Yamaha RX-V2067 DC_PRT issue

[OddyAte]

Hello everyone,

New to this forum but glad to be here. I purchased a defective Yamaha RX-V2067 2 years ago, hoping it's an easy fix. Sadly it has a DC_PRT too high issue (~200-220 at all times) that triggers protection. I have a friend that repairs electronics but because he did not have enough time, we kinda kept delaying the search for what could be wrong with the amplifier. Today, we took it apart again, removed both (not sure if it's the correct term) power amplifiers/sound amplifiers that driver each channel. So this way, only the logic boards and power supply remained connected. We discovered that it still triggers the protection, so we are pretty sure that it's not those that are faulty.

We traced that the issue starts with IC902 pin 1 that has the high value. If we used a resistor between pin 1 and ground (pin the issue stops and it does not trigger protection anymore, but if we connect the power amplifiers again, there is a buzzing (probably voltage) coming through on all channels (into a speaker). IC902 pin 1 and 3 do not have the values the service manual states, and we also checked LMT_DC that is created by Q9010 + Q9011 and on the emitter side of Q9010 the voltage is 0 instead of 0.3.

Sadly we could not continue with the search for the issue today, but I would like to ask your opinion on what should we be looking for. Are there specific things that tend to break that may cause these symptoms? We did not check R9008 that is the resistor between the LMT_DC and DC_PRT because we could not find it and we ran out of time.

Thanks a lot and have a great day!

[fzabkar]

Service manual:

https://elektrotanya.com/yamaha_rx-v2067_htr-9063_rx-a2000.pdf/download.html

[OddyAte]

Thanks, that's what we used to get this far

[mzacharias]

Use the "Protection Cancel" function outlined in the service manual to allow troubleshooting voltages without shutdown.

Normally, a DC PRT error indicates a DC problem at one or more amp channels. That is where I would start, even though if I read you post correctly you removed the amp modules?

There are other things that can cause such an error, like a floating ground reference for example but for now I would re-install the amp modules and check the amplifier DC output if any, and whether there might be only one channel triggering the protection function, or if all channels have an offset (or none for that matter).

It's unlikely to be a power supply issue as such, even though unbalanced supplies can cause offsets, but the error reported would usually be a "PSxxx" in that case.

[OddyAte]

Thanks for the reply. Yes, we removed both amplifer board completely (all wires disconnected & desoldered) but the P1-1 value did not change from the 200 range. So then we installed a 6Kohm resistor on IC902 Pin 1 and Ground that dropped it to the normal range of values (40-50). Then when we connected back one of the amplifier boards, it started triggering protection again but this time on the low side (reading of 9-15 on P1-1). We bumped the resistors value to 10Kohm to get it back in the normal range but the speaker we connected had a bad buzzing sound on all outputs, even tho only 1 amplifier board was connected.

check the amplifier DC output if any, and whether there might be only one channel triggering the protection function, or if all channels have an offset (or none for that matter).

what exactly do you mean by this? checking for voltage on the speaker connection ports?