I have a non-working Pioneer SC-85 receiver that's been scrapped for parts. I still have all of the original power supply boards/transformer, and the class D amplifier assembly board, seen here: Imgur: The most awesome images on the Internet
Is it feasible to connect the output of a separate preamplifier to the input terminals on this board, in order to make use of the 9 amplifiers?
I've labeled what I think are the input terminals in the last image in the album.
The schematics for a similar receiver can be seen here: PIONEER SC-87,89,LX78,LX88.pdf | Electrical Connector | Electronic Engineering.
So far, all I've managed to do is get the per-channel relays to pull in, by shorting each "RY" terminal to "XDCERR", on the FFC connector on the bottom left of the board. I tried connecting a preamp to the FR+ and FR- terminals at the top left of the board, but didn't a high-level signal coming off of the speaker terminals.
Thank you!
Is it feasible to connect the output of a separate preamplifier to the input terminals on this board, in order to make use of the 9 amplifiers?
I've labeled what I think are the input terminals in the last image in the album.
The schematics for a similar receiver can be seen here: PIONEER SC-87,89,LX78,LX88.pdf | Electrical Connector | Electronic Engineering.
So far, all I've managed to do is get the per-channel relays to pull in, by shorting each "RY" terminal to "XDCERR", on the FFC connector on the bottom left of the board. I tried connecting a preamp to the FR+ and FR- terminals at the top left of the board, but didn't a high-level signal coming off of the speaker terminals.
Thank you!
From what I can see in the pictures, the board takes:
- Main power supply: +/-62V
- Gate drive supply: +15V referenced to -62V
- Signal processing supply: +/-12V
- Another unknown supply: +/-12V
- Another unknown supply: +/-8V
- Digital sequential interface, maybe for a latch: DATA, CLK, OE.
- Standby, mute, ready, error and temperature signals.
Of course, a way to use the board can be found, but some skill and some intensive reverse-engineering is required. Enables or relays may be driven from a latch with serial input. Some lines may be bidirectional. Studying the bottom side of the board is required.
- Main power supply: +/-62V
- Gate drive supply: +15V referenced to -62V
- Signal processing supply: +/-12V
- Another unknown supply: +/-12V
- Another unknown supply: +/-8V
- Digital sequential interface, maybe for a latch: DATA, CLK, OE.
- Standby, mute, ready, error and temperature signals.
Of course, a way to use the board can be found, but some skill and some intensive reverse-engineering is required. Enables or relays may be driven from a latch with serial input. Some lines may be bidirectional. Studying the bottom side of the board is required.
I see there 3 issues, most of them already mentioned by Eve but let me put a different perspective on it:
The infrastructure: case, power supply/voltages, cooling (fan) etc. - solvable or even easily done.
Status handling: Standby, mute, ready, error and temp - doable, takes effort and time, some could be ignored (standby, mute, ready) or hard wired.
Digital interface: You have to analyze the data stream, protocol, commands, settings, user interface. That would mean a huge investment in time, programming (i.e. arduino or Raspberry Pi) to rebuild the functions completely. Immense time investment and quite some money if you don't have such a platform already. If you don't do such development and programming already, try to shut these things down, hard wire them or try to remove them altogether. If that's not an option and functions of it are needed (sry, didn't look at the service manual, page stopped working), it's better to drop the project and go for other amps or actually buy a different SC-85. I know, that's not the question and not a real solution but that shows how severe this point is.
The infrastructure: case, power supply/voltages, cooling (fan) etc. - solvable or even easily done.
Status handling: Standby, mute, ready, error and temp - doable, takes effort and time, some could be ignored (standby, mute, ready) or hard wired.
Digital interface: You have to analyze the data stream, protocol, commands, settings, user interface. That would mean a huge investment in time, programming (i.e. arduino or Raspberry Pi) to rebuild the functions completely. Immense time investment and quite some money if you don't have such a platform already. If you don't do such development and programming already, try to shut these things down, hard wire them or try to remove them altogether. If that's not an option and functions of it are needed (sry, didn't look at the service manual, page stopped working), it's better to drop the project and go for other amps or actually buy a different SC-85. I know, that's not the question and not a real solution but that shows how severe this point is.
