Solved: Yamaha AVR RX-V667 turns off with PS1 PRT 3L - TOP254PN IC gets very hot

[cprogrammer]

Hi. I came across this forum when my Yamaha suddenly started randomly turning off. Even the standby LED would turn off. The only way to turn on the receiver is to remove the power plug and put it back after 20 secs or so. Thanks to this forum I came across using diagnostic mode to find the error. Every time the AVR switches off, I use Info + Tone Control + Power button to find the fault and every time it is PS1 PRT 3L. I downloaded the service manual. I could find nothing much related to PS1 PRT 3L. All i can figure out that some output is low somewhere. In the last few days, I have managed to open the receiver, learned how to remove and put the boards back again. I have done a thorough visual inspection and found no bloated caps, etc. I have checked the voltages too. All look ok. As per the manual PS1 PRT monitors ACBH, ACBL, AC_12, AC-5, ±12, ±7, +3.3D, +1.8D PG116 (Normal Value 38-141  0.49v-1.825v). In the diagnostic mode I'm getting reading of 89 (well within the normal range).

Another funny thing is that the AVR switches off even when in standby mode. So it seems that the problem is with the standby power supply (for some funny reason that board is marked video 2 board). I have check the diodes, capacitors and resistors on this board. All are matching the rated values. Even the voltages on this board are fine (except for pin 3 of IC371). The board is giving me 5.64 volts where it is marked +5.5v. I'm seeing that this powers the digital board (the board with HDMI sockets). I measured the votages on the board. All are fine. e.g

AC_12  - 14.7v (measured)
AC-5     - 6.8 (measured)
IC906 RP130Q331D-TR-F (3.3v DIGITAL (1) PCB, Pg 83,84,112) - 3.28v (measured on the IC terminal)
IC907 RP130Q331D-TR-F (3.3v DIGITAL (1) PCB, Pg 83,84,112) - 3.28v (measured on the IC terminal)
IC33  R1172S331B-E2-F (3.3v DIGITAL (1) PCB, Pg 83,84,108) - 3.24v (measured on the IC terminal)
IC31  RP130Q181D-TR-F (1.8v DIGITAL (1) PCB, Pg 83,84,108) - 1.76v (measured on the IC terminal)
IC101 NJM7812FA (3-Terminal 12v regulator)              - 12.03v (measured on video board)
IC102 KIA7912PI (1A 3-Terminal 12v Regulator)           - 11.92v (measured on video board)

The only thing odd is the IC TOP254PN (IC 371 in the service manual). It gets very hot, extremely hot and too hot to touch. My guess is that this IC has gone bad and this is what is causing the PS1 PRT 3L error. I'm trying to source this IC locally but all sites, it is on backorder. However IC TOP258PN is easily available. Can I replace TOP254PN with TOP258PN? Is there a way I can put my own 5v power supply to replace the standby power supply board?

Thank you for taking time to read this post.

NOTE: I'm not a pro. Electronics was my favourite hobby in school and college. But I never learnt it professionally. I can solder. My concept of electricity, ohms law, etc is very clear. I know how diodes, transistors work and I know how to test components like caps, resistors, diodes, transfomers, etc using a multimeter. I have a LCR meter. In the last few days I have learned a lot, but not knowing things is making the repair and troubleshooting difficult. Also I don't want to throw away the AVR. It is 10 years old and in this age of use and throw, i'm sure that Yamaha service will either tell me this is beyond repair because they no longer have spare boards. Also I know, most these official service centres don't do is component level replacement.

[samnmax]

If TOP254PN is getting hot, but it's still supplying a stable 5.5V (5.64V is OK), it might be that something is pulling too much current from this rail.
It seems +5.5V supplies IC73, IC77 EN5327QI DC-DC converters, check their outputs: should be 3.4V and 1.8V respectively, according to the service manual. 1.8V is further regulated to 1.2V by IC76 and IC83.
I bet you have a short somewhere below the 5.5V rail.

[cprogrammer]

Thank you for letting me know that the fault could be with the ICs mentioned.. I will try this first thing tomorrow morning and report the voltages.

[cprogrammer]

Ok I managed to look at IC73 and IC77. The voltages are 3.29v and 1.78v.

There is another thing I did. I disconnected all connectors to the digital board. IC371 still gets super hot. Now this power board connects to another board below. So i removed this board completely out of the case and just connected the ac cord. IC371 still gets hot. Is there anything else on this board that could be causing a short?

