LA500A opto comp leveling amp BUILD THREAD 500/51X

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hasbeen
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby hasbeen » Sat May 14, 2016 9:39 am

In some of the pictures the builder is holding the component in place with a thumb and soldering with the other hand.

I am curious as to how one can apply the solder in such a manner. I usually have solder in one hand and iron in the other while PCB is laying on a flat surface.

Thanks.

:?: :?: :?:

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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby Joe Malone » Wed May 18, 2016 10:44 am

hasbeen wrote:In some of the pictures the builder is holding the component in place with a thumb and soldering with the other hand.

I am curious as to how one can apply the solder in such a manner. I usually have solder in one hand and iron in the other while PCB is laying on a flat surface.

Thanks.

:?: :?: :?:


We often hold solder and the part with one hand. It just takes lots of practice.

But also several of the photos show us reheating a component while pressing on it to seat it neatly which is probably the best way for most kit builders.
Joe :-)
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby MattM » Tue Jun 14, 2016 2:10 am

Just finished building my second of two LA500As, and just ordered two more. LOVE these kits. Great layout, very logical assembly process, looking forward to getting a lot of mileage out of them!

I went through and calibrated my first unit without any problems. Loaded up the second one expecting the same result, but I'm having a problem. When I have the unit in hard bypass (meter light off, etc.), it passes audio normally. My DMM confirms the VAC is correct and is the same coming out as going into the unit.

When I switch into either VU or GR mode, though, at first I thought the unit might not be passing audio at all. The level on the DMM would drop way down to almost zero (I didn't have my speakers on at this point...starts getting hard to think with all that 1K tone going :lol: ). When I finally listened to what was coming through, I realized that the unit was passing audio, but only very faintly and only when the makeup gain was pushed all the way clockwise.

I would also note, interestingly, that the meter DOES show audio passing, even if you can only faintly hear 1K tone when the unit is cranked. So in the above scenario, the (uncalibrated) VU meter is showing around -3db or so, and goes off scale high when I crank the makeup all the way clockwise -- exactly what you'd expect if you were sending 1K tone at +4db through the unit. The problem simply is that the output doesn't seem to match the "reality" that's hitting the VU.

So what I would infer from this so far is that something's up on the output side of the unit. Signal is getting to the meter, but it's not making it to the output from there. That leads me to think this isn't a "hard bypass" problem or anything like that, and I suspect it's not a problem with the relay, either.

Rather, my guess is that something's up with the JLM op-amp, which is on the output side of the house, no? I'm going to try swapping the op-amps in my two units and see if that does the trick, and I'll post when I do. But if you have any thoughts on where else I might attack the problem, I'd appreciate the help.

Thanks!
Matt
Last edited by MattM on Tue Jun 14, 2016 4:42 am, edited 1 time in total.

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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby MattM » Tue Jun 14, 2016 3:57 am

Swapped out the JLM99V from my other (working) unit. Same result. Other suggestions?

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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby Joe Malone » Tue Jun 14, 2016 8:11 am

MattM wrote:Just finished building my second of two LA500As, and just ordered two more. LOVE these kits. Great layout, very logical assembly process, looking forward to getting a lot of mileage out of them!

I went through and calibrated my first unit without any problems. Loaded up the second one expecting the same result, but I'm having a problem. When I have the unit in hard bypass (meter light off, etc.), it passes audio normally. My DMM confirms the VAC is correct and is the same coming out as going into the unit.

When I switch into either VU or GR mode, though, at first I thought the unit might not be passing audio at all. The level on the DMM would drop way down to almost zero (I didn't have my speakers on at this point...starts getting hard to think with all that 1K tone going :lol: ). When I finally listened to what was coming through, I realized that the unit was passing audio, but only very faintly and only when the makeup gain was pushed all the way clockwise.

I would also note, interestingly, that the meter DOES show audio passing, even if you can only faintly hear 1K tone when the unit is cranked. So in the above scenario, the (uncalibrated) VU meter is showing around -3db or so, and goes off scale high when I crank the makeup all the way clockwise -- exactly what you'd expect if you were sending 1K tone at +4db through the unit. The problem simply is that the output doesn't seem to match the "reality" that's hitting the VU.

So what I would infer from this so far is that something's up on the output side of the unit. Signal is getting to the meter, but it's not making it to the output from there. That leads me to think this isn't a "hard bypass" problem or anything like that, and I suspect it's not a problem with the relay, either.

Rather, my guess is that something's up with the JLM op-amp, which is on the output side of the house, no? I'm going to try swapping the op-amps in my two units and see if that does the trick, and I'll post when I do. But if you have any thoughts on where else I might attack the problem, I'd appreciate the help.

