this technician, while more cooperative than others, is in no way interested in getting to the bottom of this issue. He only interest in quick, easy fix then move on to different jobs. I infact had to beg, nag him since April to take on this project. With that said, I know he definitely dont want to get involve, reading, posting on here....!!. Unfortunately, trying to fix this amp, I have had to research, reading, reach out, beg people to take on the job, push them to do things (that I learned, read on the forums)!!. So far I cost me over $1500 trying to fix it... I know I was a stupid investment... I was hoping by spending a little more, I could save the amp and keep it for another 20 years. Wish I can find some one around here that really know how and interest in solving problem...
There has to be someone in southern CA that can fix this. Maybe someone here can post a recommendation,
or even offer to tackle it themselves.
or even offer to tackle it themselves.
Hi nguyenphananh,
I agree with Ray on finding a good tech in your region.
I'm so sorry for your experience so far. I wish you were in my area.
-Chris
I agree with Ray on finding a good tech in your region.
I'm so sorry for your experience so far. I wish you were in my area.
-Chris
Plan B:
1) test it somewhere else (a friend´s? some local AV shop?)
2) IF it works there, confirming it works fine outside your home (otherwise it would be a scam), sell it, and buy something that works at your home.
1) test it somewhere else (a friend´s? some local AV shop?)
2) IF it works there, confirming it works fine outside your home (otherwise it would be a scam), sell it, and buy something that works at your home.
I wish I can find some one that know how to fix it around here.. I will love to have him/her work on it. If you know some one, please let me know
Like I said... It was a bad investment!!. I was hoping by paying "a little bit more", I can keep this amp for another 20 years. Little by little... by now I already spent too much, cant justify throwing it away. Also I wished I have extra $3-4k to buy another one (then we wont have this problem in the 1st place). Oh well...just have to find way to deal with it....
I know it is not just my home. One of the shops that scammed me turned on and within an hour, the amp went into protection mod. Just that after reset, they stated the amp didnt shut down again... so they dont know what to fix (and charge me $190 flat fee for.... doing nothing!!)
If I know it works reliable outside my house, I would fix whatever wrong at my house to keep it. In fact, I also have another Emotiva amp that works perfect. The Emotiva is perfect for movie, but for hifi music.. it is not even close to Rotel's sound quality.
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Some update: No the unit is not fixed yet!!
Rotel's service bulletin calls for replacement of the 5 resistors (5 channels) and 5 ICs). The original resistors were under voltage (which cause shut down)... so I had them replaced while ago (which didnt fix the issue). Rotel "authorized" technician, while rebuilt the protection circuit, refused to replace the ICs. According to him, these IC are reliable, rarely break down (which cause distortion and shut down if defective, according to Rotel's). Also if 1 of these break down, only 1 channel be shut off, not all 5's (makes sense to me). So I ordered and had a local tv repair shop replaced 5 IC NE5534N. I picked up the amp today. To be cleared, i dont think the amp is fixed yet. But I notice a significant changed!!. Before the replacement of the ICs, the amp ran EXTREMELY HOT!!. Infact it was SO SO HOT that it was uncomfortable to touch!. If you leave your hand on 1 spot for long, you might get burn!!. I always thought that was normal for class AB amp, since my Emotiva amp (which works perfectly fine) also ran very hot. Thats why I had 2 computer fans on the top case to keep cool (yet it still VERY HOT!?). Well, after the ICs replacement, the amp run (after an hour)...... COOL???. Infact, it is barely hotter than the OFF amp??. I temporary removed the 2 cooling fans, it is still running cool... So looks like the ICs have something to do with the heat generated!! Just strange the temperature suddenly dropped significant after the ICs replacement.
P.S. 3 hrs into watching TV, the protection circuit kicked in again (and working fine after I cycled the power on/off. So I know it is not fixed yet. At lease all the recalled parts are new (we can eliminate them as potential causes).
Rotel's service bulletin calls for replacement of the 5 resistors (5 channels) and 5 ICs). The original resistors were under voltage (which cause shut down)... so I had them replaced while ago (which didnt fix the issue). Rotel "authorized" technician, while rebuilt the protection circuit, refused to replace the ICs. According to him, these IC are reliable, rarely break down (which cause distortion and shut down if defective, according to Rotel's). Also if 1 of these break down, only 1 channel be shut off, not all 5's (makes sense to me). So I ordered and had a local tv repair shop replaced 5 IC NE5534N. I picked up the amp today. To be cleared, i dont think the amp is fixed yet. But I notice a significant changed!!. Before the replacement of the ICs, the amp ran EXTREMELY HOT!!. Infact it was SO SO HOT that it was uncomfortable to touch!. If you leave your hand on 1 spot for long, you might get burn!!. I always thought that was normal for class AB amp, since my Emotiva amp (which works perfectly fine) also ran very hot. Thats why I had 2 computer fans on the top case to keep cool (yet it still VERY HOT!?). Well, after the ICs replacement, the amp run (after an hour)...... COOL???. Infact, it is barely hotter than the OFF amp??. I temporary removed the 2 cooling fans, it is still running cool... So looks like the ICs have something to do with the heat generated!! Just strange the temperature suddenly dropped significant after the ICs replacement.
