Hello to you all, I've posted the text below as a reply to an old thread but thought might as well start a new one. I have this Rotel RSX-972 amplifier. At first I thought it was completely dead. It did nothing when I pushed the power button. At one moment I left it when still had it powered on, I was doing something else and after about 5 minutes I heard the relay click.. No display or what ever but it kept clicking. Was happy since there was something alive. Opened it up and saw some bad solder joints. resolderded them, still the same. Now pulled the front off and did the same. Turned on and the display turned on and off with the relay click. Been puzzling around and came at the point it stayed on and actually produced sound. So happy again, put it all back together and... nothing. Started to test the different boards by pulling out the inside cables of their sockets and figured out that when I left the cable to the front out, and turned it on it clicked instantly. When I put the cable back in it again took a while and the clicking (front blinking with is as well)interval started to go faster and faster until it reached the point it stays on. So my assumption is something takes too long to get to the minimal amount of current to keep everything on. Any suggestions what this could be? I already changed the capacitors in the power supply but this doesn't work... I am on a dead end now and would be very happy if I get this Rotel working again since it is a very nice piece! Help would be appreciated! Cheers
I believe the uP featured a super-cap for memory retention. Make sure it's operable.
Testing all PA channels for DC offset is quickest test of health. Perhaps this will get you started... Let us know what you encounter.
TTYL
Testing all PA channels for DC offset is quickest test of health. Perhaps this will get you started... Let us know what you encounter.
TTYL
Many thanks for your reply, mostly appreciated! I already replaced the memory cap, saw people mention it online. I’ve measured the offset from the different channels with multimeter on 2000m:
C=279
SL=279
SR=277
FL=281
FR=277
Maybe worth mentioning that with all the internal boards connected no relais clicks. The values climbed slowy up to the ones above.. when I disconnect the cable from the digital board to the front panel relay starts clicking..
C=279
SL=279
SR=277
FL=281
FR=277
Maybe worth mentioning that with all the internal boards connected no relais clicks. The values climbed slowy up to the ones above.. when I disconnect the cable from the digital board to the front panel relay starts clicking..
If I'm interpreting correctly, all five channels read almost 300mV. Are you measuring them at the speaker binding posts? These seem a bit high, but all remarkably similar. 100mV or lower is generally regarded as acceptable. However, I've not been able to find a spec in the service manual for output offset error or for bias current adjustment. Am I overlooking it?
I'm a bit confused---- are you still experiencing fault issues? Are you telling me that "disconnect[ing] the cable from the digital board to the front panel relay starts clicking" allows fault relays to close and deliver audio to the speakers? Would you provide more detail? The only relay I've been able to discover is a relay that applies power to the main power transformer. Can you confirm that for me?
For now, I'll assume that your issue is due to excessive DC offset in the PAs, though that's not entirely clear. Before tackling offsets in five power amp stages, I'd like to understand what the system will require--- i.e. a "specification" that we may have to infer if we can't find it in documentation. Each of the five amps appears to have a "DC" signal (eg. coming via RL245 at the FL-OUT). Each of the five DC signals is summed into one DC line and passes to connector CN205, near upper right corner on page 27 of the manual. The schematic claims it connects the MAIN CN205. I can't find the claimed destination on a Main board. Can you help me locate it?
Thanks!
I'm a bit confused---- are you still experiencing fault issues? Are you telling me that "disconnect[ing] the cable from the digital board to the front panel relay starts clicking" allows fault relays to close and deliver audio to the speakers? Would you provide more detail? The only relay I've been able to discover is a relay that applies power to the main power transformer. Can you confirm that for me?
For now, I'll assume that your issue is due to excessive DC offset in the PAs, though that's not entirely clear. Before tackling offsets in five power amp stages, I'd like to understand what the system will require--- i.e. a "specification" that we may have to infer if we can't find it in documentation. Each of the five amps appears to have a "DC" signal (eg. coming via RL245 at the FL-OUT). Each of the five DC signals is summed into one DC line and passes to connector CN205, near upper right corner on page 27 of the manual. The schematic claims it connects the MAIN CN205. I can't find the claimed destination on a Main board. Can you help me locate it?
Thanks!
Thanks again for all the effort already! Cant rind cn205 as well, but when I look in the amp and on the green assembly pic on pag. 21 on the left. That connects to CP908 on page 23 bottom right. In the scheme I can find that one on page 32 right below “power supply”, doe that help? Also at the moment I dont get any sound out of it since it isnt going at all.. even front display isnt turning on because of the relais clicking all the time(only when I disconnect the digital board CP553).. multimeter setting was 2000m so I suppose the values are a bit high as you mention. If you need more info please tell! Thanks again!!
