Racal MESL - UK Vintage Radio Repair and Restoration Discussion Forum

PETERg0rsq · 14th Oct 2019, 9:42 pm

I am fault finding on a Racal 9087, and have cleared every fault except this last one on the output board.

Basicaly no output

I have traced the IF to this component which is a bolt in module called an MESL.

Does anyone have an idea what its function is?

Basically RF enters from the left, from about 100MHz to 1GHz from the synthesizer, but nothing is leaving

My guess is it is a pin diode attenuator (ignor the X2 marking as that is a component reference. There is an X1 but that is a mixer!) possibly for AM modulation.

Anyone have another opinnion as to what is does?

I presume the tiny component is a diode (do not want to probe it in case it is a tunnel diode).

I do have voltage on the inductor, but it does not look too healthy.

buggies · 14th Oct 2019, 10:45 pm

Dunno what the device is- but MESL was a company (Microwave and Electronic Systems Limited ) that was at Newbridge, Edinburgh and merged or was taken over by Racal.

Radio Wrangler · 15th Oct 2019, 12:03 am

They did RF microelectronocs and SAWs for the rest of the Racal group and split into a security products (doppler microwave and PIR sensors) group.

David

Alistair D · 15th Oct 2019, 10:07 am

George and David, you are both correct. I worked in the security systems division for most of my career. Many years ago the security business was sold off and became a separate company so I had no contact with the microwave side of things where your module would have been made.

What I can tell you is that MESL is currently owned by Honeywell so there is a slim chance that they could help. The MESL name seems to have been dropped but they are still at the same premises in Queen Anne Drive, Newbridge.

Here are a couple of Racal fora that may be of assistance.

https://groups.yahoo.com/neo/groups/Racal6790GM/info
https://groups.yahoo.com/neo/groups/Racal_Dana/info

Al

Radio Wrangler · 15th Oct 2019, 11:04 am

Had a tour round once from Neil GM8IID

David

PETERg0rsq · 15th Oct 2019, 3:00 pm

Many thanks for all the information.

I had thought that MESL was the component name

Just tracing out the circuit that controles the device, to try and work out what it is supposed to do.

Pinning my hopes on it being an attenuator, or AM Modulator, as the control connection is stuck at 6Vdc no matter what I change.

Tracing back further to the DtoA chip, I might not be getting any Chip enable signal to the control line latches.

The Racal Dana Group is my Yahoo group

14th Oct 2019, 9:42 pm	#1
PETERg0rsq Heptode Join Date: Jun 2009 Location: St Helens, Lancashire, UK. Posts: 641	Racal MESL I am fault finding on a Racal 9087, and have cleared every fault except this last one on the output board. Basicaly no output I have traced the IF to this component which is a bolt in module called an MESL. Does anyone have an idea what its function is? Basically RF enters from the left, from about 100MHz to 1GHz from the synthesizer, but nothing is leaving My guess is it is a pin diode attenuator (ignor the X2 marking as that is a component reference. There is an X1 but that is a mixer!) possibly for AM modulation. Anyone have another opinnion as to what is does? I presume the tiny component is a diode (do not want to probe it in case it is a tunnel diode). I do have voltage on the inductor, but it does not look too healthy. Attached Thumbnails __________________ SPECIALIST.....Knows everything about nothing EXPERT..........Knows nothing about everything

14th Oct 2019, 10:45 pm	#2
buggies Heptode Join Date: Jan 2009 Location: West Lothian, UK. Posts: 761	Re: Racal MESL Dunno what the device is- but MESL was a company (Microwave and Electronic Systems Limited ) that was at Newbridge, Edinburgh and merged or was taken over by Racal. __________________ George

15th Oct 2019, 12:03 am	#3
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,864	Re: Racal MESL They did RF microelectronocs and SAWs for the rest of the Racal group and split into a security products (doppler microwave and PIR sensors) group. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

15th Oct 2019, 10:07 am	#4
Alistair D Nonode Join Date: Jan 2010 Location: Edinburgh, UK. Posts: 2,008	Re: Racal MESL George and David, you are both correct. I worked in the security systems division for most of my career. Many years ago the security business was sold off and became a separate company so I had no contact with the microwave side of things where your module would have been made. What I can tell you is that MESL is currently owned by Honeywell so there is a slim chance that they could help. The MESL name seems to have been dropped but they are still at the same premises in Queen Anne Drive, Newbridge. Here are a couple of Racal fora that may be of assistance. https://groups.yahoo.com/neo/groups/Racal6790GM/info https://groups.yahoo.com/neo/groups/Racal_Dana/info Al __________________ I won't tell you how I discovered that.

15th Oct 2019, 11:04 am	#5
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,864	Re: Racal MESL Had a tour round once from Neil GM8IID David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

15th Oct 2019, 3:00 pm	#6
PETERg0rsq Heptode Join Date: Jun 2009 Location: St Helens, Lancashire, UK. Posts: 641	Re: Racal MESL Many thanks for all the information. I had thought that MESL was the component name Just tracing out the circuit that controles the device, to try and work out what it is supposed to do. Pinning my hopes on it being an attenuator, or AM Modulator, as the control connection is stuck at 6Vdc no matter what I change. Tracing back further to the DtoA chip, I might not be getting any Chip enable signal to the control line latches. The Racal Dana Group is my Yahoo group __________________ SPECIALIST.....Knows everything about nothing EXPERT..........Knows nothing about everything