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Which DIY Techpro PSU


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In my school we have a few Tecpro headsets http://www.blue-room.org.uk/public/style_emoticons/default/headsetsmiley.png and beltpacks, but for some reason there is no power supply. I'd like to make one, but I've seen 3 different methods:

  1. Just put 24V on pin 2 with pin 1 as ground
  2. ClearCom2 PSU- the same, but with an "R/C output filter" (whatever that is http://www.blue-room.org.uk/public/style_emoticons/default/blink.gif)
  3. BlueCom PSU - uses a ton of different components, none of which are available individually, so you have to overbuy

What's the difference between them, and whats the cheapest I could get away with? http://www.blue-room.org.uk/public/style_emoticons/default/wink.gif

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In my school we have a few Tecpro headsets http://www.blue-room.org.uk/public/style_emoticons/default/headsetsmiley.png and beltpacks, but for some reason there is no power supply. I'd like to make one, but I've seen 3 different methods:

  1. Just put 24V on pin 2 with pin 1 as ground
  2. ClearCom2 PSU- the same, but with an "R/C output filter" (whatever that is http://www.blue-room.org.uk/public/style_emoticons/default/blink.gif)
  3. BlueCom PSU - uses a ton of different components, none of which are available individually, so you have to overbuy

What's the difference between them, and whats the cheapest I could get away with? http://www.blue-room.org.uk/public/style_emoticons/default/wink.gif

 

A 24v DC supply on pin 2 with pin 1 as ground is fine, but you also need to put a few "termination" components on the audio line (pin 3) or it won't work properly (the call light may come on permanently, and you will get feedback in all the headsets).

These are R2, C5, R4 on the bluecom diagram.

 

So you connect a 270R or 220R resistor to pin 3.

Then a 4K7 resistor from that to ground, and also a 10uF 35V capacitor from that to ground (across the 4K7 resistor, make sure the + is at the right end)

 

Those are the only parts you need to add. You do not have to use the exact values as long as they are close. You should be able to get them from Maplin.

 

You should also make sure the 24V Power supply has overcurrent/short circuit protection on it - if you use a recent plug-in power pack then it should be built in. If not, put a fuse in line.

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Here's a couple of shots of the finished article. You'll have to excuse the dust, it's been in my garage for rather a large number of years! If the PSU is at one end of the chain, you don't really need two XLR connectors, one will do.

 

http://mydesk.myzen.co.uk/_Useful/TecproTerm1.jpg

 

http://mydesk.myzen.co.uk/_Useful/TecproTerm2.jpg

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I asked the same question a few years ago and made one which is still working fine as a 2nd portable unit when we want to use comms away from our main venue (as our comms PSU is racked up & installed in the venue.

The images of my finished unit have fallen off the edge of the internet but diagrams are still there.

Link - http://www.blue-room.org.uk/index.php?showtopic=44052

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I asked the same question a few years ago and made one which is still working fine as a 2nd portable unit when we want to use comms away from our main venue (as our comms PSU is racked up & installed in the venue.

The images of my finished unit have fallen off the edge of the internet but diagrams are still there.

Link - http://www.blue-room...showtopic=44052

Thanks, but now I'm even more confused http://www.blue-room.org.uk/public/style_emoticons/default/huh.gif - the schematic there uses even more components. What are they for, and do I need them?

 

 

 

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Thanks, but now I'm even more confused http://www.blue-room.org.uk/public/style_emoticons/default/huh.gif - the schematic there uses even more components. What are they for, and do I need them?

 

The essential components in this schematic are R2, R3 & C1. As Tim said, if you use a modern 24V wall wart with over-current protection and decent smoothing then you don't need the supply smoothing components R1 & C2. Perhaps you should get one of the teachers in the Technical Department to help you.

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  • 3 weeks later...

BlueCom PSU - uses a ton of different components, none of which are available individually, so you have to overbuy

I've got spare BlueCom PSU PCBs. I'm sure we could get something sorted for you. You can have a PCB for a couple of quid plus postage if you PM me.

 

Many moons ago, before I made any BlueCom's, I made my own PSU for a Tecpro setup. The PSU is easy. The key point is to remember the audio termination network (which I believe I copied from here from Tom's thread: http://dmx512.com/we...cpro/tptech.htm). If I'd've read this thread more fully before replying I'm sure Tim or John will already have described this... and of course these components are on the Bluecom PSU schematic...

 

I don't like the look of that ComClone PSU - there's no audio termination for Canford/Tecpro. Go with the BlueCom circuit.

 

Kevin

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  • 2 weeks later...

.

.

Thanks, but now I'm even more confused http://www.blue-room.org.uk/public/style_emoticons/default/huh.gif - the schematic there uses even more components. What are they for, and do I need them?

 

The essential components in this schematic are R2, R3 & C1. As Tim said, if you use a modern 24V wall wart with over-current protection and decent smoothing then you don't need the supply smoothing components R1 & C2. Perhaps you should get one of the teachers in the Technical Department to help you.

 

 

 

Now I'm completely confused, we had a problem running 6 stations due to volt drop on the end of a run of fst with loop resistance around 80ohms, IIRC I measured the current of the 6 at around 400mA and added a second PSU near them. Following the above link I find a 330 ohm resister which can only source 72mA from 24V (that would be into a short circuit).

 

Edit:

It's great to see this thread as I'd never got around to opening a PSU to see what's in them, I've never really thought it so in some ways I've been quite surprised how little there seems to be.

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Following the above link I find a 330 ohm resister which can only source 72mA from 24V (that would be into a short circuit).

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That statement is totally meaningless to me, please clarify.

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Following the above link I find a 330 ohm resister which can only source 72mA from 24V (that would be into a short circuit).

 

That statement is totally meaningless to me, please clarify.

 

He means, The schematic linked in your post has a 330R resistor in series with the 24V supply - I'm not sure why that is there but it doesn't look right to me.

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Following the above link I find a 330 ohm resister which can only source 72mA from 24V (that would be into a short circuit).

 

That statement is totally meaningless to me, please clarify.

 

He means, The schematic linked in your post has a 330R resistor in series with the 24V supply - I'm not sure why that is there but it doesn't look right to me.

 

Thanks. That circuit was taken from the original ComClone 2 power supply. Look at the BlueCom power unit schematic which has resettable fuses and is intended to work with a 24VDC wallwart supply. If the wallwart has over-current protection you can omit the fuses.

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  • 3 weeks later...

Thanks for everyone's help so far.

I made the ComClone circuit (without the big 330R 2W resistor ), and today my power supply came from China so I could finally test it. When connected I can hear sound from the mic and other belt packs fine, but there is also a loud buzzing noise. I think this must mean I messed up in the termination components somewhere, but I can't find it.

Here are some pictures:

IMG_20170525_211618.jpgIMG_20170525_211632.jpgIMG_20170525_211640.jpg (Photo 1, Photo 2, Photo 3)

 

I know it's a bit of a mess and at high risk of a short circuit right now, but once I get it working properly I will move it to a proper stripboard http://www.blue-room.org.uk/public/style_emoticons/default/tongue.gif

Could the issue come from using a cheap power supply?

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I made a Bluecom system using a standard no-name switch mode wall-wart power supply. I had lots of hum and buzz problems. The fault was quickly found to be caused by the power supply which was a Class 2, double insulated one. I ended up breaking open the wall-wart and re-boxing the guts in a plastic box with a 3 pin IEC power inlet, mains power switch and connecting the mains earth to the output negative. Audio line termination components and a 3 pin XLR were included as well. Hum and buzz problems were solved as well as having all the power supply and termination components in one box.

 

Peter

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