RA-820 Manual can be gotten at https://elektrotanya.com/rotel_ra-820.pdf/download.html
Do the not a robot thing, then go to download. Wait about 15 seconds or so, for the green download box to appear. Ignore all the busy ware stuff.
Do the not a robot thing, then go to download. Wait about 15 seconds or so, for the green download box to appear. Ignore all the busy ware stuff.
I haven't been into a RMB-1075, but you can download the tech manual here: https://elektrotanya.com/rotel_rmb-1075.pdf/download.html#dl
It basically looks like a 5 channel version of a RB-991.
Per
It basically looks like a 5 channel version of a RB-991.
Per
Per,
Thank you very much for the reply.
I have downloaded it all there service manuals (as they have two).
I was just wondering as I have one and I use it for my center and surrounds and have had it powered on probably for the past six years without turning it off. Or just turning it off for a very short time and it keeps on chugging along.
Thank you very much for the reply.
I have downloaded it all there service manuals (as they have two).
I was just wondering as I have one and I use it for my center and surrounds and have had it powered on probably for the past six years without turning it off. Or just turning it off for a very short time and it keeps on chugging along.
Hi exojam,
Well, I'll just say this. Failure rate is determined by mostly temperature. Days to failure is more a run hours thing. Additionally, your power company likes to play at night. On top of that, storms that have lightning even far away can put substantial voltage surges on the AC mains. So it doesn't make any sense to run your equipment when you won't be using it. By the way, either equipment has warmed up and stabilized by 20 minutes (we'll give it 1/2 an hour then), it will never settle in. Also, as power demands change, most equipment will heat and cool. So arguments as to why you "should" leave your equipment running are flawed at best.
Don't do that. Don't turn it on and off all day long either, a happy median is what you need, but at least turn it off at night.
Well, I'll just say this. Failure rate is determined by mostly temperature. Days to failure is more a run hours thing. Additionally, your power company likes to play at night. On top of that, storms that have lightning even far away can put substantial voltage surges on the AC mains. So it doesn't make any sense to run your equipment when you won't be using it. By the way, either equipment has warmed up and stabilized by 20 minutes (we'll give it 1/2 an hour then), it will never settle in. Also, as power demands change, most equipment will heat and cool. So arguments as to why you "should" leave your equipment running are flawed at best.
Don't do that. Don't turn it on and off all day long either, a happy median is what you need, but at least turn it off at night.
What Chris said.
Running the amp constantly on for six years is more than 50,000 hours - way beyond the expected lifetime of electrolytic capacitors.
Ok, the caps will not have been running at 85 degC, but even at idling the heat production in the RMB-1075 is probably well over 20W.
Which inside the box means - let's just say an 'elevated warm' temperature.😓
Per
Running the amp constantly on for six years is more than 50,000 hours - way beyond the expected lifetime of electrolytic capacitors.
Ok, the caps will not have been running at 85 degC, but even at idling the heat production in the RMB-1075 is probably well over 20W.
Which inside the box means - let's just say an 'elevated warm' temperature.😓
Per
At the end of the day, you can tell simply by hanging your scope on the filter capacitors (AC coupled) and looking at the ripple waveform.
In this case, those caps have every reason to be defective, but check them anyway. If they are still good - then great. Try and treat your equipment properly from now on.
In this case, those caps have every reason to be defective, but check them anyway. If they are still good - then great. Try and treat your equipment properly from now on.
Well for the first four years I don’t really have a reason why the amp has been staying on for 24x7. It was never anything I read that made me decide to leave it on so let’s just get that clear. As for the past two years, I do have a reason that I don’t feel I need to get into as to why it has been on all day long. I’ll see if I can get the rest of the family to get in the habit of turning it off along with the other amplifier that they do turn on when they need it and off when it’s not needed. I am really not down in the family room anymore to monitor that.
When I get my Adcom under the scope, I’ll try to pull out the Rotel also and see what it looks like.
On a sidenote, none of my equipment runs on basic home, electricity. I have everything running through two 2kVA EquiTech BPT’s. And again this is just a sidenote, as I know, it does not concern my leaving the amp on as I do.
Thank you very much for the replies.
When I get my Adcom under the scope, I’ll try to pull out the Rotel also and see what it looks like.
