Clansman Pressel help please - UK Vintage Radio Repair and Restoration Discussion Forum

WW2Mike · 26th Mar 2019, 6:21 pm

I have a Clansman IB3 intercom box in my vehicle. From there, I have a crew box connected. Instead of using the pressel (PTT), I've connected the headset directly and wired a switch between PTT pin F and E. E is the PTT and headphone return. The problem is that the PTT is active all the time and won't shut off when opening the switch. What am I missing? Does the PTT need to be pulled high when not grounded? I can't find a pressel schematic. The reason I am doing this is so that the cabling has a ww2 appearance. Thanks

ex seismic · 26th Mar 2019, 7:50 pm

Assuming you don't want to transmit over a radio, which is what it sounds like from your message, I would use the pressel box set to Live Mic then hide it away somewhere.

Martin G7MRV · 27th Mar 2019, 12:47 pm

Have you tried with a pressel/standard handset? Are you sure the IB3 and crew box are working properly?

Ive checked the harness manuals and tech EMERs but they dont have the pressel box in them either!

WW2Mike · 27th Mar 2019, 2:38 pm

Quote:

Originally Posted by ex seismic

Assuming you don't want to transmit over a radio, which is what it sounds like from your message, I would use the pressel box set to Live Mic then hide it away somewhere.

It's on all the time. That's the problem. I am trying to control it using a switch instead of the PTT.

Quote:

Originally Posted by Martin G7MRV

Have you tried with a pressel/standard handset? Are you sure the IB3 and crew box are working properly?

Ive checked the harness manuals and tech EMERs but they dont have the pressel box in them either!

Yes, a pressel (PTT) controls PTT just fine with the IB3 and crew box, I'm trying to make my own period-looking PTT using a switch between E and F to control the Clansman throat mic.

Martin G7MRV · 27th Mar 2019, 4:25 pm

Thats fine, just wanted to check you'd ruled out a fault in the rest of the system.

Why on earth do you want to use those gawd awful throat mics!?

Have you checked that the switch and plug combination gives the expected continuity readings between pins E and F when not connected to the boxes? And have you tried the switch only without the mic?

I think without the audio gear diagrams you'll need to work by 'divide and conquer'!

Sparky67 · 27th Mar 2019, 9:20 pm

Hi,

I read your post with interest as I wired up a harness with similar boxes some years ago and had no issues with it (apart from burbling ANR headsets...!). Our system was just used for audio, with pressels to activate the mics.

I have just revisited the wiring diagrams and one point to note is there is no individual PTT wire(s) in the 12-way interconnecting cables. PTT is signalled by current sensing via the mic pair - the boxes placing a low impedance across the relevant A or B mic wires. Radios connected to the harness use this to activate PTT via their harness connector, unlike the hard switch in the pressel box connected to the handset/headset connector. So, if your radios are PTT'ing you may have a too-low impedance arriving permanently across their mic connections in the harness connector?

Joe Bell's article written for VMARS may help...

http://www.vmarsmanuals.co.uk/newsle..._interface.pdf

Cheers

Martin
G4NCE

WW2Mike · 28th Mar 2019, 4:25 pm

Thanks. Last night I took apart a pressel to find that pressel switch is multi-pole and also controls one of the mic signal lines as well as the PTT. My original WW2 switch is only single pole, so it looks like I would have to operate in hot mic all the time, unless I repurpose my switch to control the mic signal (and wire the PTT to be on all the time). Would that work, or would the hi Z be susceptible to creating noise?

ex seismic · 28th Mar 2019, 11:51 pm

I have an armoured vehicle with Clansman fitted using an IB3 and crew boxes as you have. I run the Pressels in Live Mic and use that Crew Box position as well. No problem with noise while using A vehicle headsets and it means that for the driver especially the intercom is hands free operation. (Unless he wants to use a radio). The Clansman microphones are noise cancelling which no doubt helps.

