Rohde&Schwarz, EK07D Restauration

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Hallo Wolfgang,
danke! Hab mir Hamminkeln aufsuchen mussen aber ja, gleich nebenan:-)
73
hans

idiot aber es gibt noch mehr hier..im anhang

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den anhang:-)

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Okay. The power supply arrived! It looks a bit ugly due to the corrosion but the transformer doesn't seem to be affected too much.
I will have a thorough look at the unit this weekend and check the status of the caps and other stuff. Looks like the unit is repaired/modified while it was already affected by the corrosion. The selen gleichrichtern and other parts are replaced. Doesn't look too badly done. I am tempted to to try the unit as is after the check-up. I will use a variable auto transformer to gradually apply power to see what happens and how the various voltages will appear. Some cleaning might be good as well.

Mooie verzameling ontvangers Hans!

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Thought it might be nice to upload a picture of the actual receiver as well. I cleaned up the face plate and knobs already.
The inside looks still very neat, apart from some dust here and there it looks pretty much untouched.

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Hi Wout,

build like a tank and probably heavy! Wish you happy receptions, what type of antenna do you use?
best
hans

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Hi Hans,

Currently, I am using just a random length of wire. About 10m long, hanging outside at about 7 meters above the ground.
To get something that looks like 50 Ohm, I am using a transformer after the wire.

Nothing special really.

Wout

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Latest update... the power supply is doing a good job. All voltages are there and very close or at the values in the manual.
I put it in my EK07 and the radio came to life! This was really an exciting moment! Dial lights started to light up, tubes started to glow, great glow from the regulator tubes - very nice!

:biggrin:

I do face some additional challenges though. One of these was a mechanical one, I will post more about this later.

The other challenge is that the local oscillator (which is quite an interesting topology in the EK07!) - which is generating all necessary frequencies to create the IF - doesn't lock at the bands V and up. This means that you can't tune into any station or, in the best case, you will hear a station but the receiver is drifting up and down. I guess this might have to do with an issue in das 'Steuerteil', I am looking into this now. Blatt 5 in the repair manual of the radio is describing quite closely what I am facing.

Anyone any ideas suggestions...?

The lower bands seem to work OK, I am surprised how accurate the frequency dial actually is! CW and SSB reception works as well with the built in BFO.

Keep you posted, also with more pictures!

Enjoy your weekend.

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That can be a Problem around the 2nd Mixer.

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I am surprised how accurate the frequency dial actually is! CW and SSB reception works as well with the built in BFO.

The tuning capacitor in the oscillator part is made from one massive block of a spezial metal alloy what have extremly low temperatur drifts. (may be this is a OEM part from the Tronser company)
There are 32 screws for adjust the liearity.
A mechanical peace of arts in that radio, typical for Rohde+Schwarz. A normal emplyoee was working up to 3 years to get the money for one of this radios that time. The oscillator self is hermetical closed and have inside a chemical dryer what ca be reactivated by put it for one hour in the kitchen oven at 70 degrees C

greetings
Martin

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Last weekend I was looking at the schematics and sitting stand-by with my old Philips oscilloscope to find out why the receiver LO was not locking/synchronizing. I was suspecting something would not be OK in the 'Steuerteil'. Fault analysis in this receiver is particularly complicated because of the weight (65kg) - you don't easily turn this 'tank' around when you want to put a probe at a certain point. Also, all 'modules' are well shielded and encapsulated with heavy CuAg . Not to mention the main oscillator enclosure Martin talked about in his last post, what a piece of mechanical and electronics art!

Sometimes things are more easy than expected. I should have better looked at what the R&S Engineers and designers had already thought of. I am always impressed by R&S equipment and how it's designed (and built). Here, the 'Überwachungseinrichtung' helped me out - quickly. The switch in position 14 indicated a way too low current flow through Rö47. I noticed this earlier but somehow didn't pay too much attention to it - wrong!

I took the simple (perhaps quick and dirty) approach to just replace Rö47 to see what would happen. As I didn't have an ECC801S or even an ECC81 in my junkbox, I 'borrowed' the tube from the 'Eichoszillator'.

I switched on the filaments again... then the high voltage and... BINGO! The receiver LO worked (locked) immediately in all band positions and the meter reading in position 14 of the Überwachungs switch was right in the middle of the red mark on the scale. I will look out for a pair of these triodes to have the 'Eichoszillator' working again and to have one as a spare.

All other tubes measured (with the Überwachungs switch) as the manual indicated.

I couldn't resist to connect an 'antenna' (10m of wire outside of the house) immediately and started to listen on various bands. What a joy to listen to this receiver and to go over the long dial with that very smooth running tuning wheel! Although I didn't measure anything specific, the receiver looks quite sensitive to me. The conditions on the 14MHz radio amateur band were quite good as after a while I received 2 radio amateurs from the East Coast of the US with very high signal strength in single side band (the BFO only is not ideal for SSB but it works). Radio stations in AM are sounding really nice despite the somewhat limited band width. All features on the received seem to work fine.

Date codes in this receiver are indicating it's from 1960. All components and perhaps even the tubes are original. Just one double triode gave up and after replacing this one everything works perfect again…! What a quality product.