Marconi TF995A/5 Signal Generator

I have an uncle who for for many years up until his retirement worked as an engineer for the UK Civil Aviation Authority. At some point during his career he was able to purchase an old Marconi signal generator that has become surplus to requirements.

Years passed and the signal generator quietly gathered dust up in the attic until a recent clearout saw it delivered to the workbench of G7IVF to see if possibly, just possibly,  it might find a home here. Silly question really…

However, because the unit hasn’t been powered up for a considerable amount of time, it is safest to assume that some investigation and repair work will be necessary. More to come on this…

Meanwhile here are some pictures of the generator as well as an interesting piece of history in the form of a label that was attached to the unit showing it was withdrawn from service and placed in to storage in 1976 before being sold on.

Marconi signal generator image 1
The Marconi TF995A/5 sits hopefully on the bench of G7IVF
Marconi signal generator image 2
Bright sunlight after so many years in the attic. The Marconi is suddenly full of hope…
Marconi signal generator image 3
Yes! It’s going to become part of the radio station G7IVF. A happy signal generator!
Marconi label front
Part of the ongoing history of this unit – the original label from the CAA.
Marconi label rear
The last time this unit was used properly – 1976. Forty years on, the story is about to continue…

8 thoughts on “Marconi TF995A/5 Signal Generator”

  1. Hello,
    My name is Rieks Buter, from the Netherlands, age 74 and retired electronic technician, reparing all kinds of electronics instruments, Radio sets and electronic controlled (CNC)machines and keep doing it as long as I like and am able to.
    I have a Marconi TF995A/5 for may be 20 jears or longer.
    Did not use it, bud switchet it on now and than.
    It looks like the frequentie it produses is still within reasable tolerancys.
    After I found this artikle in darkandscary I put it on the bence and looket inside. It is in a better state than yours, bud there is also a lot of dust inside.
    I’m going to investigate how the Elco’s surfived this far, and try to get it in usable order again.
    Thank You for waking me up.

    1. Hi Rieks.
      Many thanks for the comment. Its great to hear of another old Marconi unit still being worked on. Good luck in bringing it back to life!
      Chris G7IVF

    1. Hi Lorenzo

      Many thanks for contacting me at darkandscary. It’s great to hear of another person who has a Marconi signal generator. I’m sorry to hear that your one is not working properly.

      I have spoken to my friend who helped me to repair my Marconi and we both think that it would be a good idea to check all of the capacitors on your device. If they are the original capacitors (or replacement capacitors from the past that are very old) then this can certainly cause issues. Old electrolytic capacitors dry out and can go either short circuit or open circuit and this might be the cause of the problems. As you will see from the various posts I made, we replaced several large electrolytic capacitors with modern ‘motor run’ capacitors. There are some other smaller capacitors hidden away here and there which were replaced as well. If I remember correctly, there were also some issues with resistors that had failed and needed replacing. It’s worth testing them to see that they have not changed value too much.

      Good luck in restoring your Marconi! I hope you are successful in making it work.

  2. Hello! I have also a TF995A/5, I was afraid to plug it in incase I didnt do something right but I’m just trying to figure out an actual place to get it looked it. Any suggestions? I’m not to sure what I’m looking at to get it appraised

    1. Hi Jessie
      Many thanks for contacting me at darkandscary. Yet another Marconi signal generator hopefully coming back to life…
      My mentor for these sort of things is a fellow member of my local amateur radio club and has taught me a tremendous amount. There are many others too who have knowledge of building/repairing/maintaining old valve-based equipment. I would recommend this as a good starting point – try to find a club local to yourself and see if they might be willing to offer some advice. You never know… you might pick up a new hobby on the way!

      I wish you the best of luck in getting your TF995A/5 going once more. Please do let me know if you have any success.

    1. Hi Frank. Apologies for the delay in getting back to you. I’ve been keeping an eye on Ebay for these generators to be offered for sale. Good specimens are very rare. There have been a few offered for sale recently where I would not be tempted – either the seller wants way too much money or something feels ‘off’ in the description.
      Good luck in securing a unit – I hops someone might be able to help.

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