Yamaha RX-V995 Surround Sound Receiver shuts down...


I have a Yamaha RX-V995 Amplifier that, at any given time, will just shut off. All I have to do is power it back on and sometimes it will work for hours and other times it will shut off right away. It would not hold the last settings and I found the memory cap to be defective, you know, leaky cap syndrome. That was a 4.7F 5.5V cap. at any rate, I went over it with a fine tooth comb looking for loose solder joints and other caps that might be leaky, found and re-soldered a few cracked joints on a regulator board buried in the bottom of this beast, all else looks fine. It does have some power relays for the speaker outputs and B+ power. I remember replacing those on the fisher amps years ago... I was wondering if anyone has worked on one of these and what you might of found. This unit is loaded and looks clean sadly; I do not have a schematic. Nothing leaked into it from the top. It doesn't appear to have smoked any transistors or resistors, at least none of the major 'let the smoke out' components. The power to the proc seems steady and there isn't any noticeable ripple on any of the power buss lines that I have found. I really haven't checked for DC showing up on the outputs as of yet, not really sure how the safety circuits work in this unit. It doesn't run too hot when on for hours at a time. I thought finding and replacing the 4.7F cap would have taken care of it, but still shuts down. To reply to me directly just take caps out of my address.

Thanks in advance,

Markus snipped-for-privacy@uakron.edu

Reply to
Loading thread data ...

The nature of this failure suggests to me that there is a speaker wire shorting intermittently.

Yamaha's have diagnostics built in that can tell us whether it was an over-current (shorted speaker wire) situation, a DC offset problem on an amp channel, a power supply problem, etc.

You may e-mail me direct if you would like some help with this; I am an authorized Yamaha servicer.

email to:


and reverse the domain name.

Mark Z.

Reply to
Mark D. Zacharias


This is my Cousins amp, I've been in the repair business for over 30+ years. If it has a wire coming out of it I will at least look at it. I work on TV's that have tons of built in diagnostics; the days of trim pots seem to be gone. I really appreciate your help. Speaker testing>>>

I thought of that and ran over at his house last week with my ohmmeter, all lines were in the 3ohm range. This is using a Fluke digital VOM. I do have an impedeance meter that I could dig out to do some testing on the speakers didn't take it with me. I thought that one of his cats might of bit through the wiring. I ran the wires with my hand and found nothing of note wrong with the wires jackets. Due to the age of the unit and finding that mem cap leaking I could only think that, perhaps, there is some leaky i.e. 10uf@50V cap in the power amps pre driver section pulling the DC offset up. Is there some sort of built in Diags? He couldn't find the manual; however, I haven't seen any owners manuals have too much in the way of technical information. Sometimes too much info for the average consumer is dangerous. I get VCRs in that the user opened up to try to fix it and frankly I would rather turn those ones down.

I looked at all the boards for cracks and they really look clean. I blew out all of the dust so that I could get a good look at them, for the age of the unit it really is clean. He has it mounted in a cabinet that has a glass door on the front of it.

Thanks again for the reply,


Reply to

The Yamaha monitoring circuit tests all the psu rails and therefore any rail going high/low in voltage by more than say 20% will cause the unit to trip. There are 2 severities however. If the power trips so rarely it'll be difficult to know whether its the 1/2 sec (serious) or 3 sec (not so..) mode. I recently had a smaller Yamaha in recently with just this symptom. turned out to be a leaky diode causing a low -25v rail for the FDP drive. In any other manufacturers unit the screen would be off (or dim as in this case) but here it causes a trip. The diagnostics don't really help with an error code of 16% reading for the psu rail... normal value 23%.... weird values but basically correct at

16/23rds of the rails normal value. Your problem will doubtless be one of the rails but with so many you'll just have to test each in turn. Thats a bit tricky in the few seconds you get I've also had a 5v reg go s/c so that 10v is put through to other areas without tripping !!

Diagnostics is usually hold 2 buttons like set menu & prog+ on front panel then bring out of standby. There are 2 diag modes, one where the protection is removed... this can be very dangerous if you have a serious rail fault and could cause untold extra damage so needs to be used wisely.

If you need the pdf manual, I can send it when back off my hols.. regards Andrew


Reply to
Cliff Top

Sounds like you're an authorized servicer as well. Where are you? I already sent him the manual - he should have it by now.

Mark Z. (Wichita, KS.)

Reply to
Mark D. Zacharias

Thanks for all of your help, I'll let you know how I make out.

take care and have a great weekend,


Reply to

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.