Solved: Yamaha AVR RX-V667 turns off with PS1 PRT 3L - TOP254PN IC gets very hot - Page 1
Forum section: electronics / repair

author: cprogrammer
author_rank: Contributor
timestamp: November 04, 2021, 09:05:13 am
content: 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.gAC_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.

author: samnmax
author_rank: Regular Contributor
timestamp: November 04, 2021, 01:51:22 pm
content: 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.

author: cprogrammer
author_rank: Contributor
timestamp: November 04, 2021, 02:29:01 pm
content: 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.

author: cprogrammer
author_rank: Contributor
timestamp: November 04, 2021, 03:43:10 pm
content: 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 perhttps://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

author: wraper
author_rank: Unknown
timestamp: November 04, 2021, 03:53:39 pm
content: 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.

author: cprogrammer
author_rank: Contributor
timestamp: November 04, 2021, 04:29:13 pm
content: Quote from: wraper on November 04, 2021, 03:53:39 pmOk. 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.

author: wraper
author_rank: Unknown
timestamp: November 04, 2021, 06:34:58 pm
content: Quote from: cprogrammer on November 04, 2021, 04:29:13 pmIt'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.

author: samnmax
author_rank: Regular Contributor
timestamp: November 05, 2021, 07:21:20 am
content: 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...

author: cprogrammer
author_rank: Contributor
timestamp: November 05, 2021, 08:53:20 am
content: Quote from: samnmax on November 05, 2021, 07:21:20 amI 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 videohttps://youtu.be/SOQX_bldUfM

author: samnmax
author_rank: Regular Contributor
timestamp: November 05, 2021, 12:39:10 pm
content: 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 upIf everything fails, I bet substituting this part of the circuit with a decent 5V PSU should work fine.

author: cprogrammer
author_rank: Contributor
timestamp: November 05, 2021, 01:29:03 pm
content: Quote from: samnmax on November 05, 2021, 12:39:10 pmI 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.

author: cprogrammer
author_rank: Contributor
timestamp: November 05, 2021, 03:17:45 pm
content: 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 purposes1. 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 L37012. Remove L37023. Remove R37124. Remove R37105. Remove C37106. 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, etcMy 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

author: wraper
author_rank: Unknown
timestamp: November 05, 2021, 04:09:35 pm
content: 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.

author: cprogrammer
author_rank: Contributor
timestamp: November 05, 2021, 04:33:51 pm
content: Quote from: wraper on November 05, 2021, 04:09:35 pmDid you mean L3701?Quote from: wraper on November 05, 2021, 04:09:35 pmI'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.

author: wraper
author_rank: Unknown
timestamp: November 05, 2021, 04:59:32 pm
content: Quote from: cprogrammer on November 05, 2021, 04:33:51 pmNo, just remove the fuseQuoteYou 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.

author: cprogrammer
author_rank: Contributor
timestamp: November 05, 2021, 05:11:47 pm
content: Quote from: wraper on November 05, 2021, 04:59:32 pmWithout 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).

author: wraper
author_rank: Unknown
timestamp: November 05, 2021, 05:24:31 pm
content: QuoteOk, 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.

author: samnmax
author_rank: Regular Contributor
timestamp: November 08, 2021, 08:39:19 am
content: 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.

author: cprogrammer
author_rank: Contributor
timestamp: November 08, 2021, 09:05:34 am
content: Quote from: samnmax on November 08, 2021, 08:39:19 amWaiting 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.

author: wraper
author_rank: Unknown
timestamp: November 08, 2021, 10:23:02 am
content: Quote from: cprogrammer on November 08, 2021, 09:05:34 amRemove the socket and solder it directly. You are compromising heat transfer to the PCB which acts as a heatsink and worsening insulation.

author: cprogrammer
author_rank: Contributor
timestamp: November 08, 2021, 03:39:37 pm
content: Quote from: wraper on November 08, 2021, 10:23:02 amOk. 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?

author: wraper
author_rank: Unknown
timestamp: November 08, 2021, 04:03:34 pm
content: "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?

author: cprogrammer
author_rank: Contributor
timestamp: November 08, 2021, 04:10:26 pm
content: Quote from: wraper on November 08, 2021, 04:03:34 pmI 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.

author: cprogrammer
author_rank: Contributor
timestamp: November 08, 2021, 04:29:45 pm
content: Quote from: wraper on November 08, 2021, 04:03:34 pmOk. 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?

author: wraper
author_rank: Unknown
timestamp: November 08, 2021, 04:40:11 pm
content: Quote from: cprogrammer on November 08, 2021, 04:29:45 pmI 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.

author: cprogrammer
author_rank: Contributor
timestamp: November 08, 2021, 04:46:44 pm
content: Quote from: wraper on November 08, 2021, 04:40:11 pmThank you so much for being patient and explaining things. 1.5W makes sense because I have HDMI control on in my settings. As per user manual, power consumption in standby state with HDMI control on and without any HDMI signal is 2.7WI feel overjoyed.Is the heat because I'm using 12v AC as input to LM317. My LM317 is one of those cheap Chinese counterfeits.

