Tech Chat Museum Signals Rack 2.0 - Pi-COW, Pi-Pat, Pi-Text

Nice to see you've found a suitable enclosure.

Minor update

Freed up from doing battle with the PYE K12, I'm back to spend a little time on version 2.0 of the signals rack.

As I mentioned in the opening post, I decided I would like to fit an LCD monitor in to the device, so set about finding trying to find one. The trouble being I needed 5" and 4:3, checking usual sources I found a job lot of six all with BNC break out boxes, PSUs all nicely packed in a flight case. A bit of a gamble as state unknown and no returns, well for £60 I felt it was worth the risk. Happy to say five out of the six work, one D.O.A. which considering they all could have been duff is a result.

Next I needed to rearrange all the module bays as the original configuration was not as I wanted. To the left is where I want to install the modulators, the centre will house the monitor and the right will have the final 4-bays C.O.W. Pi-Pat, Pi-Text and IMOGen, I'm going to remove the Imogen from its enclosure and mount in the final bay card.

As you can see from the last couple of photos above, I couldn't have wished for a better fit for the 5" monitor. Moving to LCD will greatly reduce the heat in the rack generated by the 10" SONY PVM monitor.

Next job, build new C.O.W, Pi-Pat, Pi-Text onto the module cards

Being curious, I opened up the failed monitor, foolishly thinking it might be something simple. When I saw all the surface mount, I thought, "Yeah, right!". However, my eye spotted a small soldered in fuse, and thought nothing is ever that simple for me, well I was wrong, yes, it is open.

Only problem now is finding 1.5A 250V fuse that small I can solder in. Checked my stores and the smallest I have is 17mm len x 7mm dia, this is 10mm len x 5mm dia.

Edit:

I just found these, 1.6A 250V micro fuse. Should do the job, if it will fit.

It would not fit in the original space, but there was some empty real estate in the centre of the board. A little hot melt, some fly-leads and it's all sorted. That's all six working. 👍 

Spent this afternoon on a job I was least looking forward to, as there was plenty of scope to screw up, and I only get one shot at this. Using a mini angle grinder, I had to cut out a window in the centre module's plate to finish off the look of the front. Thankfully, it worked out, and I'm pleased with the result.

Now to get on with the other four right-hand modules, which will house the test signal generators & Teletext service.

More progress, today I built the three Pi's (c.o.w. / ceefax / test card gen) onto three of the modules. Then added legends to the fascia.

Next modulators.

Nice see see, the set up is looking a lot more professional.

On the home stretch now on version 2.0 of the crusty signals rack, now known as CRM1 & CRM2. I've mentioned I'd come up with an idea for the VFD display, it's now incorporated into a low rack. I also found the Pi-COW was better placed below as when the three Pi's were side by side in the top right of the rack, I had interference on the test card module, moving it below cured this.

I need to erase, edit the .BIN and blow the EPROM again for a spell mistake, see if you can spot it

Pictures below show the second test run, after curing the above mention problem.

My tribute to the racks of days gone by.

Lots of tidying up at the rear, then it can go on the shelf and sorting out the 3->1 power for the modulators.

That'll be the Text Cards then..

Power for the modulators has now been sorted, reducing the requirement of 3-plugs down to one. I used a compact splicing connector block, giving me 3 in 9 out, and housed this in an empty laptop power brick. Further reducing the number of plugs required, the three 5V supplies for the Pi's were supplied by a powered USB hub, thus just one plug.

The channel filters are mounted on the outside of the unit as the distribution unit will also be external, so makes connectivity far easier.

Final task next; connect all the video feeds to the switch and modulators, then connect back to the aerial system.

Project for version 2 now complete! To think this journey all started with the DECCA RU.4011, hopefully that's it. Overall, I'm really pleased with the way it's turned out, also pleased to have lost the SONY PVM which, being in such proximity to the signals, did cause me some headaches.

Outstanding work

Superb work Chris. 

Update:

The built-in monitor on my signals rack allows me to monitor via the Decca RU.4011, the three UHF channels as presented to my aerial distribution, basically it sees what the TV's in the museum see, hmmm but there's a flaw.

The current design leaves a gaping hole, not being able to monitor the source of the signal before it arrives at the aerial system, a fault at any of the three sources could be present, I might not notice or mistake a fault for a UHF distribution fault, been caught out on this before.

The solution; I've sourced a broadcast monitor rack, a Datavideo TLM-433, thus allowing me to separate a source fault from a distribution fault. This module is the same width as all the other kit, and I wanted to site it above the RU.4011, but I've exceeded my shelf space ....Damn. Some pondering will now follow.

Wired in the source test signals monitors. As you can see from the third photo, the internal monitor is monitoring what is being fed to the UHF aerial system. The above three are monitoring the test signals awaiting insertion, at a flick of a switch I can swap the feeds into the aerial system. The final picture shows the fourth signal which is the live teletext feed being picked up on the 10" test TV on the main bench.

I have one fault which thus far I've been unable to trace and is driving me nuts!!!

I have some really odd sound/noise getting into the system. Furthermore, I've tried to isolate it, but again without success.

• Stopped all the Pi services, no change.
• Stopped and powered off the VFD display module, no change
• Removed the CH56/CH60 combiner, no change.
• Removed the Overlap filters, no change.
• Removed modulators out of rack, no change.
• Replaced modulators, no change.
• Removed distribution system and went direct to TV, no change.
• Replaced video switch, no change.
• Switched workshop off Router, no change.
• Switched off Powerline Ethernet, no change. 
• Switched off bench lamps and workshop fluorescent lights, no change.

Totally stumped at this point! All I've observed is that as soon as I insert the yellow composite video lead into a modulator the noise starts, so video causing it, but why and how to resolve is the problem. Oh and yes, I did replace the leads.

Is the composite video overloading the modulator?

Hi Chris, very impressive work there. Well done.

I had a similar issue with a noise and only when video was present on a freeview box. That was, as Frank suggests the composite signal over driving the modulator. I was also getting some patterning on other UHF frequencies. The box went in the bin.

Best regards

Jon