[Premium-Rx] Rohde & Schwarz EK-56/57 Help needed

[Heinz Breuer]

Hello Bruce,
I have a large box holding a non working EK 57 in pieces sitting in my storage for at least 10 years waiting for its turn on the bench. Another box has several manuals.
I will take a look what I have.

Generally the synthesizer in the EK 056 turn out to be a problem almost 50 years after they were built. The synthesizer consists of more than a handful of different modules. 

R&S used early TTL logic and incorporated a very exotic scheme of operating voltages to provide the needed 5V. They are operated with 18V supply voltage and an elevated ground using the 13V supply voltage, which are both supplied by the power supply. The difference is the needed 5V for the TTL logic. Unfortunately there are many other parts on the 13V rail. If one fails and the 13V rail goes lower the TTL ICs are all fried. 

I have a elderly friend who has worked on different EK 056 for several decades and probably is one of the last surviving specialists. He just repaired the synthesizer in one of my EK 056/4. I have three other non working EK 056 (two /4 and one plain EK 056) and hope that I can convince him to take a look.

vy 73 Heinz DH2FA, KM5VT

Von meinem iPhone gesendet

> Am 17.09.2020 um 03:05 schrieb Bruce Gentry via Premium-Rx <premium-rx at mailman.qth.net>:
> 
> I have a Rohde & Schwarz EK-57 I am beginning to repair.   The oscillators 3 and 4 are not working, and are likely all that is wrong with it. I have a set of manuals, but the schematics for the oscillator 3 and 4 module and the modules that control it are different.   The manuals have the same circuit as  the EK-56 I have.   They cover the version of the receiver where the oscillator 3 and 4 module is large, has two coax connectors, and a large female connector that accepts a male connector that is a small piece of circuit board.  The EK-57 has a very different module from the EK-56 and the manuals I have.  The module is smaller, has two coax conectors, and two stacked 8 pin male connectors. There are a larger number of modules associated with it to control it.   All of the modules in question have part numbers starting with EK-56, and many of them interchange between the 56 and 57 receivers.  Can anyone help me with the correct schematics for the smaller oscillator 3 and 4 module, and the others that control it?   I can provide photos and all available information needed to help  get me the correct schematics. Thanks,
> 
>  Bruce Gentry, KA2IVY
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