boatman

When the original design was done 7 years ago there were many more sources of components and all the values were chosen for an optimal design. The resistor values have been rationalised down to only 9 different values from 21 to make sourcing the components easier. There are a few compromises in doing this which is why I emphasised that the design hasn't been tested, but should work OK.

Brian and I have rationalised the resistor values so that now 9 different values are used rather than 21 in version 1.3. I have also redone the PCB to change C22 from 100nF to 47uF. This is the de-bounce capacitor for the call button and some builders were finding the 100nF was far too small. 47uF should be adequate. It is possible to fit a 47uF capacitor in the C22 position on version 1.3 but the silk screen marking is less clear. PLEASE NOTE that these changes are all untested but we would welcome a guineapig builder to test them for us. The link to the zip file containing all the changes is HERE.

The schematic is now updated to version 1.4. As well as rationalising the resistor values, I have changed C22 from 100nF to 47uF. This is the call button de-bounce capacitor and some builders were finding that there was a audible bump on the line when the call button was pressed hence the value change. The PCB has been updated to allow for an electrolytic cap at C22. The new zip file contains all the new gerbers, schematic, assembly diagram and parts list. PLEASE NOTE: none of these changes have been tested but I am confident they will work OK. The files can be found in the next post.

I will update the schematic to version 1.3a and post it here ASAP.

1: Try Farnell part 1848267. 2: The test point can be just a short loop of tinned copper wire. 3 & 4: Your choices look OK to me. I have used JLC PCB for boards and their quality is good.

Did you try swapping the headsets around to see if it's the headset or the beltpack?

You could also try Bryant Unlimited (previously known as Bryant broadcast).

Try approaching the technical department of your local secondary school.

Popcorn anyone?

It's nothing to do with Bluecom but differing resistor values in audio line terminations. You'll get the same effect when adding or removing beltpacks from a system. Luckily it's very easy to adjust the sidetone on Bluecom beltpacks.

You should also look at these three posts for more info on the front panel jack: https://www.blue-room.org.uk/index.php?showtopic=57825&view=findpost&p=495750 https://www.blue-room.org.uk/index.php?showtopic=57825&view=findpost&p=513207 https://www.blue-room.org.uk/index.php?showtopic=57825&view=findpost&p=534036

If it helps the schematic for this beltpack can be found here.

I wouldn't recommend anything less than 32 ohms. Lower impedances will work but will draw a significant current from the power supply and might destroy the protection resistors R16 & R20. The standard headphones for comms systems are 400 ohms.

The XLR pin allocations match and the power requirements are within range, so it won't do any damage. We will be interested to hear if if works well.

Great. I'll try and change the schematic and parts list but I don't know when that will be.

Have you managed to do any testing to reduce the 'thump'? I have also tried changing C22 but with no help. Would increasing R12/22 slow the charge rate of C22 slowing the time for TR2 to turn on? I doubt that I will be able to do any testing for the foreseeable future. The rate at which TR2 turns on needs to be slowed down significantly. That means changing C22 to a much larger value (try 10uF or even 47uF). Remember to observe the polarity if using an electrolytic or tantalum cap and the rating will need to be 40V. You could try changing R12 & R22 to 100k but that might mean that TR2 doesn't turn on fully. My money is on making C22 as large as possible.

Unfortunately I'm not able to do any testing just now but if someone could try changing C22 from 100nF to either 1uF (or even 10uF) that might solve the "thump" problem.

There's no schematic in the technical documentation so I can't be sure but I think it probably will.

How about two three section pantographs inside the wings. If they are each made of six two-foot long struts they should easily fit behind the set, will extend to almost six feet on either side and will droop appropriately. A couple of strings to make them extend and retract and the job is done. Some sort of concertina style covering will be needed.

OK, that's possible. There are two new zip files with cutouts for 8.2mm round buttons here. I must emphasise that these have NOT been manufactured as PCBs so will have to be checked.

Two new files for Beltpack and PSU panels. Version 2 has a 9mm cutout for an 8.2mm circular button. WARNING: these files have not be manufactured as PCBs so should be thoroughly checked to make sure they are correct.BeltpackPanels_V2.zip PsuPanels_V2.zip

Unfortunately the LED is too close to the button to allow for an 11mm round hole; it would also require a change to the PCB. However, a 13mm x 8mm aperture may be possible to accommodate the larger rectangular button.

The spec for all the buttons is on page four of the data sheet which is on CPC's website.

Found them at last! Mouser stock the correct white button (Alps part 4093-3). A pack of 10 for €1.41 and there are 125 in stock.

CK components switches also have a 3.3mm square shaft and Farnell have over 1,700 of these in stock. The short side should be OK but the long side might be a bit tight. The CK Components G002x series would fit perfectly but don't sem to be stocked by Franell.