searching for suitable LDR's to fix LA4a

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strangeandbouncy

Well-known member
Joined
Aug 8, 2004
Messages
2,112
Location
West Sussex. UK
Wotcha, Guys,

Hope that "The Lab" is the right place for this. Thousand pardons extant if not . . .

I have a fire damaged LA4a that has had it's LDR's removed/lost/whatever. Apparently, the only surfaces to be seriously damaged by the action of smoke was the lead-in wires of the LDR's! Etched right through . . . Bizarre . . . . Apart from this, the unit passes audio, ,but obviously no Gain Reduction. Sadly, the carcasses of the LDR's are no longer in situ. - Bah!

Do any of you Esteemed Gentlefolk know where to find suitable replacements? I have tried the ones available from Maplins . . . and they are not suitable at all! - No Siree . . . Are they the same as T4b? If so, can anyone help?

Thanks,

ANdyP
 
I used to have a la4, I dont recall the part number but mine had a tiny LDR similar to the part used in the forssell limiter, totally different from the t4b assembly, its about the size of a small capacitor.

the part number in the LA4 manual is HM13-0499-02 red. No idea if this was a urei in house number or not. I have a silonex ldr I can send for you to try if you like. The la4 I used to own had a part similar installed, I dont think it was the original factory part but they can definitley be made to run with a four leg ldr. Mine sounded pretty nice.

also, looking at the schematic, the ldr gets 15 volts through a 47ohm resistor, might be useful info for selecting the right part.

hope this helps

dave
 
Great link all the same, Peter! I am not sure that Mr Soundguy's(ex)La4a is the same as mine, since these LDR's were obviously not too tiny. I am referong to the LDR inside a T4B . . . i seem to remember a tech telling me that they were the same, or perhaps similar to La3/La2. Thanks for the offer, tho' Dave! by the way, What exactly do you mean by a four-leg LDR?

thanks ever so much for your replies, guys, most appreciated.


ANdyP
 
I've been searching for Clairex CL5M5L or Silonex NSL 5910.

Silonex only seem to do NSL 5912 . . . is this the same? or does anyone know of a supply of the original Clairex/Silonex/Whatever?

Cheers,

ANdyP
 
andy

here's a photo. I dont think it was stock, but you might have better luck trying to make an off the shelf part work than searching out whatever they used. I didnt install this LDR, I bought it like that so cant really comment on wether or not there is a direct replacement or if you need to tweak the circuit to make a current part work.

la4.jpg


the ldr has a piece of tape on it in the upper left part of the photo.

dave
 
From the old place

http://66.102.9.104/search?q=cache:0-7IVrX1sEsJ:www.recording.org/postp155462.html%26highlight%3D+site:www.recording.org+t4b&hl=en

http://66.102.9.104/search?q=cache:T5bn1wuURM4J:www.recording.org/posts19084-0.html%26postdays%3D0%26postorder%3Dasc%26highlight%3D+site:www.recording.org+t4b&hl=en
 
sorry for the offtop
2 soundguy :

And what it for an element in the metal case on the end of a PCB (it is marked as K1)? The relay?
You did a photo? If "yes" it is possible to ask to make you some more
"porno pic's"... ? :roll: :guinness:
Especially from paths on a payment... though probably the cover of the case with a bottom does not open...

In advance thanks
 
Here is the link for the LA manuals in case you do not have it:

http://www.jblproservice.com/navigation/Vintage%20JBL-UREI%20Electronics.html
 
There were a couple of versions.

Early ones used big silver discs like the ones in the T4. NSLs, Silonex or Clairex. -NSL are the only people still in the business as Far as I know.

later ones used Vactrols, though often-as on Eddie Audio's site, the exact model can be switched or swapped for preference.

Don't forget to re-set the GR tracking and GR zero as necessary, though vacrols are understood to be more consistent than all the others.

Hey CJ, I'm back... was that you at SFO on the bike with the basket and paniers, pulling all the empty coke cans from the trash baskets? -Sorry for the harsh words, dude!

Keith
 
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