Home Theater Questions? Ask a Technician for Answers ASAP
Hi and welcome to JustAnswer, I’m Louie. Sorry you had to wait awhile but I’ll do my best to help.
Initially, let's try and review the basics. Proposed preliminary checks (if have not been done):
I understand and yes please; an update when conveniently able.
Apologies for delays, Internet down and back but sluggish.
There are four (4) reasons why the auto-protect would kick in:
The last may be caused by a failed 3-terminal regulator and/or even a cold solder/loose connection or leaked capacitor.
And yes; metal chassis as common DC ground for the secondary voltages. From the main transformer, the voltages are:
From these, the power supply circuit produces:
No prob;...later then.
That black block is a relay (RY151). It does the actual switching of the main transformer. This relay is powerd by the +9.27V at the emitter of Q1503. It is triggered on by the presence of PWR_RY voltage +2.97V at resistor R1501. This PWR_RY voltage +2.97V is an output of the CPU when it receives an input to turn on the RX-V377.
The CPU also processes other sensors' outputs; i.e. if it has to kick-in auto-protect mode by halting the output of PWR_RY voltage +2.97V. These sensors monitor:
Thus failure/fault on any of the above and auto-protect mode kicks in, CPU stops the +2.97V, Q1503 turns off, relay turns off, no 120V to main transformer.
Please post back with clear pictures of all the circuit boards. Click HERE.These pictures would then serve as common references.
Appreciate the pictures.
May we step back to the basic(s); "...The fuse in the transformer is good. The primary transformer is hot...." but have you checked fuse F1501?
When attempting to turn on, can you hear/feel a click from relay RY151?
I understand and later then when conveniently able.
I would make use of the time to further review the Service Manual and schematic diagrams.
Why is the brown wire cut please?
As long as the volume control is set to minimum, no further damage when testing without speakers connected.
Have you spliced back the brown wire?+
Please carefully access the OPERATION (2) board. Attempt to turn on the Yamaha and determine the presence and consistency of:
A friendly reminder: voltage measurements by its very nature requires that the unit be plugged in and turned on. It is therefore LIVE! Please exercise due care and caution.
Please click on the linked HERE of each part below for their specification/data sheet:
These specification/data sheets are in Portable Document Format (PDF) file and can be viewed in most web browser. Right click on the link to "Save as", click on the link to open the file and/or click on the Download button to download the file. It would require Adobe Acrobat Reader or equivalent for this purpose.
Q1503 is the part designation on the board. 2SA1708 is the real Part Number.
Part Number KDS160 is used both for D1508 and for D1509.
It is safe to test the unit with no speakers connected but with volume down. It would only fully turn on if auto-protect mode is not kicking in.
And yes please; when conveniently able.
Hi again and appreciate the update.
Strongly consider passive tests; i.e. not powered / not plugged in.
Use alligator clips with wires similar to the items shown HERE. Join/connect ALL common grounds (metal/chassis) of the three (3) RX-V377 to the black probe of the multi-meter.
Choose any (test) point. Get an Ω reading of say of the cathodes of D1508 and D1509 of the third/new RX-V377. This is now our reference/template.
Then move to the the cathodes of D1508 and D1509 of the second/Florida unit. Read Ω compare.
And then to the first RX-V377.
Repeat for any/all test points.
Glad that the above test method may serve your purpose.
Appreciate the update.
And good to hear that the issue with the second/Florida unit has been resolved, congratulations.
Please post back with clear pictures of the "...two HDMI cards..." Click HERE.These pictures would then serve as common references.
Two (2) potential approaches:
Both of the above are 'shotgun/blind' method; i.e. no identified culprit hence suspect all.
I will try to run a search for replacement Digital/HDMI boards within that price range.
Unfortunately, no readily available replacement boards in my search; sorry.
I realize that the above information may perhaps be not what was expected. Unfortunately, there is no quick-n-easy fix and neither is there a workaround. Our last bet would be with Yamaha; sorry for having to be the bearer of bad news.
Is further information/assistance still needed with this?
May I suggest passive tests first; i.e. alligator clips to the boards for ground connection to the multi-meter black probe.
And then the red probe to a test point on the good board, then to the bad board.
Check for Ω readings.
Any update(s) ?