Jump to content

Tim's triple 3a restoration


TimmyTonga

Recommended Posts

Thanks to everyone who has helped me with the 'difficult' bits of this. I thought I'd just show you what it was all about.

I wanted to hear a pair of 3as, and the only way I was going to do that was to restore a pair myself.

They don't turn up in the UK that often, but a bunch of them came together, which is to say two pairs of scruffy but relatively untouched 3as

3a boxes.jpg

woofers.JPG

 

 

and a pair of Improved.

 

Improved.jpg

 

This is what I ended up with, thinking I could get maybe two decent pairs of speakers out of it.

 

Both the 3as have A2/3 woofers and A19 tweeters, and all seem to work. All eight pots cleaned up OK ,

dirty pot.jpg

except one that had broken plastic wiper pins,

and I got a refurbished original from Larry to replace that.

At least one woofer is looking a bit marginal, but conversations I've had on this board suggest that it may be OK.

 

The Improved arrived already 'restored', but you see they have KEF tweeters in, and I would obviously be looking to replace those with the correct units, although they could take a while to find.

 

I did a lot of research about caps and read all the relevant threads on this board. Given that I had no idea what the units would sound like and particularly how good the tweeters were going to be, I was rather with RoyC in using good but good value caps, calculating I could always go upmarket later if I wanted to. I also took quite a sentimental view towards preserving as much of the original aesthetic as possible, and as a result came up with replacing the 6uf with an Erse MET cap, but fixing it inside the original case using part of a cable tie, pre-shaped with a heat gun over a sacrificed capacitor,

forming.jpg

 

and then sealing it to the case using wax from the original AR cap.

6uf box.jpg

 

The case will get flipped over, and will look the same as originally except it will be around the other way (which it has to be, because the wax-filled end is now empty of wax). 

 

I have also chosen good mid and low caps that will fit the original clips, although I will have to fit a discreet extra cap in parallel for the low.

 

The Improved sound great, but I think the 3as will sound better. That's why, in the end, I will probably stick the better grill-cloths on them and to some extent sacrifice the Improved.

That's the bones of it, and I will update as I get further in.

Regards/Tim

Link to comment
Share on other sites

Nice work Tim...  If Kef tweeters are T27´s, they are are not late SP1032´s???

Kimmo

 

Link to comment
Share on other sites

Interesting difference between my original pot and the refurbished one from Vintage-AR;

pots1.jpg

 

metal shaft vs. plastic.....you can see below why I needed the replacement;

 

pots2.jpg

 

the plastic sheered off, leaving some inside the screwhole. I had reckoned that I would drill it out and replace the plastic widget with the one from V-AR, but unfortunately the plastic version is a one-piece, so I will have to use the V-AR shaft as well. Perhaps the decision to change to plastic was a sound one, as it may have removed a weakness.

Tim

Link to comment
Share on other sites

"Perhaps the decision to change to plastic was a sound one, as it may have removed a weakness."

Actually the metal shaft version is the later one. The plastic versions (red and black) would sometimes melt from heat.

Roy

Link to comment
Share on other sites

I'm not saying I got all the pots this good;

clean pot.jpg

 

but they weren't far off. Having rehabilitated eight of them I obviously found my own favoured methods, and Rule #1 as far as I'm concerned is don't use anything abrasive, as it's the quickest way to lose your silver-plating.

I recommend this;

brasso.jpg

alternated with this

lemon.jpg

 

a gloopy mixture of the latter applied with a cotton bud. (I know that's a hell of a lemon, but we have a friend visiting from Valencia)

*tbh, the alternating may be more to do with alleviating the tedium than anything more scientific. The bad ones took several hours each.

And yes,  I'm resigned to the fact that I may end up replacing some of them with L-pads if they have annoying dead-spots, but I'm not going down without a fight....

 

Tim

Link to comment
Share on other sites

Non-abrasive sounds like a good idea but I think you want baking soda, not powder, to mix with the lemon juice. Baking powder contains some baking soda but to clean tarnish the soda should work better.

-Kent

Link to comment
Share on other sites

Yeah, it's hard to get that Dr Oetker's over here anyway.

I like to use Simichrome polish. Not sure of the advantage of neutralizing the acids in the lemon with baking soda -- maybe applying them alternately with a rinse ...

