PEQ500A kit BUILD THREAD

[vicolas]

I'm having issues with one of my PEQ500 units

Specifically the PEQ500A PCB is where I've diagnosed the problem. When I plug the completed unit into into my lunchbox it takes a second before it starts outputting a noisy signal on its own.

All my solder joints look good and I even resoldered to see if I might've had a bad spot.

Any ideas or suggestions on what to check? I've pored over the joints. It seems like there might be a faulty component but I'm at a loss.

Thanks

[Joe Malone]

I'm having issues with one of my PEQ500 units

Specifically the PEQ500A PCB is where I've diagnosed the problem. When I plug the completed unit into into my lunchbox it takes a second before it starts outputting a noisy signal on its own.

All my solder joints look good and I even resoldered to see if I might've had a bad spot.

Any ideas or suggestions on what to check? I've pored over the joints. It seems like there might be a faulty component but I'm at a loss.

Thanks

The PEQ500A pcb is passive so cannot make any noise unless it is unstablising the BIO500T pcb.

Since you have 2 PEQ500A swap the 2 x BIO500T pcbs between the 2 PEQ500A to see if the fault stays with the BIO500T or the PEQ500A pcb. And swap the 2 small pcbs between PEQ500A. Once you narrow down to the problem pcb attach clear in focus well lit top and bottom photos of that pcb so I can check it over for you.

Biggest problems we see are soldering. Especially unsoldering pins on the 10 pin headers or solder shorted pins on the 10 pin headers.

[vicolas]

Here's two pictures of the PEQ500A

PXL_20241224_065548806.jpg

PXL_20241224_065342653.jpg

In case you're concerned about the orientations of the relays--I made sure they matched the PCB/pictures.

When I hooked it up to my BIO500T PCBs both of them had the same behavior with this PCB specifically. Please let me know if you need any more detailed photos.

Thanks

[vicolas]

I'm having issues with one of my PEQ500 units

Specifically the PEQ500A PCB is where I've diagnosed the problem. When I plug the completed unit into into my lunchbox it takes a second before it starts outputting a noisy signal on its own.

All my solder joints look good and I even resoldered to see if I might've had a bad spot.

Any ideas or suggestions on what to check? I've pored over the joints. It seems like there might be a faulty component but I'm at a loss.

Thanks

The PEQ500A pcb is passive so cannot make any noise unless it is unstablising the BIO500T pcb.

Since you have 2 PEQ500A swap the 2 x BIO500T pcbs between the 2 PEQ500A to see if the fault stays with the BIO500T or the PEQ500A pcb. And swap the 2 small pcbs between PEQ500A. Once you narrow down to the problem pcb attach clear in focus well lit top and bottom photos of that pcb so I can check it over for you.

Biggest problems we see are soldering. Especially unsoldering pins on the 10 pin headers or solder shorted pins on the 10 pin headers.

Hi Joe -- New development -- looks like it's not my EQ500A after all.

My upper 10R keeps burning up on the BIO500T. Anything I should investigate to understand the cause of that?

PXL_20250104_052726611.MP.jpg

PXL_20250104_052859879.jpg

PXL_20250104_052911824.jpg

[Joe Malone]

I'm having issues with one of my PEQ500 units

Specifically the PEQ500A PCB is where I've diagnosed the problem. When I plug the completed unit into into my lunchbox it takes a second before it starts outputting a noisy signal on its own.

All my solder joints look good and I even resoldered to see if I might've had a bad spot.

Any ideas or suggestions on what to check? I've pored over the joints. It seems like there might be a faulty component but I'm at a loss.

Thanks

The PEQ500A pcb is passive so cannot make any noise unless it is unstablising the BIO500T pcb.

Since you have 2 PEQ500A swap the 2 x BIO500T pcbs between the 2 PEQ500A to see if the fault stays with the BIO500T or the PEQ500A pcb. And swap the 2 small pcbs between PEQ500A. Once you narrow down to the problem pcb attach clear in focus well lit top and bottom photos of that pcb so I can check it over for you.

Biggest problems we see are soldering. Especially unsoldering pins on the 10 pin headers or solder shorted pins on the 10 pin headers.

Hi Joe -- New development -- looks like it's not my EQ500A after all.

My upper 10R keeps burning up on the BIO500T. Anything I should investigate to understand the cause of that?

PXL_20250104_052726611.MP.jpg

PXL_20250104_052859879.jpg

PXL_20250104_052911824.jpg

Tests to do to the BIO500T PCB
Does the 10R burn without the BIO500T plugged into the PEQ500A pcb and no JLM99v fitted? Y/N
Does the 10R burn without the BIO500T plugged into the PEQ500A pcb and one JLM99v fitted? Y/N
Does the 10R burn without the BIO500T plugged into the PEQ500A pcb and two JLM99v fitted? Y/N

[vicolas]

Tests to do to the BIO500T PCB
Does the 10R burn without the BIO500T plugged into the PEQ500A pcb and no JLM99v fitted? Y/N
Does the 10R burn without the BIO500T plugged into the PEQ500A pcb and one JLM99v fitted? Y/N
Does the 10R burn without the BIO500T plugged into the PEQ500A pcb and two JLM99v fitted? Y/N

Does the 10R burn without the BIO500T plugged into the PEQ500A pcb and no JLM99v fitted?

