college101
Well-known member
Looks good!!!
All things LA2a related
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originalscottyg
Member
Thanks!! The meter I used is a Sifam Retro R25ASQ. The integrated illumination is via LED rated for 12VDC 40 mA. It was suggested to me to use some diodes and caps in a voltage doubler configuration tapped off the heater secondaries to feed the meter LEDs. Suggested values for the caps are 100uF 25v. A current limiting "dropping" resistor for the LED was mentioned as well. One question is since the meter has the LEDs integrated into the meter and is labeled as 12V 40mA, do I need an external dropping resistor, or is that already incorporated into the meter? For the diodes, can I just get 2 more of the IN4007s that are used in the main power supply? Will I need any more filter caps? I will breadboard this and measure the output when I get a few minutes, but I thought I'd ask here as well.
Thanks in advance for the help!!
Thanks in advance for the help!!
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college101
Well-known member
OK guys..if you been following me...here goes!!
I got a Yamaha MG102c mixer today...set the cd player up, ran a line to the 2A input
Set it to +4....we have positive movement BUT
NOTHING when in GR mode...what should I look for?
I got a Yamaha MG102c mixer today...set the cd player up, ran a line to the 2A input
Set it to +4....we have positive movement BUT
NOTHING when in GR mode...what should I look for?
college101
Well-known member
thestudio... most of the people on here are real DIY types...they make their own cases...get creative and unique
Guys whats up with my GR not registering?
Guys whats up with my GR not registering?
originalscottyg
Member
college101- Sorry, I don't think I am going to be much help to you for troubleshooting. I am pretty much a noob myself.
The expected behavior is that when the the gain reduction pot is off (full CCW) the meter should rest at the 0VU mark on your meter in gain reduction mode, provided you zero'd out your meter with the zero adjust pot. As you turn up the gain reduction, if there is decent input signal, the needle should begin to deflect to the left in time with the music, eventually getting "buried" on the left end of the meter. Sorry, to restate the obvious, but you did ask what to look for in GR mode. Does the needle not move from the zero mark even if you turn the GR knob all the way up (fully CW)? If you are getting a normal looking signal on +4 mode (needle averaging around zero, peaking up to +3 or more) without having to crank the gain past noon, and the needle doesn't budge in GR mode if you sweep the GR knob to both extremes, then there is definitely a problem. Probably a problem that I can't help you with unfortunately. I left mine at work today, but I'll probably have it at home tomorrow if you need some voltage references.
On another topic, I breadboarded the voltage doubler I mentioned above with some IN4001's (50V 1A) and some 100uF 35V electrolytics. The output voltage is about 16VDC when I feed in about 6VAC. Should I use a voltage divider to tap off the 12VDC I need for the meter LED? If so, I am guessing I should calculate resistor values so that I limit the current to 40mA as specified on the meter. Or does that mean that the meter's LED is internally current limited to 40mA? I know this is easy stuff, but I am a noob and would appreciate any hand holding available ;-)
thestudio - you might try here:
http://www.diy-racked.com/diy-talk/viewtopic.php?f=7&t=18
I don't think he has the hinged front panel, but otherwise they are pretty close.
Hope that helps.
On second thought, it looks like the full cases are quite a bit deeper than the original. They look nice, though.
The expected behavior is that when the the gain reduction pot is off (full CCW) the meter should rest at the 0VU mark on your meter in gain reduction mode, provided you zero'd out your meter with the zero adjust pot. As you turn up the gain reduction, if there is decent input signal, the needle should begin to deflect to the left in time with the music, eventually getting "buried" on the left end of the meter. Sorry, to restate the obvious, but you did ask what to look for in GR mode. Does the needle not move from the zero mark even if you turn the GR knob all the way up (fully CW)? If you are getting a normal looking signal on +4 mode (needle averaging around zero, peaking up to +3 or more) without having to crank the gain past noon, and the needle doesn't budge in GR mode if you sweep the GR knob to both extremes, then there is definitely a problem. Probably a problem that I can't help you with unfortunately. I left mine at work today, but I'll probably have it at home tomorrow if you need some voltage references.
On another topic, I breadboarded the voltage doubler I mentioned above with some IN4001's (50V 1A) and some 100uF 35V electrolytics. The output voltage is about 16VDC when I feed in about 6VAC. Should I use a voltage divider to tap off the 12VDC I need for the meter LED? If so, I am guessing I should calculate resistor values so that I limit the current to 40mA as specified on the meter. Or does that mean that the meter's LED is internally current limited to 40mA? I know this is easy stuff, but I am a noob and would appreciate any hand holding available ;-)
thestudio - you might try here:
http://www.diy-racked.com/diy-talk/viewtopic.php?f=7&t=18
I don't think he has the hinged front panel, but otherwise they are pretty close.