author: wraper
author_rank: Unknown
timestamp: November 08, 2021, 04:52:11 pm
content: Different linear regulators will dissipate the same amount of heat given that voltage drop on them and current is the same. 12-5.5=6.5V 6.5V*0.27A=1.76W to dissipate. 6.5V*0.86A=5.6W which is a significant amount of heat.

author: cprogrammer
author_rank: Contributor
timestamp: November 08, 2021, 05:31:23 pm
content: Now that I have an adjustable PS hooked up in place of the original 5.6 volts I can carry out an experiment to simulate PS1 PRT 3L as an academic exercise. I will keep on reducing the voltage and see what happens. I guess I should get PS1 PRT 3L.The original problem was most probably TOP254PN shutting down when it got too hot. My replacement IC will take one more day to arrive as per the latest tracking information from the courier agency. So I can utilize tomorrow to carry out this test.

author: cprogrammer
author_rank: Contributor
timestamp: November 09, 2021, 03:48:38 am
content: Quote from: cprogrammer on November 08, 2021, 05:31:23 pmI indeed get PS1 PRT 3L when I reduce the output on the 5.6v rails.

author: cprogrammer
author_rank: Contributor
timestamp: November 09, 2021, 04:26:13 pm
content: Quote from: samnmax on November 05, 2021, 12:39:10 pmMy IC hasn't yet arrived so I was doing some reading on the TOP25x data sheet. This is what I came across. Should I be worried because of the lower Rds of 1.7 ohm vs 5.4 ohm. Should I put a 4 ohms resistance between pin3 of the IC and the transformer?QuoteAnother thing I noticed. The Rds in off state (resistance between D and S pins) of TOP254PN is around 800 ohms. This almost proves that the IC TOP254PN has gone bad. Am I right in assuming that?

author: wraper
author_rank: Unknown
timestamp: November 09, 2021, 05:20:37 pm
content: Quote from: cprogrammer on November 09, 2021, 04:26:13 pmNoQuoteDo you mean out of circuit? Did you measure it in diode mode? In what direction? MOSFETs have a body diode in opposite direction to normal "polarity" of MOSFET.

author: cprogrammer
author_rank: Contributor
timestamp: November 09, 2021, 05:27:11 pm
content: Quote from: wraper on November 09, 2021, 05:20:37 pmYes, out of the circuit as I have already removed the IC in preparation for the new IC that will most probably come tomorrow. I measured in both directions. With the red pin of multimeter on D and black on S, it gives me around 800 ohms. If I reverse it, it gives me around 700 ohms. No, I didn't measure it in diode mode.

author: wraper
author_rank: Unknown
timestamp: November 09, 2021, 05:31:14 pm
content: Quote from: cprogrammer on November 09, 2021, 05:27:11 pmIf it's really in ohms and not kiloohms, it's not right.

author: cprogrammer
author_rank: Contributor
timestamp: November 09, 2021, 05:35:53 pm
content: Quote from: wraper on November 09, 2021, 05:31:14 pmIt is in ohms and not kilo ohms. Exactly what I thought that it is not right and I think this is the reason why this IC gets super hot and shuts off after a min or so. The surprising thing is that the board is still giving out 5.64 volts output.

author: cprogrammer
author_rank: Contributor
timestamp: November 10, 2021, 03:20:13 am
content: Since I'm replacing TOP254PN with TOP258PN, I need some help. The specs of these two IC are almost the same, except higher wattage for TOP258PN vs TOP254PN and Rds on of 1.7 ohm for TOP258PN vs 5.4 ohm for TOP254PN.Now on page 10 of the datasheethttps://www.mouser.in/datasheet/2/328/tophx_family_datasheet-1511305.pdffor these IC, it saysQuoteNow on page 19 of the datasheet, it illustrates how to use a resistor between the pin M and pin S to limit the current (i have attached the illustration as attachment 1). Now to limit the drain current of TOP258 to be the same as TOP254, I have to limit that to 33%. To do that I have to refer to Figure 55b on page which roughly puts 21K resistor between pin M and S. I have attached the figure as attachment 2.On page 31 of the datasheet for Design checklist, it always says one can put a resistor between the drain and the source pin to limit the resistance. This is what is exactly quotedQuoteSo as per my understanding, there are two ways to replace TOP258PN with TOP254PN.1) Put a resistance between Pin D and Pin S to account for the difference between the Rds on of the two ICs. The difference is 5.4 - 1.7 = 3.7 ohms. My reasoning is that this will require me to put high wattage resistors.2) Put a resistor between Pin M and Pin S and that will automatically limit the drain current to 33% of the typical drain current of TOP258. This allows one to use a higher capacity IC and lowers the heat sink requirement. I find this method better than 1) above as I can use ordinary resistor around 21K to limit the current to 33%. I already have a 22K resistor.Little knowledge can be dangerous. I'm suspecting that could be the thing that will vapourise the yamaha power board when I replace TOP254PN with TOP258PN. Unfortunately TOP254PN isn't available here in India / lead time to order it is too long. Let me know if I'm on the wrong path.