Yes, it's burning on the first test.

Does the 10R burn without the BIO500T plugged into the PEQ500A pcb and two JLM99v fitted? Y/N

Yes, this was the test I was doing when I first observed the issue. I haven't tried a single yet, but I figure we don't need to reach that step yet. (Trying to save some 10R's )

[Joe Malone]

Tests to do to the BIO500T PCB
Does the 10R burn without the BIO500T plugged into the PEQ500A pcb and no JLM99v fitted? Y/N
Does the 10R burn without the BIO500T plugged into the PEQ500A pcb and one JLM99v fitted? Y/N
Does the 10R burn without the BIO500T plugged into the PEQ500A pcb and two JLM99v fitted? Y/N

Does the 10R burn without the BIO500T plugged into the PEQ500A pcb and no JLM99v fitted?

Yes, it's burning on the first test.

Does the 10R burn without the BIO500T plugged into the PEQ500A pcb and two JLM99v fitted? Y/N

Yes, this was the test I was doing when I first observed the issue. I haven't tried a single yet, but I figure we don't need to reach that step yet. (Trying to save some 10R's )

Seems to be a solder short on the -V socket to the ground plane. Test with ohm meter between -V and 0v socket. Once fixed change 10R 1/4w carbon resistor

[vicolas]

Seems to be a solder short on the -V socket to the ground plane. Test with ohm meter between -V and 0v socket. Once fixed change 10R 1/4w carbon resistor

I can't seem to get the resistance to level out. It seems to be all over the place.

I started with re-seating the socket you pointed out; however, the issue persisted. I've reseated all the sockets and this still continues to happen. My other PCB will hover somewhere between 6 - 6.3M

[Joe Malone]

Seems to be a solder short on the -V socket to the ground plane. Test with ohm meter between -V and 0v socket. Once fixed change 10R 1/4w carbon resistor

I can't seem to get the resistance to level out. It seems to be all over the place.

I started with re-seating the socket you pointed out; however, the issue persisted. I've reseated all the sockets and this still continues to happen. My other PCB will hover somewhere between 6 - 6.3M

You can see the heat burn where there is some type of low ohm short to the ground plane at this socket. I would run a sharp utility knife around the top and bottom of that solder pad to see if that fixes it or not.

PXL_20250104_052911824.jpg

[ylinjohto]

Hi!

I have two of these in the making. Another one is completely finished and the other one has Peq board done and BIO I was planning to do this evening. Before that I wanted to check that everything works and went to studio with the finished one and for my great disapointment it has some issues.

It powers up normally I guess and sound is ok. The problem is that it has about 20db extra gain and with boost fully clockwise gives only 1db of boost. All frequencies are probably working but kind of hard to tell as the boost is minimal. Cutting filters are working ok. Trim pot seems to do very little.

Any ideas what I have done wrong? I can test the other PEQ board if it is the same and I´ll give you photos of the unit later on.

Kind Regards
Matti

[Joe Malone]

Hi!

I have two of these in the making. Another one is completely finished and the other one has Peq board done and BIO I was planning to do this evening. Before that I wanted to check that everything works and went to studio with the finished one and for my great disapointment it has some issues.

It powers up normally I guess and sound is ok. The problem is that it has about 20db extra gain and with boost fully clockwise gives only 1db of boost. All frequencies are probably working but kind of hard to tell as the boost is minimal. Cutting filters are working ok. Trim pot seems to do very little.

Any ideas what I have done wrong? I can test the other PEQ board if it is the same and I´ll give you photos of the unit later on.

Kind Regards
Matti

HI
Ok need to test the BIO500T PCB by itself with 2 wire loop test. If you have any 10 pin ribbon cable to 10 pin ribbon cable to do the attached test or soldering 2 wire loops under the pcb as shown so it can be loop tested by itself to see if it is working ok. With both loops fitted and plugging in the pcb only to a 500 rack or tester you should have the same audio level with the rack powered and the rack not powered.

If you have audio with no power on rack but no audio with racked powered up then the problem is on the BIO500T pcb.

[ylinjohto]

Hi! I made the test and BIO has the same level powered or not.
I finnished the other BIO yesterday and both units behave the same.
Here are some photos and measurements:

IMG_20250918_101742018.jpg

IMG_20250918_101839209.jpg

IMG_20250918_102902175.jpg

[ylinjohto]

Moro photos:

IMG_20250918_102922611.jpg

IMG_20250918_102935467.jpg

IMG_20250918_103007775.jpg

[ylinjohto]

Two wire test measurement:

two wires test.png

Eq Curves:

Eq curves.png

Thank You for helping with this. I cant find any obvious solder trails or so.

Matti

[Joe Malone]

Two wire test measurement:
two wires test.png

Eq Curves:
Eq curves.png

Thank You for helping with this. I cant find any obvious solder trails or so.

Matti

When you say they were both the same. Do you mean the 2 BIOs with the jumper wires fitted or the whole EQs?

So are both Eq are boosting the same 20dB?
The passive Eq circuit should loose 20dB and the BIO500T should make up that with 20dB gain with a couple of dB trim from the trimpot to match them to unity.

What are you using to test?

Is the test AD/DA fully balanced in and out?

Do the blue leds light and can you hear the relay click on and off?