MAC Rack kit Build Thread from October 2016 with slow attack led

[Joe Malone]

Comp has new pull switches for threshold to activate the slow attack feature with orange led on front panel
Final led colours are red for link and green for power on. (Not the blue and green as shown)

MAC RACK KIT Build Thread using LA500SCv3 & LA500POTv4 kits like our LA500A comps so has very little wiring to do

MAC rack kit uses 2 x dINgO kits
dINgO schematic at the link below
http://www.jlmaudio.com/dingo/dINgOv4 f ... ematic.pdf


Blank dINgO PCB with full overlay shown (All parts numbers in () or [] brackets are not used with JLM99v opamps)


dINgO kit with all small parts shown. There will also be PCB XLR's in MAC rack kit.


If you are not 100% with resistor colour codes use a multimeter to check values as you place the resistors


Fit all resistors at once bending the legs sightly outwards to hold them in place. This helps to make sure no resistors are put in the wrong position.

Start with fitting of the 10k resistors into the PCB and bend the legs slightly outwards so they do not fall out when PCB is turned over.




Fitting of the 33R resistors



Fitting of the 5k1 resistors



Fitting of the 10R resistors



Fitting of the 470R resistor



Turn over PCB on flat surface and solder and trim all resistors legs





Fit the two 24v zener diodes with stripes lined up with stripe on PCB and solder and trim legs






Fit the 4 x 47pF ceramic caps folded flat to the PCB and solder and trim legs



Fit the 3 x 100nF mono caps with one folded flat to the PCB and solder and trim legs






Fit the 2 x gold pin sets to the PCB and solder. Best to solder one pin on each and check if they are sitting straight before soldering all pins.




Fit the 2 x 10uF & 2 x 100uF electro caps the check way around to the PCB and solder and trim legs. (+leg is the long leg of the cap)





Fit 2 x 10pin IDC headers to the PCB and solder and trim legs.












Fit 24v relay to the PCB and solder and trim legs. Make sure stripe on relay matches stripe on PCB





Fit 4 x 470uF 16v Non Polar electro caps to the PCB and solder and trim legs. These are Non Polar so can be fitted either way around.




Fit 2 x 3way terminal block to the PCB and solder and trim legs.



Fit 12 pins for the 2 x JLM99v opamps to the PCB and solder and trim legs.











Fit Male and Female XLR to the PCB and solder and trim legs. There maybe left over 3 way terminal blocks in the kit.



Trim side of Female XLR with sidecutters as shown










Fit input polarity jumpers as shown for correct phase.



Fit 2 x JLM99v opamps to the 12 sockets on the PCB


Fit ground link jumper beside XLR. Thid dINgO is built and ready. Build second dINgO and then move on to MAC PCB kits.






THE LA500SCv3 PCB is the MAC PCB but with no hand wiring and slow attack parts added

NEW LA500SCv3 PCB has extra MAC part so no meter wiring is needed in MAC rack kits
and some extra holes under U1 & U2 optos which are not used for now


MAC schematic at the link below is the same.
http://www.jlmaudio.com/MAC/MACSCH.pdf

LA500SCv3 PCB parts kit


LA500SCv2 PCB. PCB overlay has all values and there are no options.
so PCB can be assembled directly from overlay.


Fit all 8 x BAT85 diodes with there Cathode POLARIZED black stripe matching the white stripe on the MAC PCB overlay



Solder all BAT85 diodes while holding PCB firmly upside down on flat surface. Make sure none of the center close pads are NOT shorted together.


Cut all diodes legs off at top of the solder joint and double check no solder joints missed soldering or are shorted together.


If you are not 100% with resistor colour codes use a multimeter to check values as you place the resistors


Fit all resistors at once bending the legs sightly outwards to hold them in place.
This helps to make sure no resistors are put in the wrong position.


Solder all resistors while holding PCB firmly upside down on flat surface.
Cut all resistor legs off at top of the solder joint and double check no solder joints missed soldering.


Fit and solder DIP8 socket in other opamp position. Make sure the POLARIZED socket matches the PCB overlay.



Fit and solder 3 x 1uF MONO caps in place.




Fit 2 x 100pF ceramic caps in place.



Fit and solder IDC headers in the POLARITY shown. Do not reverse. Triangle on header indicates pin 1 which is the square pad on the PCB.


The front opening in the IDC headers should both now be facing as shown below.




Fit and solder Electro caps to PCB. The 5 x 100uF caps are POLARIZED so must have there long positive leg fitted to + marked on PCB overlay.





