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MDS-JE780 deck upgrade

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Graphene

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Few days ago when I disassembled my MDS-JE780 to replace the battery I noticed that +-12v power supply of this deck is very simple. After a little searching I found that power supply of MDS-JB980 uses +-6v regulator ICs in this power line. it turns out that board of JE780 actually have places for regulator ICs, but they are not mounted.

JE780 power supply

JE780shema1.jpg

JB980 power supply

jb980shema1.jpg

IC141 is for +6v and IC241 is for -6v

jb980shema.jpg

So i decided to mount this part of the power supply in my JE780. There is 8 components in total: C141,142,143,241,242,243 and IC141,241.

 This is how it looked before:

DSCF3213.JPG

And this is how it looks now:

DSCF3215.JPG

I also replaced capacitors after rectifier:

DSCF3214.JPG

It's hard to tell if this upgrade did something in terms of sound and noise level, but it is definitely better than original 470u capacitors.

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Jim Hoggarth once said to me that he thought there wasn't much different in a 980 (from 780). Looks like you have identified one item. I wonder if there are others. The 980 is definitely heavier, IIRC.

As a side note, I have myself tried "upgrading" some models (nothing to do with 780 or 980) to match Japanese domestic specs, and ran into problem after problem where Sony made slight changes to the circuit design, similar to what you spotted. Almost looks like intentionally to frustrate hackers and "refurbishers", but who knows? - may have been for good engineering reasons.

Can you explain why one set of rails is +/- 12 and the "superior" set +/- 6? Shows how little I know about this stuff......

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+-6V is output of 7806 and 7906 ICs. The task of these ICs is to stabilize and filter voltage. In JE780 these ICs are not mounted to lower the price of the unit. Also JB980 uses NJM2114D OP amps in DAC output and headphone amp wich are FAR more superior then 4558D OP amps used in JE780.

I've never seen JB980 insides before, but judging from the circuit I think JE780 and JB980 actually share the same main board,  Sony just removed some of the "optional" parts of the circuit in JE780 to cut the price, but left mounting spots on the board, so it is possible to "turn" JE780 into JB980 (well, at least on the inside).

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