This is my first post here even if I read here in this really prof forum from a long time.
I would like to draw your attention on PSU of the SX202 at 220v, it is not the same given to the domestic costumer of symetrix and it is rated at 19Vac, I never get importance to it but when last week I bought a used 2 unit here in Italy, reading about how US user paid attention on the PSU that nowday is rare to find because of the importance to have exactly 16Vac of output, I do some mesure on it, and I come out "disturbed", why?
The export PSU send out 23Vac!!! (against the 16Vac of US PSU and this could be a good new for US owner that need to find a replacement to the hard to find original PSU) but what I found not serious from the guys of symetrix is that with this extra power the 78M15 and 79M15 after few seconds become already untoucheable because of their hot temperature!
Here I quote an old post from ulysses on rec.pro.audio:
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Looking at the schematic, I can see that all of the pre-regulator
filter caps are conservatively rated such that an input voltage up
around 25VAC would not destroy them. If there was any detrimental
effect from increasing the power supply voltage by a few volts, it
would be increased dissipation in the 78M15 and 79M15 voltage
regulators. They would run a little hotter and die a few days sooner.
I'm sure any quality AC transformer in the 15-20VAC range and capable
of at least 200mA will be fine.
ulysses
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Only the range sometimes is few mA more than 200 so at least 250mA will be preferable, (mine , the export PSU is rated at 500mA that means that is possible to run 2 units with it).
What I note too was that even the LT1469CN8 run hot but the 15v they receive is still less than the max 18v they are rated so I dont care to much about, or I must care?
At the end my question is: I know a factory that does PSU on specific if I ask them to have one at 16Vac and at least 300mA I will have some benefit other than longer life of 78M15 and 79M15 ?