author: floobydust
author_rank: Super Contributor
timestamp: November 10, 2021, 05:20:01 am
content: OP, ensure electrolytic capacitors C3707 47uF 16V, C3708 10uF 50V are perfect. I outright replace these because they are highly stressed, on 24/7 and are essential for the TOP switch IC to work properly. It is common on many SMPS for these get old and dry out, go low value and then the IC blows.

author: cprogrammer
author_rank: Contributor
timestamp: November 10, 2021, 06:38:31 am
content: Quote from: floobydust on November 10, 2021, 05:20:01 amThank you so much. It makes sense. Few days back when this problem occurred and I started checking the values of all capacitors and resistors (I removed them one by one and tested), the only two components that did not match were C3705 (0.1 μF) which measured 0.006 μF) and C3708 (10 μF) which measured 7 μF).I replaced C3705 which was a SMD cap with a ceramic cap (representative image attached below). 10 μF electrolytic capacitor was replaced with a 10 μF 63v.C3707 is still measuring 47 μF. But I don't have a meter which tells me the ESR. So to be on the safe side I will replace C3707 too. Thank you for enlightening me of these two caps. Ever since this problem occurred, I have gained some knowledge in electronics. I think I have gained some knowledge of how a SMPS based power supply works. Few days back I didn't know what a MOSFET was. Even if I fail to repair the PSU, I have managed to make a another (transformer based)PSU using LM317, which I tested to work as a substitute for the SMPS based 5.6v supply. The only issue is that with this substitute, I have to plugin in two power cords to switch on the AVR.

author: wraper
author_rank: Unknown
timestamp: November 10, 2021, 10:10:12 am
content: There is no X terminal in in ICs with PN suffix, so you cannot attach a resistor to that. M pin allows to make current the limit dependent on input voltage, so it's not just adjusting the current limit. Current limit is a protection feature and should not matter during normal operation. So my suggestion is to not bother with that.

author: wraper
author_rank: Unknown
timestamp: November 10, 2021, 10:24:39 am
content: Also their current limits are not so wildly different to bother, 254PN has 1A limit 258PN has 1.65A limit.

author: wraper
author_rank: Unknown
timestamp: November 10, 2021, 10:39:43 am
content: QuoteIf you place a resistor in series of either of them, it will not change the current limit as current is sensed completely internally within the IC. That quote from the datasheet is about something else. It's a way to measure a heat dissipation which would be with ICs with higher RDS(on)

author: samnmax
author_rank: Regular Contributor
timestamp: November 10, 2021, 01:28:33 pm
content: The lower Rds of the TOP258PN is actually a good thing, as it will generate less heat.

author: cprogrammer
author_rank: Contributor
timestamp: November 10, 2021, 01:31:03 pm
content: Thanks to everyone in this forum. A big thanks and lots of gratitude to all of you @wraper, @samnmax, @floobydust. You folks really rock and were a great help to an ignoramus that i'm.I had ordered 2 nos of IC TOP258PN. It came today. But before I put the IC, I replaced one more cap suggested by @floobydust. With bated breath I connected the power supply to this board without connecting it to the AMP. It was a total terror switching on the mains. I connected a voltmeter also to the 5.6v out. Switched on and absolutely no voltage. Feeling sad, I connected back the old malfunctioning IC and the I could see 5.7 volts. Connected the board and the amp switched on. But after a minute or so, the AVR turned off. As usual the diagnostic showed PS1 PRT 3L.With no hope left, I removed the TOP254PN (the malfunctioning one) and connected the the other TOP258PN IC. Connected and switched on the mains and lo and behold, the AVR turns on and stays on. No more PS1 PRT 3L. The new IC doesn't at all get hot. So it looks like I got one bad IC and one good IC out of the two purchased. I will order two more so that this AVR lasts as long as it does. Had this AVR since 2011 and it has been my main system. Amazon firestick, Chromecast, PS4, my HTPC and mac mini are all connected to this AVR. Just didn't want to go through the trouble of buying a new AVR. This one is good enough for my needs.The only difference is that I get 5.46 volts in standby state and 5.42 volts in powered on state. Earlier this used to be 5.64 volts in standby state. I don't remember the voltage in powered on state with the earlier IC.But it looks like, the trouble is behind. Wonder what will happen with slightly below spec of the voltage. To be sure, I turned on the diagnositics by pressing INFO + Tone control + power on button.DC is 50 (within range as per service manual)PS1 / PS2 is 89/86 (withing range as per service manual).

author: samnmax
author_rank: Regular Contributor
timestamp: November 10, 2021, 02:26:56 pm
content: Glad we could help! Hope it lasts at least 10 years more