https://mou.sr/49rXudp Like this one ?
Avalon vt-737sp
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pucho812
Well-known member
Yes that is a pdip thru-hole part and the correct chip
TheseGoToEleven
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While you’re waiting, you may as well desolder the opamp. If you don’t have one of the desoldering guns like a Haiko that makes it easy, then you might want to cut all the legs off so you can desolder them individually.
Then before putting the new opamp in, do a test: set the gain & output knobs to zero, give the Avalon a line input signal, and let us know what voltages you see on solder points 5, 6, 7 & 8 (the pins for the XLR line in and output jacks). In theory output should equal input. Let’s make sure you are getting appropriate output before putting the new opamp in.
Then before putting the new opamp in, do a test: set the gain & output knobs to zero, give the Avalon a line input signal, and let us know what voltages you see on solder points 5, 6, 7 & 8 (the pins for the XLR line in and output jacks). In theory output should equal input. Let’s make sure you are getting appropriate output before putting the new opamp in.
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Wow. U must have a camera in my living room. Just did exactly what u said but didn’t do that test. Long day so
I’ll try that test tomorrow. It was tough cutting those legs and clearing holes but it’s in and working !! Just have to calibrate completely but meter is working perfectly. Thanks to all of you that kept me going. Any of you guys come to New York dinner and drinks on me. I will update tomorrow just to make sure it 100%. But it’s not pinning anymore and feeding it 1k at 0dbu I was able to play with it and get meter to zero out. K. Thanks again !!
I’ll try that test tomorrow. It was tough cutting those legs and clearing holes but it’s in and working !! Just have to calibrate completely but meter is working perfectly. Thanks to all of you that kept me going. Any of you guys come to New York dinner and drinks on me. I will update tomorrow just to make sure it 100%. But it’s not pinning anymore and feeding it 1k at 0dbu I was able to play with it and get meter to zero out. K. Thanks again !!
pucho812
Well-known member
Vu meter adjust. Line input a +4dBu signal. Sine wave @1k. Have both input and output at center detent. No eq, no compression, meter looking at output. The output unit level should match the meter and vice versa. So +4 at the output should be 0VU. If you do not have a perfect +4 output I believe I shared calibration instructions before. If not I can. There are 2 trim pots in play, one is level one is the meter output.
Oh and great job on the unit.
Oh and great job on the unit.
Thanks. Real close to finishing it with the help of all of you guys. Feeding 1k at 4dbu I got 600v at input and output to start. I zeroed out meter and began compressor readings. To
Measure -10 dbu I used a reference of 120v at the output and 269v for -3 dbu. I got those references by feeding 1k at -10 and -3 dbu and reading voltage at output with meter and compressor buttons off. I then engaged both meter and compressor and did the 12o’clock and 9p’oclock respectively. Hope I explained this somewhat ok and is correct. I was trying to google what -10dbu and -3dbu corespond to in voltage.
Measure -10 dbu I used a reference of 120v at the output and 269v for -3 dbu. I got those references by feeding 1k at -10 and -3 dbu and reading voltage at output with meter and compressor buttons off. I then engaged both meter and compressor and did the 12o’clock and 9p’oclock respectively. Hope I explained this somewhat ok and is correct. I was trying to google what -10dbu and -3dbu corespond to in voltage.
pucho812
Well-known member
600v? You mean 1.23V? Where is the 600v coming from
Brian Roth
Well-known member
I was wondering the same thing! Perhaps this calculator would assist the OP.
https://sengpielaudio.com/calculator-db-volt.htm
Bri
pucho812
Well-known member
Maybe he left out a decimal point?
Brian Roth
Well-known member
Well, as Grandad Roth would say "Something's haywire here!" <g>
Bri
Bri
K. Maybe I was measuring wrong. I was measuring one side to ground and one side to pin 2 and 3. Going across pin 2 & 3 I get 1.20 volts on input and out. Either way I think meter is correct. Thanks for that website. I had it once in my bookmarks and used it. I did notice compressor work intermittently and when I looked at pot one of the wires broke off. Gonna try and resolder but I think it was the actual lead that came off. Might have to get new one. K.
pucho812
Well-known member
Ouch.Well I couldn’t save the pot. Have to order another. The lead has broken off. But I think I have the meter calibrated and everything is good.
Yeah. Just ways things are going for me lately. Haha. Ever get that feeling ? Anyway, I think it’s almost complete and hopefully I can enjoy it for years to come. Once I get into my future house I would like to set up a correct workbench and get a better understanding and knowledge for how circuits work. I have all my gear in storage now while working on house to sell. So whatever time I do have to work on things at a small apt we have it’s a chore setting things up and putting back away. Gonna order pot on Monday so I guess I’ll update later in week. Also do u guys give advice on other units.
TheseGoToEleven
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- Sep 4, 2020
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Thanks for the offer! I’ve just passed the official repair center in LA/Glendale while riding the train, and gave them a wave for you. NY is a fair ways off
pucho812
Well-known member
Your in my neck of the woods.Thanks for the offer! I’ve just passed the official repair center in LA/Glendale while riding the train, and gave them a wave for you. NY is a fair ways off
pucho812
Well-known member
I know that feeling. I’ve had it since the top of February. It’s a long story. But I am surviving and not destitute, so cracking on as best I can.
Well if I learned anything from this endeavor it’s called perseverance I think. lol. I’m either very stubborn or like my wife says, very motivated. Sometimes it seems like hard times come easy but u have to grind thru it to finally get to the other side. That’s what it definitely felt like repairing this unit. I see light at the end of the tunnel. K will update once I replace pot.
Got the compression pot and replaced. Things are about finished. The front instrument jack is loose but I think it’s the black plastic washer. Nothing that can’t wait. All my stuff is in storage and I think I will put the 737 away for awhile. Thanks to everyone that helped. Especially PUCHO !! Haha. Do u guys join a lot of these posts? I bought an Ada MP1 classic that needs repair and was on that site. I might put it away too but might try and work on it. Trying to fix house and move has put a lot of adventures on hold. K thanks again. My email is [email protected] for future reference but I’ll still watch this post
