Soviet East German Radio

[pwdrive]

Schematic for the Saalburg 5170 for anyone following:

http://85.144.220.212/nvhr/RFT_5170.pdf

Lawrence.

[Murphyv310]

Hi.
The valve line up then is this.
ECC85 (no diodes in this valve NWM) double triode FM RF and Mixer.
ECH81 Triode Heptode AM Mixer, oscillator and FM first IF amplifier
EBF89 FM second IF amp and AM first IF amp also AM detector,
EABC80 Triode AF preamp and FM discriminator.
EL84 Audio output.
EZ80 HT rectifier
EM84 Tuning indicator.

Regarding your fault you must have HT to the ECH81 Heptode screen grid or FM wont work so it can only be switch (4,5 & 6) contacts, R12, a broken connection, print or dry joint. I take it you have checked the resistance of R12 or checked both sides for volts.

[Murphyv310]

Hi.
The valves are numbered by the "Pro Electron" system, more or less widespread in Europe since the 30's, https://en.wikipedia.org/wiki/Mullard%E2...esignation

On the valve list on your set I haven't complicated it by adding AVC and other salient features.
I also read you like the audio quality. Get a Tandberg radio, most have proper infinite baffle speaker enclosures, even my 1941 Sølvsuper (Soelvsuper) 3 has and the audio has to be one of the best in a table model http://www.radiomuseum.org/r/tandberg_soelvsuper_3.html

Good luck with the repair, don't hesitate to ask and take on board the advice. Even now with over 50 years under my belt in this trade (also hobby since I was 12) I still ask if I get stuck.

[Terry]

Regarding your fault ... it can only be switch (4,5 & 6) contact ...

Further to Trevor's post, contacts 4 & 5 are OK, as is the sliding contact, or FM wouldn't work so only contact 6 can be a problem.

Unless it has suffered some physical damage - highly unlikely - the problem almost certainly* lies elsewhere, and Trevor has listed all the alternatives.

Interesting that the set uses the US standard AM IF of 455kHz. As we know in the UK, this caused problems with the reception of the Home Service (908kHz), later Radio 4 (909kHz) due to beats with the second harmonic of the IF. Interestingly, there was a high power transmitter at Burg, near Magdeburg, in East Germany, used for propaganda broadcasting to West Germany that would have caused the same problem!

Also interesting is the multi-lingual footnotes - including English - on the circuit diagram.

Now that is possible to see how the drive cords are configured, I can say that they are a doddle compared with the horrific Philips arrangement I had to contend with in the 60s!

* There is, I suppose, the possibility that the set has been used solely on FM for an extended period of time and a substantial amount of tarnish has built up on contact 6 but, obviously, this will only need to be investigated if there is no HT present on the 'hot' end of R12.

[Murphyv310]

Hi.
Yes Terry is quite correct in stating "6" on the switch bank it is of course on the same section of the switch as the other two I mentioned.

[Nowhere-Man]

I tested R12 recently and was surprised to get no volts. I have no isolation transformer so I used a gripper around the meter probe to keep fingers well away. So that led me to figure the switch was the problem. One thing that I did notice is the German schematic doesn't use broken HT lines but they cross. In such a case I assume they connect.
Last night I simply worked on an estimate of how to access the switch. The board is simply tagged down but contacts from the pushbuttons are soldered down. I haven't found a single disconnection anywhere around the board so it was very well soldered. Just before removing the board I plan on a meter check of the board tracks. No reason not to check the valve holder too. Of course pcb boards are very new to me. I haven't encountered anything as modern.

[Murphyv310]

Don't worry about an isolation transformer on this set as it has a isolated transformer. Just be careful around the mains switching.

[Nowhere-Man]

I've been a bit sluggish lately with the weather so radio work has been a bit slow. On the lazy days I may just go over schematics. After this I will be tackling a queue of 50's sets including a McMichael. I will post updates on the Saalburg and believe I can lift the board up without major difficulty.

[Nowhere-Man]

Looks like my neighbour from Sweden has had her bike stolen on Xmas day. I noticed she'd left it unlocked and the wind had blown it over. I picked it up and was going to make it secure on return home (as I was rushing out). On return home I noticed the bike was gone. Someone must have spotted it and got over the gate. At least we'll know the day and time bracket of the theft but she was a bit careless to leave it in view.

[Nowhere-Man]

I just did a few more quick tests and have found my R12 is bang on spec resistance wise and there is a good connection to the Triode anode of ECH81. However HT side is dead. I tried pushing switches with the meter between HT and opposite side of R12 and zilch. There is no chance of any voltage drop of 100 odd volts on R12. Thus my job is clear: access the knob circuit and restore connection and clean all contact points. Any experiences of piano buttons welcome. I did notice R12 tab on HT side had some play.