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Kramer VP-725DSA Repair – Part 1

January 2nd, 2013 No comments

I’ve acquired another bit of hardware that was heading towards the skip – a Kramer VP-725DSA Presentation Switcher/Scaler. Its problem is that it no longer responds to any of the buttons on the front control panel, and is permanently stuck on DVI 1. When controlling it via its network control application, it does respond to the virtual button presses, but then almost immediately jumps back to its previous state, and intermittently does a factory reset.

First up I whipped out the front control panel PCB and checked out the DVI 1 button. The button checks out as I had suspected, and I turned my attention to the switch mode power supply (SMPS).

The four voltage rails (+5, -5, +15 and -15) all tested fine, but on further inspection the resistor R3 looked rather crispy. Even with no load attached to the output of the SMPS, the resistor gets pretty hot. I’ve tested the resistor out of the circuit and it reads 75K, which is what I guess it should be. The colour bands are rather cooked – currently purple, black, brown, gold, but they may have originally been violet, green, orange, gold.

For now I’m going to focus my attention on the SMPS, as I suspect there’s some issue with its output which is upsetting the rest of the unit – excess ripple, noise, etc. I’ve just got to track down what is pulling excess current through R3. I’ve emailed Kramer to see if there’s a service manual available before I start poking around further. I guess that one of the electrolytic capacitors is out of spec, but there’s no visible problem with any of them.

To be continued…

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Theatre Rigging Refit – Part 3

August 7th, 2012 No comments

The first stage of my rigging improvement program is complete – i.e. raising the upstage roll-drop support framework.

It took a lot longer than I expected to complete this stage, as a lot of time was spent tweaking and re-tweaking the alignment of the three support struts. I’ve also redone the hanging points for the existing ‘hemp’ line-set above the framework, and installed a new additional line-set. Lastly I’ve installed a length of Unistrut on the end wall, which will replace the timber rail that is still there at the moment.

Next the ropes and pulleys on the roll-drops themselves need to be replaced, and new cloth fitted, as there’s far too many layers of paint on the existing ones. After all that the roll-drops can be reattached to the support framework.

A lot to do before production begins on panto in another couple of weeks!

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Theatre Rigging Refit – Part 2

July 31st, 2012 No comments

I’ve made a reasonable amount of progress so far. The roll-drops are down, the fan heater is gone,  the cyc is now supported independently, and the Unistrut has been removed.

Tomorrow I’m hoping to get the Unistrut refitted in its new position, and at the weekend I hope to get some new Unistrut bolted above the pin rail.

I need to try and get the place tidied up for a free hire that we’re giving on Tuesday, so I want to get as much completed as possible in the next five days.

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Theatre Rigging Refit – Part 1

July 23rd, 2012 No comments

This month’s project is to sort out some of the rigging above the upstage area of The Little Theatre’s stage.

The existing upstage rigging consists of three pieces of Unistrut at 4m above the stage, from which are attached five roll-drops (also known as oleo or olio drops) which are used for back-drops.

I have a few issues with the current installation:

  • Firstly the tops of the roll-drops are below the level of the lighting bars, which means the border that is used to hide the rolled up drops casts a very noticeable shadow.
  • Secondly, and more importantly, the rope and pulleys that have been used up until now are far from appropriate.
  • Thirdly a number of the fixings used to suspend the Unistrut are less than ideal, i.e. Coach screws and M8 set screws, some of which are loose or just look rough because M10 nuts have been used as washers.

The ultimate goals of the project are to raise the Unistrut supports by 0.6m, taking them to about 0.5m above the lighting bars, and secondly to replace all the rope and pulleys on the roll-drops. The roll-drops already need new cloths, so we’ll be fitting larger ones anyway.

The current plan for the next few week is as follows:

  1. Order additional Unistrut, fittings and fixings.
  2. Completely remove the roll-drop assemblies from the Unistrut.
  3. Remove a 4KW fan heater that’s in the way on the SR wall.
  4. Install new supports for the cyc screen, as it currently hangs from the ends of the Unistrut, but it must remain at the current level.
  5. Remove the Unistrut and all associated studding (threaded rod) and fixings.
  6. Remove the pulleys that are used to install and remove the roll-drop assemblies from the Unistrut.
  7. Refit the Unistrut at 4.6m above the stage using M10 fixings through-out, with each set screw passing completely through each supporting timber, with a hefty 50mm washer on either end, complete with spring washer.
  8. Refit the pulleys so the roll-drops assemblies can be later raised back onto the Unistrut, but this time have two different mounting positions so it’s more of a vertical lift.
  9. Install Unistrut about 4.4m up the SR wall, above the pin rail using M10 Rawlbolts, so the new head blocks (pulleys) have something more solid than a piece of timber to be attached to.
  10. Replace pulleys and rope on the roll-drop assemblies.
  11. Raise the roll-drop assemblies back into place and attach to Unistrut.
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UPS Repair – Part 3

March 29th, 2012 No comments

New relays have been fitted, the unit reassembled, and powered back up. So far everything looks good, but I won’t know for sure if the problem has really been fixed until I get some under or over voltages, but I’m fairly confident of the repair.