If I leave the power on, the standby led also goes off after few mins. As per https://www.power.com/sites/default/files/product-docs/tophx_family_datasheet.pdf, this ic has Accurate hysteretic thermal shutdown function automatically and recovers without requiring a reset

[wraper]

Remove L3702 and connect multimeter in apms range instead of it to measure current. If current is larger than 2A, it's highly suspicious. Considering 0.2W standby consumption spec, current should be <50mA in standby.

[cprogrammer]

Remove L3702 and connect multimeter in apms range instead of it to measure current. If current is larger than 2A, it's highly suspicious. Considering 0.2W standby consumption spec, current should be <50mA in standby.

Ok. i will try this tomorrow as this will require desoldering/soldering. But as mentioned earlier IC371 is getting super hot even when CB379 is disconnected. i.e. without any boards connected to this power supply board.

Another thing I failed to mention is that this issue is getting worse as time goes by. When the first time it occurred around little more than a week back, the AVR would play sometimes for 3-4 hours continuously. Few days back this become around 20 mins. Now it doesn't last beyond 5 mins. And as long as it is on, everything works - I get proper sounds. All the HDMI and AV inputs work. When I opened the case first time, I noticed faint signs of carbon above this power supply board on the inside grey coloured surface. Now this could be a normal thing because we have a relay. Even though the relay is enclosed, I believe carbon could be escaping and getting deposited above. Or maybe this is part of IC371 material that has been escaping because it has been getting hot. I really don't know the reason for the faint black stain. I have attached a picture.

[wraper]

Even though the relay is enclosed, I believe carbon could be escaping and getting deposited above. Or maybe this is part of IC371 material that has been escaping because it has been getting hot. I really don't know the reason for the faint black stain. I have attached a picture.

It's just a dust from air. It tends to accumulate where heat sources cause air flow or where high voltage is present. There is no carbon in relays BTW.

[samnmax]

OK, if IC371 is getting hot even when its board is disconnected from everything else except AC, there must be a problem on that board...
Could it be a problem in the transformer or perhaps in only one of the diodes in D3709? So that it is only rectifying one of the secondary windings, and the other is shorted? Just speculating here...

[cprogrammer]

OK, if IC371 is getting hot even when its board is disconnected from everything else except AC, there must be a problem on that board...
Could it be a problem in the transformer or perhaps in only one of the diodes in D3709? So that it is only rectifying one of the secondary windings, and the other is shorted? Just speculating here...

I have been checking all diodes, resistors. All diodes check out fine. C3705 turned out to be 60 nF instead of 100 nF. I replaced it with a ceramic capacitor since I don't have a smd version. But even that didn't solve the issue. Now the question I have is if TOP258PN can replace TOP254PN. If I place an order TOP258PN today, it will arrive next week. TOP254PN is just not available in any of the online stores here. The fear that I have is if i put TOP258PN, will it blow up the board. From whatever I read in the data sheet, it looks like TOP258PN is a higher wattage version. But I don't have electronics knowledge and my reasoning could be totally wrong about replacing TOP254PN with TOP258PN.

I was discussing this in another forum and one member says that his Marantz AVR too had a problem with the standby power supply and his unit had TOP258MN which had to be replaced. I have also come across a youtube post where Yamaha RX-V465 had a power problem. The board looks almost like mine and the IC replaced was TOP254PN. In fact, the I can see the RX-V465 board having the 8 pin socket which makes replacement of this ic very easy. here is the video https://youtu.be/SOQX_bldUfM

[samnmax]

Yes, TOP258PN is a higher power version of the TOP254PN. It has lower Rds (1.7ohm vs 5.4ohm) and a higher current limit (1.65A vs 1A). It don't see why it could not be compatible.
I think it's worth trying to replace it. Be sure to test it first with the load disconnected in case it blows up
If everything fails, I bet substituting this part of the circuit with a decent 5V PSU should work fine.

[cprogrammer]

Yes, TOP258PN is a higher power version of the TOP254PN. It has lower Rds (1.7ohm vs 5.4ohm) and a higher current limit (1.65A vs 1A). It don't see why it could not be compatible.
I think it's worth trying to replace it. Be sure to test it first with the load disconnected in case it blows up
If everything fails, I bet substituting this part of the circuit with a decent 5V PSU should work fine.

I just finished removing D3709 from the board. It was very difficult to remove. I almost destroyed the copper trace pads, but all ok now. The diode is ok. Also the transformer is fine.