26th Mar 2019, 6:21 pm	#1
WW2Mike Retired Dormant Member Join Date: Aug 2018 Location: Hunt Valley, Maryland, USA. Posts: 5	Clansman Pressel help please I have a Clansman IB3 intercom box in my vehicle. From there, I have a crew box connected. Instead of using the pressel (PTT), I've connected the headset directly and wired a switch between PTT pin F and E. E is the PTT and headphone return. The problem is that the PTT is active all the time and won't shut off when opening the switch. What am I missing? Does the PTT need to be pulled high when not grounded? I can't find a pressel schematic. The reason I am doing this is so that the cabling has a ww2 appearance. Thanks

26th Mar 2019, 7:50 pm	#2
ex seismic Heptode Join Date: Sep 2009 Location: Tonbridge, Kent, UK. Posts: 686	Re: Clansman Pressel help please Assuming you don't want to transmit over a radio, which is what it sounds like from your message, I would use the pressel box set to Live Mic then hide it away somewhere.

27th Mar 2019, 12:47 pm	#3
Martin G7MRV Heptode Join Date: May 2008 Location: Selby, North Yorkshire, UK. Posts: 951	Re: Clansman Pressel help please Have you tried with a pressel/standard handset? Are you sure the IB3 and crew box are working properly? Ive checked the harness manuals and tech EMERs but they dont have the pressel box in them either! __________________ I got food in ma belly and a license for ma telly My Blog - http://g7mrv.blogspot.com

27th Mar 2019, 4:25 pm	#5
Martin G7MRV Heptode Join Date: May 2008 Location: Selby, North Yorkshire, UK. Posts: 951	Re: Clansman Pressel help please Thats fine, just wanted to check you'd ruled out a fault in the rest of the system. Why on earth do you want to use those gawd awful throat mics!? Have you checked that the switch and plug combination gives the expected continuity readings between pins E and F when not connected to the boxes? And have you tried the switch only without the mic? I think without the audio gear diagrams you'll need to work by 'divide and conquer'! __________________ I got food in ma belly and a license for ma telly My Blog - http://g7mrv.blogspot.com

27th Mar 2019, 9:20 pm	#6
Sparky67 Heptode Join Date: Feb 2008 Location: Great Barr, Sandwell, West Midlands, UK. Posts: 589	Re: Clansman Pressel help please Hi, I read your post with interest as I wired up a harness with similar boxes some years ago and had no issues with it (apart from burbling ANR headsets...!). Our system was just used for audio, with pressels to activate the mics. I have just revisited the wiring diagrams and one point to note is there is no individual PTT wire(s) in the 12-way interconnecting cables. PTT is signalled by current sensing via the mic pair - the boxes placing a low impedance across the relevant A or B mic wires. Radios connected to the harness use this to activate PTT via their harness connector, unlike the hard switch in the pressel box connected to the handset/headset connector. So, if your radios are PTT'ing you may have a too-low impedance arriving permanently across their mic connections in the harness connector? Joe Bell's article written for VMARS may help... http://www.vmarsmanuals.co.uk/newsle..._interface.pdf Cheers Martin G4NCE Last edited by Sparky67; 27th Mar 2019 at 9:26 pm.

28th Mar 2019, 4:25 pm	#7
WW2Mike Retired Dormant Member Join Date: Aug 2018 Location: Hunt Valley, Maryland, USA. Posts: 5	Re: Clansman Pressel help please Thanks. Last night I took apart a pressel to find that pressel switch is multi-pole and also controls one of the mic signal lines as well as the PTT. My original WW2 switch is only single pole, so it looks like I would have to operate in hot mic all the time, unless I repurpose my switch to control the mic signal (and wire the PTT to be on all the time). Would that work, or would the hi Z be susceptible to creating noise?

28th Mar 2019, 11:51 pm	#8
ex seismic Heptode Join Date: Sep 2009 Location: Tonbridge, Kent, UK. Posts: 686	Re: Clansman Pressel help please I have an armoured vehicle with Clansman fitted using an IB3 and crew boxes as you have. I run the Pressels in Live Mic and use that Crew Box position as well. No problem with noise while using A vehicle headsets and it means that for the driver especially the intercom is hands free operation. (Unless he wants to use a radio). The Clansman microphones are noise cancelling which no doubt helps.