In some of the receiver chassis that I have recycled there are dual voltage secondaries for the power amplifier. There is also a relay for switching between the two voltages (SecH and SecL).
One example is the Onkyo TX-SR504. Another example is the TX-SR707.
I assume the receiver receiver switches between the two solely based upon user configuration of the speaker impedance setting menu?
One example is the Onkyo TX-SR504. Another example is the TX-SR707.
I assume the receiver receiver switches between the two solely based upon user configuration of the speaker impedance setting menu?
Yeah it’s to deal with low/high 4/8 speaker impedances
Historically it was a mechanical switch on rear panel, sometimes now controlled through software/menus, ultimately via relays
Historically it was a mechanical switch on rear panel, sometimes now controlled through software/menus, ultimately via relays
After removing the original amplifier main board (and MCU/digital board) I wonder if there is an easy (enough) way to still use the original power button and the existing power transformer board (that has the fuses and relay on it).
I wonder if anyone else has done that with recycling an Onkyo TX-SR504 to house, power and cool their project amplifier?
Perhaps an on/off switch for the main relay would be simpler and quicker. (But not as neat looking.)
I wonder if anyone else has done that with recycling an Onkyo TX-SR504 to house, power and cool their project amplifier?
Perhaps an on/off switch for the main relay would be simpler and quicker. (But not as neat looking.)
It's easy enough to use the existing soft switch on the front panel.
The standby supply board normally supplies the processor (which you've removed), which then monitors that soft power switch, and sends a turn on signal back to the standby board to turn the relay RL901 on , which then turns on the main TX on
So you just need to use that standby voltage to on your soft switch via a little extra circuitry to provide a constant on signal rather than a momentary one.
TXSR707 example shown in attached pic
JL901 connector shows 12V standby volts going out to micro, PD is the return signal to turn relay on (simply grounded to enable RL901)
This has nothing to do with the 4/8 secondary switching, you can use/choose either secondary once the main TX is on.
The standby supply board normally supplies the processor (which you've removed), which then monitors that soft power switch, and sends a turn on signal back to the standby board to turn the relay RL901 on , which then turns on the main TX on
So you just need to use that standby voltage to on your soft switch via a little extra circuitry to provide a constant on signal rather than a momentary one.
TXSR707 example shown in attached pic
JL901 connector shows 12V standby volts going out to micro, PD is the return signal to turn relay on (simply grounded to enable RL901)
This has nothing to do with the 4/8 secondary switching, you can use/choose either secondary once the main TX is on.
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Well it took all of 5 minutes to find the blown KEC KTC5242 KTA1962 on the SBR channel. Clipped those off and it powers up. Drivers on that channel seem to be ok. Re is open on one side so clipped it off. Odd to see the lower quality outputs and drivers on the SR/SL/SBR/SBL channels. (KEC versus the Sanken used on the FR/LR/C.)
So originally I was scrapping this to recycle for parts and a chassis/heatsink/power supply for my QUAD405-2.
But since it is alive I was wondering if it made any sense at all to feed the balanced R+ and R- output of my PCM1794 DAC project into the L and R inputs and try using the L+ and R+ outputs as a quick balanced amplifier experiment? (Set to the low impedance mode, pure direct mode.) Does this make any sense? Or is this a bad fire extinguisher class experiment?
So originally I was scrapping this to recycle for parts and a chassis/heatsink/power supply for my QUAD405-2.
But since it is alive I was wondering if it made any sense at all to feed the balanced R+ and R- output of my PCM1794 DAC project into the L and R inputs and try using the L+ and R+ outputs as a quick balanced amplifier experiment? (Set to the low impedance mode, pure direct mode.) Does this make any sense? Or is this a bad fire extinguisher class experiment?
Every penny counts in production 😉
I thought the first idea was a bit crackers, but each to his own 😛
If you're only using two outputs why leave the reast burning up watts? regardless of what mode you're in they'll still be running.