To make it funnier the service manual does not include full schematics, only protection cicuit blocks. Pictures of bottom side of PCB will reveal if the logic interface is just feeding a latch for multiplexing some enable or status signal, or if there is a MCU. A latch has a straight protocol (enter all the bits sequentially, then enable output). A MCU won't be as simple.
EDIT: Given the fact that all input connectors include +/-12V it could happen that the board that plugs in vertically in all them is used for +/-12V distribution through channels.
EDIT: Given the fact that all input connectors include +/-12V it could happen that the board that plugs in vertically in all them is used for +/-12V distribution through channels.
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I just realized, I've misspelled your name, Eva. I'm really sorry, didn't mean to mutilate your name. 🙁
I just realized the power supply is extremely underdesigned. And by that I mean really vastly! The amp promises 200W per channel maximum power at only 2 channes driven. It means these two channels together have an output of 400W, without calculating any losses, controlling electronics, display, effects, heat - but the amp maximum power consumption with all losses included is maximum 330W, at least if it's true what's in it's official spec sheet. Looking at the cooling (just the simple, slim L-shaped aluminium profile) it will probably have problems dissipating that power. But how much is it really able to deliver? 330W/9 equals only 36,6W per channel (no losses, which is ofcourse impossible). 😱
To make it a really decent amplifier, you'd have to replace the power supply, the cooling, the control panel for all channels (or a bunch of pre-amplifiers), the case, the protections and a lot of work. Seeing that, it's probably not worth modifying it at all.
I just realized the power supply is extremely underdesigned. And by that I mean really vastly! The amp promises 200W per channel maximum power at only 2 channes driven. It means these two channels together have an output of 400W, without calculating any losses, controlling electronics, display, effects, heat - but the amp maximum power consumption with all losses included is maximum 330W, at least if it's true what's in it's official spec sheet. Looking at the cooling (just the simple, slim L-shaped aluminium profile) it will probably have problems dissipating that power. But how much is it really able to deliver? 330W/9 equals only 36,6W per channel (no losses, which is ofcourse impossible). 😱
To make it a really decent amplifier, you'd have to replace the power supply, the cooling, the control panel for all channels (or a bunch of pre-amplifiers), the case, the protections and a lot of work. Seeing that, it's probably not worth modifying it at all.
I appreciate everyone's help on this. You've both made it clear to me that what I had originally hoped to accomplish is more complex than I'd anticipated.
Eva,
I do have all of the original power supply hardware, and I believe it is still capable of delivering the indicated voltages to the board.
I did try powering up the amplifier board with the vertical board connected, and did see +/-12V on the indicated contacts, which led me to believe that the 12V was being passed "through" the amplifier board, and on to something upstream (preamp?).
I will take photos of the bottom of the board as soon as I get home.
ICG,
My initial assumption (hope) was that this digital interface you describe ultimately ends up "deciding" whether or not to pull in a relay that interrupts the signal path to between the preamplifier and amplifier, and that by energizing this relay coil directly, I could effectively bypass the entirety of the interface in one fell swoop. From my very weak grasp on the information that both of you have provided, I gather I was incorrect.
Eva,
I do have all of the original power supply hardware, and I believe it is still capable of delivering the indicated voltages to the board.
I did try powering up the amplifier board with the vertical board connected, and did see +/-12V on the indicated contacts, which led me to believe that the 12V was being passed "through" the amplifier board, and on to something upstream (preamp?).
I will take photos of the bottom of the board as soon as I get home.
ICG,
My initial assumption (hope) was that this digital interface you describe ultimately ends up "deciding" whether or not to pull in a relay that interrupts the signal path to between the preamplifier and amplifier, and that by energizing this relay coil directly, I could effectively bypass the entirety of the interface in one fell swoop. From my very weak grasp on the information that both of you have provided, I gather I was incorrect.
