Yamaha RX-V992 won't power on

no

increase

voltages increase linearly and match + and - ? Any SIL protection device eg (uP)C1237 , get the data on it and work around its inputs and outputs , could be IC failure or genuine bad/erroneous bad input

volume

(while

still

windings;

around

If microcontroller based, then similar sort of skirting around process, but not so easy working out the relevant inputs/outputs

I removed the temporary jumper from across the relay contacts. And:

Let's talk function and not label... The obvious "pink cap" (0.01 uF/50v) is across the ~12v secondary of the small transformer near the AC input. It is an AC filter cap. I measured 4 vac across it. Replaced with a mylar and it's a reasonable 12 v now.

Here's that little PCB:

I replaced C312.

Any other suggestions?

The supercap (0.047F / 5.5v) on one of the function PCBs is obviously leaking and corroded. I removed it (it caused no further damage to the PCB) and will get a replacement today. Shouldn't the unit boot if this was the cause of pulling down the 5v line (I'm guessing at this -- haven't found it in the schematic so don't know what, exactly, it's hooked to...)?

Symptoms remain unchanged with new filter cap and removed super cap.

Ideas welcome.

Thanks.

What do the extra labels mean next to many of the components on the schematic?

Next to a transistor is its label "Q302" and next to that is "s10".

Just on this small board there are these extra labels from "s10" through "s37".

What is this "s" designation for?

Thanks.

Looking at the schematic, it might indicate a part whose value changes (or is/is not installed) based on which version of the board is being used. Note that parts with the "s" labels don't have a specific value listed - compare C308, marked just "s14", with C307, marked "1000/25". Also note that the fuses and transformer all have "s" labels; these parts often are different for a power supply with 120 V vs 240 V input. Also, it doesn't make sense to have J301 and Q302 installed at the same time; J301 would just bypass Q302 in that case. Both J301 and Q302 have "s" numbers. Somewhere on the schematic or in the manual there should be a table of "s" number to part number based on the version of the board.

To your original problem, have you tried unplugging CB304 and measuring the voltage across +MB and G, or across C307? Those should be pretty close to 12.5 V DC. If you have a scope, also measure the same place for AC ripple; if you don't, put your multimeter on AC and measure the same place - you should have much less than 1 V AC. If there is a lot of ripple, check C307 and C308.

Matt Roberds

I can try to help. You can email me at:

mark snipped-for-privacy@labolgcbs.net

and reverse labolgcbs to read "sbcglobal"

Mark Z.

Replaced the supercap (0.047F/5.5V), no joy. Same symptoms.

The "+MB" 12v line coming from the "sub power supply" board is 14.2v with very little (0.05V) ripple.

The "switch on" signal (PRY) that runs the mains relay comes from the main controller, IC1 (HD643361-A49P).

I jumpered manually the PRY signal from the 12v (actually 14) to the PRY line. This gives the same symptom as pressing the power button: mains relay clicks, volume control LED lights and goes out.

Not being to check DC voltages at the pins on this IC (we're not powered on yet) the schematic does call out 2 scope checks to do on IC1: the oscillator signal for; and the RESET signal which triggers when the mains input cable is connected (and, curiously, NOT when the power switch is pushed). I'll check these tomorrow.

Thanks.

Schematic of IC1 and "power down detect" circuit is here:

THis maybe a stupid suggestion but, I've found this many times in sub micro processor units that get moved, hit, vibrated etc... Have you check to see if the processor has a xtal and is so, is it operating?

Many times the crystal will break loose from their connections inside, due to vibration...

Also, I saw another piece of equipment that monitors the elimination of a florescent display, if no light, no processor. Basically if that part of the circuit fails, the rest will wait. That makes perfect sense because you don't want to be operating blindly on some equipment.

Jamie

Not stupid at all. As a matter of fact the Yamaha factory service manual says that this is one of the first steps to take when diagnosing (I now see after rereading this section...)

I'll look at that next.

Thanks.