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Class D Switching Power Amplifiers and Power D/A conversion

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Old 15th May 2010, 12:11 AM   #311
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back to one of the original questions posed in this thread...
this week i had an LG home theater system come in for repair with the complaint of "very little audio from the speakers"... sure enough it was only putting out a couple of watts to the speakers at full volume, but it was not distorted. what i found when i opened it up was interesting, the 32V rail to the power amp was reading less than 5V. the amp was otherwise working normally. after replacing the power supply board, the unit was back to 50W/ch output. so, by using a controllable 0-32V supply for the amp, you can use the power supply as a volume control on LG class D amps.
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Old 15th May 2010, 12:16 AM   #312
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Quote:
Originally Posted by unclejed613 View Post
back to one of the original questions posed in this thread...
this week i had an LG home theater system come in for repair with the complaint of "very little audio from the speakers"... sure enough it was only putting out a couple of watts to the speakers at full volume, but it was not distorted. what i found when i opened it up was interesting, the 32V rail to the power amp was reading less than 5V. the amp was otherwise working normally. after replacing the power supply board, the unit was back to 50W/ch output. so, by using a controllable 0-32V supply for the amp, you can use the power supply as a volume control on LG class D amps.
This is the way the volume is controlled on the Panny amps using a combination of adjustable voltage to the output stage & digital attenuation. This is what makes the power supply board expensive & difficult to troubleshoot & repair.

Do you know anything about this PS board in the Panny XR-57?
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Old 15th May 2010, 01:10 AM   #313
jkeny is offline jkeny  Ireland
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Does anyone know where I might pick up a XR-57 PS board for a reasonable price?
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Old 15th May 2010, 05:34 AM   #314
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i'd have to look that up on monday. i might be able to get you a part number.
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Old 15th May 2010, 10:50 AM   #315
jkeny is offline jkeny  Ireland
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Thanks unclejed,
I think there is an official online shop for Panasonic parts, there the PS board is something like $200 AFAIR not counting posting (I'm in Ireland & they probably don't even post to here).

So if you have a cheaper source or know of second hand working PS boards, I would be interested, thanks.
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Old 2nd November 2011, 05:46 PM   #316
eld is offline eld  United States
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It has been a long while, but I thought I would update two more things I have done to the SAXR-55.

1) Replaced all the stock RCA 5.1 channel in's and the subwoofer out with Vampire CM2FCB. Very positive results when fed with a good blue ray. Better than optical and coaxial connections. Remember to hold the DVD button down for several seconds on the remote to switch from direct 6CH and 2CH.

2) Replaced the stock oscillators with TXC 10ppm oscillators from Digikey. I had to run new leads to the capacitors.

Still enjoying the Panny, especially having the modded Behringer EP2500 holding the low end with two Bipolar Eclipse SW8200 subs.

Working on plans for a new 7.1 400UcD Hypex amp, looking forward to running my mains as large.

Here are the new pics:
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Old 21st June 2013, 09:20 AM   #317
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Default i2s to SA-XR59

Hi there,

I know this thread is rather old, but I'm wondering if someone did a working input-connection of i2s to the panasonic sa-xr59 (or 57/58)?

There is a thread by pawelp where he managed to connect i2s to sa-xr55s. He just was feeding the i2s lines to the PWM-processor. By this, your are loosing nearly every feature like volume control, which I want to preceive.

Thanks!
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Old 20th April 2014, 03:27 PM   #318
john65b is offline john65b  United States
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Hey all, Been a while - I have an XR25 and an XR45. The 25 has nasty static or no sound on all but Digital in...weird. The 45 has static popping also on all inputs.

I believe both have issues wit the power supply - the 45 has some deep discoloration due to heat at the SMPS IC - IC701, and the Zeners D734/D733, while the 25 has minimal heat discoloration.

Anyway, anyone know the voltage out at the CP606 on 25 and 45? These seem to be the main power out to amp board - I get GRND (Brown), 10.3v (Grey), 10.3V (Blue) and yes, all positive...
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Old 21st April 2014, 12:03 AM   #319
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Correction - that voltage out of CP606 varies from low of 4.5v to 41.5v with increase in volume - this is not like a regular power supply - amp....rails vary with volume...
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Old 21st April 2014, 01:51 AM   #320
john65b is offline john65b  United States
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Well, both XR45 and XR25 are working from the optical inputs now (which is the only way to run these panny amps anyway)...both have static and crackles/pops on COAX and analog in....but who cares...sounds quite nice...

The ribbons were not properly seated to one of the pcbs.......
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