I have to admit, I don't know if it's actually possible or not to bypass all that or not. You can probably cut off a lot of the circuits controlling the amps, but you have to replace some of them and lose control over different things and functions and not everything can be replaced. But the service manual does not provide enough information about what does exactly what - that alone dimishes chances a lot to get it easily done. I am also not sure if you can get enough help remotely (forum) to solve all the problems. I haven't found any datasheet on the amp ICs yet, but maybe someone else got some ideas to use the board or the amplifiers.
I'm sad and sorry because I'd really like to help and find myself unable to provide anything truely helpful. 🙁
I'm sad and sorry because I'd really like to help and find myself unable to provide anything truely helpful. 🙁
This class D technology is probably subcontracted, "ICE-something" named nodes in the schematic resembles "ICEpower". The power supply technology is from the age where SMPS were used only in space shuttles. In youtube there are videos showing the new Pioneer dance speakers, a copy of Funktion One, but that brand is a renewal of old Turbosound... Few things new under the sun.
Fault sources on a channel per channel basis are: IRS2092 protection/enable, DC protection, HF protection.
Standby function, mute function, rails protection and fan/thermal protection seem to be common to all channels.
The relays may be tied to IRS2092 enable for gating some channels or others, or may use separate activation.
Fault sources on a channel per channel basis are: IRS2092 protection/enable, DC protection, HF protection.
Standby function, mute function, rails protection and fan/thermal protection seem to be common to all channels.
The relays may be tied to IRS2092 enable for gating some channels or others, or may use separate activation.
Eva,
Photos of the back of the board can be seen here: Imgur: The most awesome images on the Internet
I really can't say enough how grateful I am to both of you for your help. This is my first time digging in to the guts of an amplifier, my first time posting to this board, and I'm blown away by the work you've both put in to helping me.
My motivation to get this thing going stems from having recently finished building a set of LXmini+2 speakers, seen here: LXmini design. It's an actively crossed-over design, so I need six channels of amplification. The relatively low power requirements of the speakers had me thinking the old receiver amplifier would be suitable, in spite of its unimpressive specifications.
I've started acquiring parts for a more fully "DIY" amplifier, utilizing six Hypex UcD180HG with HxR modules. The parts should arrive within the next three months, so with a little patience, I'll be good to go. In the meantime, I'll take one last stab at bypassing as much as I possibly can on the Pioneer amplifier, without worrying too much about rendering it unusable (I won't connect it to any speaker of significant value to me, either).
Again, thank you for all of your help!
Photos of the back of the board can be seen here: Imgur: The most awesome images on the Internet
I really can't say enough how grateful I am to both of you for your help. This is my first time digging in to the guts of an amplifier, my first time posting to this board, and I'm blown away by the work you've both put in to helping me.
My motivation to get this thing going stems from having recently finished building a set of LXmini+2 speakers, seen here: LXmini design. It's an actively crossed-over design, so I need six channels of amplification. The relatively low power requirements of the speakers had me thinking the old receiver amplifier would be suitable, in spite of its unimpressive specifications.
I've started acquiring parts for a more fully "DIY" amplifier, utilizing six Hypex UcD180HG with HxR modules. The parts should arrive within the next three months, so with a little patience, I'll be good to go. In the meantime, I'll take one last stab at bypassing as much as I possibly can on the Pioneer amplifier, without worrying too much about rendering it unusable (I won't connect it to any speaker of significant value to me, either).
Again, thank you for all of your help!
Found a service manual with a bit more info here: PIONEER SC-89 SC-87 RRV4550 AV RECEIVER Service Manual free download, schematics, eeprom, repair info for electronics
This manual is the one I downloaded too. Only partial schematics. The important sections are missing. The enable logic for IRS2092 and relays is not shown.
Fortunately there are no logic ICs or MCUs on the bottom side of the PCB.
