Radio Shack Optimus 18 rebuilding... - UK Vintage Radio Repair and Restoration Discussion Forum

ekjdm14 · 16th Feb 2019, 3:33 pm

Hi all, my first technical question on the forum.

I acquired, along with some other equipment, a pair of Radio Shack/Realistic Optimus 18 speakers which I plan to do some refurbishment to.

The cabinets themselves are tatty and will likely never be perfect due to moisture damage blowing the veneer from the bottom portion of one. This isn't of a huge concern to me as the worst of it can be hidden when installed although I do intend to make them look as good as I can.

The main focus for me is the functional restoration of these, which will also be a challenge. Aside from the fact that the crossovers need to be rebuilt, the one with the worst moisture damage also had a dead woofer. On further investigation the coil was well and truly pinched in the magnet, I have disassembled the unit carefully (To such a degree that the cone and voice coil may yet be salvageable) and what has happened is the bonding holding the magnet assembly together has been compromised by moisture and the assembly has shifted which pinched the voice coil.

What I would like to know is, what does anyone think about the prospects of repairing this sort of damage. It's possible no doubt, but future reliability? Also I would appreciate advice on such repairs for a novice (I'm reasonably proficient in the electronic side of things and mechanically competent, just never rebuilt a speaker before!). Especially important would be the type of adhesive to use in reassembly of the magnet.

Thanks, Dan.

snowman_al · 16th Feb 2019, 5:08 pm

Hi Dan,
You may find them as Realistic Nova 7 speakers too?

Unless they are of special value to you, I would say use them as a test of your skills, but do not spend a lot of money on them.

Start with the dislodged magnet before committing to any other work. It will be a problem unless you can ensure it is centred perfectly. To fix it back on there are special adhesives but they are expensive. 'JB Weld' epoxy for metal repairs has been recommended before on other forums. Ordinary off the shelf epoxy does not appear to be good enough.
If you get it working great, move on. If not it might be difficult to find a replacement then you have to decide how / if to continue.

Alan

Edward Huggins · 16th Feb 2019, 6:05 pm

There are some interesting (and disturbing) videos on the Nova 7 on youtube!
Unless you have a special interest in USA designed 3 way units, er, other speakers are available....

ekjdm14 · 16th Feb 2019, 11:39 pm

My thoughts/motives are exactly as Alan suggests, they'll never sound great nor will they look good, but there are skillsets I wish to develop for possible future use and these will be the perfect guinea pig for my practice. Also the look of them would be in keeping with the kind of system I may build for the garage in future (where their cosmetic condition and sound quality are not of ultimate importance).

I had thought of chemical metal type solutions as I've had good luck with them in the past, and it sounds like the way to go here. I'll have a search for the Nova 7 videos on YouTube shortly. In case I don't find them, what is the disturbing aspect about? [Edit-: Oh, I see what is disturbing haha. Quite a lot of Anglo Saxon mixed with lots of speaker abuse and rather odd "music"]

It's not that I have a special interest in American audio kit, more that I have a special interest in how things are repaired & if it can be done by my own fair hands! (Hence my recent acquisition of a Marconiphone 4417 to have a look at a Garrard record changer, and to work on my veneer/chipboard repair skills as it's "rough"

Thanks for the replies gents.

16th Feb 2019, 3:33 pm	#1
ekjdm14 Banned Join Date: Feb 2019 Location: Congleton, Cheshire, UK. Posts: 609	Radio Shack Optimus 18 rebuilding... Hi all, my first technical question on the forum. I acquired, along with some other equipment, a pair of Radio Shack/Realistic Optimus 18 speakers which I plan to do some refurbishment to. The cabinets themselves are tatty and will likely never be perfect due to moisture damage blowing the veneer from the bottom portion of one. This isn't of a huge concern to me as the worst of it can be hidden when installed although I do intend to make them look as good as I can. The main focus for me is the functional restoration of these, which will also be a challenge. Aside from the fact that the crossovers need to be rebuilt, the one with the worst moisture damage also had a dead woofer. On further investigation the coil was well and truly pinched in the magnet, I have disassembled the unit carefully (To such a degree that the cone and voice coil may yet be salvageable) and what has happened is the bonding holding the magnet assembly together has been compromised by moisture and the assembly has shifted which pinched the voice coil. What I would like to know is, what does anyone think about the prospects of repairing this sort of damage. It's possible no doubt, but future reliability? Also I would appreciate advice on such repairs for a novice (I'm reasonably proficient in the electronic side of things and mechanically competent, just never rebuilt a speaker before!). Especially important would be the type of adhesive to use in reassembly of the magnet. Thanks, Dan.

16th Feb 2019, 5:08 pm	#2
snowman_al Octode Join Date: Dec 2018 Location: Llandeilo, West Wales, UK. Posts: 1,092	Re: Radio Shack Optimus 18 rebuilding... Hi Dan, You may find them as Realistic Nova 7 speakers too? Unless they are of special value to you, I would say use them as a test of your skills, but do not spend a lot of money on them. Start with the dislodged magnet before committing to any other work. It will be a problem unless you can ensure it is centred perfectly. To fix it back on there are special adhesives but they are expensive. 'JB Weld' epoxy for metal repairs has been recommended before on other forums. Ordinary off the shelf epoxy does not appear to be good enough. If you get it working great, move on. If not it might be difficult to find a replacement then you have to decide how / if to continue. Alan __________________ Never Leave Well Enough Alone...

16th Feb 2019, 6:05 pm	#3
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,327	Re: Radio Shack Optimus 18 rebuilding... There are some interesting (and disturbing) videos on the Nova 7 on youtube! Unless you have a special interest in USA designed 3 way units, er, other speakers are available.... __________________ Edward.

16th Feb 2019, 11:39 pm	#4
ekjdm14 Banned Join Date: Feb 2019 Location: Congleton, Cheshire, UK. Posts: 609	Re: Radio Shack Optimus 18 rebuilding... My thoughts/motives are exactly as Alan suggests, they'll never sound great nor will they look good, but there are skillsets I wish to develop for possible future use and these will be the perfect guinea pig for my practice. Also the look of them would be in keeping with the kind of system I may build for the garage in future (where their cosmetic condition and sound quality are not of ultimate importance). I had thought of chemical metal type solutions as I've had good luck with them in the past, and it sounds like the way to go here. I'll have a search for the Nova 7 videos on YouTube shortly. In case I don't find them, what is the disturbing aspect about? [Edit-: Oh, I see what is disturbing haha. Quite a lot of Anglo Saxon mixed with lots of speaker abuse and rather odd "music"] It's not that I have a special interest in American audio kit, more that I have a special interest in how things are repaired & if it can be done by my own fair hands! (Hence my recent acquisition of a Marconiphone 4417 to have a look at a Garrard record changer, and to work on my veneer/chipboard repair skills as it's "rough" Thanks for the replies gents. Last edited by ekjdm14; 16th Feb 2019 at 11:45 pm.