FREQ500 KIT Build Thread

[Joe Malone]

Hello Joe, I just completed my first of two Audio Path PCBs. Per the build guide, I went to test it, inserted the two jumpers, connected it to an extender...and when I powered on my rack, the two 4R7 resistors instantly fried. Any troubleshooting tips?

Best to post here or send me photos of the top and bottom of the pcb.

Most common problem that burns the 4R7 protection resistors
First is opamps plugged in the wrong way around.
Second is 100uF electro caps fitted the wrong way around.

[Everett]

Followup: Thanks Joe for all your troubleshooting help and testing info. After I corrected polarity on the Opamps, LEDs and related fallout, everything finally tested good. Also very happy to learn about Plugin Doctor to look at the EQ curves of JLM hardware and other plugins. The EQ’s sound and look great in my JLM chain!

[Joe Malone]

Followup: Thanks Joe for all your troubleshooting help and testing info. After I corrected polarity on the Opamps, LEDs and related fallout, everything finally tested good. Also very happy to learn about Plugin Doctor to look at the EQ curves of JLM hardware and other plugins. The EQ’s sound and look great in my JLM chain!

Always great to hear you have the EQ up and going and sounding good

Yes Plugin Doctor is very useful for seeing what is going on and if stereo is matching well.

[thegrobinson]

Joe,

Thanks for the kits! The part checklist /identifier page is incredibly handy.

I just finished building mine and I’m 90% there.

Audio level in and out is spot on.

All switches and LEDS working as expected.

However, i hear no change on the mid band. LEDs respond to push pull, but there’s no boost or cut. I’ve tried moving the mid band module to another spot on the ribbon cable and no change. I’ve checked for cold joints and shorts, but I can’t see any obvious error. Where should I start looking?

PCB photos attached.

Thanks,
G

[Joe Malone]

Joe,

Thanks for the kits! The part checklist /identifier page is incredibly handy.

I just finished building mine and I’m 90% there.

Audio level in and out is spot on.

All switches and LEDS working as expected.

However, i hear no change on the mid band. LEDs respond to push pull, but there’s no boost or cut. I’ve tried moving the mid band module to another spot on the ribbon cable and no change. I’ve checked for cold joints and shorts, but I can’t see any obvious error. Where should I start looking?

PCB photos attached.

Thanks,
G

I cannot see any attached pcb images? Attach Clear in focus well lit top and bottom photos of the cob do I can check it over for you.

[thegrobinson]

Sorry. Not sure what went wrong. I’ll try attaching them again

IMG_1170.jpeg

IMG_1171.jpeg

IMG_1168.jpeg

[Joe Malone]

Sorry. Not sure what went wrong. I’ll try attaching them again


IMG_1170.jpeg

IMG_1171.jpeg

IMG_1168.jpeg

Ok looks like nice neat soldering. Check the 2 pads that have exposed the copper next to them are not shorted to the ground plane and the 2 pads on the 10 pin header haven’t fully flowed so reheat them with a tiny bit more solder. Definitely try swapping the opamps with another module and test if pulling the switch cut works ?

[Perihelion]

Heya,
I've got a Freq500 here that works great, but there is a slight pop sound on the output when the IN toggle is disengaged. However, it gets really bad when the HPF is engaged and the IN toggle is then disengaged. Here's a video:

https://youtube.com/shorts/ilCOfqtJ8Yw

Is there any way to alleviate this? Revision of the filter PCB is 240405.
The LO card does have the wire jumper installed.

[Joe Malone]

Heya,
I've got a Freq500 here that works great, but there is a slight pop sound on the output when the IN toggle is disengaged. However, it gets really bad when the HPF is engaged and the IN toggle is then disengaged. Here's a video:

https://youtube.com/shorts/ilCOfqtJ8Yw

Is there any way to alleviate this? Revision of the filter PCB is 240405.
The LO card does have the wire jumper installed.

First unplug any input to the FREQ500 and see if the switching pop goes away or not encase it is DC coming from the audio gear before the FREQ500?

Since it is on the turn off I presume somehow the back emf of that relay on the main audio pcb is getting into the audio. Is the audio output going into a +18dBu A/D etc ? So there is the correct audio path levels.

Adding either a diode like 1N914 or 1N4002 etc across the relay coil would be worth a try to see if that fixes this. Anode stripe to + on coil and Cathode to - on coil or same could work with 0.1uF 50v mono cap across the coil instead.

If this doesn't fix it send me top and bottom photo of the main audio pcb

Let me know what you find.

[Joe Malone]

Hello Joe, I just completed my first of two Audio Path PCBs. Per the build guide, I went to test it, inserted the two jumpers, connected it to an extender...and when I powered on my rack, the two 4R7 resistors instantly fried. Any troubleshooting tips?

Send me a photo of the top and bottom of the audio pcb with the jumpers still fitted so I can check it over for you

[Perihelion]

Adding either a diode like 1N914 or 1N4002 etc across the relay coil would be worth a try to see if that fixes this. Anode stripe to + on coil and Cathode to - on coil or same could work with 0.1uF 50v mono cap across the coil instead.

I stuck a 104 cap across the coil and it completely eliminated the click! Thanks so much!

There is a little puff of white noise on the output when the push/pull gain pots are switched between boost and cut. This happens on all 5. Is there a way to remove it? If not, that's cool, it's just a minor annoyance and I can live with it.

[Joe Malone]

Adding either a diode like 1N914 or 1N4002 etc across the relay coil would be worth a try to see if that fixes this. Anode stripe to + on coil and Cathode to - on coil or same could work with 0.1uF 50v mono cap across the coil instead.

I stuck a 104 cap across the coil and it completely eliminated the click! Thanks so much!

There is a little puff of white noise on the output when the push/pull gain pots are switched between boost and cut. This happens on all 5. Is there a way to remove it? If not, that's cool, it's just a minor annoyance and I can live with it.

There can be a soft tick or pop when switching from boost to cut which depends on sound playing or dc offset if no sound. It is part of the vintage design so is hard to remove. If running at full pro audio level like +18dbu it should be very minimal.