How do i upgrade UREI 545 parametrics?

[Spendor]

I posted this once but had no replies - thought I'd try once more. I have a pair of blackface 545 Eq's - i haven't used them for ages as they are noisy. I'm not talking heaps here, but when i flick the bypass switch the noise disappears. Could it be that these are just noisy units - they are getting on in years - but it would be nice to use them or maybe I should sell them on and make a Pultec or even the calrec?
Were these considered a good unit?
Would it be relatively easy to improve them and bring them into use again? Are there opamps with better specs I could drop in to replace the existing ones. What else could I do to improve them?
Any thoughts greatly appreciated!
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[okgb]

iirc , it uses the same obsolete I.C. as in the
la4 comp , so look for companies that make retro-fit
ic adaptors , jlm i think makes one , not so cheap however

 

[amorris]

I just recently rebuilt 2 la4s and the rc4136 is still very available from digikey. (1233 in stock) but the chip has been said to have bad specs. tangible technology sells retro boards that plug in so you can put in better faster chips.

to check if this is the noise, take one out and see if it gets a little quieter. leaving the downstream chips in. cumulativley, it should get 1/n quieter.

 

[gar381]

http://www.tangible-technology.com/optical/LA4_fee.html#about

GARY

 

[Spendor]

Thanks you all for the information - although expensive I think It will make them usable again. Cheers.