My Tannoys grew up

[graham67]

Hi Edward,

If they havent been touched for 25 years, it is almost certain they will need refoaming.

I see you are in London, so I can highly recommend Wembley Loudspeakers who refoamed my 385 HPDs at a very reasonable cost a couple of years ago.

atb

[cooky]

The driver looks fine, foam looks good. I'd replace the crossover gasket foam and clean the pots with deoxit etc and maybe reflow all the solder joints on the crossover-10 minute job. Wembley and Lockwood do the 'quick and dirty' refoam ie they stick it to the front of the cone and in my opinion I wouldn't buy a pair done that way..

[walpurgis]

Wembley and Lockwood do the 'quick and dirty' refoam ie they stick it to the front of the cone and in my opinion I wouldn't buy a pair done that way..

Neither would I, unless they were cheap and I was planning to replace the surrounds and do it properly.

By the way, it could be that those are original surrounds, as the white glue holding them under the Girdacoustic cone ribs appears as new and undisturbed.

[cooky]

Neither would I, unless they were cheap and I was planning to replace the surrounds and do it properly.

By the way, it could be that those are original surrounds, as the white glue holding them under the Girdacoustic cone ribs appears as new and undisturbed.

Yeah I was going to suggest they may well have been re-coned at some point.

[Edward]

Geoff and Frank you both are agreeing with each other but appear to be saying the opposite. Not clear if these speakers have been reconed or had new surrounds now.

Anyway the reason I took the driver out for now was that I was getting partial sound from that one speaker which at some point was cured for a while by moving the treble energy pot. So the idea was to deox that pot. Putting it all together after the deox it worked fine for a while, but then I started getting hum from that speaker. So a rapid switch off and now have to have a think. Suspect that some rust or something has loosened in the pot creating a weak short. Is there an easy way of opening up the pot, replacing it or simply bypassing it?

[walpurgis]

Geoff and Frank you both are agreeing with each other but appear to be saying the opposite.

No. A recone would be as I described, showing intact glue on the bracing ribs.

The treble controls aren't pots, they're rotary switches and definitely do benefit from cleaning. Switch cleaner is fine, just keep away from the plastic of the crossover.

If you work the controls back and forth a few times, you should find any apparent faults start going away.

[Edward]

No. A recone would be as I described, showing intact glue on the bracing ribs.

The treble controls aren't pots, they're rotary switches and definitely do benefit from cleaning. Switch cleaner is fine, just keep away from the plastic of the crossover.

If you work the controls back and forth a few times, you should find any apparent faults start going away.

Thanks Geoff. Yes rotary switches (I used the terminology frank used). I have worked the controls back and forth a lot but that did not help. I'll try more.

What do you think may be causing the hum?

cheers
Edward

[cooky]

Geoff and Frank you both are agreeing with each other but appear to be saying the opposite. Not clear if these speakers have been reconed or had new surrounds now.

Anyway the reason I took the driver out for now was that I was getting partial sound from that one speaker which at some point was cured for a while by moving the treble energy pot. So the idea was to deox that pot. Putting it all together after the deox it worked fine for a while, but then I started getting hum from that speaker. So a rapid switch off and now have to have a think. Suspect that some rust or something has loosened in the pot creating a weak short. Is there an easy way of opening up the pot, replacing it or simply bypassing it?

OK the foams look good so for a 40 year driver with a foam life expectancy of 20 years max and judging by the appearance of the strut glue line they dont look to have been re foamed so they've likely been reconed within the last 15 years or so..
'Hum' seems a weird speaker HF fault.
Swap L/R speakers over and see if the hum follows the speaker-if it doesn't, its your amp.
You can open the switches(rotary) up but its a pain to do-i'd flush the sh!t out of them and manipulate the switches .
It's possible to hard wire the tone controls(or should I say energy and level controls....), bypassing the switches but I've never done it.

[JohnJo]

And now the crossover.

Hi Edward. Is there burning on the 2.2ohm resistor, bottom right of this crossover?

It looks scorched to me but photo is out of focus. Try re-flowing these solder joints.

It's the short resistor, about half the length of the others and is a known fail point, have a read at this website http://www.cma4ch.org/chemo/attivita/xover385a.html

Those do not look like the original foam surrounds. Mine were exactly the same as the those in the photo Roy posted of Mike's.

I have the gold plated speaker plugs. They measure the same resistance on my multimeter as the original Tannoy ones, 0.1 ohm, which is just the resolution of the meter. You'd need a milliohm meter to get a truer reading. The big plus is they're less prone to corrosion and most importantly the contacts are spring loaded so always stay tight.

I bypassed the switches on mine with soldered wire links. Certainly an improvement in clarity but cleaning the switches might be just as good.

[Edward]

Hi Edward. Is there burning on the 2.2ohm resistor, bottom right of this crossover?

It looks scorched to me but photo is out of focus. Try re-flowing these solder joints.

It's the short resistor, about half the length of the others and is a known fail point, have a read at this website http://www.cma4ch.org/chemo/attivita/xover385a.html

Those do not look like the original foam surrounds. Mine were exactly the same as the those in the photo Roy posted of Mike's.

I have the gold plated speaker plugs. They measure the same resistance on my multimeter as the original Tannoy ones, 0.1 ohm, which is just the resolution of the meter. You'd need a milliohm meter to get a truer reading. The big plus is they're less prone to corrosion and most importantly the contacts are spring loaded so always stay tight.

I bypassed the switches on mine with soldered wire links. Certainly an improvement in clarity but cleaning the switches might be just as good.

Hi John

Yes I did notice that scorching. I think I will have to get the xover out again and measure everything with the MM to detect cold joints or broken tracks and reflow as required. Hopefully that will sort things out. I'll also measure the standard 4 pin plug but like you my MM only goes to 0.1 ohm (+\- 0.8%). I assume I will also be able to measure the various continuities of the rotary switch.

If I found reflowing stuff does not work I may ask you which joints you hard wired to bypass the switches. Or perhaps you could let me know anyhow.

Failing all that I may just get Mark Pitcher's (mainlytannoy) drop in crossover boards and be done with that for now. Or perhaps Paul (RFC) can also do drop in boards. My project does not cost justify his external (rather wonderful) crossovers.