There is one 16 pin TSSOP IC between 4th and 5th channel (left to right) on top of signal/12V connectors. There is another 14 pin TSSOP IC between 5th and 6th channels. These could be shift registers, like 74HC164 or 74HC165, with 8 outputs, driven from DATA, CLK and OE signals, which can convert 1 bit serial to 8 parallel to drive the enables, or ever vice-versa to read shutdowns. What are the part numbers? What is written on the chips?
Apart from that, there are some fundamentals to multi-channel amplifier module operation. Essentially:
- The module has to be put out of "standby mode". Power mode. There is a "STB" signal but the polarity and voltage level is not clear. Probably 5V, but don't know if active high or low.
- If no faults present (XOLERR, XBERR, XDCERR, XTEMPERR5), the module has to be put out of "mute mode". There seem to be separate mute inputs for channels or groups of channels (ICEMUTEA, ICEMUTESB, MUTEFH), again the level and polarity is not known.
- If faults still not present, the relays have to be enabled, there seem to be signals for that too (RY_FW, RY_AF, RY_CR, RY_FH, RY_B), again the level and polarity is not known.
- If faults present, usually critical faults automatically turn off something ("latched off") apart from sending a signal to main microcontroller, thus requiring a "rearm" sequence for enabling again, while mild faults just send a signal to main microcontroller which responds with some action to alleviate the problem.
There is also another possible function for the 16 and 14 pin ICs near signal connectors, these could be logic gates for combining channels into drive signals and vice-versa, or could be latches so that some faults result in latching off some channels or relays.
And one more hint: The IRS2092 is enabled through pin 5 "CSD", the pin has internal pull-up by default (becomes a pull down if there is a short circuit, so that connecting a capacitor results in a timed disable/enable cycle, the pull down turns back into pull up when CSD voltage goes low enough, but circuit driving CSD can be more complex). The enable of the IRS2092 can be reverse engineered following pin 5. The enable of the relays can be reverse engineered too. Or it can be just tweaked/hardwired, but then protections are lost.
Fortunately there are no logic ICs or MCUs on the bottom side of the PCB.
There is one 16 pin TSSOP IC between 4th and 5th channel (left to right) on top of signal/12V connectors. There is another 14 pin TSSOP IC between 5th and 6th channels. These could be shift registers, like 74HC164 or 74HC165, with 8 outputs, driven from DATA, CLK and OE signals, which can convert 1 bit serial to 8 parallel to drive the enables, or ever vice-versa to read shutdowns. What are the part numbers? What is written on the chips?
Apart from that, there are some fundamentals to multi-channel amplifier module operation. Essentially:
- The module has to be put out of "standby mode". Power mode. There is a "STB" signal but the polarity and voltage level is not clear. Probably 5V, but don't know if active high or low.
- If no faults present (XOLERR, XBERR, XDCERR, XTEMPERR5), the module has to be put out of "mute mode". There seem to be separate mute inputs for channels or groups of channels (ICEMUTEA, ICEMUTESB, MUTEFH), again the level and polarity is not known.
- If faults still not present, the relays have to be enabled, there seem to be signals for that too (RY_FW, RY_AF, RY_CR, RY_FH, RY_B), again the level and polarity is not known.
- If faults present, usually critical faults automatically turn off something ("latched off") apart from sending a signal to main microcontroller, thus requiring a "rearm" sequence for enabling again, while mild faults just send a signal to main microcontroller which responds with some action to alleviate the problem.
There is also another possible function for the 16 and 14 pin ICs near signal connectors, these could be logic gates for combining channels into drive signals and vice-versa, or could be latches so that some faults result in latching off some channels or relays.
And one more hint: The IRS2092 is enabled through pin 5 "CSD", the pin has internal pull-up by default (becomes a pull down if there is a short circuit, so that connecting a capacitor results in a timed disable/enable cycle, the pull down turns back into pull up when CSD voltage goes low enough, but circuit driving CSD can be more complex). The enable of the IRS2092 can be reverse engineered following pin 5. The enable of the relays can be reverse engineered too. Or it can be just tweaked/hardwired, but then protections are lost.
