Grundig SO 302 U/S Restoration, First time, Looking for advice and tips

[Brad Beard]

Hey guys,

I recently bought this old Grundig console at an antique shop. Not knowing anything about old radios, I obviously immediately turned it on. The good news is, it seems to be working perfectly fine, with little to no hum. I've since refrained from turning it on except for quick testing. I hot glued (don't judge me) a P226 cartridge into the tonearm to replace the original which was trashed, and while it sounds decent on some records, it's pretty shrill on others.
Oh, and for anyone that looks it up on google: someone in it's previous life added a completely new face panel across the front of the cabinet! Took me a while to realize, until I found the screws and wood filler, haha. It's since been repainted a very 60's electric turquoise for a friend.

Here are my goals:

• Replace any caps in need. (I'm guessing all the paper caps and the large "can" cap. The paper caps I can replace without too many questions, but the can has me a little intimidated.)
• Replace the power cord with a three prong (seems easy enough but I'd still like advice)
• Add an aux input to the tape recorder input (already tested this with a DIN to 3.5 cable into a CD player and it seems to work perfectly)
• Upgrade the ceramic cartridge to a magnetic cartridge (One of the main reasons I added the AUX input was to bypass the record player and test the sound quality of the stereo with a clean signal. I'm not sure if the new magnetic cartridge should be plugged into the original ceramic input or the tape recorder input)
• Possibly re-foam the original speakers, which sound great, but I think they're 7x11 ovals, so I have no idea where to get foam for those.

Sorry for asking a thousand questions but it seems like the best way to get the answers. Also, hi! I'll try to post pictures of the bottom of the can cap later, along with a schematic.

 

[gadget73]

Are the speakers actually using foam surrounds? I'd expect cloth or pleated paper.

yeah, paper caps and the can. The ones with the clear ends are likely polystyrene. Those hold up fine, but keep heat away from them. They shift value or just outright fail depending how much heat they get.

The can isn't any big deal. Its 2 - 4 capacitors with the negatives all going to the case and the + leads to invididual terminals. The easy way to change them is mount a terminal strip and hang new caps on it. Looks like you've got plenty of room for it.

This may have a selenium rectifier. If you have a silver flat box screwed to the chassis somewhere with wires coming from the cap and the transformer, thats it. Their fail mode is high internal resistance so the output voltage drops. If the voltage jives with the schematic, its serviceable. If not, a silicon bridge and a resistor to drop the voltage will sort you out.

Cord I'm fairly indifferent about. If you want 3 prong, the green attaches to the chassis at a handy spot. Just beware that it might cause hum or noise. I've not really had issues with it but some have.

Mag cart needs a preamp, but you can run the output from the preamp to the phono input without much fuss. They aren't really equalized or anything.

 

[Dandy]

Hi Brad, welcome. That looks a nice console. For more info go here https://www.radiomuseum.org/r/grundig_stereo_console_so302us.html. They may send you info about that model, on request, without joining.

Also, Grundig speakers are excellent. Do they have foam surrounds? I suspect not, like Gadget.

 

[Brad Beard]

First of all, I'd just like to thank you guys for all the help. It took me a short lifetime to order the parts, switch them out, and wrap my head around the can cap replacement, but so far, it seems to be a success. As usual, many other things got in the way, but I'm glad I took my time and thought it through. Google translate and wiring diagram charts helped me out with the rest. The good news is, we have signs of life!

I just have a few remaining questions:

• Just curious, but is there an easy way to add an EQ inline between say, the turntable and the speakers? Having tested an Audio Technica turntable in through the new preamp, everything worked great, but there was still a harsh "brightness" to the sound. Having said that, this was before I replaced the caps, so I'm not sure if those would have affected the tone of anything at all. The console has a bass and treble control, but they aren't much help. Really, I'd be happy to just dial some of those mids out of it. Everything I've seen while searching is a large rack-mount EQ.
• The speakers are definitely paper, I was just concerned about the foam seals turning to dust, although I now realize that's probably not much of an issue.
  I'll definitely keep the Grundig speakers if I can, but would there be any benefit to replacing them with a modern car audio 6x9 made from something like polypropylene? I've read that modern replacement speakers will more than likely be less efficient than the original paper cone speakers designed for the set and would sound worse, but just thought I'd ask.

I'm definitely not expecting incredible sound quality out of this thing, but I think it'd be reasonable to aim for something comparable to an entry-level AT turntable through some powered speakers. If I try everything and can't get it to a happy medium, I can always just switch out the record player for a compact modern unit. The cabinet is currently with the friends I'm restoring this for. They don't actually care if it works or not, but I like a challenge, so I figured I'd try. Plus, those buttons are too fun to play with for it not to work.

Thanks again. Hopefully, I'll have it mounted back inside the cabinet this weekend.

 

[gadget73]

I'd expect the original speakers to be a lot more efficient, which is a good thing when dealing with low power tube amps. They're also probably a good match to the box they are in. At a minimum I'd give them a listen before changing anything.

How are you actually connecting the turntable? If its a mag cart with no preamp fed direct into the Grundig, it won't work well. You need a phono preamp to make this work correctly. That will have the EQ in it. The RIAA curve has a big boost to treble and a large cut to the bass when it gets cut on the record, the preamp puts the bass back in.