Cable to CP908 is three conducors?
If yes, make sure no speakers connected and unplug this cable--- I believe it will disable protection circuit. Does relay stay activated?
If this is the case, measure DC output at all 5 channels.
If yes, make sure no speakers connected and unplug this cable--- I believe it will disable protection circuit. Does relay stay activated?
If this is the case, measure DC output at all 5 channels.
3 wires correct, with digiboard connected no relay, without still clicking.. al 5 measured, with cp908 disconnected, between 385 and 395..
It's very strange that all have so uniformly excessive output offset. Suggestive of some systematic problem, but I can't imagine what.
Would you report voltages
Base QL201
Base QL202
+ terminal of CL206
Output FL-OUT
Please measure with black lead on chassis ground, and report signed voltages, eg. -380mV
Thank you!
P.S. I'm traveling. You might not hear from for 12 hours.
Would you report voltages
Base QL201
Base QL202
+ terminal of CL206
Output FL-OUT
Please measure with black lead on chassis ground, and report signed voltages, eg. -380mV
Thank you!
P.S. I'm traveling. You might not hear from for 12 hours.
Base QL201 -> 890mv (between both legs 580mv)
Base QL202 -> 890mv (between both legs 559)
+terminal CL206 -> 328mv
FL out -> 278
All this with CP908 and digiboard connected..
Holidays? Cheers again!
Base QL202 -> 890mv (between both legs 559)
+terminal CL206 -> 328mv
FL out -> 278
All this with CP908 and digiboard connected..
Holidays? Cheers again!
Would you measure voltage across RL212? What kind of voltmeter are you using?
To be very specific, with meter leads probing directly across RL212 rather than with meter lead connected to ground.
To be very specific, with meter leads probing directly across RL212 rather than with meter lead connected to ground.
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I'm still not understanding details. Relay is no longer clicking, i.e. no longer in protection mode? Does disconnecting CP908 have any effect upon protection behavior?
Amp offset voltages seem a bit high, but are there any other remaining problems?
When I push power on, nothing happens. When i disconnect the cable from the digital board (cp553) Relay starts clicking. I’m using a digital multimeter.
With probes left and right of the resistor(language barrier here, sorry) no volts, resitance vakue of 1440 with mm on 2000ohms. No voltage coming through. With black on chassis 488 mv.
I also noticed with CP 908 disconnected the values from the offset are higher but it takes about 30 seconds to reach that value.. it climbs up very slowly.. with cp908 connected it also climbs up slow but not that slow..
With probes left and right of the resistor(language barrier here, sorry) no volts, resitance vakue of 1440 with mm on 2000ohms. No voltage coming through. With black on chassis 488 mv.
I also noticed with CP 908 disconnected the values from the offset are higher but it takes about 30 seconds to reach that value.. it climbs up very slowly.. with cp908 connected it also climbs up slow but not that slow..
And no, only when clicking protection mode is kicking in with clicking. When not clicking relais is dead and nor doing anything.. voltage in the power amp though with measurements as above.. I believe the relay is just for standby mode?
The other things are that the whole unit isnt turning on at the moment, no frontdisplay because in my opinion the preamp part is unable to stay powered..
Maybe I'm finally starting to understand.
I thought you were having a protection mode problem caused by power amp offset error, a common failure in general--- but a faulty assumption on my part. If I understand correctly, the amp won't even power-on unless you intervene by disconnecting a cable--- right? I still can't spot the cable (cp553) or identify which circuit boards are being disconnected. Would you refer to specific pages and both ends of the cable so that I can locate which two PCBs are involved? I know I'll be embarrassed when it becomes clear.
So far, I locate only a single relay (RLY901) on page 33; it applies power to the main power transformer. Are there other relays I'm not spotting?
Thanks again.
I thought you were having a protection mode problem caused by power amp offset error, a common failure in general--- but a faulty assumption on my part. If I understand correctly, the amp won't even power-on unless you intervene by disconnecting a cable--- right? I still can't spot the cable (cp553) or identify which circuit boards are being disconnected. Would you refer to specific pages and both ends of the cable so that I can locate which two PCBs are involved? I know I'll be embarrassed when it becomes clear.
So far, I locate only a single relay (RLY901) on page 33; it applies power to the main power transformer. Are there other relays I'm not spotting?
Thanks again.
I’ll do that in a minute, am busy cleaning the thing now, lots of nicotine in it(picked it up second hand for €20).. I see one thing now that is weird, my knowledge isnt that great.. in the picture, the “white” thing from front L, is the other way around compared to the other ones..
Attachments
CP553 (not 552) can be found on the digital board, pag. 22 bottem left corner, and pag 28 on the bottom next to text “digital board”.. and no there is only one relay!