On a sidenote, none of my equipment runs on basic home, electricity. I have everything running through two 2kVA EquiTech BPT’s. And again this is just a sidenote, as I know, it does not concern my leaving the amp on as I do.
Thank you very much for the replies.
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Hi exojam,
Well, it isn't my deal to examine why you do what you do. Just the technical realities of doing so. You make your own decisions past that.
I would run power amps directly off the mains. Anything in between, no matter how high the current rating, will add impedance. Power amps draw current very dynamically, so minimum resistance is best within reason. Any noise filtering or isolating (you might be better off floating your power than trying to balance it) is the most effective for your source and signal processing equipment.
Sadly, it is the job of the internal power supply and regulators to isolate your electronics from the big bad AC mains. If those are done right, you don't need anything else. Often they are not done well. For all of my systems, they are plugged into the mains directly, on the big system, the power amp only has a straight run to the panel to keep the current draw from bouncing the AC to the rest of the stuff. It's all practical and common sense. I have zero noise issues, and you shouldn't either. Yes, I run turntables so if I had a noise problem, it would be front and centre. Two systems are 98 and 99 dB / watt efficiency. Noise issues will certainly show up there!
Well, it isn't my deal to examine why you do what you do. Just the technical realities of doing so. You make your own decisions past that.
I would run power amps directly off the mains. Anything in between, no matter how high the current rating, will add impedance. Power amps draw current very dynamically, so minimum resistance is best within reason. Any noise filtering or isolating (you might be better off floating your power than trying to balance it) is the most effective for your source and signal processing equipment.
Sadly, it is the job of the internal power supply and regulators to isolate your electronics from the big bad AC mains. If those are done right, you don't need anything else. Often they are not done well. For all of my systems, they are plugged into the mains directly, on the big system, the power amp only has a straight run to the panel to keep the current draw from bouncing the AC to the rest of the stuff. It's all practical and common sense. I have zero noise issues, and you shouldn't either. Yes, I run turntables so if I had a noise problem, it would be front and centre. Two systems are 98 and 99 dB / watt efficiency. Noise issues will certainly show up there!
The way my system runs like:
100 amp circuit breaker panel in the basement feed off main line from the house. The EquiTech’s have one 20 amp line for itself. Than they run up to two outlets per BPT. Than each amp plugs into an outlet. Pretty simple and provide super clean power.
The amps are going to do as you stated above but I rather provide them clean power to start with, super simple and to me worth it.
I also have two of rack mounts Equitechs that I use for my guitar amps. Although I have not been able to play for a long time for personal reasons.
So I have derailed this thread enough so if you care to continue, please shoot me a PM. I may actually have some questions to run by you later on if you do not mind providing me some teaching.
100 amp circuit breaker panel in the basement feed off main line from the house. The EquiTech’s have one 20 amp line for itself. Than they run up to two outlets per BPT. Than each amp plugs into an outlet. Pretty simple and provide super clean power.
The amps are going to do as you stated above but I rather provide them clean power to start with, super simple and to me worth it.
I also have two of rack mounts Equitechs that I use for my guitar amps. Although I have not been able to play for a long time for personal reasons.
So I have derailed this thread enough so if you care to continue, please shoot me a PM. I may actually have some questions to run by you later on if you do not mind providing me some teaching.
I think that it is maybe time to go back to the original theme for this thread - improving the Rotel RA-820AX. (Remember that?)
I recently had three 820'ies in for upgrading and was almost done with the first when I noticed some strange MHz spikes on the scope trace. Hmm.
OK, the upgrade includes faster semiconductors and higher overall open loop feedback, but I had never seen that before. So I started to poke around the Miller caps and other possible places to try to find the root cause of these spikes - no response. Warning: Kids - do not try this at home!!
Until, in my desperate wisdom, I tried to put a 100nF cap that happened to be lying around - across the speaker terminals.
By the time I had pressed and the scope had finished the Autoset process - the channel's driver emitter resistors burst into fire.🔥 Power off!
No transistors or heat sinks felt hot and no fuses were blown. The speaker protection relay circuit had not clicked. But the channel was very dead.
And so were all drivers, all power transistors and their 0.22R 2W emitter resistors!
What happened? -- (Why am I asking you this? - How would you know?)
Except perhaps those that have studied Doug Self's books more closely than me. In the chapter on Output Networks / Output Inductors he writes:
I can now definitely second that.
