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Old 8th April 2015, 08:45 PM   #1
esiuda is offline esiuda  United States
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Join Date: Sep 2011
Default Crown SL-2 Project

Thinking about restoring a Crown SL-2 I have owned since new. It works, but the bass seems muddy. (might just be me)

Any suggestions on changing out the op amps?

I would think I should replace all the caps on the board, due to the age any way. Suggestions on upgrading them?

I am fair with a iron, and have a good adjustable temp iron. I have also built several kits, so I am good on the mechanics of it, but short on the theory.

Any help, suggestions would be greatly helpful!
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Old 8th April 2015, 09:00 PM   #2
rayma is offline rayma  United States
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Join Date: Apr 2011
Location: Upper midwest
Originally Posted by esiuda View Post
I would think I should replace all the caps on the board, due to the age any way.
Yes, there are lots of electrolytic coupling caps in this unit, so replacing them should be an easy upgrade.
If you are still unhappy after that, try bypassing some circuit blocks entirely, like the low filter block,
and the tone control block. Only after that should you try replacements for the 5532 op amps.
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Old 28th April 2015, 12:44 PM   #3
esiuda is offline esiuda  United States
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Ok, before I start replacing parts, maybe you can offer some suggestions on where to start.

I finally hooked everything up in my new apartment, and at first I thought the speakers were blown... Bass was slightly muddy, but sounded eh, low Midrange the same, mid highs to highs sounded like a cracked or separated speaker cone, kind of buzzy and shrill.

I figured it was just my Ipod, so I pulled a CD player out of storage, and it was the same, as a last resort, I hooked up my home theater processor and everything was good!

So the Crown SL-2 is definitely bad. Any suggestions? As I said before, I was planning on replacing the caps, but with what type?

Any other suggestions would be helpful!
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Old 30th April 2015, 09:48 PM   #4
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Join Date: Jan 2010
Location: Jeffersonville, Indiana USA
Read your power supply voltages under load. any sag, you know which caps to replace first.
I find if I buy electrolytic caps over 3000 hours service life, they are premium in most other respects. Brands made outside the country of fake concrete schools and bridges, with the QA paperwork only tradition, have been Nichicon, Rubicon, Panasonic, Vishay Sprague. Others from the country of origin of 99% of all consumer products, that have worked okay so far in my hifi & organs, have been united chemicon and multicomp. I USA you are not allowed to know the country of origin of a product you buy until it has been shipped to your door.
Film caps and ceramic caps are not usual suspects of problems, unless an output transistor has failed and sent rail voltage banging through the driver and preamp areas through the base of the output transistor.
Bad solder joints and oxidized connectors are more problems than components, other than the speaker disconnect relay contacts. Cleaning the speaker relay contacts (if any) are sort of a first step on a 10 year old amp anway. Any disconnects in the signal path, like 1/4 phone plugs with the internal switch, are also candidates for the anti-oxigen patrol. No sandpaper or emory cloth, it leaves particles of insulating oxide embeded in the contact. Files or picks only.
Ribbon cables and any connector with a punch in contact to the wire, that needs to be removed and replaced after 10 years.
Unless you think a Crown is immune to a bad solder joint, I found one in a 98 Peavey product that every tech in there since then had missed. Since it made the output slam to positive rail frequently, there had been several such tech entries.
Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,1.3K, SP2-XT's, T-300 HF Proj's, Steinway console, Herald RA88a mixer, Wurlitzer 4500, 4300

Last edited by indianajo; 30th April 2015 at 09:52 PM.
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Old 30th April 2015, 10:31 PM   #5
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Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
You might want to replace the 3-leg regulators with the Super Regulators that Janneman redesigned for the DIYAUDIO store, or Peranders which have a smaller form factor. Unfortunately, the rails are a bit high to use the Linear Tech LT1963A. FWIW, I easily fit the original SR's into a much older IC-150.

If you're not uncomfortable with adapters, consider the OPA4134 to replace the TL074 in the phono sections. (Is a JFET opamp necessary here?)

Favorite electro coupling caps are Elna Silk or Nicchicon Muse, both available from DK.
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