Panasonic/Technics SA-DV280 - diyAudio
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Old 23rd July 2008, 11:30 AM   #1
OXAUDIO is offline OXAUDIO  United Kingdom
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Default Panasonic/Technics SA-DV280

Does anyone 'out there' have any experience of this receiver(the heart of a stacking system) ?
The unit trips back to standby a second or two after switching on.
At first I suspected IC601(RSN311W64B) the 6 channel output IC, but the trip still operates with all power removed from IC601, and even if the primary AND secondary windings of the power transformer T701 are totally disconnected from circuit. All components on the AC IN PCB (Q726 Regulator, Q791 Relay Drive, and associated components, check out OK. Before I spend at least 20.00 on a new output IC is there something I'm missing? I should add that the tests have ben performed with only 2 speakers connected, these to the main RH & LH LF outputs
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Old 31st July 2008, 07:47 AM   #2
OXAUDIO is offline OXAUDIO  United Kingdom
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Default SADV280(Part II!)

Following up on my post above, I discovered, on checking the unit again, that I had NOT removed all DC power connections to the output IC in this receiver. The 6-channel output IC has 8 seperate DC supplies, 4 Positive and 4 negative. Of these, one + and one - go to internal protection circuits at pins 15 & 16 of the O/P IC. I hadn't disconnected these two lines. Once I did so, the receiver powered up OK, so the RSN311W64B( from where DO they get these numbers!) is, after all, the culprit. I'm posting this info. in case it helps anyone else who visits this forum
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Old 27th October 2008, 07:17 PM   #3
OXAUDIO is offline OXAUDIO  United Kingdom
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Default Technics SADV280

AS a follow-up to my earlier posts regarding problems with this model, I discovered that one of the outputs had gone s/c to the -30v supply line('as a result of playing it too loud') according to the owner. This, in turn caused both 8 ohm 25 watt rated speakers I was using to test the amplifier to go short-circuit(which I hadn't realised, since the protection circuit was operating) Having carefully fitted a new output IC, which cost about 30, I powered up the unit, with the same speakers connected, and, lo & behold, the amp's protection circuitry tripped again(as it of course should!)THAT was when I checked the speakers!!!
The moral of this tale is of course CHECK, CHECK, AND CHECK AGAIN, anything that may have caused failure BEFORE APPLYING POWER.
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