Partial Success!!!
1. Connected a low-level source to "FR+" and "FR-"
2. Connected a speaker to speaker terminals
3. Bridged "GGND" to "AMUTE"
4. Bridged "V+12FL" to "RY AF" (Output relay audibly pulls in)
5. Bridged GGND to pin 5 on IRS2092
It's a miracle I haven't fried anything yet.
I suppose the next step is to figure out how to get the IRS2092s to enable on their own, without a crude jumper.
1. Connected a low-level source to "FR+" and "FR-"
2. Connected a speaker to speaker terminals
3. Bridged "GGND" to "AMUTE"
4. Bridged "V+12FL" to "RY AF" (Output relay audibly pulls in)
5. Bridged GGND to pin 5 on IRS2092
It's a miracle I haven't fried anything yet.
I suppose the next step is to figure out how to get the IRS2092s to enable on their own, without a crude jumper.
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"4094C" could be SN74HC4094, a 8(+1) shift latch register. I recommend downloading the datasheet and comparing pinout to PCB, to find out if the DATA,CLK,OE signals are routed to the corresponding pins in the IC. There could be protection resistors or capacitors in the way. Tracing the STR IC pin is also needed, it may be connected in parallel to OE or not. Tracing the 8+1 outputs of this IC could lead to the enable circuits of the 9 IRS2092, if I am right.
CSD pin enable circuits could be as simple as transistors, resistors, diodes, to pull the CSD pins down for STBY/MUTE and release them for RUN, and some more diodes, transistors, logic gates, to check if any of the CSD pins goes low when released (RUN mode) and supposed to be high, which would signal a short circuit fault, almost surely by pulling _AMPOVERLOAD down (this part of logic is missing from schematic).
CT08 could be SN74ACT08, a quad 2 input AND gate, but again the pinout has to be verified.
Be careful, the signals in the connectors and in the PCB in most places seem to be 5V logic, so use a 7805 or something to get 5V to drive the pins. A series resistor like 470ohm is also useful for tests, just in case voltage is applied to a logic output, in which case there would be significant voltage drop across the protective resistor.
To understand CSD pin the input section of IRS2092 must be understood. It is intended to work with +/-5V. The CSD pin is referenced to -5V and its voltage can vary from -5V to +5V, forcing the pin outside these limits will blow the IC. The IC turn on threshold is CSD going over 70% of that 10V excursion, so >2V w.r.t GND. In case of a short circuit the CSD pin has to go as low as 30% of its excursion, so -2V, for clearing the fault, then to 70% again (2V) for re-enable.
I recommend studying the datasheets of the ICs. The classic ones from IR are somewhat cryptic.
CSD pin enable circuits could be as simple as transistors, resistors, diodes, to pull the CSD pins down for STBY/MUTE and release them for RUN, and some more diodes, transistors, logic gates, to check if any of the CSD pins goes low when released (RUN mode) and supposed to be high, which would signal a short circuit fault, almost surely by pulling _AMPOVERLOAD down (this part of logic is missing from schematic).
CT08 could be SN74ACT08, a quad 2 input AND gate, but again the pinout has to be verified.
Be careful, the signals in the connectors and in the PCB in most places seem to be 5V logic, so use a 7805 or something to get 5V to drive the pins. A series resistor like 470ohm is also useful for tests, just in case voltage is applied to a logic output, in which case there would be significant voltage drop across the protective resistor.
To understand CSD pin the input section of IRS2092 must be understood. It is intended to work with +/-5V. The CSD pin is referenced to -5V and its voltage can vary from -5V to +5V, forcing the pin outside these limits will blow the IC. The IC turn on threshold is CSD going over 70% of that 10V excursion, so >2V w.r.t GND. In case of a short circuit the CSD pin has to go as low as 30% of its excursion, so -2V, for clearing the fault, then to 70% again (2V) for re-enable.
I recommend studying the datasheets of the ICs. The classic ones from IR are somewhat cryptic.
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