The more I think about it, more I think it is better to have one's own 5v PS. The Yamaha PS is way too complicated for me. The thing I have to figure out is that there is a AC detect line that goes from this board to the digital board. Also there is Relay RY371 that gets powered by Q3802 when you press the push button switch. I think this comes through the connection CB379 via PRY_IN. I can build a PS using LM318 with a pot to select preset 5.6 v output. Tomorrow I have to be at my in-law's place. I will try this on Sat. I have made regulated PS using LM318 before and I do have all components to build one. Meanwhile I have also placed an order for TOP258PN which will take a week or so. The impatience to fix this is killing me.

[cprogrammer]

I just thought of a way to disable the SMPS portion. This my understanding. Please feel free to correct me if I'm wrong. This SMPS is just for standby function. It serves two purposes

1. Enough power so that when you press the power button (soft touch) or the press the power on button on remote, the unit powers on.
2. Provides 5v power supply to the digital board so that the HDMI inputs can be switched even if the AVR is just in standby and not on.

The Yamaha power supply is way too complicated. Primarily because it a SMPS based supply. This PS is not used for any critical function like powering the AMP. The AMP has its own power supply that uses bridge rectifiers and a big capacitor bank. This power supply is turned on by a Relay RY371. This in turn gets turned on through a transistor Q3802.

Steps to disable the in-built Yamaha Power supply and provide our own 5.6 supply. The steps below will ensure most components will get isolated with minimum amount of desoldering.

1. Remove L3701
2. Remove L3702
3. Remove R3712
4. Remove R3710
5. Remove C3710
6. The capacitors C3701, C3717 (.022 uF) will continue to power optocoupler EL816(M) IC375. This is required to provide the AC PWR Detect line.
7. Connect an auxiliary power supply 5.6v on CB379 or use an existing mobile phone charger, etc

My guess is that this should work. Just have to try this out. Tomorrow I will be busy visiting in-laws. I will try this on Sunday. Will post if this results regardless of success or failure

[wraper]

F3701 is all you need to remove to disable it. No need to disconnect its output. However IMHO you are doing yourself a disservice by trying to replace the PSU. Which is extremely simple BTW.

[cprogrammer]

F3701 is all you need to remove to disable it. No need to disconnect its output.

Did you mean L3701?

However IMHO you are doing yourself a disservice by trying to replace the PSU. Which is extremely simple BTW.

I'm not doubting that it is simple for people who have knowledge. But it is way too complicated for me. I really don't like SMPS. Over the years I have had to discard few equipment just because the SMPS failed and I couldn't figure out what had failed. There are too many components in a SMPS and hence multiple points of failure. In at least two cases I have had mosfets failed and never found a replacement. In one case I had a catastrophic failure of the SMPS. I don't mind when the equipment and power supplies are two separate units (like laptops and its charger). SMPS are very efficient but the idea of the 230v mains supply coming inside without a transformer scares me. In contrast it is so easy to repair a transformer based PS and for most of the case the regulator ICs are still available today.

[wraper]

Did you mean L3701?

No, just remove the fuse

I'm not doubting that it is simple for people who have knowledge. But it is way too complicated for me. I really don't like SMPS. Over the years I have had to discard few equipment just because the SMPS failed and I couldn't figure out what had failed. There are too many components in a SMPS and hence multiple points of failure. In at least two cases I have had mosfets failed and never found a replacement. In one case I had a catastrophic failure of the SMPS. I don't mind when the equipment and power supplies are two separate units (like laptops and its charger). SMPS are very efficient but the idea of the 230v mains supply coming inside without a transformer scares me. In contrast it is so easy to repair a transformer based PS and for most of the case the regulator ICs are still available today.

You literally could avoid doing any fault finding, replace all of the components besides the transformer and coils, and spend only a few $ on replacement parts. Not to say you still haven't measured the current consumption.

[cprogrammer]

Did you mean L3701?

No, just remove the fuse

Without the fuse, the relay RY371 will get cut off and also CB378 which goes to the main transformer. So when the power button is pressed, relay RY371 will not activate. That's my understanding. But I have not actually double checked.

The IC TOP254PN is no longer available here. It has a large lead time. I'm thinking of replacing it with TOP258PN, which is readily available in many online stores here in India (including element14). The worst case situation where TOp258PN doesn't work, I will disable the in-built SMPS. Since TOP258PN will take at least a week to arrive, I was thinking of building 5.6v PS using LM318 (I have plenty of these with me).