Roger

Link to comment
Share on other sites

On 7/2/2016 at 8:03 AM, TimmyTonga said:

Interesting difference between my original pot and the refurbished one from Vintage-AR;

pots1.jpg

 

metal shaft vs. plastic.....you can see below why I needed the replacement;

 

pots2.jpg

 

the plastic sheered off, leaving some inside the screwhole. I had reckoned that I would drill it out and replace the plastic widget with the one from V-AR, but unfortunately the plastic version is a one-piece, so I will have to use the V-AR shaft as well. Perhaps the decision to change to plastic was a sound one, as it may have removed a weakness.

Tim

Hmmm, didn't think that was possible ... I probably have one of those around somewhere if you need it.

Roger

Link to comment
Share on other sites

4 hours ago, owlsplace said:

Yeah, it's hard to get that Dr Oetker's over here anyway.

I like to use Simichrome polish. Not sure of the advantage of neutralizing the acids in the lemon with baking soda -- maybe applying them alternately with a rinse ...

Roger

5 hours ago, JKent said:

Non-abrasive sounds like a good idea but I think you want baking soda, not powder, to mix with the lemon juice. Baking powder contains some baking soda but to clean tarnish the soda should work better.

-Kent

If I'd had any sense I would have used potassium bitartrate on its own (which over here is called 'cream of tartar'), and Wikipedia explains why;

https://en.m.wikipedia.org/wiki/Potassium_bitartrate

'Baking Powder’ in the UK is a mixture of sodium bicarbonate, and potassium bitartrate, and the former was working against me, apparently.

Maybe I could have shaved an hour off the cleaning time.....

Link to comment
Share on other sites

4 hours ago, TimmyTonga said:

If I'd had any sense I would have used potassium bitartrate on its own (which over here is called 'cream of tartar'), and Wikipedia explains why;

https://en.m.wikipedia.org/wiki/Potassium_bitartrate

'Baking Powder’ in the UK is a mixture of sodium bicarbonate, and potassium bitartrate, and the former was working against me, apparently.

Maybe I could have shaved an hour off the cleaning time.....

That looks promising ... I always wondered what that stuff was used for ... might get some use out of the peroxide mixture in the future here.

Roger

 

Link to comment
Share on other sites

Got a decision to make now. With this;

collapsed former.jpg

 

...no-one seems to think this is anything other than a recone. I've refoamed its twin and it looks and feels fine.

I can't imagine having one woofer original and the other reconed.

So the alternative is to accept that the Improved pair is to be sacrificed and take the woofers out of them. They look like this;

improvedwoof1.jpgimprovedwoof2.jpg

The one I've taken out has no marks on the back and the date is obscured, but otherwise looks like my 3a ceramic-ferrite woofers. Do we think they are A3's?  

The new surrounds measure up as the right ones (i didn't do them), but the dustcaps look like they were replaced as well.

There are no serial numbers on the back of the cabs.

Neither course of action is ideal. Perhaps I would put the Improved woofers in the 3as until something else turns up.

Anyone's thoughts welcome.

 

Tim

 

 

Link to comment
Share on other sites

On 7/4/2016 at 7:11 AM, owlsplace said:

That looks promising ... I always wondered what that stuff was used for ... might get some use out of the peroxide mixture in the future here.

Roger

 

as a tangent, I have a great sugar cookie recipie that uses cream of tartar....

Link to comment
Share on other sites

23 hours ago, TimmyTonga said:

Got a decision to make now. With this;

collapsed former.jpg

 

...no-one seems to think this is anything other than a recone. I've refoamed its twin and it looks and feels fine.

I can't imagine having one woofer original and the other reconed.

So the alternative is to accept that the Improved pair is to be sacrificed and take the woofers out of them. They look like this;

improvedwoof1.jpgimprovedwoof2.jpg

The one I've taken out has no marks on the back and the date is obscured, but otherwise looks like my 3a ceramic-ferrite woofers. Do we think they are A3's?  

The new surrounds measure up as the right ones (i didn't do them), but the dustcaps look like they were replaced as well.

There are no serial numbers on the back of the cabs.

Neither course of action is ideal. Perhaps I would put the Improved woofers in the 3as until something else turns up.

Anyone's thoughts welcome.