Thanks!
Matt


From you description it has to be the output transformer and or its ribbon cable and connections. Check the 10 pin header on the transformer top has the 7 pins around the outside soldered and it not cracked. Check you have soldered all 10 pins on the transformer header on the main BIO pcb and there are no shorts between pins. If connections look good swap transformer and ribbon separately with your other comp to see which part the fault stays with. You can test the output transformer with a meter on the large solder pads on top. Each winding should have around 12 to 15ohm depending on your meter. Test the 3 windings +1 to -1 & +2 to -2 & +3 to -3.

Let me know what you find.
Joe :-)

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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby MattM » Tue Jun 14, 2016 9:06 am

Hi Joe, checked the ribbon cable connections, and... oops.

The pin in the upper left corner (as you're looking at the transformer) either snapped off or melted into the plastic when it was assembled. There's no broken pin in the ribbon cable or anything like that. Any way to bypass that, even temporarily, for testing purposes?

transformer_header.jpg
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby Joe Malone » Tue Jun 14, 2016 9:44 am

MattM wrote:Hi Joe, checked the ribbon cable connections, and... oops.

The pin in the upper left corner (as you're looking at the transformer) either snapped off or melted into the plastic when it was assembled. There's no broken pin in the ribbon cable or anything like that. Any way to bypass that, even temporarily, for testing purposes?

transformer_header.jpg


If the pin has been pushed down by the ribbon cable you can pull the pin back up to the correct height with pointy nose pliers but reheat the solder joint for it on the other side after to make sure it isn't cracked once you have pulled it up and you should be working. If not sure send me a photo of the other side of the connector so i can see.
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby MattM » Tue Jun 14, 2016 1:50 pm

OK, unscrewed the transformer from the module so I could get a better look at the pins underneath. They look exactly like you'd expect -- not pushed under, slipped, or anything. It's as if the pin was manufactured to the wrong length, because it has a very clean, square bevel to it that doesn't look like it snapped off. Again, the short pin is the top left -- the pin above pin #1.

transformer_header2.jpg


transformer_header3.jpg


There's really nothing to pull on with my pliers. I suppose I could try forcing it from underneath so that rather than entering the IDC at a clean 90, it comes in at a tighter angle, but I don't want to make it worse than it already is. I'm not sure there's enough extra length that this would work, anyway -- the pin still might not make contact with the mated part in the ribbon header.

Jumper time? First goal would be to test to make sure this really _is_ the only problem I'm dealing with.
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby Joe Malone » Tue Jun 14, 2016 2:26 pm

MattM wrote:OK, unscrewed the transformer from the module so I could get a better look at the pins underneath. They look exactly like you'd expect -- not pushed under, slipped, or anything. It's as if the pin was manufactured to the wrong length, because it has a very clean, square bevel to it that doesn't look like it snapped off. Again, the short pin is the top left -- the pin above pin #1.

transformer_header2.jpg


transformer_header3.jpg


There's really nothing to pull on with my pliers. I suppose I could try forcing it from underneath so that rather than entering the IDC at a clean 90, it comes in at a tighter angle, but I don't want to make it worse than it already is. I'm not sure there's enough extra length that this would work, anyway -- the pin still might not make contact with the mated part in the ribbon header.

Jumper time? First goal would be to test to make sure this really _is_ the only problem I'm dealing with.


Wow wonder how the tester made contact with it as we 100% test them :-(.

Ok easiest is to solder a wire to that pin at the solder joint under the header and take that wire to P+ large solder pad behind the BIO500 10 pin header and see if the comp now works.
Joe :-)

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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby MattM » Wed Jun 15, 2016 6:08 am

Confirmed! I ran a test lead from +1 on the transformer (which is connected to the pin that's short in the IDC header) to P+ on the PCB. Full tone, full compressor functionality.

So in the interest of not having a single wire soldered between the two pieces while the rest of the connections are on a ribbon cable, I made a detachable connection point between the two pieces that I can stuff under the ribbon cable.

transformer_coupling4.jpg


Not really necessary, one, and two, if I were to swap something out, I'd probably deal with the short pin at that point anyway. But at least for now I can still remove the transformer without having to break out the soldering iron again.

Now to get this puppy calibrated & back to work. Thanks for your help & I'm looking forward to building the two additional units I have on the way... 8)
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby MattM » Wed Jun 15, 2016 7:40 am

Just wanted to confirm how the stereo linking works, because I don't notice any difference in my two units.

I have two units seated next to each other in a Radial Powerhouse. Each of them are calibrated correctly -- when I dial up -5 db, I get a consistent reading in GR and VU modes on each device.