The RA-820 has no output inductor (actually very few Rotels have) and no Zobel network (although the pcb is clearly prepared for that).
Instead, it uses a 0.22R 2W series output resistor (not sure if it is wirewound or metal oxide) - and not sure what that resistor should do - or protect.
Admittedly, in normal use without letting a nosey plonker like me anywhere near it - all is absolutely fine and the amp is totally stable.
PS. I found the reason for the spikes on the scope - my trusted old Tek TDS210 was saying its last goodbye with this final spiking prank on me.
Well, RIP old mate and thank you for the 40 years.
(And hello again to my even older Philips PM3375, which sprang back into life with just a little bit of TLC. Oh, the blessings of the analogue scope option).
Per
I recently had three 820'ies in for upgrading and was almost done with the first when I noticed some strange MHz spikes on the scope trace. Hmm.
OK, the upgrade includes faster semiconductors and higher overall open loop feedback, but I had never seen that before. So I started to poke around the Miller caps and other possible places to try to find the root cause of these spikes - no response. Warning: Kids - do not try this at home!!
Until, in my desperate wisdom, I tried to put a 100nF cap that happened to be lying around - across the speaker terminals.
By the time I had pressed and the scope had finished the Autoset process - the channel's driver emitter resistors burst into fire.🔥 Power off!
No transistors or heat sinks felt hot and no fuses were blown. The speaker protection relay circuit had not clicked. But the channel was very dead.
And so were all drivers, all power transistors and their 0.22R 2W emitter resistors!
What happened? -- (Why am I asking you this? - How would you know?)
Except perhaps those that have studied Doug Self's books more closely than me. In the chapter on Output Networks / Output Inductors he writes:
"When a shunt capacitor is placed across a resistive load in this way, and no output inductor is fitted,
it is usually found that the value with the most destabilising effect is nearer 100 nF than 2 uF."
it is usually found that the value with the most destabilising effect is nearer 100 nF than 2 uF."
I can now definitely second that.
The RA-820 has no output inductor (actually very few Rotels have) and no Zobel network (although the pcb is clearly prepared for that).
Instead, it uses a 0.22R 2W series output resistor (not sure if it is wirewound or metal oxide) - and not sure what that resistor should do - or protect.
Admittedly, in normal use without letting a nosey plonker like me anywhere near it - all is absolutely fine and the amp is totally stable.
PS. I found the reason for the spikes on the scope - my trusted old Tek TDS210 was saying its last goodbye with this final spiking prank on me.
Well, RIP old mate and thank you for the 40 years.
(And hello again to my even older Philips PM3375, which sprang back into life with just a little bit of TLC. Oh, the blessings of the analogue scope option).
Per
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Hiya Per!
Completely predictable. Some manufacturer's have a phobia about output inductors (they are not evil!!!) and zobels. These components are important for stabilizing amplifiers. Excluding them saves money, and sometimes can be spun into a story about superior design (not!).
I have seen amps blow up due to destabilizing capacitive loads. That would be some speakers and some stupid speaker wire. One an amplifier breaks into full oscillation, two things happen. The output waveform is limited only by supply voltage. and the frequencies are normally so high that both banks of outputs are on at the same time. The only things that limit current are the emitter resistors and power supply impedance. Hence your completely destroyed output stage.
It is also very common for the amplifier to need recompensating when you change output transistors types. Also, non-inductive emitter resistors buy you phase margin. Simply using inductive emitter resistors for replacement can make an amplifier unstable (okay, we'll spin it - "conditionally stable" lol!). The old test was a 10 kHz square wave and you look at the edges, 1 KHz if the response wasn't that high.. A Bode plot would also show this, but you have to remove input circuit filtering to do that.
That Philips oscilloscope is a very good 'scope. Good choice. I have a PM 3070 and PM 3365A along with my others, and these have the best traces. Very sharp and clean compared to any of my Tek scopes. My HP scopes have better traces than my Tek scopes as well.
-Chris
Completely predictable. Some manufacturer's have a phobia about output inductors (they are not evil!!!) and zobels. These components are important for stabilizing amplifiers. Excluding them saves money, and sometimes can be spun into a story about superior design (not!).