P.S. 3 hrs into watching TV, the protection circuit kicked in again (and working fine after I cycled the power on/off. So I know it is not fixed yet. At lease all the recalled parts are new (we can eliminate them as potential causes).
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The protection IC and the input IC have nothing to do with heating the amplifier.
The idle current is the one that determines the degree of heating of the amplifier, especially at a low level on the output, and this current can be adjusted. Probably the technician adjusted the current to a lower value.
The idle current is the one that determines the degree of heating of the amplifier, especially at a low level on the output, and this current can be adjusted. Probably the technician adjusted the current to a lower value.
Hi nguyenphananh,
I agree with sesebe, you probably ran into a competent technician for a change.
If the input ICs were oscillating, they could have caused the amps to run hot. It is entirely possible that Rotel ran into a batch of fake parts. The 5534 is normally extremely reliable.
One question that just occurred to me. Is it possible a low voltage regulator has failed that powers the op amps? Easily overlooked.
-Chris
I agree with sesebe, you probably ran into a competent technician for a change.
If the input ICs were oscillating, they could have caused the amps to run hot. It is entirely possible that Rotel ran into a batch of fake parts. The 5534 is normally extremely reliable.
One question that just occurred to me. Is it possible a low voltage regulator has failed that powers the op amps? Easily overlooked.
-Chris
I did the measurement like you suggested. Setting the multimeter at Ohms 200. The measurement using the probes between the outer RCA shells (from 1 RCA to another) was ALL 0.4 - 0.5 with BOTH the power On or Off. The resistance (both power On or Off) between the RCA shells and the chasis's ground was 100.7 (all of them). I dont know what these number meant.... just post it here since you suggestted.
Regarding the heat situation, I also emailed and asked the "Rotel technician" who worked on my amp. This is his reply, which inline and similar to what you stated in earlier posts
"....It's interesting about the running temp. While it was here, I had been aware of the heat issue that you mentioned, but that never occurred while here. I also kept looking at the AC current draw (from the AC mains) and it was running at the listed idle current. If the idle current were too high, it would run hot, but it should be able to run hot if the idle current is normal.
There is the possibility that while replacing those ICs, some parameter changed slightly. The input stage runs class A, and might have been affected by the new ICs. The part of that top board (the input board) that does run hot are along the row of heat sinked parts. The one thing that could cause those to run hot are the resistor that were changed by your local guy, and checked out while here. They were correct and installed without any issue...."
I looked at that thread and noted the use of the speaker wire cable brand - Straightwire. I bought some of this exact same type some years ago and found it caused overheating in my amplifiers.
Speaker cable issues have been dismissed as a cause because these were removed and the protection circuit still activated.
That could still happen if the amplifier was excessively hot at the time and needed time to cool down.
+1.
I have already noticed this problem with cables whose conductors are very close or with cables whose conductors are flat and braided.
it can be a good lead
Hi nguyenphananh,
Those readings look good. The readings between gnd shells is made without any cables plugged in. You are showing a 100R resistor between RCA signal common and chassis "ground", which is expected. This is to allow a ground reference, but reduce circulating ground currents. Power on or off doesn't matter for those measurements. Power off preferred or measuring between the shell and signal would probably trip protection on. It would certainly make a huge bang in the speakers if they were hooked up and the amp was on!
Speaker wires that have high capacitance can make many amplifiers unstable and they break into oscillation at a high frequency. This will often cause the heat sinks to get warm or hot, and may even blow the fuse.
Those readings look good. The readings between gnd shells is made without any cables plugged in. You are showing a 100R resistor between RCA signal common and chassis "ground", which is expected. This is to allow a ground reference, but reduce circulating ground currents. Power on or off doesn't matter for those measurements. Power off preferred or measuring between the shell and signal would probably trip protection on. It would certainly make a huge bang in the speakers if they were hooked up and the amp was on!
Speaker wires that have high capacitance can make many amplifiers unstable and they break into oscillation at a high frequency. This will often cause the heat sinks to get warm or hot, and may even blow the fuse.
I really doubt that.
Speaker cables are not the issue, since i have tried multipke times without speaker connected...still same result.
As of right now I am stuck and dont know what else to do. Yesterday i pulled out an old pre amp, a Denon AVR 3805, and connected to the Rotel. 4 hrs into watching movies, the protection circuit kicked in!!. So it is confirmed and eliminated the defective preamp factor....
As of right now I am stuck and dont know what else to do. Yesterday i pulled out an old pre amp, a Denon AVR 3805, and connected to the Rotel. 4 hrs into watching movies, the protection circuit kicked in!!. So it is confirmed and eliminated the defective preamp factor....
Hi, i did this test few days ago and posted the result here. I may have done it wrong, but i got 0Vdc (and 0Vac) on the amp. I didnt meadure the preamp cuz it inside the cabinet...which requires to remove..