Stereo VU meter kit BUILD THREAD

Support for JLM Audio Kits

Moderator: Joe Malone

verticalmammal
Posts: 5
Joined: Wed Feb 24, 2021 5:24 am

Re: Stereo VU meter kit BUILD THREAD

Post by verticalmammal »

Joe Malone wrote:
Wed Feb 24, 2021 1:29 pm
Voltages are correct. Have you retried the pcb since cleaning it? Also first turn the trimpot back 25 turns encase you have one on full gain. With no meters connected measure volts across +M- on both sides and let me know what volts you read?
Yes, unfortunately still no joy, same symptoms. Voltage is 0.002v across the left meter leads, and 6.22v across the right. Turning the pot has no effect. I'm not sure exactly how these pots work, do they have stops on either side of the range? I can spin mine more than 24 turns in either direction, maybe I broke the pot somehow during install or setup? Or maybe that's normal? If I go too far CW I hear a soft click once a rotation, I'm assuming that's the top of the range?

User avatar
Joe Malone
Site Admin
Posts: 1780
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: Stereo VU meter kit BUILD THREAD

Post by Joe Malone »

verticalmammal wrote:
Wed Feb 24, 2021 2:45 pm
Joe Malone wrote:
Wed Feb 24, 2021 1:29 pm
Voltages are correct. Have you retried the pcb since cleaning it? Also first turn the trimpot back 25 turns encase you have one on full gain. With no meters connected measure volts across +M- on both sides and let me know what volts you read?
Yes, unfortunately still no joy, same symptoms. Voltage is 0.002v across the left meter leads, and 6.22v across the right. Turning the pot has no effect. I'm not sure exactly how these pots work, do they have stops on either side of the range? I can spin mine more than 24 turns in either direction, maybe I broke the pot somehow during install or setup? Or maybe that's normal? If I go too far CW I hear a soft click once a rotation, I'm assuming that's the top of the range?
OK the 10uF cap on that side should be blocking the dc so may have a solder short under it. Remove the 10uF and retest the +M- to check the DC is gone or not? With cap removed should be 6.2v on + side and 0v other - side of cap pads.
Joe :-)
JLM Audio
Capturing Audio without Injury

verticalmammal
Posts: 5
Joined: Wed Feb 24, 2021 5:24 am

Re: Stereo VU meter kit BUILD THREAD

Post by verticalmammal »

Joe Malone wrote:
Wed Feb 24, 2021 2:54 pm
OK the 10uF cap on that side should be blocking the dc so may have a solder short under it. Remove the 10uF and retest the +M- to check the DC is gone or not? With cap removed should be 6.2v on + side and 0v other - side of cap pads.
Dude, you are a genius. I could see the solder bridge on the bottom when I removed it. Zipped it off with my iron and now we're right as rain. I'd like to make a small donation to the charity of your choice as a show of thanks, let me know who you'd like it to go to.

User avatar
Joe Malone
Site Admin
Posts: 1780
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: Stereo VU meter kit BUILD THREAD

Post by Joe Malone »

verticalmammal wrote:
Wed Feb 24, 2021 3:21 pm
Joe Malone wrote:
Wed Feb 24, 2021 2:54 pm
OK the 10uF cap on that side should be blocking the dc so may have a solder short under it. Remove the 10uF and retest the +M- to check the DC is gone or not? With cap removed should be 6.2v on + side and 0v other - side of cap pads.
Dude, you are a genius. I could see the solder bridge on the bottom when I removed it. Zipped it off with my iron and now we're right as rain. I'd like to make a small donation to the charity of your choice as a show of thanks, let me know who you'd like it to go to.
Cool great to hear that got it working :-)

Charity link below thanks.
https://donateplanet.com/charities/read ... in-cancer/
Joe :-)
JLM Audio
Capturing Audio without Injury

verticalmammal
Posts: 5
Joined: Wed Feb 24, 2021 5:24 am

Re: Stereo VU meter kit BUILD THREAD

Post by verticalmammal »

Joe Malone wrote:
Mon Mar 01, 2021 9:37 am
Cool great to hear that got it working :-)

Charity link below thanks.
https://donateplanet.com/charities/read ... in-cancer/
Done and done. Super-impressed with how you honed right in on the issue with your troubleshooting steps. I had my suspicions about the caps on that side as I mentioned (although it was for the wrong reason), but even if I maybe could have found it on my own eventually, I definitely couldn't have figured it out anywhere near as fast as you did. Between that and the help you provided me with my order this donation is the least I can do. Thanks again.

User avatar
Joe Malone
Site Admin
Posts: 1780
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: Stereo VU meter kit BUILD THREAD

Post by Joe Malone »

verticalmammal wrote:
Mon Mar 01, 2021 12:01 pm
Joe Malone wrote:
Mon Mar 01, 2021 9:37 am
Cool great to hear that got it working :-)

Charity link below thanks.
https://donateplanet.com/charities/read ... in-cancer/
Done and done. Super-impressed with how you honed right in on the issue with your troubleshooting steps. I had my suspicions about the caps on that side as I mentioned (although it was for the wrong reason), but even if I maybe could have found it on my own eventually, I definitely couldn't have figured it out anywhere near as fast as you did. Between that and the help you provided me with my order this donation is the least I can do. Thanks again.
Cool :-) Thanks :-)
Joe :-)
JLM Audio
Capturing Audio without Injury

Cfeedback
Posts: 7
Joined: Sun Feb 21, 2021 9:57 pm

Re: Stereo VU meter kit BUILD THREAD

Post by Cfeedback »

Joe Malone wrote:
Wed Feb 24, 2021 7:34 am
Cfeedback wrote:
Wed Feb 24, 2021 3:38 am
Great, that was the solution.

