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Grundig Studio RPC 350 need help

Posted 7th November 2016 at 10:01 AM by Keepsake10

Question for transistor experts.
I recovered the amplifier module from a old Grundig studio RPC 350. This amplifier is a classical concept of the time (around 70) differential input with CCS, driver, darlington complementary finals (BDW 94 / 95) It has DC transistor protection for the output and as well a kind of thermic protection switch on the heater sink (this protection cut entirely the main if heater sink get too hot).
I changed all electrolytic Cs and checked the rest of the parts. The rectifier bridge was replaced with fast recovery rectifiers and both 10.000/30V capacitors where replaced with 18.000F/40V. Measured values as shown by Grundig are ok and the offset can be done within Grundig specifications (the old 1Kohm trimmers will be as well replaced with multi-turn ones to get much easier control).
There is one issue I cant get fixed. The original schematic show the T2004 as BD517. Actually in this place was used a small Motorola in TO92 package...
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