Receiver woes - basic advice needed

[jim999]

Hello all, thank you for taking the time to read my post.

I have a Yamaha RX-V2400 receiver with an odd issue and would like some basic advice. First about me - I am in computer science, with BASIC electronics knowledge, and I fix most things around the house, but this is a bit above me.

The receiver randomly cuts out, and just before cutting out, the fan goes crazy for about 1s. I ran the receiver in debug mode and it said it cut out due to thermal protection.

I am suspicious that it is not /really/ a heat problem because..
- It can sometimes happen within the first few seconds of starting it up, other times it can run a heavy load for hours without issue.
- the fan does not ramp up (it has 3 levels it can run), but rather, bursts and then shuts off
- in debug mode I can see it's temperature reading. It starts at ~50 and goes up to ~80 (may not be degrees, units unsure, may be some multiple of a sensor reading). HOWEVER, sometime it jumps up and down by about 20 erratically
- I can open the receiver and put my hand on the heat sink, it doesn't get hot, just warm

Now, I am suspicious that the temperature sensors are bad, which I can probably fix, but before trying my hand at ripping this thing apart I was hoping for some other suggestions. I am also thinking of running it with protect mode turned off (except over current protect).

One suggestion I received was to check the ground. The power plug is 2 pronged, and with my tester I confirmed that the grounds on the sub boards are short with the chassis.

I really don't have the money for a new one or a repair shop. Any hints or advice would be welcome.

 

[Harald Kapp]

A jump in the temperature reading could also mean the sensor has one or more bad solder contacts. Try to locate the sensor and inspect any solder points related to the sensor. Re-solder bad looking contacts.
It may help...

 

[shrtrnd]

I don't know if you've opened-up the chassis yet, but the first thing I'd do, is open
up the unit and use compressed air to clean-out the dust inside of it.
The temperature sensors may be tripping because it's actually hot inside the chassis
from dust accumulation.

 

[jim999]

Thanks for your feedback. Strangely enough, particularly given how my computers look, the inside of the amp is very clean. I got the compressed air in there anyway, but barely any dust came out.

I have a schematic and found the two thermal sensors (X0515A00). Unfortunately to get at them beyond visual from the top I will need to remove several boards that are connected to the heat sink and full of thermal grease. I'll have to go pick some up before I start this.

Thanks!!

 

[jim999]

I wish I had a clip on thermal sensor or an IR one so that I can test if its giving accurate readings!

 

[shrtrnd]

It sounds like a circuit problem.
One other thing I'd check first is the load (speakers) you've got on your Receiver/Amp.
Are the speakers able to handle the amp output?
How long are your wire runs to the speakers and is the wire gauge large enough?
Anything else that might need to be checked causing the load on the amp.
I admit it's probably a circuit problem, but I always try to eliminate the obvious before
getting down to the nitty-gritty in the circuitry.

 

[jim999]

Thanks. I did check the load (speaker capacity and impedence) against the settings. To rule all of that out, I just disconnected everything and ran the receiver with nothing connected. Turned it to the radio and cranked it up. Without the speakers to drive it didn't get too hot, but it warmed up and it cut out with the same issue while nothing was connected

One more oddity, which I think is unrelated, is that in the debug mode it can tell me the impedance setting; the receiver supports either 8 or 6 in the settings, and beside that, it tells me the power limit cutoff. In my debug screen it says 4ohms, with a cutoff of 0 (should be around 150 in whatever unit they use). However, since the issue happens without any speakers attached I assume this is perhaps a missing feature in the firmware, etc.

thanks again for your insights!

 

[shrtrnd]

Is it programmed correctly for the load then?

 

[jim999]

yes, the load is set correctly in the settings. I'm not sure that it would matter in this case, though, as it shuts off even when there are no speakers attached..

thanks again