Hello, fellow audio enthusiasts.
I have a pair of 30 years old Wharfedale Laser 90B speakers (pictures: 1, 2). I remember them having a very clear, warm tone. Lately the tweeter's have started to sound grainy, cutting in and out so I want to change the capacitors in the crossover.
The board is simple, three coils and 4 capacitors. Two of them are large enough to have their values clearly written, 450 and 4.7 uF. The smaller two have only this marking:
Measuring them is not an option since their value is probably completely off.
Last option would be to try dissecting the crossover, but I don't know the tweeter's frequency response... Quite mysterious.
Any ideas are most welcome.
I have a pair of 30 years old Wharfedale Laser 90B speakers (pictures: 1, 2). I remember them having a very clear, warm tone. Lately the tweeter's have started to sound grainy, cutting in and out so I want to change the capacitors in the crossover.
The board is simple, three coils and 4 capacitors. Two of them are large enough to have their values clearly written, 450 and 4.7 uF. The smaller two have only this marking:
Measuring them is not an option since their value is probably completely off.
Last option would be to try dissecting the crossover, but I don't know the tweeter's frequency response... Quite mysterious.
Any ideas are most welcome.
Last edited:
I had no batteries for my good camera, but I do have some taken quickly with my phone.
They're out of focus
, but maybe the shape and color tells something.
You can barely figure out "99-8330".
http://deviantpics.com/images/GxPgX.jpg
http://deviantpics.com/images/SAnXw.jpg
http://deviantpics.com/images/PhDt1.jpg
They're out of focus
, but maybe the shape and color tells something.You can barely figure out "99-8330".
http://deviantpics.com/images/GxPgX.jpg
http://deviantpics.com/images/SAnXw.jpg
http://deviantpics.com/images/PhDt1.jpg
They are "bipolar" caps which means they are not polarity concious. Can't help with the values though (the ALCAP 93-8330)
Is there any more writing on the lower half of the cap, the bit we can't see ?
If the tweeter is cutting out completely the caps wouldn't be the first suspects tbh. Other than poor connections and poor joints it could well be a problem with the tweeters themselves.
Is there any more writing on the lower half of the cap, the bit we can't see ?
If the tweeter is cutting out completely the caps wouldn't be the first suspects tbh. Other than poor connections and poor joints it could well be a problem with the tweeters themselves.
They are indeed bipolars. In doubt, replace them with mylar or even PP substitutes, they are not expensive anymore, and they will settle that part of the equation once and for all.
Which doesn't mean there are no other problems, but that's a simple and worthwhile fix for present and foreseeable problems related to capacitors
Which doesn't mean there are no other problems, but that's a simple and worthwhile fix for present and foreseeable problems related to capacitors
Heres a pic of the "90" crossover
Kolumny Wharfedale Laser 90 - graj?, a impedancja ∞ can't quite make out the values though
These caps are still available at falcon acoustics, maybe the dimensions can help narrow down the value?
rgds
James
Kolumny Wharfedale Laser 90 - graj?, a impedancja ∞ can't quite make out the values though
These caps are still available at falcon acoustics, maybe the dimensions can help narrow down the value?
rgds
James
Attachments
OK, so, we looked carefully underneath the mystery capacitor, there's definitely no other markings. Also, one is turned in a way so you can see the ALCAP 93-8330 repeating.
A quick check on the solder side of the board, the joints were nice and shiny so I suppose a bad connection is not the case. I'm a bit scared connecting the tweeter directly to the amplifier, maybe if I only played a sinewave over a few kHz to see if it breaks up then... But I rather wouldn't, this is only about a 10 euro investment, if we manage to figure the value out.
Nice find on the polish discussion and crossover picture, tvi. I did a little detective work and tried to match the capacitors in size with my blurry picture.
Animated
I first overlapped the biggest cap so that "ALCAP" writing would be the same size, and then rearranged the others. Looks promising. Still, because of the bad quality, I can't tell exactly the value, could be 4, 6, 8 uF... What makes you think 6, sofaspud?
The other thing is, the middle-sized capacitor in the Laser 90 crossover is a lot smaller than the one in 90B's, even though the specs for Laser 90 and 90B are the same, except the 90's are 3 liters bigger in volume.
Maybe it has something to do with 90B's middle capacitor being ±10 low loss. Don't know if that makes them bigger.
I'm going to try contacting Wharfedale directly (too optimistic?), also, maybe Falcon Acoustics knows something about those weird old markings (could it mean they were custom made?) and open the speaker again to get exact measurements of width and length of the little bugger.
A quick check on the solder side of the board, the joints were nice and shiny so I suppose a bad connection is not the case. I'm a bit scared connecting the tweeter directly to the amplifier, maybe if I only played a sinewave over a few kHz to see if it breaks up then... But I rather wouldn't, this is only about a 10 euro investment, if we manage to figure the value out.
Nice find on the polish discussion and crossover picture, tvi. I did a little detective work and tried to match the capacitors in size with my blurry picture.
Animated
I first overlapped the biggest cap so that "ALCAP" writing would be the same size, and then rearranged the others. Looks promising. Still, because of the bad quality, I can't tell exactly the value, could be 4, 6, 8 uF... What makes you think 6, sofaspud?
The other thing is, the middle-sized capacitor in the Laser 90 crossover is a lot smaller than the one in 90B's, even though the specs for Laser 90 and 90B are the same, except the 90's are 3 liters bigger in volume.
Maybe it has something to do with 90B's middle capacitor being ±10 low loss. Don't know if that makes them bigger.
I'm going to try contacting Wharfedale directly (too optimistic?
), also, maybe Falcon Acoustics knows something about those weird old markings (could it mean they were custom made?) and open the speaker again to get exact measurements of width and length of the little bugger.
You could try asking here,
UK Vintage Radio Discussion Forums
There is a hifi forum for older gear on the site.
It a forum like this and is very highly moderated but friendly non the less. You have to join to see anything.
UK Vintage Radio Discussion Forums
There is a hifi forum for older gear on the site.
It a forum like this and is very highly moderated but friendly non the less. You have to join to see anything.
You can see everything except the 'Modern' section without joining. You need a minimum number of posts before the 'Modern' section becomes visible. This helps keep the forum for vintage enthusiasts. The old Wharfedales should qualify for the vintage audio section so this won't be a problem.Mooly said:
They have it!
The good people at Wharfedale scanned the original service sheet and sent it to me.
http://www.deviantpics.com/images/2012/11/30/2.jpg
So, for anyone who will someday google this, the crossover is:
1x 450 uF
1x 4.7 uF, ±10% LL
2x 6 uF.
Sofaspud had a good guess.
The biggest one will have to be electrolyte bipolar, and the others I'll change for some kind of film capacitor.
Thank you all for helping!
The good people at Wharfedale scanned the original service sheet and sent it to me.
http://www.deviantpics.com/images/2012/11/30/2.jpg
So, for anyone who will someday google this, the crossover is:
1x 450 uF
1x 4.7 uF, ±10% LL
2x 6 uF.
Sofaspud had a good guess.
The biggest one will have to be electrolyte bipolar, and the others I'll change for some kind of film capacitor.
Thank you all for helping!
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