2 x 3.3uF acaps are NON polar types so can go in either way around on the PCB.






Fit and solder 4 trim pots as shown 1k = 102 code. Place pot so trim screw is in corner shown below







Fit and solder 3 pin header as shown below



Fit shunt to the 2 pins to the left



Fit and solder 78L05 5v regulator as shown below



Fit and solder NSL32 optos as shown below. Short legs are LED & Long legs are LDR on NSL-32.
The NSL32 Cathode has a dot marked on the case which goes to -K. Be gentle with the wire legs on the opto when shaping them for the PCB.
Note: If you are building a stereo matched pair. Fit the 2 optos in the plastic bag marked U1 into the U1 position on each separate PCB and same for the bag with the U2 pair.
If building just one comp use the 2 optos in the bag and either opto can go into U1 or U2.




Plug in OPA2604AP opamp the correct way around as shown below and put the built LA500SCv2 and the 3 switches left over back in the plastic bag and move on to the LA500POTv2 kit.





Note LA500POT PCB has been replaced with dedicated MACPOTv2 (needs 2 jumper wires added) & now MACPOTv3
Just build the MACPOT pcbs as their overlay shows as no mods or changes are needed.

MACPOTv3 has the 2 missing 0v ground on the makeup pot pins fixed so the 2 jumpers are not needed.

LA500POTv4 kit Custom build photos for MAC RACK kit



Start with fitting of the two 12k resistors into the PCB and bend the legs slightly outwards so they do not fall out when PCB is turned over.






Fit 10 pin IDC header as shown below








Fit 2 x 0ohm link resistors as shown below





Cut off locate tabs on pots and fit as shown below












Bolt all pots and switches in place on the front panel. Pots must have there locate tags cut off as shown earlier on this page.
Switches should have the rear nut wound about 2mm up the thread and washer and lock washer go on the behind the front panel so when fitted to front panel only just enough thread for the front nut is left. This makes the fornt panel look correct and gives the length needed for mounting the MAC pcb on the end of the long switch legs.



















































The photos below show the old mac pcbs in the original mac build thread but the ribbon cable works the same.
Plugs ribbon into the centre IDC10 on the dingo pcb to the IDC10 connector not on the edge of LA500SC pcb and then to the MAC link pcb.
(LA500SC pcb edge IDC10 is used by LA500POT pcb ribbon cable)











Compressor setup procedure
1. Set MAC to Threshold pot fully CCW, Makeup pot to CCW. Ratio switch to 3:1, Meter switch to VU, HPF switch to FLAT.
2. Apply 1kHz tone to MAC input so you have the reference level of +4dBu (1.23vac) on the MAC output between pin 2 & 3 of the XLR.
3. Or plug MAC output into VU or PPM meter that is calibrated to 0VU = +4dBu. If voltage not correct level adjust 1kHz generator level until correct.
4. Adjust meter 0VU trim pot for the desired level of 0VU on the meter.
5. Switch Meter switch to GR and adjust Zero GR trim pot for 0VU on the meter.
6. Switch back to VU and meter should be reading 0VU and turn up Threshold pot until you have -5dB on the meter.
7. Switch Meter switch between GR and VU and adjust the Balance trim pot until the same reading is seen in both GR and VU.
8. Check that with both channels set the same and link switch on meters both still read -5dB. If not realign both comps again.

[ghaudio]

Hi Joe,

I ripped one of the 3 x blue 100nf mono ceramic caps for one of the dingo kits on the stereo MAC when pulling it out of its cardboard/tape wrapping.

Would it be possible to get the exact specs for those so I can order a replacement? Seems like less trouble than asking for a replacement of such a small component all the way from Australia.

Was thinking I'd just go up to the electronic supply store but wasn't sure that I'd have the same thing even if it looked the same and had 104 on the front.

[Joe Malone]

Hi Joe,

I ripped one of the 3 x blue 100nf mono ceramic caps for one of the dingo kits on the stereo MAC when pulling it out of its cardboard/tape wrapping.

Would it be possible to get the exact specs for those so I can order a replacement? Seems like less trouble than asking for a replacement of such a small component all the way from Australia.

Was thinking I'd just go up to the electronic supply store but wasn't sure that I'd have the same thing even if it looked the same and had 104 on the front.

The caps are 100nF or 0.1uF Mono ceramic caps. They are usually blue or yellow mustard colour. But any 0.1uF cap that will fit in there will be fine to use.

