Forums - New build have questions about installing meters

Verified Member

Posts: 8

New build have questions about installing meters
12/18/16 at 16:34:38

This is the second set amp I have built. The first being a get set go. On that amp I did not put meters on it. This zkit is for a friend and he insisted on having meters on it I have them laid out in the chassis but I need to figure out how to actually wire the meters and the back lights. I did find a post on these forums that said to use the number 3 pin from the output tubes to the positive side of the meter and the negative side of the meter goes to the respective ground for pin 3. wiring the positive side of the meter is not a problem I'm just not sure if I am supposed to wire the negative side of the meter to the board ground or two another pin on the output socket.
Also I've never wired any sort of lights on an amplifier before and I'm trying to figure out how to wire the back lights I have no idea where to begin with those. Thank you in advance for any help that you may be able to give me.

Ill post pictures of the project as soon as I figure out how to post pictures.

Also i have not done a shootout between the get set go and this zkit but after a quick listen I think I'm going to like this zkit better.

Matt

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Core32

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Posts: 1862

Re: New build have questions about installing meters
Reply #1 - 12/18/16 at 16:50:49

I think your information is off a bit.
If you look at the schematic for the ZKIT1 you will see that pin number 3 of the output tubes are tied together, then this "pin 3 junction" is tied to the 150ohm resistor / 1000uF capacitor common point which then go to ground.
If you are using a mA meter and wire it the way you state from pin 3 of each tube to ground, that is the same as shorting pin 3 to ground because a mA meter is basically a very low impedance shunt (short).
Give me the part number and/or link for the meter you plan to use and I will see if I can help you draw up the correct connections.

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Orangeamcs

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Posts: 8

Re: New build have questions about installing meters
Reply #2 - 12/18/16 at 17:16:09

Tried to post a link to the post I got my info from. It won't let me until I post a few more times. The meters are basically a standard 100ma meter w backlight from ebay. I already blew the lights out of them so I'll have to order another set. Hopefully they are correct or if they won't work that I can get something to fill holes in this amp with out having to make a new top plate.

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Core32 Seasoned Member Posts: 1862	Re: New build have questions about installing meters Reply #3 - 12/18/16 at 17:22:25 Then just send me a model number and I will search for them on Ebay. No need to kill another set if they are not useable.
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Orangeamcs Verified Member Posts: 8	Re: New build have questions about installing meters Reply #4 - 12/18/16 at 17:23:34 Actually core32 the post I was referring to had responses from you. That's what I was going by. You posted a schematic w a toggle to switch between each tube since you didn't have room for 2 meters in your build. Thanks for your help.
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Orangeamcs Verified Member Posts: 8	Re: New build have questions about installing meters Reply #5 - 12/18/16 at 17:25:46 Ebay meters were item number 131674776791
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Core32

Seasoned Member

Posts: 1862

Re: New build have questions about installing meters
Reply #6 - 12/18/16 at 17:40:37

Ok. To do this using the actual ZKIT board (I did not, but wired point-to-point) you will need to NOT solder the sockets into the board but use wire from the sockets to the board.
Is that how you are doing it? If not, you will need to cut traces on the board to disconnect the pin 3s from the rest of the circuit and wire to the meters.
If you don't feel comfortable doing this then it may not be an option for this build.

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Orangeamcs Verified Member Posts: 8	Re: New build have questions about installing meters Reply #7 - 12/18/16 at 17:48:37 I am using a board. It's actually all built already. And meters are installed in top panel. I don't think I'll have actually problem cutting traces. I can just Mark the board and drill actually hole through the trace correct?
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Core32

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Posts: 1862

Re: New build have questions about installing meters
Reply #8 - 12/18/16 at 17:59:56

I don't have a board to look at so it's hard to tell. I usually take an exacto knife to slice through the trace in a convenient spot where I can remove a small portion. The idea is that you need to completely isolate each pin 3 from the rest of the circuitry on the board WITHOUT messing up the rest of the connections on the board.
Once you do that you will take an isolated socket pin 3 to the meter + with a wire, then take the meter - with a separate wire back to the trace where you cut that is still connected to the junction of the 150ohm/1000uF parts that IS NOT GROUND.
Then repeat for the other meter from the other isolated socket pin 3.
I can try to draw a quick sketch later tonight if you want but I am out of time for now.

