rc4136 replacement in Urei LA4A

[antoniosolo]

I am doing the mod myself to my silverface la4a which is a later model so the rc4136 doesn't need soldering to pop in the brown dog adapters.  Which opamp can I swap out the TI RC4136's with that will not require any other modification for current draw differences or bandwidth differences?  Thank you so much in advance for any help or advice you can offer.

 

[nielsk]

TL075
I've got some if you can't find 'em

 

[VanGenz]

RC4136 Upgrade Adapter
http://cimarrontechnology.com/rc4136upgradeadapter.aspx

 

[antoniosolo]

So I popped in some of what I believe are 2604's on browndog adapters and the xfmr fried in about 4 minutes.  Eddie Chiletti says the 2604's could not have been the issue and he wasn't involved in the sale anyway so.....How in the heck did this happen?

 

[sahib]

I have 4 silver faces and all of them are modded with 2604s and Browndog PCBs. However, last week I was in Istanbul and maintained a pair of black face for a friend. I popped in the 2604s and the output transformer screamed of oscillation. I did not have much time to go through the problem and put the 4136 back. Did you have the same problem?

 

[antoniosolo]

No. I was told it was plug and play.  I am told that something else was the issue so I am awaiting the tech to show up with a new xfmr to correct the situation.  I want to keep the 2604's.

 

[amorris@home]

the rc4136 is still available. I just ordered some last year and they worked fine. the pin out is unique.

 

[kazper]

Adapters
http://www.jlmaudio.com/4136%20to%202%20x%20NE5532.htm

http://www.tangible-technology.com/optical/LA_4_index.html

Manual:
http://www.jblproservice.com/pdf/Vintage%20JBL-UREI%20Electronics/UREI-LA-4%20manual.pdf

What is the specs for the output transformer?

 

[antoniosolo]

24v center tapped I am told at least 3/4 amp.  UA tells me nothing and sends me elsewhere.  I realized I installed the opamps without paying attention to pin 1.  Could that have caused the xfmr failure?

 

[antoniosolo]

Update......thankfully I didn't kill it or the xfmr....I had no idea the opamps went in a certain way, corrected the alignment and she is alive and well....so far.....I have faith and learned my lesson.  I remember asking if they went in a certain way.  Someone didn't answer me!

 

[sahib]

You certainly didn't ask here. You naturally have to align the notches on the socket and the opamp.

Anyhow, good job that nothing serious happened.

 

[antoniosolo]

I asked not here but somewhere else and got no reply.  Thank you all for your help in this matter.  Thumb:  Guiness: Guiness

 

[okgb]

usually a semi circle to indicate the top with a smaller dot to show pin 1
can't blame that on no one telling you , if you're not sure , do more research
but i've certainly wasted too much of my own time being impatient .

 

[antoniosolo]

Movie TEN COMMANDMENTS quote:
"too many ears tie a rats tongue"
not that any of you are rats but you may resemble a rat or be born in the year of the rat!
I won't mention the suppliers name as I don't want to blame him,  but I did ask in our many emails if they went in a certain way....I am more than helpful in my field,  even if a guy says he can't afford it,  I offer to talk him through as I can understand at times.....

 

[antoniosolo]

Oh well....I did smoke those 2604's and these scratchy sounds and inability to control gain in the la4a happened with no warning...... so I replaced my rc4136 but at C1 I put the extra oa2134 that the seller threw in for me to try out.  Sounds as smooth as ever...maybe even better...yes I am still kicking myself!

 

[antoniosolo]

Brown Dog/Phil Maltby has agreed to replace the 2604's I burnt and has introduced me to some other opamps he is mounting on his boards.  Awesome customer service if you ask me. 

 

[Wrekdahouse]

Hello, i've just aquired a pair of silver LA4's,  one has the stock rc4136 opamps,  but the other one is fitted with:
IC1: rc4136
IC2: TL075
IC3: ECG997 P3122NAE

is this second LA4 upgraded or modded ?

any further info is really welcome,

best regards,

Patricio

 

[Wrekdahouse]

bump ?

 

[SIXTYNINER]

ba-bump

 

[okgb]

I have abunch of these I.C,'s
if anyone needs