I connected -DC of VU2 with PGND of the output stages and now everything is wonderful.

Thanks again for your help...
Cool great to hear that fixed it. When you have 2 power supplies like this you have to reference them to each other.
Yes, you're right, I would never have stumbled over it so quickly.
I will remember in any case if I should have such a problem again.
The subject of ground loops is sometimes really complex, I think.

PS: The JLM AUDIO website/shop/forum is really first class, and very interesting.
And your know-how is remarkable.


Many Thanks and stay healthy

mobtownstudios
Posts: 6
Joined: Fri Jan 15, 2016 12:59 am

Re: Stereo VU meter kit BUILD THREAD

Post by mobtownstudios »

Hi all!

The VU build was fun and relatively easy!

I have not been able to get the LEDs to light up. There is voltage headed there which I am metering at 11.57v on each LED tap.

Any idea why they are not lighting up?

The VU meters themselves are working wonderfully, however.

Thanks!!
63951564818__84CFD78D-B5B4-425A-8491-9CD7D9AC0A15.jpg
You do not have the required permissions to view the files attached to this post.

User avatar
Joe Malone
Site Admin
Posts: 1780
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: Stereo VU meter kit BUILD THREAD

Post by Joe Malone »

Hi Mat RLamp for the 5v led backlight is 680R. You have fitted the 10R option for meters with lamp backlight. Meter backlights should have been very bright for a second or two before burning out. If not hopefully you have the lamp wires reversed. Change to 680R first before reversing if that is the problem.
Joe :-)
JLM Audio
Capturing Audio without Injury

mobtownstudios
Posts: 6
Joined: Fri Jan 15, 2016 12:59 am

Re: Stereo VU meter kit BUILD THREAD

Post by mobtownstudios »

Update:

Looks like I miss this instruction.

The 2 x RLAMP resistors = 680R for new 5v LED Lamp meters and 8 x diodes are NOT fitted just 4 wire links as shown.

So I fixed that, but the voltage on the LEDs still clocks in at 11.57v.

Are my LEDs blown? Or just not getting the right voltage?

User avatar
Joe Malone
Site Admin
Posts: 1780
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: Stereo VU meter kit BUILD THREAD

Post by Joe Malone »

Hi Mat posted at the same time as you see above post.
Joe :-)
JLM Audio
Capturing Audio without Injury

mobtownstudios
Posts: 6
Joined: Fri Jan 15, 2016 12:59 am

Re: Stereo VU meter kit BUILD THREAD

Post by mobtownstudios »

Thanks Joe for replying!

Yeah, no luck there with the new resistors and diode removal with the 4 jumpers. I tried a continuity tester with the LEDs and they appear to be blown.

Would these be good replacements LEDs?
https://www.amazon.com/Adafruit-Accesso ... B00XW2MY84

All this soldering is fun! Wish I had more kits to build!

Is that voltage of 11.5v correct?

User avatar
Joe Malone
Site Admin
Posts: 1780
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: Stereo VU meter kit BUILD THREAD

Post by Joe Malone »

Hi Mat yes they look fine. Any 2 clear white 5mm led around 1000mcd or more will work in there with the 680R. Each led has about 2.5 to 3.5v across it. So voltage at terminals will be 5v to 7v as the 2 are in series. They maybe brighter or duller so RLamp can be changed afterwards to make brighter down to 470R or duller up to 2k. Mount them exactly the same way as they are in the back of the meters. They have a polarity which is easy to see internally in the led as they are clear.

Continuity testing doesn’t really work with the leds. If you tried the reversing of the lamp power wires with no luck then they will be dead. But they should have been very bright for a couple of seconds if they burnt out.
Joe :-)
JLM Audio
Capturing Audio without Injury

mobtownstudios
Posts: 6
Joined: Fri Jan 15, 2016 12:59 am

Re: Stereo VU meter kit BUILD THREAD

Post by mobtownstudios »

Yes. Very bright then turned/blew out.

I measured 12v at the led terminals. Is that acceptable?

mobtownstudios
Posts: 6
Joined: Fri Jan 15, 2016 12:59 am

Re: Stereo VU meter kit BUILD THREAD

Post by mobtownstudios »

Joe Malone wrote:
Fri Apr 09, 2021 9:36 am
Hi Mat yes they look fine. Any 2 clear white 5mm led around 1000mcd or more will work in there with the 680R. Each led has about 2.5 to 3.5v across it. So voltage at terminals will be 5v to 7v as the 2 are in series. They maybe brighter or duller so RLamp can be changed afterwards to make brighter down to 470R or duller up to 2k. Mount them exactly the same way as they are in the back of the meters. They have a polarity which is easy to see internally in the led as they are clear.

Continuity testing doesn’t really work with the leds. If you tried the reversing of the lamp power wires with no luck then they will be dead. But they should have been very bright for a couple of seconds if they burnt out.
Thanks Joe!

New LEDs and fixing the resisters/diodes did the trick! Glowing wonderfully!

If I wanted to use 1 LED in each meter for a gentler glow would I have to do anything else other than that? Would I need a resister anywhere in the chain?

Screen Shot 2021-04-11 at 3.59.06 PM.png
You do not have the required permissions to view the files attached to this post.

Post Reply