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Orangeamcs

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Posts: 8

Re: New build have questions about installing meters
Reply #9 - 12/18/16 at 18:09:53

I think I can handle that. So basically it's in line with pin 3 to the rest of the board. Would i tie the negarive side back in before or at the the 0.1 uf resistor. I believe that is the xmas come early addition to this board. I think k it can figure this out. Or I'm at least alot closer. That is solved kinda, now need to figure out the back lighting on gauges.

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Steve Deckert

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If the 1st watt
sucks why continue?

Posts: 6350

Re: New build have questions about installing meters
Reply #10 - 12/18/16 at 18:40:30

Christmas holidays are the very best time to build amplifiers! You can easily install your meter without modifying the board by simply unsoldering the 150 ohm 5 watt cathode resistor's end that connects to ground. Install a wire from this now free resistor lead to the + on your meter. Connect the - on the meter to the ground location on the circuit board where the resistor was soldered.

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Orangeamcs Verified Member Posts: 8	Re: New build have questions about installing meters Reply #11 - 12/18/16 at 19:37:46 Steve, Since I have 2 gauges already installed in my board would i just run them in a series from the 150 5w then back to the ground. They would both read the same instead of individually but at least they would both work then. Matt
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Core32

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Posts: 1862

Re: New build have questions about installing meters
Reply #12 - 12/21/16 at 15:35:17

Unless it's just to fill the chassis hole, having two in series like that doesn't make much sense.
For the backlighting of that meter you will still need to generate less than 12VAC or DC from your power transformer. If you need help with that I might have some ideas. What did you try before that you say blew the lamps?

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Orangeamcs

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Posts: 8

Re: New build have questions about installing meters
Reply #13 - 12/23/16 at 23:33:15

Chassis already has holes in it that's why I have to do 2 meters. I tried hooking backlight up straight I. Line with powerfrom power fuse. I knew better but for some reason I tried it. A friend suggested hooking backlight up to the heater circuit. Wish I could figure out how to post a picture. Also listening to this with the speakers my friend has it could use a little less Bass. I used a 6dj8 input tube. Still I feel the speakers are Bass heavy, which they may just need to go and something good else pit in there place but would changing to el84 outputs reduce any of the bottom. I'm considering just getting a handful of tubes to roll.
Thanks
Matt

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NYUser

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Posts: 1

Re: New build have questions about installing meters
Reply #14 - 03/26/22 at 14:09:42

I am in the process of acquiring parts to build the ZKit1. I plan to install a 100MA panel meter and will wire it as suggested by Steve. The meter has a stated DC resistance of 630 ohms. When placed in series with the 150 ohm cathode resistor I assume the total resistance will be 780 ohms (i.e., 150 + 630). Will the increased resistance have any negative effect on the circuit or the performance of the amplifier? I realize this is an old thread, and apologize if this is an uninformed "newbie" question.

Thanks in advance! Jim

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bobc

Senior Member

Posts: 66

Re: New build have questions about installing meters
Reply #15 - 05/14/22 at 15:03:16

I found 100ma panel meters with internal resistance of 2ohms. The additional resistance of your meters will likely impact biasing of the tube(s).

Now I do not have NOS bejeweled movement meters, just HUA 45mm round panel meters, but they work and are useful in diagnosing tubes, knowing clipping etc.

One way to mitigate the high meter resistance is use a volt meter and measure across a small resistor value. Can also make this switchable.

If you do one meter per side then change the signle 150R cathode resistor to 300R per tube. Keep the bypass cap the same.

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svartemarten Verified Member Posts: 8	Re: New build have questions about installing meters Reply #16 - 01/01/25 at 15:50:52 Hi Bobc Where did you find the Meters with only 2 Ohms? Having trouble finding such ones. most I come across are 630 Ohms Chinese ones? My build is in https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1717444782/0
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bobc Senior Member Posts: 66	Re: New build have questions about installing meters Reply #17 - 01/01/25 at 19:21:58 I found them on eBay. Alternatively you can get a 100mv meter and measure across 1 ohm.
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svartemarten Verified Member Posts: 8	Re: New build have questions about installing meters Reply #18 - 01/03/25 at 15:36:15 thanks
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