off as soon as I power

Well I have narrowed it down to the main power board on the very bottom of the unit or the faceplate assy.

[freakaftr8]

Re: Pioneer elite vsx-51 shutting off as soon as I power

Well I think Ive narrowed it down to the unit going into power DC protect mode. 3 transistors on the main board on the very bottom and I'm going to have to dig in a little deeper and try to figure out why the protection circuit is being enabled

[freakaftr8]

Re: Pioneer elite vsx-51 shutting off as soon as I power

Hey tibimakai where is the thermal fuse located in the main transformer? I noticed you replaced them before. I have no ac voltage off the secondary side of the transformer. The little 3 pin connector with blue/black/blue connector. No voltage there.

[Longbow]

Re: Pioneer elite vsx-51 shutting off as soon as I power

All this board swapping to find out you don't have any power? No voltage on the secondary? What about the primary? If the primary of the main transformer is indeed open, there are a couple of possibilities. Leads to the thermal fuse are often broken out to a separate pin on the transformer. The fuse is on the primary side of the transformer - see above. You can short out an open thermal fuse using that pin, according to your own judgement. If no separate outboard pin exists, there is nothing to lose by trying to locate the fuse. Many times it is mounted right under some insulating tape near the outside of the transformer. If you can see the outline or bump underneath the tape, there is a chance you can replace it or jumper it at your discretion. If the fuse is located somewhere inside the transformer windings, then you can start looking for a new transformer.

[freakaftr8]

Re: Pioneer elite vsx-51 shutting off as soon as I power

No I have power. There is standby. But as soon as I press the power button the blue halo around the power button lights up immediately along with sometimes the HDMI light and then immediately goes off again like my click click as many times as I press the power button. Like I said I'm not fluent receivers but I am fluent in televisions in my guess would be some kind of ADC protection error. However I do seem to be able to trace a few things out and I do have a schematic. Its leading me to believe something is wrong on the bottom mainboard. I have already tested the digital board. I tried the board and my other receiver in it powered it up and it worked. I've also tested the amp module with no shorts but yet I can completely disconnect the amp module with the same problem. If I disconnect the amp module completely on my other receiver the other receivers still turns on so it doesn't matter if the amp module is connected or not to power up. have also found that if you leave the sideboard disconnected from the digital board on the good receiver it does the click click also. So this is obviously something not getting a signal to the digital board. Which leads me to believe it could be a protection fault. I was only contemplating a thermal fuse but I'm not sure if that would cause A standby to be working or not working. I would only assume standby would still be present because that comes off of the main primary board where the AC input goes. The voltage is directly driven to the digital board For standby voltage. I'm not sure what I'm seeing on the outputs of the secondary side of the main transformer where they go into the mainboard. I'm seeing something like to volts on the two yellow wires that connect to the mainboard however having these wires disconnected from the mainboard doesn't change anything even on the good receiver. I can leave that connector disconnected and it'll still attempt to power Up.

[bobcaygeon]

Re: Pioneer elite vsx-51 shutting off as soon as I power

Not sure how the VSX-51 matches up internally but I've repaired a VSX-40 and a VSX-1021 which was exhibiting the same problem. Basically it would power off seconds after power on. All the outputs transistors tested OK. I found that rigging a piece of dupont wire to each channel output (off the connector in the middle of the amp board) to my multimeter probe was the easiest for me to figure out which channel was showing DC at power on as the connector is not really accessible with all the boards in place. (or having any Pioneer "jigs" available to me). In my experience also, if you leave the protection cable disconnected, it will shut down due to a false "overtemp" error.

On the VSX40, I found (by accident) that if I powered it up as rapidly as I could (with it auto shutting down) it would eventually come on and stay on, but then if I hit one of the pre-driver transistors on the SL channel with freeze spray, it would shut itself off. In my case it seemed like one of the pre-driver transistors had gone leaky. I replaced the KTC3206 with a 2SC2229 (as that is what I could find available) which fixed the issue. On the VSX1021, on the same hunch I just went ahead and replaced that transistor in the faulty channel and fixed that one also.

[freakaftr8]

Re: Pioneer elite vsx-51 shutting off as soon as I power

Problem resolved! Blown thermal fuse in the main transformer on the primary side. Checked the black and blue cable and sure enough the pins are open. Bypass for now but thermal fuse on order. My suspicions were correct along with other people. The guy I got it from probably had something on top of the receiver covering up the vent holes will he was blasting it loud.

Might I add this was a real pain in the butt to try to find the thermal fuse. I Damn near destroyed the transformer but luckily it's okay

[luchura]

Re: Pioneer elite vsx-51 shutting off as soon as I power

Can you please share where it is hiding the fuse top, bottom, by the input connector or other side. Do I need to remove the transformer?
Thank you.
Lucho