Soviet East German Radio

[Nowhere-Man]

I gatheredThe board has small clamp brackets around the edges you just twist to unlock. Then you have about 5 or so soldered points which support the board and all at chassis potential. The first one I desoldered was simply a fixing lug. I know people have removed boards on this unit from old threads. I want to clean the board too and change the wax caps. The tuning mech will be left alone.

[Murphyv310]

Hi.
Where is R12 located as I cant see it on any of the layouts in the service manual, mind you I'm half blind

[Nowhere-Man]

Excuse me, I'm an idiot. As was pointed out to me there are indeed screws you need to take out to make life easier. I ask everyone try to be patient as this develops as I feel a bit out of my depth. The last radio I worked on was a decade older with rotary knobs and large valves. So it's a bit of a jump.
The good news is no disaster so far and I have the board loosened up. I figure I'm now supposed to remove the plastic white waveband knobs so as to be able to clear the board and ease out. I see no grubscrew and feel it must be a push fit to the rod. Till I know I daren't use force and amazingly nobody online has commented on removal of plastic knobs. R12 simply drops HT and by my estimate should have 100 odd volts and that should feed the Triode anode so it can oscillate. The Mixer anode was fine but the manual gives 110 or so for thee triode anode. R12 had no volts and no continuity to HT when knobs were pressed. The variable capacitor was also dormant. So I have my troubles. PS wires break easily on this receiver so I took pics.

[Crackle]

It may have been a good idea to remove the knobs before releasing the printed circuit, sometimes it takes considerable force to pull a knob off the shaft.
I use a strong thin nylon cloth and feed it under and all around the edge of the knob, pulling it as far around the knob as possible, then gather it all up and twist it so the knob is gripped.
You can then pull evenly on the knob using the cloth, but be warned the plastic knobs can still sometimes snap or crack.

edit.
I have just re-read your post again, I now believe you are talking about the push button caps, sorry, I thought you were talking about the volume and tuning knobs.
Sometimes the plastic caps on the push buttons are actually moulded onto the shaft. The only way of removing them is to crack them.

Are you sure the push buttons have to come of, often they just pull backwards through the front panel with the printed circuit once their screws are released from the case.



Mike

[Alistair D]

Something along the lines of these might be helpful for removing stubborn knobs.

http://www.ebay.co.uk/itm/CAR-DOOR-CARD-...SwjDZYYzEX

Al

[Crackle]

Oh Al! they look a little vicious, you would have to use some form of protection on what you were levering against.

Mike

[Terry]

Are you sure the push buttons have to come of, often they just pull backwards through the front panel with the printed circuit once their screws are released from the case.

I agree with Mike here but I don't think it applies here because the photographs of the chassis show that it comes out of the cabinet complete with scale and knobs.

I am concerned here that what you are doing could lead to considerable harm being caused yet leave you no further forward with your dismantling attempts - and none of us want to see that happen.

Take a very careful look at what holds the entire assembly in the cabinet. When you've identified the fixings it should take only a matter of seconds to remove the unit from the cabinet. One little thing to look out for - make sure you disconnect the loudspeaker (unless it has very long wires) so that the chassis is completely free when you remove it. The speaker should be the only thing left in the cabinet when the chassis is removed.

[Crackle]

Hi NWM
I have been looking at the Saalburg 5170 on the Radio Museum.
From the photos on there it looks like once unscrewed, and a few wires to the speaker transformer etc removed, the whole chassis will slide out backwards together with the dial, knobs and push buttons.
The printed circuit looks like it is accessible from under the chassis and the components from above the printed circuit. It should be even possible to spray switch cleaner into the push button switch cases. R12 could be checked for continuity, and maybe the fault identified.
I appreciate that you like to learn for yourself but I feel you may be making the job more difficult than necessary, this may add more faults than were originally there.
Of course I am not the one sitting in front of the radio, so cannot see precisely what you can see, there may be some reason the chassis cannot be removed from the radio and worked on, so please tell me to shut up if I am talking rubbish.  

Mike

edit
If the push button switch assembly really has to be removed then It may be possible to do this once the chassis is removed from cabinet and the knobs and dial glass have been removed, there may be no need to remove the push button caps.

[Nowhere-Man]

To clarify I was reluctant to dismantle but the evidence for an HT break was pretty clear. I even did ohms tests with all the knobs being used and not a flicker. The resistor that drops HT volts does show continuity to the anode but dead on HT connection. And no volts are on it. I tried the usual rapid switching and cleaning method but no joy.
Another thing I can now appreciate is the board shows some signs of age and slight discoloration. It's not pristine.
As to the knobs I will take it easy. I will need to ponder it but without the knobs it would be easier to ease the board clear. However maybe it can be done with knobs still on.
To be safe I jotted down the output transformer wires just in case one pops off as they are thin and brittle.
Definitely no disaster so far or any trauma but I'm seeking info first before just forcing knobs. However it's clear I had a few tactical rethinks.
I will see if I can ease the board clear without removing knobs. I labelled all screws and put into plastic bags. Thanks for the tips and suggestions.

[peter scott]

I know nothing about this set but the service info appears to suggest that the whole chassis plus board, tuning scale and glass comes out of the cabinet as one assembly that should give reasonable access to components. Are you working with this assembly out of the cabinet?
If not then it looks like it is held in place by four screws in the under side of the case.

I must admit it looks as if the components associated with the piano keys are mounted on a daughter board that is soldered onto the main PCB and that might be a little tricky to remove.

Peter