Having a issue with AM.. No signal present even when hooked up to Signal Generator.. All other bands work although not great but receives signals..
Audio is very low I am using 3.2 ohm speakers...All tubes check good..
Has anyone worked on this model??
Thanks
Skip
Skip, so when it switches from SW to Broadcast doesn't it use the same circuitry? Check the switch contacts, trimmer and coupling caps that are unique to Broadcast.
Skip
By AM do you mean BC? (they are all AM except the FM band).
If the SW (KW if German) work and BC (MW if German) does not, like ROd suggested, check the switch. And of course - the coils.
Ok Broadcast Band does not work.. No signals at all Even with Signal generator hooked up..
The SW band do work as does the FM band But not great weak signals..
Skip
Adding a bit to what Rod said -
I'd probably first check to see if the oscillator is doing its thing when on BC. To check the oscillator, I usually put another radio (on BC) nearby to "listen" for the oscillator as I tune the radio under test across the band.
If it's not oscillating, I'd check the band switch (dirty?), BC oscillator coil bad...
I suppose it could be something before that, like the antenna transformer/related band switch... But I might expect a tiny bit of signal to find its way to the mixer.
Ok Found problem One of the wires from the BC OSC coil was off Very hard to reattach But was able to Now radio works on BC band.. Next Alignment..
Also I am using 3.2 ohm speakers the back of radio says 5 ohm.. Audio is low.. especially on FM. Do they make 5 OHM speakers?
Skip
Ok A little history on radio.. This was giving to me by a Antique dealer that has me fix ,repair get working any radio he gets in..as arrived by me it was without speakers..my guess is the radio had the broken wire when i received it.. after replacing the filter caps radio was powered up.. that's how i found it did not work on BC band.. I hooked up 2 speakers 3.5 ohms only ones i had for testing purposed. the stereo decoder was present but had a coil broken off so its not hooked up..tubes checked by emission on tester..
so i will hook up a couple of antennas . I noticed a loop antenna in there it has a broken wire also I think I can fix it.. question is what is the loop for AM(BC) or FM/
I will look at coupling caps next..
Thanks
Skip
The early 50s Grundigs have a dipole foil antenna attached to the inside of the cabinet approx. 19-20 inches extending from center of the cabinet down each side for FM and a ferrite rod loop antenna mounted above the chassis for AM. The Graetz 4R-216 I'm working on now has just a pair of 20 AWG wires for the FM. The FM antenna is then fed to the radio with twin lead wire. Let me know if you want a photo.
Skip
You probably already know this but every single ERO cap has to go. I had never seen anything as bad before I saw them. So, unless the job is just to make it sing to sell it, (which it might) I would replace them.
Ok replaced 4 coupling caps feeding the output tubes.. radio now has good sound on BC, and the SW bands.. But on FM the sound is extremely low I can hear stations but barely audible..
So where do I look for problems in FM Not at all familiar with FM circuits..
Skip
The radio belongs to the antique store for sale.. so i just have to get it to play..
Skip
I do not have a whole lot of experience with Germans, but if you have not replaced all paper caps, do not count on decent performance. I had to. Yes it was over 30 of them. You could pick and choose but then all the DC chopping (driving) caps have to go at a bare minimum, and then some.
In the German sets of the 50's, the two most problematic areas are the tuner module and it's associated tube, and the detector circuit, which is generally a 6T8 (can't remember the Euro tube equivalent number ATM)
Skip, There's an electrolytic cap in the FM discriminator circuit that should be replaced. It's a low voltage cap around 4-5 mfd and will be in the secondary circuit of the last IF transformer. These always cause problems if not replaced. Be careful with polarity, all the ones I've replaced have positive lead to ground.