What is supposed to happen next? If I want to stereo link the units, what do I need to do? Simply pull out the stereo link pots on both units? Only the first? Is there some other connection that needs to be made? As it stands, I don't notice any difference in the metering at all. In fact, if I remove 1K tone from one of the units, its meter reacts as you'd expect it to, but the other unit doesn't seem to react at all. If it's stereo linked, shouldn't we see some sort of reaction from the other (linked) unit in response to a change in signal level from the first (master) unit?

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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby Joe Malone » Wed Jun 15, 2016 8:04 am

MattM wrote:Just wanted to confirm how the stereo linking works, because I don't notice any difference in my two units.

I have two units seated next to each other in a Radial Powerhouse. Each of them are calibrated correctly -- when I dial up -5 db, I get a consistent reading in GR and VU modes on each device.

What is supposed to happen next? If I want to stereo link the units, what do I need to do? Simply pull out the stereo link pots on both units? Only the first? Is there some other connection that needs to be made? As it stands, I don't notice any difference in the metering at all. In fact, if I remove 1K tone from one of the units, its meter reacts as you'd expect it to, but the other unit doesn't seem to react at all. If it's stereo linked, shouldn't we see some sort of reaction from the other (linked) unit in response to a change in signal level from the first (master) unit?


To link the 500 rack must have pin 6 linked or switch any comp link to on between the 2 slots the comps are fitted too.

Set both comps to the same switch and threshold settings and pull both makeup controls outwards so both blue link leds are on. The sidechains are now linked. Works like all old 1176 1178 LA2A and LA3A linking does.

You can prove the pin 6 link is in your 500 rack by turning down one threshold pot and both comps should still show equal gain reduction.

Remember this is NOT a modern VCA comp controlled by DC voltages which when linked switches control to the left controls. You must always set both LA500A comps to the same settings.
Joe :-)

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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby MattM » Wed Jun 15, 2016 12:43 pm

OK, got it. I have a Radial Workhorse, which has those nice LINK-> switches on the back of the unit. First time I've used them, and they work great.

I set both units to show -5db on the VU.
I then pulled both link knobs so the blue lights are lit.

The meters move _slightly_ off -5db -- one goes 1/2db higher, one goes 1/2db lower.

If I understand the calibration instructions, tweaking R18 (the MATCH trim) should cause the linked meter to move in VU mode. I'm not seeing any effect on either unit when I turn R18.

Of course, I can always fiddle with the Balance/GR trim, but that causes the meters to become uncalibrated in standalone mode. It took me another few minutes to get them recalibrated again, so I suspect that's not what I'm supposed to do...or is it?

Sorry, the message at the top of the thread talks about "original" and "modified" pots, but I think that's in reference to an older version of the PCB, so I'm not clear what the instructions are telling us to do.

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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby Joe Malone » Wed Jun 15, 2016 1:46 pm

MattM wrote:OK, got it. I have a Radial Workhorse, which has those nice LINK-> switches on the back of the unit. First time I've used them, and they work great.

I set both units to show -5db on the VU.
I then pulled both link knobs so the blue lights are lit.

The meters move _slightly_ off -5db -- one goes 1/2db higher, one goes 1/2db lower.

If I understand the calibration instructions, tweaking R18 (the MATCH trim) should cause the linked meter to move in VU mode. I'm not seeing any effect on either unit when I turn R18.

Of course, I can always fiddle with the Balance/GR trim, but that causes the meters to become uncalibrated in standalone mode. It took me another few minutes to get them recalibrated again, so I suspect that's not what I'm supposed to do...or is it?

Sorry, the message at the top of the thread talks about "original" and "modified" pots, but I think that's in reference to an older version of the PCB, so I'm not clear what the instructions are telling us to do.


If the comps are with +/-0.5dB at link that is perfect. Usually double checking the mechanical meter -20 point is set properly before cal and do the normal cal process twice will get perfect match.

STEREO Match procedure shouldn't be needed with comps ordered in a pair one one order from us. As we would have supplied match U1 and U2 opto already.

If you move the BAL Match jumper over to the right match position the balance trim pot becomes the GR trimpot and the other ST Match trimpot becomes the VU trimpot. So it is no longer a balance pot but separate trimpots for each. So the heavier compressing comp can be backed off slightly.
Joe :-)

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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby MattM » Wed Jun 15, 2016 3:12 pm

Ah, OK, got it. Yes, they're a matched pair. I'm curious what the advantage/disadvantage is to having the VU and GR handled on different pots rather than in standard, "balance" mode? Took me quite a while to get the hang of the balance pot. Even if you're not matching for stereo, is there an advantage to "balance matching" the GR and VU values rather than just throwing the MATCH jumper to the other pin and tweaking the values separately?

Damn. These things sound RIDICULOUS on drums. :shock:

We gonna have a good time now....

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