UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Offered and Wanted Messages > Sets, Parts and Service Information Wanted (private buyers only, no swaps)

Notices

Sets, Parts and Service Information Wanted (private buyers only, no swaps) If you need help obtaining components, sets or equipment, post a message here. Private buyers only - no traders. No swaps.

Reply
 
Thread Tools
Old 11th Jan 2019, 12:55 pm   #1
Mark James
Pentode
 
Join Date: Apr 2012
Location: Chorley, Lancashire, UK.
Posts: 224
Default Marconi Terminating unit TM 5551

Does anyone have a spare Marconi Terminating unit type TM 5551? This is for my Marconi TF 995A/5 Signal Generator. The manual lists it as 75Ω in and 52Ω & 75Ω out. I have looked at the stalls at all of the meetings over the summer but have been unable to locate one. Any help would be much appreciated. I am of course happy to pay for the item and postage.

Mark
Mark James is offline   Reply With Quote
Old 13th Jan 2019, 3:44 pm   #2
Julesomega
Hexode
 
Julesomega's Avatar
 
Join Date: Dec 2012
Location: Stockport, Greater Manchester, UK.
Posts: 251
Default Re: Marconi Terminating unit TM 5551

If you want precision measurements a 'minimum loss pad' should be used, otherwise it won't really matter.
The TF 995A/5 goes up to 220MHz, and you could make an accurate matching pad with small resistors, or better with surface mount types. The 50ohm side should see 87ohms in shunt with 43ohms going to the 75ohm side.
For 87ohms use 100 in ||el with 680ohms.

What does matter is that you don't force a 50ohm BNC plug into a 75ohm skt as that will enlarge the 75ohm 'hole'.
__________________
- Julian

It's good here
Julesomega is offline   Reply With Quote
Old 13th Jan 2019, 4:34 pm   #3
Julesomega
Hexode
 
Julesomega's Avatar
 
Join Date: Dec 2012
Location: Stockport, Greater Manchester, UK.
Posts: 251
Default Re: Marconi Terminating unit TM 5551

Sorry, just noticed you said 52ohms. That would need 41.5ohms between ports and 93.9ohms across the 52ohm port.
You can get close enough to 41.0 with two 82's, and 93.7 with 100//1500
__________________
- Julian

It's good here
Julesomega is offline   Reply With Quote
Old 13th Jan 2019, 6:55 pm   #4
Mark James
Pentode
 
Join Date: Apr 2012
Location: Chorley, Lancashire, UK.
Posts: 224
Default Re: Marconi Terminating unit TM 5551

Thank you for the help. Any chance of a diagram with exactly how I should wire it!? (Electrical work was not my day job).

Thanks,

Mark
Mark James is offline   Reply With Quote
Old 15th Jan 2019, 10:15 am   #5
davidw
Heptode
 
davidw's Avatar
 
Join Date: Sep 2006
Location: Woodbridge, Suffolk, UK.
Posts: 508
Default Re: Marconi Terminating unit TM 5551

Mark,from manual section 2 page 20 a copy of the circuit (you need just the bit inside the box), hope it helps
Attached Thumbnails
Click image for larger version

Name:	osc1.jpg
Views:	32
Size:	29.2 KB
ID:	176461  
__________________
Dave G1AGK.
My perception is my reality!
davidw is offline   Reply With Quote
Old 15th Jan 2019, 10:27 am   #6
Mark James
Pentode
 
Join Date: Apr 2012
Location: Chorley, Lancashire, UK.
Posts: 224
Default Re: Marconi Terminating unit TM 5551

Yes it does - thank you for looking out the details.

Mark
Mark James is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 8:44 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2018, Paul Stenning.