 

Tim

 

 

I'd hate to see a recone, too, especially because the replacement cones are lighter and stiffer, and will change the response of the woofer....RoyC, are there replacement voice coils available that could replace the damaged one while keeping the original cone?

Link to comment
Share on other sites

34 minutes ago, michiganpat said:

I'd hate to see a recone, too, especially because the replacement cones are lighter and stiffer, and will change the response of the woofer....RoyC, are there replacement voice coils available that could replace the damaged one while keeping the original cone?

There is a replacement voice coil, which is closer in spec to the original than the replacement cone is. I agree, it is the preferable way to go if the cone can be separated from the old voice coil without too much damage. Of course a new spider (and surround) must also be installed.

Roy

Link to comment
Share on other sites

 

 

3 hours ago, RoyC said:

There is a replacement voice coil, which is closer in spec to the original than the replacement cone is. I agree, it is the preferable way to go if the cone can be separated from the old voice coil without too much damage. Of course a new spider (and surround) must also be installed.

Roy

The vexing thing is, I can't find anyone in the UK who might be prepared to take on replacing the voice coil without replacing everything else. Wembley Loudspeakers ridiculed the idea.

Anyone with any suggestions or contacts - I'd be very glad to hear from you.

EU would also be OK, but the shipping anywhere else would be too painful.....

Happy to ship the parts over from the US though, if that's the only place they can be found.

regards and thanks 

Tim

Link to comment
Share on other sites

Can I ask a stupid question......?

The former is in two pieces, but if you turn the woofer on its front, the lower piece falls back into its correct position, and stays there if the woofer is turned over again very gently.

former.JPG

 

Given that the coil is at least intact, as it still reads the correct impedance, could I not find some way of reuniting the two pieces of former, and thus stand a chance of changing....nothing?

shimming would be a challenge, I grant you....

Link to comment
Share on other sites

5 hours ago, frankmarsi said:

Both are the standard kit wholesaled by MWA. The voice coil is close (dcr 3.5 ohms vs original 2.6 ohms), the cone is the thin/stiff one mentioned above, and the spider is not as compliant as original. Other than a better spider, there are no other options available. I can sometimes save the original cone using that replacement voice coil with a more compliant spider.

Roy

Link to comment
Share on other sites

On 4/7/2016 at 7:09 PM, TimmyTonga said:

Got a decision to make now. With this;

collapsed former.jpg

 

...no-one seems to think this is anything other than a recone. I've refoamed its twin and it looks and feels fine.

I can't imagine having one woofer original and the other reconed.

So the alternative is to accept that the Improved pair is to be sacrificed and take the woofers out of them. They look like this;

improvedwoof1.jpgimprovedwoof2.jpg

The one I've taken out has no marks on the back and the date is obscured, but otherwise looks like my 3a ceramic-ferrite woofers. Do we think they are A3's?  

The new surrounds measure up as the right ones (i didn't do them), but the dustcaps look like they were replaced as well.

There are no serial numbers on the back of the cabs.

Neither course of action is ideal. Perhaps I would put the Improved woofers in the 3as until something else turns up.

Anyone's thoughts welcome.

 

Tim

 

I have had the same problem with broken voice coil, managed to repair, see this post:

Don't sacrifice the Improved versions, due to the lack of the rheostats and an in general better cross-over, they sound better than the normal 3a, in my opinion.

BRgds Klaus

Link to comment
Share on other sites

Thanks Klaus, that's really encouraging! The repair you've undertaken was pretty much exactly what I had in mind as per my post from Tuesday, and it's great to hear that it was a success. I will definitely be attempting something similar.

regards/Tim

 

Link to comment
Share on other sites

50 minutes ago, KlausDK said:

Don't sacrifice the Improved versions, due to the lack of the rheostats and an in general better cross-over, they sound better than the normal 3a, in my opinion.

BRgds Klaus

I would sacrifice the Improved. The AR3a's sound much better, the Improved could not charm me.

But that's me ^_^

Link to comment
Share on other sites

50 minutes ago, KlausDK said:

Don't sacrifice the Improved versions, due to the lack of the rheostats and an in general better cross-over, they sound better than the normal 3a, in my opinion.

BRgds Klaus

I would sacrifice the Improved. The AR3a's sound much better, the Improved could not charm me.

But that's me ^_^

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...