Damaged speaker. Repair or replace?

[Spxleisure]

Hi another newbie here.

I am thinking about restoring an old Bush valve amp radio. I have a small tear in the speaker paper and wondered whether it's worth sourcing a comparable speaker or going for something new. (see photos) must await advice, do not know where to start really.

[Stuart R]

Hello and welcome!

I've never done it, but search on this forum and people have done successful loudspeaker cone repairs with tissue paper and PVA glue, I think.

How far on with your project are you? That looks like it could be a Bush DAC90A and there could be other components need replacing before you get any sound at all out of the speaker if the set has not been used for a while.

If it is a DAC90A or similar set are you aware of the safety issues associated with the 'Live Chassis' design? There are two ways that the mains lead can be attached, choose the wrong way and all the metalwork of the radio will become live and potentially lethal. Get that bit right there are plenty of parts on the set that can give you a surprising nip if you know what you're doing - even with the set unplugged.

Sorry if this is teaching you to suck eggs, but I'm basing this answer on "do not know where to start".

Please take time to read up on this via the forum and go carefully. There's plenty of help available here.

Regards,

SR

[Lloyd 1985]

Hi,

Welcome to the forum!

I often repair speakers with damaged cones, the favourite repair is to use a bit of tissue paper (kitchen towel, bog roll, or similar) and some slightly watered down PVA glue. Cut a small piece of tissue that covers the rip, place it on the cone and dab the glue on with a small artists paintbrush, or even a cotton bud. Leave it to dry and the speaker will be fine again.

If the speaker is completely ruined, then a post in the parts wanted section might get you one, Bush used these speakers in quite a few of their radios.

Regards,
Lloyd

[Nickthedentist]

I'd definitely repair the existing Celestion unit.

Not only will the set be kept original, but the performance will be as-intended. Modern or different speakers may not work nearly so well.

Note that the central/inner suspension can become detached in these speakers giving rise to a buzzy/rattly sound, but this is an easy fix too: do a forum search.

Could you post a pic showing the damage?

N.

[Spxleisure]

Stuart
Thanks for the advice it is a DAC90A and I popped into a local electronics repair guy and he was advising me of the same issues about the live chassis etc. He advised I source a wiring diagram to be on the safe side. I suspect they may be available from others on the forum although I am not sure. The set itself is a little dusty inside so I suspect some of the wiring does need an overhaul. Hopefully the valves will be Ok but it sounds as if I have come to the right place for knowledge and information. Thanks again Dave

[paulsherwin]

Certainly you should try to repair a tear. There's nothing to lose and a high chance of success. In the past I've repaired them with nothing more than a strip of old newspaper and some wallpaper paste.

If you find you do need a replacement a forum member is likely to have something suitable from a scrap set.

[Spxleisure]

Here goes

[paulsherwin]

The main tear is an easy repair. The torn suspension is a bit trickier, but after you have patched the main tear you will probably find that you can join the torn edges of the suspension with glue without the need to patch. Alternatively you can just leave the suspension unrepaired - it's unlikely to have an audible effect.

[emeritus]

"Traditional" solvent-based Evo-stik Impact is excellent for joining paper or card edge-to-edge, and remains flexible.

[G6Tanuki]

I don't like using Evo-Stik or equivalents on this sort of thing - it always seems to remain heavy even when set - and adding extra mass to the loudspeaker of an old radio will only further compromise the already-poor treble response!

I've had success in the past using "Tyvek" [the slightly-shiny stuff the white untearable envelopes are made from] - I dislike using ordinary tissue-paper/bog-roll-type paper as these days it's often made from recycled paper and so has very short fibres which lead to poor tensile-strength so you end up using more paper (meaning more added mass... poorer audio response....) to effect a repair.

[Spxleisure]

Got myself a circuit diagram, just need to get my head around it.
Found another problem with a lose wire. Looks like it comes from R17 the volume control unit but I am not sure if this should be a loop to the voltage regulator. Wire seems too short for anything else. Any one out there can help me?
Regards, Dave

[emeritus]

Only a very thin film of Evostik is necessary; it is very strong. I haven't had to repair a speaker cone for ages, but for assembling box-like structures of heavy paper, I apply it to the edges using a plastic glue spreader, being careful not to get any on the surface. I use 250ml tins rather than tubes, as with a tin it is possible to dip the tip of a spreader in the glue to pick up only what is needed and transfer glue to the edge of the paper.

[McMurdo]

there's actually a proper speaker repair glue, which is black, comes in a tube and dries just like a rubber glove or a thinner equivalent, It wont tear and sticks like mad. It is formulated to repaur speaker cone tears at any point.
Unfortunately I can only get it from JBL (the speaker makers) and it's made by a US firm called CP Moyen, type RS-3087.

There's a supplier on Amazon UK who sell an 'equivalent' here:

https://www.amazon.co.uk/MG-Chemical.../dp/B005T8Y5WW

I haven't tried the latter type, but it's also stocked by RS's sister company Allied Electronics where you can download the datasheets.

[Ed_Dinning]

Hi, The Dac90a is a great set to start on from the point of view of a simple circuit, but you need to beware of the potentially live chassis.
Have a good read of the notes in this forum about repairs and do not be tempted to power up until the mains filter and audio coupling cap (That Cap) have been replaced.
Do your initial powering up with a lamp limiter, a valuable piece of kit that is easily and cheaply made.
#
Ed

[Boater Sam]

Can't be sure where that red wire is from, follow the circuit diagram from where the other end goes.
The wire is shot anyway and needs replacing. If there are a lot that are losing the insulation like this one you will need to replace them. PTFE insulated wire is handy near things that get hot like this.
I assume you are referring to the mains dropper resistor as the "voltage regulator"?

[electrogram]

The red wire is for the mains voltage selector and is attached to the top part of the the dropper, as is its other end, as it should be for 240 volt mains. The attached end can be moved to other tappings lower down the dropper for lower voltage mains - 220 or 200 volts. These latter are very unlikely these days. I usually remove this wire altogether

[Spxleisure]

Electro gram

Thanks for your message - one end of the wire is attached to the mains voltage selector but appears to loop over. It has broken at that end. As the wire is pretty short in length I can only assume it connects back on the dropper on the other side ( to create the loop) on that side it sits alongside the wire coming up from the Valve (V5) or R17 on the circuit diagram. Are you able to concur with my thinking?

[AC/HL]

This should clarify, the link is only needed for legacy mains voltages in the UK.

[Spxleisure]

From the feedback, it seems as if I can simply take the wire away without any harm being done. Any other comments anyone?

[paulsherwin]

That is correct.