Sir MarkHu . . . . .
Seems like he didn't come back and elaborate, my end comment was relevant to not even knowing of what his problem was and if he even HAD
any 7VDC supply.
case you say that you HAVE
that voltage present , but with it being high.
I can give you this start off, with the two supplied schematic snippets .
Observe the right GREY
section for the derivation of the 7 VDC raw DC supply, which is using a linear AC line transformer derived voltage.
Good for 50 years if we use it regularly, to keep the electrolytic capacitors dielectrics reformed.
Now engage your brain into gear and note that they have an arrowed in 5K at 10 watt load resistor, temporarily utilized to gradually drain that C1320 of its charge, if you are wanting to work on this supply, shortly.
Now you need to follow the lil' RED
" weenies" path to the left and down where it then enters into another section of circuitry.
Notice that this raw 7 VDC supply is now responsible for the input power needs of four lower voltage supplies.
It feeds into pin 5 of IC268 and 266 which regulate down to two stable . . .+5HDM and +5D power supplies out of their pin 4's.
Do note that these are SWITCHED supplies . . .ON or OFF . . .. that require an activating voltage at their pin 1 CONTROL inputs.
Now, drop down to the bottom two IC264 and 265 which are different and being self contained switch mode regulators
Your 7 VDC supply comes in to pins 2 of each of them AND
if you have activation voltage on their pin 7's a variable power pulse train comes out of their pin 3 to ring the hell out of inductors L2601 and L2602, while schottky diodes D2602 and 2601 are busy collecting and rectifying those inductive rings peak voltages and busily passing them on as as rectified DC to the C2601-2602 and CC2603-2605 storage capacitors and creating the +3.3D and +1.2D supply sources.
Now refer to the top left corner and see that if you DON'T have the HTX_PON and 5D_PON and 5D_PON activations to the regulators, they will be idle and NOT
pulling power from that +7VDC supply, so it will be higher
in voltage, than in its normal operating conditions, with the regulators pulling power from it and its responding to the loading with a reduction of available voltage.
Now . . .go ye forth and check out those possibilities . . . . .as being the REAL
cause of :
" The mysterious 7 volt supply aberration
PERTINENT SCHEMATIC PORTIONS . . . . . FOR REFERENCING . . .
View attachment 41896
73's de Edd