I have seen amps blow up due to destabilizing capacitive loads. That would be some speakers and some stupid speaker wire. One an amplifier breaks into full oscillation, two things happen. The output waveform is limited only by supply voltage. and the frequencies are normally so high that both banks of outputs are on at the same time. The only things that limit current are the emitter resistors and power supply impedance. Hence your completely destroyed output stage.
It is also very common for the amplifier to need recompensating when you change output transistors types. Also, non-inductive emitter resistors buy you phase margin. Simply using inductive emitter resistors for replacement can make an amplifier unstable (okay, we'll spin it - "conditionally stable" lol!). The old test was a 10 kHz square wave and you look at the edges, 1 KHz if the response wasn't that high.. A Bode plot would also show this, but you have to remove input circuit filtering to do that.
That Philips oscilloscope is a very good 'scope. Good choice. I have a PM 3070 and PM 3365A along with my others, and these have the best traces. Very sharp and clean compared to any of my Tek scopes. My HP scopes have better traces than my Tek scopes as well.
-Chris
Yes, and the heat-up of a MHz rail to rail oscillation is incredibly fast - you'll never notice what happened inside the trannies.
"Destroyed in (milli)seconds"
BTW, any thoughts on air core inductors vs. ferrite cored for this application?
A bit off-topic on the PM3375:
You never truly realise what an 8 bit digital scope pixel trace can mask away until you switch to the near infinite resolution of an analogue scope.
That said, the digital part of the Philips PM 3375 is pretty darn good too, and I specially like the easy one-button-press switch between the two.
Here, all I needed to do was to replace the incandescent pilot lamp in the display with two white micro LEDs.
But just getting access to that part of the scope was quite an operation. So many parts and pcbs inside that box!
The small fan on the back has also gone quite noisy, I will have to put in a modern silent one.
Anyway, the engineering and quality is impressive - probably explains why Fluke decided to acquire that part of Philips.
(Or was it just to get rid of a major competitor)?
"Destroyed in (milli)seconds"
BTW, any thoughts on air core inductors vs. ferrite cored for this application?
A bit off-topic on the PM3375:
You never truly realise what an 8 bit digital scope pixel trace can mask away until you switch to the near infinite resolution of an analogue scope.
That said, the digital part of the Philips PM 3375 is pretty darn good too, and I specially like the easy one-button-press switch between the two.
Here, all I needed to do was to replace the incandescent pilot lamp in the display with two white micro LEDs.
But just getting access to that part of the scope was quite an operation. So many parts and pcbs inside that box!
The small fan on the back has also gone quite noisy, I will have to put in a modern silent one.
Anyway, the engineering and quality is impressive - probably explains why Fluke decided to acquire that part of Philips.
(Or was it just to get rid of a major competitor)?
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You would want an air core inductor. An Iron core would require fewer turns of wire, making DCR much lower but it isn't a problem here. That and you really don't want anything with a B-H curve. If you aren't careful you may also have core saturation issues too, air cores cannot saturate. Basically, copy what everyone else does. A 10R resistor in parallel damps the inductor and limits impedance rise.
Nice recovery on the scope. My lamps are still okay, but I have had to get into that area before. The fan was never quiet, even new. My original PM3070 didn't have a fan, but did have a spot for one. Now it does (factory post install).
Fluke wanted into this segment of the T&M market. They bought Philips T&M division (I thought they originally partnered with it). But Philips as a company is cheap. I suspect they saw the R&D costs for this market segment going beyond what they wanted to spend and wanted out. Philips then bought into the medical instruments market through Agilent. Really well made stuff got cheaply made in true Philips fashion.
Yes, in analogue mode these are super 'scopes!! That's why I bought the PM 3070. Later I got the PM 3365A. It does store large features so you can measure them well. At 8 bit, it does really well.
Nice recovery on the scope. My lamps are still okay, but I have had to get into that area before. The fan was never quiet, even new. My original PM3070 didn't have a fan, but did have a spot for one. Now it does (factory post install).
Fluke wanted into this segment of the T&M market. They bought Philips T&M division (I thought they originally partnered with it). But Philips as a company is cheap. I suspect they saw the R&D costs for this market segment going beyond what they wanted to spend and wanted out. Philips then bought into the medical instruments market through Agilent. Really well made stuff got cheaply made in true Philips fashion.
Yes, in analogue mode these are super 'scopes!! That's why I bought the PM 3070. Later I got the PM 3365A. It does store large features so you can measure them well. At 8 bit, it does really well.