LDM

00:00 - Intro
00:30 - Servo amplifiers module
01:53 - Figuring out the pinout
02:57 - Test
04:21 - Opening the instrument
07:15 - What's inside the electro-mechanical assembly
Examples of EPR transducers:
• LDM #140: Honeywell Ai...
• LDM #122: Engine Press...
• LDM #123: Engine Press...
Other EPR indicators:
• LDM #292: Boeing 727/7...
• LDM #109: Engine Press...
• LDM #83: Reverse Engin...

[@wolpumba4099]

EPR stands for Engine Pressure Ratio. It is a key parameter in the operation of a jet engine and is often used as a measure of engine thrust. EPR is calculated by dividing the turbine discharge pressure by the compressor inlet pressure. This ratio is displayed to the pilots on a gauge in the cockpit and is used to control the power output of the engine.
*Positive Points:*
1. EPR indicator is not expensive, bought for $25 from eBay USA (0:07 - 0:10).
2. The device has five identical servo amplifiers (0:41).
3. It contains power transistor screwed on a plate for power dissipation (0:56).
4. The device is functional and works perfectly after applying 115 volts (3:21 - 3:22).
5. It contains a synchro control transformer for each servo control (7:59 - 8:01).
6. The device has a spring which permits to have the off position (4:16).
*Negative Points:*
1. The EPR indicator is quite heavy (0:12 - 0:14).
2. The device is soldered which could make modifications or repairs difficult (0:14 - 0:16).
3. The device is very complicated to open (6:20).
4. It is not clear what all the components inside the box are; some are unidentified (1:38 - 1:40).
5. The device has a non-electrical part with no wire connected to it, the purpose of which is unclear (8:10 - 8:13).
*Summary:*
- 0:04 Introduction and presentation of the EPR indicator purchased from Ebay USA for $25.
- 0:14 Noted the weight of the EPR indicator and that it is soldered.
- 0:21 Noted a tape on the indicator.
- 0:24 Identified a module on the rear of the EPR indicator, specifically the servo control amplifiers.
- 0:30 Noted a subd connector.
- 0:41 Identified five identical servo amplifiers with only two transistors each.
- 0:56 Noted a power transistor screwed onto a plate for power dissipation.
- 1:09 Identified a bridge rectifier and a filtering cap.
- 1:17 Noted five indications on the EPR indicator.
- 1:30 Noted that there is an amplifier for each indication.
- 1:33 Identified the contents of the box as the electromechanical assembly, motors, and feedback devices.
- 1:51 Noted that transformers are the power supply for each amplifier.
- 1:57 Identified the primary side and a connection on that side.
- 2:12 Concluded that there's a pair of pins for the power supply of each amplifier.
- 2:19 Suggested applying 115 volts to one of the amplifiers to test functionality.
- 2:26 Found three pins with a resistance of 240 ohms between each pair of pins.
- 2:49 Noted a synchro input and suggested connecting a synchro transmitter to test functionality.
- 3:10 Turned on the power supply and confirmed that the EPR indicator works.
- 4:16 Identified a spring which allows for the off position.
- 5:54 Opened the instrument.
- 7:18 Noted that the inside of the electro-mechanical assembly contained several capacitors.
- 7:41 Identified a capacitor for each reference winding of the AC motors.
- 7:52 Noted that each servo control has an AC motor and a synchro control transformer.
- 8:11 Identified a spring which is used to initialise the marking.
- 8:22 Identified connections for the solenoid.
- 8:34 Noted the presence of EMAC, not AUTO, but EMAC.
- 8:47 Conclusion and thanked viewers for watching.

[@ThermalWorld_]

I see some extreme effort explaining everything from the video.. 😯👏👏

[@jb5631]

Guess this is fully or partially AI generated? Because it doesn't make much sense to me to spend so much time describing it.

[@mattwietlispach7606]

Once again, you reverse-engineered a unit that I have and now I know how to make it work. Thanks!

[@simonkh7278]

Thank you very much
this is great overview!

[@Cyrob-org]

Hello, superbe !!! L'ouverture au chalumeau est impressionnante !!

[@davidparrot4669]

bravo pour ce morceau de bravour qu'a ete l'ouverture de l'appareil :) et un grand merci pour le partage c'est toujours un vrais plaisir de voir de tel appareil , je suis admiratif des petites mains qui montait ça a l'epoque, un travail magnifique....

[@ThermalWorld_]

Thank you Michel.
As always awesome explanation and stuff.

[@ChipGuy]

This constant humming must have been annoying in the old days. But I believe the engines of small airplanes are so loud that you need headphones anyway.