[ghaudio]

Another question for you, I managed to push one of the VU meters out of it's place in the chassis when pulling the unit from the box the other day. I noticed that there seemed to be some adhesive around the edge meant to hold it in place. Since I pushed it out it doesn't seem to stay in quite as well as the other one. What kind of adhesive do you use or recommend to hold the VU in it's place in the chassis?

[Joe Malone]

Another question for you, I managed to push one of the VU meters out of it's place in the chassis when pulling the unit from the box the other day. I noticed that there seemed to be some adhesive around the edge meant to hold it in place. Since I pushed it out it doesn't seem to stay in quite as well as the other one. What kind of adhesive do you use or recommend to hold the VU in it's place in the chassis?

The front square section of the meter is bonded to the front panel with PVA type glue which goes clear.

The round back section can unclipped from the square section by pushing down on it.

If the 2 meter halves have come apart realigning and pushing the round section home against square section should reclip it.

Or has the square meter section come away from the front panel?

[ghaudio]

Another question for you, I managed to push one of the VU meters out of it's place in the chassis when pulling the unit from the box the other day. I noticed that there seemed to be some adhesive around the edge meant to hold it in place. Since I pushed it out it doesn't seem to stay in quite as well as the other one. What kind of adhesive do you use or recommend to hold the VU in it's place in the chassis?

The front square section of the meter is bonded to the front panel with PVA type glue which goes clear.

The round back section can unclipped from the square section by pushing down on it.

If the 2 meter halves have come apart realigning and pushing the round section home against square section should reclip it.

Or has the square meter section come away from the front panel?

Yes the square meter section came apart from the front panel.

[Joe Malone]

Another question for you, I managed to push one of the VU meters out of it's place in the chassis when pulling the unit from the box the other day. I noticed that there seemed to be some adhesive around the edge meant to hold it in place. Since I pushed it out it doesn't seem to stay in quite as well as the other one. What kind of adhesive do you use or recommend to hold the VU in it's place in the chassis?

The front square section of the meter is bonded to the front panel with PVA type glue which goes clear.

The round back section can unclipped from the square section by pushing down on it.

If the 2 meter halves have come apart realigning and pushing the round section home against square section should reclip it.

Or has the square meter section come away from the front panel?

Yes the square meter section came apart from the front panel.

OK any white drying clear PVA glue on the four mounting holes and sit meter in with front panel facing down and leave to dry overnight should lock it back it to the front panel. Peal off any loose glue before re gluing. Or superglue would work but you have to be careful as any vaper dry white so must be kept behind the front panel.

[ghaudio]

Hi Joe,

can you confirm that the two 120k resistors are not used on the LA500POTv4 pcb? Didn't see them in the instructions, so wanted to verify.

Also, on the same LA500POTv4, I see the you have the LED soldered to the underside of the PCB. Do you recommend fitting the LED with the front panel and then soldering into place?

Last, are the blue LEDs just provided as an option?

Thanks! Really enjoying this kit!

[Joe Malone]

Hi Joe,

can you confirm that the two 120k resistors are not used on the LA500POTv4 pcb? Didn't see them in the instructions, so wanted to verify.

Also, on the same LA500POTv4, I see the you have the LED soldered to the underside of the PCB. Do you recommend fitting the LED with the front panel and then soldering into place?

Last, are the blue LEDs just provided as an option?

Thanks! Really enjoying this kit!

Cool great to hear you are liking building the kit

The Blue led and 2 x 120k resistors are NOT used as the comp link is done on the separate PCB. They are just part of the standard kit but used in the MAC build.

Yes always good to do a test fit and slide the orange led into the slow attack led hole and measure where to bend the led leads to mount to the LA500SC pcb perfectly. To make sure you know which was the long Led leg always cut it slightly longer.

[ghaudio]

Hi Joe,

Might be a couple silly questions, but I'm going to ask anyway since it's not in the pictures.

1) do I solder all the legs from front panel switches onto MaC PCBs? (Only one leg shown soldered in the pics)

2) do I solder tabs from meters onto the extended end of the mac PCBs?


Pretty sure it's yes on both but wanted to ask before I commit. thought maybe for serviceability there was a small chance it would be bad to solder those parts

Thanks!

[Joe Malone]

Hi Joe,

Might be a couple silly questions, but I'm going to ask anyway since it's not in the pictures.

1) do I solder all the legs from front panel switches onto MaC PCBs? (Only one leg shown soldered in the pics)

2) do I solder tabs from meters onto the extended end of the mac PCBs?


Pretty sure it's yes on both but wanted to ask before I commit. thought maybe for serviceability there was a small chance it would be bad to solder those parts

Thanks!