When one of these outputs blows on the onkyos, it causes a lot of collateral (but not expensive in the great scheme of things) in the upright daughter driver board for that channel.
And the attached portion of the manual says "not on North American Model" with regards to the menu option to set the low impedance option. (?)
I look at the main PCB and the relay is sitting there. But I look in the menu and yes, there is no option to set the impedance.
Do they somehow automatically set it (such as by switching to the low impedance mode the first time the MCU detected high current?)
Why would the High/Low secondary voltage relay be there for the North American model but no menu option to set it?
I look at the main PCB and the relay is sitting there. But I look in the menu and yes, there is no option to set the impedance.
Do they somehow automatically set it (such as by switching to the low impedance mode the first time the MCU detected high current?)
Why would the High/Low secondary voltage relay be there for the North American model but no menu option to set it?
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You can do anything you want with software 🙂
Cheaper to leave in (in production) rather than do two separate runs of boards for different territorys , in much the same way a lot of car features/options are simply disabled by software and the hardware is sitting there unused. ... or a scope with crippled features , the same hardware can be present like a 300MHz front end but software dumbed down to 100MHz, The customer can pay to unlock the feature or not.
Obviously not in the North american version of this amp, but it could be done if they'd chosen to allow it.
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So it was very cheap (sold as dead/scrap). It had the right transformer voltage I wanted and this model has a nice extruded heat sink. So it seems like a reasonable first home for the project.
This model (the TX-SR504) does not have the upright daughter card like the TX-SR707. Fortunately the drivers seem to be fine. Since it is alive I think I will listen to it and perhaps run a few experiments. In the past I thought some Onkyo amplifiers sounded pretty nice.
I wonder how they prevent the outputs from failing with 4 Ohm loads in the North American version if it is always running with the high (8 Ohm related) secondary voltage? Just relying on activation of the protection circuit?
In terms of quality or sound quality or both? They certainly seem to have some reliability issues such as the HDMI boards (TX-SR707 and many others) and KEC 2SC3200 (TX-SR501 and others).
Reliability trumps any redeeming features of a product (If indeed this brand had any in the first placc.😀)
I think the heat/HDMI and some component quality issues (such as the 2SC3200 example) did a lot of damage.
For example, when the HDMI issue started with the TX-SR707 they should have made 100% sure that all affected customers were taken care of. Instead many TX-SR707 ended up as landfill.
For example, when the HDMI issue started with the TX-SR707 they should have made 100% sure that all affected customers were taken care of. Instead many TX-SR707 ended up as landfill.
Not sure what happened to my laptop 30 minutes ago half way through the conversation😕, the keyboard went very very laggy, I killed both keyboard drivers and then initiated 11 different updates , and it's come back on responsive as ever ?!!
I also realised the USB-C adaptor had died cos the updates wouldn't run until I was on AC , good job I had a spare 😀
I also realised the USB-C adaptor had died cos the updates wouldn't run until I was on AC , good job I had a spare 😀
They don't allow 4ohm speakers on the NA version. 😉
They chance it..... as most speakers are generalised as 4ohm or 8ohm nominal and not usually 6ohm, you (and the retailer) are more likely to select the 8ohms speakers thus (hopefully) avoiding the problem.
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As it would happen I picked the speakers which were specified as "8 Ohm Compatible". (Polk Audio.)
When measured (with REW and the impedance adapter) they are absolutely 4 Ohm...
When measured (with REW and the impedance adapter) they are absolutely 4 Ohm...
To be fair they may well be 4ohm at DC but be more 8ohm (on average) across the audio band
They might just be idiots though 😀
REW with the impedance adapter measures across the audio band.
You can see my measurements across the audio band here: Polk CS1 and R50 Impedance for JLH Supply Voltage and Bias Current
You can see my measurements across the audio band here: Polk CS1 and R50 Impedance for JLH Supply Voltage and Bias Current