[wraper]

Without the fuse, the relay RY371

Ok, didn't look on the circuit long enough and didn't notice that fuse was connected to other things besides standby SMPS. Removing L3701 or D3701 will be enough.

[samnmax]

The standby power supply is a switching one for a reason, if you substitute it for a linear PSU, the power consumption may be too much for a device that may be always plugged in. You can judge if that suits your case. Personally, I would wait for the TOP258PN, or else use an existing 5V switching PSU. If you go this way, I agree that you should measure the current in both standby and power on so that you can select the correct substitute PSU.

[cprogrammer]

The standby power supply is a switching one for a reason, if you substitute it for a linear PSU, the power consumption may be too much for a device that may be always plugged in. You can judge if that suits your case. Personally, I would wait for the TOP258PN, or else use an existing 5V switching PSU. If you go this way, I agree that you should measure the current in both standby and power on so that you can select the correct substitute PSU.

Waiting for TOP258PN is exactly I'm doing. It is arriving tomorrow. I have already put a 8 pin 2 row DIP socket in the place where TOP254PN was. So I just have to plug in the new IC when it arrives tomorrow. If that fails, only then will I replace it with a substitute PSU for just the 5.5volts.

EDIT:

In the meanwhile, I have tested all components, except for TL431ACLPR = Voltage References Adj Shunt. All diodes are working as diodes. All caps are in specs. All resistor values match. The other thing I couldn't test is if the 22v zener is working as a 22 volts zener (but it is testing as diode. So i'm assuming it is ok). So I'm almost certain that it was this IC371 behind the problem.

[wraper]

Waiting for TOP258PN is exactly I'm doing. It is arriving tomorrow. I have already put a 8 pin 2 row DIP socket in the place where TOP254PN was. So I just have to plug in the new IC when it arrives tomorrow. If that fails, only then will I replace it with a substitute PSU for just the 5.5volts.

Remove the socket and solder it directly. You are compromising heat transfer to the PCB which acts as a heatsink and worsening insulation.

[cprogrammer]

Waiting for TOP258PN is exactly I'm doing. It is arriving tomorrow. I have already put a 8 pin 2 row DIP socket in the place where TOP254PN was. So I just have to plug in the new IC when it arrives tomorrow. If that fails, only then will I replace it with a substitute PSU for just the 5.5volts.

Remove the socket and solder it directly. You are compromising heat transfer to the PCB which acts as a heatsink and worsening insulation.

Ok. I will solder the IC directly. As an experiment I built a 5.5v power supply using LM317 and connected it the power supply board. The AMP turns on and works, but LM317 is getting very hot. Even in the standby state it is getting hot. It means there is a short somewhere (most probably with Digital (1) board) and probably if i let it continue, LM317 will get bad too. I think that's the reason why the TOP254PN ic went bad. So even if I put the new IC, it will work for sometime and go bad after sometime. You were right in suspecting a short in the digital board.

Now the thing is excessive current is being drawn only when there is AC detect. If I remove C3703 or C3717 or the optocoupler which provides the AC detect, then LM317 no longer heats up. But then the standby led also goes off and the avr can no longer be switched on.

How do I figure out where excessive power is being drawn?

[wraper]

"LM317 gets hot" is not an accurate indication of what's happening unlike actual current consumption you can measure. Did you put LM317 on a heatsink? Size of the heatsink? What is input voltage of LM317?

[cprogrammer]

"LM317 gets hot" is not an accurate indication of what's happening unlike actual current consumption you can measure. Did you put LM317 on a heatsink? Size of the heatsink? What is input voltage of LM317?

I have put a heat sink. and input voltage is 12v AC. I will have to measure the current. I will do it tomorrow. It starts getting hot the moment AC power is provided to  C3703, C3717, optocoupler.

[cprogrammer]

"LM317 gets hot" is not an accurate indication of what's happening unlike actual current consumption you can measure.

Ok. I just figured out how to use the multimeter to measure current. It measures 270mA in standby state and 860mA in powered on state. Should this be OK?

[wraper]

"LM317 gets hot" is not an accurate indication of what's happening unlike actual current consumption you can measure.

Ok. I just figured out how to use the multimeter to measure current. It measures 270mA in standby state and 860mA in powered on state. Should this be OK?

I guess no. Standby current spec is 0.2W (with no things attached) and 270mA means 1.5W not considering PSU losses. 270mA should not cause SMPS overheating and shutting down though.