Yes for both. Any component leg going into a solder pad on the pcb will need soldering. Make sure the PCB is sitting hard against the back of the meter and solder one or two switch legs and double check there is enough space between the pot pcb before soldering all switch legs and meter tabs to the pcb.

[ghaudio]

Hi Joe,

I've got the compressor all hooked up, all the lights work as expected, so I'm off to a good start.

Now I'm getting into calibration. I'm referencing this page for cal instructions:
http://www.jlmaudio.com/MAC/MACSCH.pdf

In the first step with all pots CCW and VU switch set to VU, I'm getting my meters pinned so far that the VU meter pot on the MAC PCB can't dial it back any further, but the needle is still pinned at max.

As far as levels that I'm sending, they seem to be standard levels. I've got -14dbfs in protools calibrated to = 1.228v = +4dbu.

Any thoughts on how to fix this?

[Joe Malone]

Hi Joe,

I've got the compressor all hooked up, all the lights work as expected, so I'm off to a good start.

Now I'm getting into calibration. I'm referencing this page for cal instructions:
http://www.jlmaudio.com/MAC/MACSCH.pdf

In the first step with all pots CCW and VU switch set to VU, I'm getting my meters pinned so far that the VU meter pot on the MAC PCB can't dial it back any further, but the needle is still pinned at max.

As far as levels that I'm sending, they seem to be standard levels. I've got -14dbfs in protools calibrated to = 1.228v = +4dbu.

Any thoughts on how to fix this?

Sorry forum update stopped my new post notifications. Fixed now.

Do you get 1.23vac at output of MAC XLR between pin 2 & 3 ? If so the VU meter should be reading low on first power up with no trimpot adjusted?

Best to email me some photos of the LA500sc pcb top and mac pcb top for now and your wiring so I can check it over.

MAC Compressor setup procedure
1. Set MAC to Threshold pot fully CCW, Makeup pot to CCW. Ratio switch to 3:1, Meter switch to VU, HPF switch to FLAT.
2. Apply 1kHz tone to MAC input at the reference level (usually +4dBM) you are going to use for 0VU.
3. Check output of the MAC between pins 2 and 3 of the rack XLR (or pin 2 and 4 of the edge connector) for 1.23vac with multimeter.
If voltage not correct adjust 1kHz generator until correct. Or plug MAC output into VU or PPM meter that is calibrated to a known level.
4. Adjust meter 0VU trim pot for desired level for 0VU on the meter.
5. Switch Meter switch to GR and adjust Zero GR trim pot for 0VU on meter.
6. Turn up Threshold pot until you have 5dB of compression on meter.
7. Switch Meter switch between GR and VU and adjust Balance trim pot until the same reading is seen in both GR and VU.
8. Your ready to rock.

MAC opto comp stereo matching mode.
1. Check Both MAC comp alignments are correct.
2. With 1k tone of same level into both MAC comps set 0VU on meter switched to VU and turn up Threshold pot to get -5dB on meter and switch to GR to check you have -5dB showing on both meters.
3. Link the comps. If meters move away from each other by more than a +/-1dB move jumper to MATCH end on the compressor which shows more gain reduction on the meter.

Original balance trim pot will now adjust GR meter level when switched to GR (U2 audio opto) and new ST Match trim pot R18 will adjust VU meter level when switched to VU (U1 meter opto)
Image

1. Setup both comp with 1k tone and set 0VU on meter switched to VU and turn up Threshold pot to get -5dB on meter.
2. Turn threshold pot off on modified comp (fully CCW)
3. Link the comps. Adjust modified VU trim pot until both comps show the same VU meter readings.
4. Switch both comps to GR and adjust modified comp new GR pot until both comps show same GR meter readings.
5. Your comps should be matched.

To check match
1. With 1k tone of same level into both MAC comps set 0VU on meter switched to VU and turn up Threshold pot to get -5dB on meter and switch to GR to check you have -5dB showing on both meters.
2. Link the comps. If meters move away from each other by more than a +/-0.5dB trim modified comps New GR & New VU trim pot until perfect match when linked.

[ghaudio]

Hi Joe,

Picture of the MAC PCB below:

I took this into a studio shop here in hollywood. Their tech helped me out. we measured +4dbu in, with all pots fully CCW, and with switches set as described in the calibration procedure.

with +4dbu in, +4du came out, on both left and right sides. Both VU meters exhibited the same behavior where they were pegged, and the blue adjustment pots could not turn them down any further.

GH_MacLA500SC3_PCB.JPG

[ghaudio]

Hi Joe, have you had a chance to review the picture? Is there something else I can send to make this easier to resolve?