Hope that helps.
On second thought, it looks like the full cases are quite a bit deeper than the original. They look nice, though.
college101
Well-known member
Ok guys...last attempt to get this right has failed again..I get signal in +4 and nothing happens in GR mode
I found a Capacitor I had that wrong value in, and swapped it out...still no change...Ive lost a lot of hope that this project is even do-able
Can you guide me again, to get back on track?
I found a Capacitor I had that wrong value in, and swapped it out...still no change...Ive lost a lot of hope that this project is even do-able
Can you guide me again, to get back on track?
simonsez
Well-known member
college101 said:
Tell us your situation right now (as much as possible), voltage test point, is it pass audio? I've just finished built my second one (I'm noobie too). Yes, You can do it...
kazper
Well-known member
college101 said:
Take a couple days-weeks off, let it sit there and then come back as if your looking at someone else's work.
Print a couple copy's of the schematic and follow it through the build. Highlight out and check for polarity and the part value.
Now as far as testing goes, read the manual. Read the Instructions posted in the thread. Do them in order and most likely you'll have a working La2A after that. If not buy a Drip PCB as he takes all your possible wiring mistakes out of the loop or send your build to someone with 2 benji's and say help....
As a note the last build I had done had a bad NOS T4B, once I placed in one from Drip the GR started working just fine. You could do a ghetto nightligt version as a test...
college101
Well-known member
Explain the ghetto night light version test Kazper...I probably need to do it~!
My unit does pass audio...it just does not work in GR mode
I will be taking new measurements soon...
My unit does pass audio...it just does not work in GR mode
I will be taking new measurements soon...
simonsez
Well-known member
college101 said:
Did you hear compressed audio when peak reduction turn CW? GR mode has nothing to do with audio, it just the meter mode selector. Did you check the voltage point already?
college101
Well-known member
I am at work today, and then college tonight...Having a baby with the wife tommorow...I wont get time to check voltage points till friday or saturday, once the new baby is sleeping!
I dont hear compressed audio when I trun peak reduction( I thought this would be affected by turning the pots on the back of the unit, I adjust those two pots and still no difference...
The needle jumps to zero when I select the GR mode,then if I have my cd player playing into my new yamaha mixer, into the 2A, the needle does not move...its like it is not even registering that signal is going through it... but the audio is playing out my guitar amp!
I dont hear compressed audio when I trun peak reduction( I thought this would be affected by turning the pots on the back of the unit, I adjust those two pots and still no difference...
The needle jumps to zero when I select the GR mode,then if I have my cd player playing into my new yamaha mixer, into the 2A, the needle does not move...its like it is not even registering that signal is going through it... but the audio is playing out my guitar amp!
Read simonsez comment once again!
The swich +10/+4/GR just changes what the VU is showing, it should not change the audio. (if correctly connected)
The LA2A should pass audio in all modes and compress when the front left (=gain reduction) knob is turned clockwise.
(And if enough signal is present on the input)
If it´s not compressing, start checking if the T4b gets enough signal from the sidechain circuit. That´s the lower left part
of the schematic. If you´re careful, you could open up the T4b and look if the EL panel is pulsating with the audio.
Getto nightlight I presume is to use the EL panel from a nightlight to test if there´s enough signal going to the T4b.
Congratulations to the new baby!
The swich +10/+4/GR just changes what the VU is showing, it should not change the audio. (if correctly connected)
The LA2A should pass audio in all modes and compress when the front left (=gain reduction) knob is turned clockwise.
(And if enough signal is present on the input)
If it´s not compressing, start checking if the T4b gets enough signal from the sidechain circuit. That´s the lower left part
of the schematic. If you´re careful, you could open up the T4b and look if the EL panel is pulsating with the audio.
Getto nightlight I presume is to use the EL panel from a nightlight to test if there´s enough signal going to the T4b.
Congratulations to the new baby!
college101
Well-known member
Thanks Sredna!
I got what he was saying...he is talking about the different mode select options for how to view the metering of the signal
I need to open up my t4b..got it from kenetek new
I got what he was saying...he is talking about the different mode select options for how to view the metering of the signal
I need to open up my t4b..got it from kenetek new
Biasrocks
Well-known member
And make sure the back panel controls are turned completely counter clock wise as this will directly effect how much (if any compression) takes place.
Mark
Mark
simonsez
Well-known member
college101 said:
You make progress, so now you can concentrate at side chain circuit. Voltage checking is important. This side chain circuit is responsible for compression action.
You're a brave man! Work at day, study at night, wife, baby...that's a lot lot harder than make this "baby" smile...so take your time and no hurry..
