Marconi TF 995A/3/S - UK Vintage Radio Repair and Restoration Discussion Forum

nightowl · 4th Jul 2022, 2:58 pm

What era would the above sigs gen be from, 50s or 60s?
Just civy usage, military useage or both?

thanks
m

WME_bill · 5th Jul 2022, 3:12 pm

Marconi TF995A.
Your picture is of the military version, as it has the extra tough steel case, the power supply mounted underneath the main panel instead of inside and the Plessey mark4 mains connector. I cannot read the CT number. The later TF995B/2 was CT520A.
It was both civilian and military useage. I have seen the later civilian TF995B/2 with military mod record stickers.
The earliest date I can find is 1960 for the TF995. It was not in the 1957 catalogue. It was still being offered 1969.
wme_bill

Oldmadham · 6th Jul 2022, 7:15 am

It looks a lot like the one we had at Wyndham in the Kimberley region of Western Australia in late 1967.

We had several VHF & UHF bearers we looked after, where the Marconi generator we had was pretty useful, with good stability.
We had a couple of HF links, too, where a routine test was to check the receiver sensitivity

Unfortunately, the HF range on the gen was obtained by mixing the gen VHF output with a single tube VHF oscillator.
The latter was very drifty, hence the derived HF would drift in & out of the Rx passband, making the tests very difficult.

As it happens, I only have a vague idea of the generator model number, but
the TF995 looks very similar, so is probably from the 1960s or very late'50s.

Boulevardier · 6th Jul 2022, 1:00 pm

Somewhere, I think I have service and operation manual for this generator. Let me know if you need it.

Mike

nightowl · 6th Jul 2022, 10:56 pm

WME Bill, tis CT402.

majoconz · 7th Jul 2022, 12:20 am

I used to repair these in the 70's - all the NZ CAA workshops had them - they usually were pretty easy to fix - you'll need a good supply of 6AK5 and 6AK6's. I built up quite a stock of attenuator bits after they had a transmitter fired up them! I bought a 995A/2M from our local auction site for not much and it worked on the low bands but the top two HF bands need a 6AK5 transplant. I had to make the 75/50ohm termination but now it's all good. Mine came with the original manual stamped 'Radio Dept, P&T Dept, Dunedin' dated 1st Oct 1968. Just remember - if you want to use it on Saturday, turn it "on" on Thursday!

4th Jul 2022, 2:58 pm	#1
nightowl Triode Join Date: Dec 2019 Location: Lanarkshire, Scotland, UK. Posts: 48	Marconi TF 995A/3/S What era would the above sigs gen be from, 50s or 60s? Just civy usage, military useage or both? thanks m Attached Thumbnails

5th Jul 2022, 3:12 pm	#2
WME_bill Octode Join Date: Oct 2007 Location: Exeter, Devon, UK. Posts: 1,554	Re: Marconi TF 995A/3/S Marconi TF995A. Your picture is of the military version, as it has the extra tough steel case, the power supply mounted underneath the main panel instead of inside and the Plessey mark4 mains connector. I cannot read the CT number. The later TF995B/2 was CT520A. It was both civilian and military useage. I have seen the later civilian TF995B/2 with military mod record stickers. The earliest date I can find is 1960 for the TF995. It was not in the 1957 catalogue. It was still being offered 1969. wme_bill

6th Jul 2022, 7:15 am	#3
Oldmadham Pentode Join Date: Sep 2019 Location: Perth, Western Australia, Australia. Posts: 199	Re: Marconi TF 995A/3/S It looks a lot like the one we had at Wyndham in the Kimberley region of Western Australia in late 1967. We had several VHF & UHF bearers we looked after, where the Marconi generator we had was pretty useful, with good stability. We had a couple of HF links, too, where a routine test was to check the receiver sensitivity Unfortunately, the HF range on the gen was obtained by mixing the gen VHF output with a single tube VHF oscillator. The latter was very drifty, hence the derived HF would drift in & out of the Rx passband, making the tests very difficult. As it happens, I only have a vague idea of the generator model number, but the TF995 looks very similar, so is probably from the 1960s or very late'50s.

6th Jul 2022, 1:00 pm	#4
Boulevardier Octode Join Date: Sep 2017 Location: Bristol, UK. Posts: 1,654	Re: Marconi TF 995A/3/S Somewhere, I think I have service and operation manual for this generator. Let me know if you need it. Mike Last edited by Boulevardier; 6th Jul 2022 at 1:17 pm.

6th Jul 2022, 10:56 pm	#5
nightowl Triode Join Date: Dec 2019 Location: Lanarkshire, Scotland, UK. Posts: 48	Re: Marconi TF 995A/3/S WME Bill, tis CT402.

7th Jul 2022, 12:20 am	#6
majoconz Heptode Join Date: Jan 2008 Location: Ashhurst, Manawatu, New Zealand Posts: 570	Re: Marconi TF 995A/3/S I used to repair these in the 70's - all the NZ CAA workshops had them - they usually were pretty easy to fix - you'll need a good supply of 6AK5 and 6AK6's. I built up quite a stock of attenuator bits after they had a transmitter fired up them! I bought a 995A/2M from our local auction site for not much and it worked on the low bands but the top two HF bands need a 6AK5 transplant. I had to make the 75/50ohm termination but now it's all good. Mine came with the original manual stamped 'Radio Dept, P&T Dept, Dunedin' dated 1st Oct 1968. Just remember - if you want to use it on Saturday, turn it "on" on Thursday! __________________ Cheers - Martin ZL2MC