Cambridge 640p Modifications
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note: there is a MC and a MM gain stage to the left and a dual mono RIAA to the right. There is not a seperate RIAA for the MC or MM.



In trying to replace the opamp caps /w ELNA Cerafines I tore up the board.
Back in went a new set of Panasonics and circa 1970 Vishay resistors,
and some new trace made of discarded leads.



I also had to fix the connection for the BG input caps.



I ran some copper lead from a Riken resistor thru the board up
and soldered to the clipped leads of the cap.
Pretty ugly, as usual, but effective ... as usual.

RIAA opamp
LM4562 /w heatsinks + Blackgate NX Hi-Q .1uF/50v on pin 4 & 8
Replaced ceramic caps /w same value silver mica
Vishay's NOS ~1970 100ohm 1/2 watt resistors
Panasonic/Matsushita 470uF/25v caps
Subsoniuc caps removed
MM opamp
OPA2228 /w Blackgate NX Hi-Q .1uF/50v on pin 4 & 8
Rubycon XYF 1000uF/35v
MC opamp stock opamp /w Blackgate NX Hi-Q .1uF/50v on pin 4 & 8
Output Blackgate NX Hi-Q 47uF/6.3V + Obbligato .22uF/640v + Vishay-Roderstein .01uf /160v
MM input
Blackgate NX Hi-Q 470uF/6.3V + .1uF/50v
Blackgate NX 220uF/6.3v 
bypassing, ground
Blackgate NX Hi-Q .1uF/50v
Power supply c9, 10, 11, 94, 95 : Rubycon YXF 100uF/25v
c55, 2, 4 : Rubycon XYF 1000uF/35v
c3, 4, 5, 6 : Rubycon YK 330uF/50v
repaced (6) rectifiers with Schottky 11DQ10

Resource: http://www.vinylengine.com/phpBB2/viewtopic.php?t=9098&start=0





The 640P benefits in terms of presence using the CineMag CMOB-2S steel core 1:1 @ 600ohm output transformers
Hookup =
IN : Orange + / Yellow -
OUT : Orange + / Red -



The old school chassis for the CineMag transformers



RCA short plugs with 4.7k resistors
Resource


10.11.2009