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UPS Repair – Part 2

March 24th, 2012 No comments

I’ve stripped the UPS down and removed the main circuit board. After a quick examination I identified four likely relays and then extracted them for testing.

Relay R406 had a high resistance across a couple of contacts, so this looks to be the AVR relay. One of the other relays (I forget which) also sounded a bit tired when I was testing it.

What I plan to do next is replace all four, since I’ve already gone to the effort of removing them. The original relays are Song Chuan 793-P-1C-3. I’m going to replace them with Omron G2R-1-E 24DC from CPC. I’ll get them ordered up within the next few days, and hopefully have it back together before the end of next week.

 

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UPS Repair – Part 1

March 23rd, 2012 No comments

I’ve a small project that should keep me occupied for a short while. I recently got my hands on an APC Smart-UPS X 1500VA (SMX1500RMI2U) which was heading to the skip. It had been replaced by an identical unit after it had developed a fault. Needless to say it happened not long after the warranty had expired, and it was not considered worth repairing.

The issue with this UPS is an “AVR Relay Weld” fault. Hopefully this should be an easy fix, assuming I can get a replacement relay, once I identify the exact offending component.

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Future projects

May 26th, 2011 No comments

Write a sound cue application

This has been on my to-do list for aeons. Up until now I’ve used a couple of applications (free and paid) for playing back sound cues during theatre shows, but they’ve all had their problems. The paid app has actually been more problematic, but it does have very useful features.

Now I can live with the problems, but I’d quite like to roll my own app largely as an excuse to learn C# and .net. I was initially hesitant about how well .net could handle playing back multiple audio streams in real-time, but the tests that I’ve done so far indicate that it should be fine.

Install new overhead mics

Microphone over stage area

The Little Theatre has a single overhead mic located above the stage area, that feeds the show relay and induction loop system. It serves its purpose as it is, but it’s far from ideal. It picks up a lot of unwanted background noise (the stage rigging mostly), and doesn’t have wide enough coverage to pick-up voices from anywhere but near the centre of the stage.

The plan is to purchase a couple of cheap mini shotgun mics (Pulse NPCD664) and hang these as low as possible a metre or so in front of the main curtain. These mics may not be a big name brand, but a lot of people use them for this purpose and find them perfectly acceptable. All I need now is to get the okay at the next committee meeting.

Redesign control box

Sound and lighting control box

Another project that needs done at The Little Theatre, is to completely redesign the layout of the control-box, since it is far from the most comfortable place to work in. The main problem is that the desk level and seating aren’t compatible, so I usually end up standing for most of the shows. Another problem is that the control box is also home to two noisy amplifiers, so there has to be a window isolating the box from the auditorium. This is far from ideal when trying to judge sound levels, or simply communicating with people on stage during a rehearsal.

So what I need to do is adjust the level of the existing worktop and floor riser, to allow people to sit comfortably. It sounds simple enough, but there are 13A sockets to move, racking to adjust, findind new locations for the DVD player, VHS player and the intercom PSU. Move the amplifiers to the cupboard underneath the control box, and extend all the cables to fit. So there’s lots of little things to do, but firstly I just need to draw up a new layout, and figure out where I can place everything in this small space.

Installing backstage ‘blues’ lighting

May 16th, 2011 No comments

A project that I recently completed, was to install ‘blues’ around the stage area at The Little Theatre in Nairn. In case you don’t know, ‘blues’ is simply the name given to the low level working lights for the cast and crew working in the wings. Typically these are just low wattage lights with a dark blue filter on them, hence then name.

So The Little Theatre up until now got blues lighting from whatever stage lanterns I had spare, which was a struggle at times since we haven’t a massive stock of lanterns. It also relied on there being a dimmer channel spare, which is sometimes also a struggle. I decided after last year’s panto that we should consider putting in a permanent set of lights, and after pricing it I found that it could be done for about £150.

After getting the okay from the committee, I ordered up the various parts, which was basically some birdies (PAR16‘s), bulbs, conduit, cable, and miscellaneous other bits and pieces to join it altogether. I think it took about 5 afternoons in total to get everything installed. The biggest challenge was drilling about 50 holes in the concrete block wall, as it just seemed to eat drill bits!

The end result of all this work is three independent sets of lights controlled from a triple gang switch in the prompt corner. There are 3 lights in the stage-left wing, 3 upstage on the back wall, and 2 in the stage-right wing, all with 35w bulbs and a dark blue filter. After a quick test it looks like I may need to need to reduce the wattage of some of the bulbs, because there is a bit of light spilling onto the stage, but I have some 20w bulbs spare anyway. In the future I plan to swap the tungsten bulbs for the blue LED equivalent.

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