|
Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
|
Thread Tools |
11th Sep 2021, 9:06 am | #1 |
Triode
Join Date: Nov 2019
Location: Melbourne, Victoria, Australia
Posts: 16
|
Marconi R1155A refurb
Hi all,
I have eventually got back to this radio and starting to refurb. One question for now ..... RF Frequency range coils L4, L5 and L6 are capacitatively tuned by C57, C58 and C59 which are located separately from the Coils. So what are the large black slotted discs(??) on top of the Coils? They look like the tops of tuning slugs, but these Coils aren't tuned this way ... hence my query. Thanks, Ian |
11th Sep 2021, 9:49 am | #2 |
Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,764
|
Re: Marconi R1155A refurb
It's a while since I had on of these , but I suspect they are ceramic trimmers, could be wrong , Mick.
|
11th Sep 2021, 12:40 pm | #3 |
Octode
Join Date: Oct 2008
Location: Littlehampton, West Sussex, UK.
Posts: 1,465
|
Re: Marconi R1155A refurb
They're cores, big ones to adjust at the low frequency end of the lower frequency bands.
You can see in the photo that they are pretty big iron dust or ferrite, I don't know which but the Bakelite screw thread is often jammed and hard to turn. They're easy to dismantle though and free off. I don't think they need to be moved much. Hope this helps Jim Last edited by G4XWDJim; 11th Sep 2021 at 12:56 pm. |
12th Sep 2021, 12:48 am | #4 |
Triode
Join Date: Nov 2019
Location: Melbourne, Victoria, Australia
Posts: 16
|
Re: Marconi R1155A refurb
Thanks Jim and Mick,
Okay, that makes sense ... I will add a Note to my circuit diagram. Tuning cores/slugs have caused me much grief in the past ... shattered cores, cores stuck to wax paper formers by possum pee etc etc ... I always like to do a full re-alignment with any refurb, so I will get these moving again before I go too much further. Cheers, Ian |
17th Sep 2021, 1:24 am | #5 |
Triode
Join Date: Nov 2019
Location: Melbourne, Victoria, Australia
Posts: 16
|
Re: Marconi R1155A refurb
Mmmm ... I have the L6 Coil apart as per photos posted by Jim. I am not keen to apply any force to the actual Core itself as I am not sure how it is connected to the threaded part. The threaded section has been covered in Varnish(??) from the top, and has no doubt seeped down into the thread.
I am assuming that the black top plate and threaded section of the Core are Bakelite ... ?? Is the best approach to try to soften the Varnish?? With what?? At the moment, I have applied reasonable force ... not at max effort just yet, but I don't wish to stuff this up. Thanks, Ian |
17th Sep 2021, 9:05 am | #6 |
Octode
Join Date: Oct 2008
Location: Littlehampton, West Sussex, UK.
Posts: 1,465
|
Re: Marconi R1155A refurb
The varnish is shellac I think which should soften if soaked in meths. I've found that they've usually cracked free once they're dismantled. Good luck.
Jim |
18th Sep 2021, 8:58 am | #7 |
Triode
Join Date: Nov 2019
Location: Melbourne, Victoria, Australia
Posts: 16
|
Re: Marconi R1155A refurb
Hi Jim and others,
I had the L6 thread soaking in Mineral Turps all yesterday and last night .... and this morning the Core moved with a bit more force ... all good now. I have L5 thread soaking in Meths now. However, the Ferrite (??) slug had separated from the Core thread. In case this is helpful to some-one else, I have tried to attach a photo ... Thinking ahead, I checked the Alignment procedure in the Manual A.P. 2458A Vol I Chap 2, para 121 - 125. This is not a complete Alignment procedure ... missing IF strip and Low frequency adjustments etc.. I can do this without it, but I would prefer to use the full official procedure. Can anyone direct me to such a write-up please ...? Cheers, Ian |
19th Sep 2021, 9:43 am | #8 |
Octode
Join Date: Oct 2008
Location: Littlehampton, West Sussex, UK.
Posts: 1,465
|
Re: Marconi R1155A refurb
There’s more info in the AP 1186 but whether it will be what you need I can’t remember not having looked at it for a long time. You might get another reply from someone on here who has that particular Air Publication.
Jim |
19th Sep 2021, 12:57 pm | #9 |
Hexode
Join Date: Feb 2007
Location: Chesterfield, Derbyshire, UK.
Posts: 483
|
Re: Marconi R1155A refurb
When I restored my 1155 a I tried everything to free up some of the slugs in the inductors, I used the correct tools for the job too but trying to remove them caused more harm than good so I left the rest of them alone. Luckily the alignment did not seem too bad when I had finished it.
|
26th Sep 2021, 12:46 am | #10 |
Triode
Join Date: Nov 2019
Location: Melbourne, Victoria, Australia
Posts: 16
|
Re: Marconi R1155A refurb
Hi all,
An update ... All 3 tuning cores L4, L5 and L6 were jammed by Shellac (Varnish) which had seeped down to the 6th or 7th Thread. One Bakelite threaded section cracked when applying pressure .... two Ferrite/Iron slugs had separated from their Bakelite threaded parts. I used Meths and Mineral Turps to soften the Shellac (took a few days) and a home-made Dental pick to clean out all the muck in threads. The three Cores are now re-assembled and rotating freely. Slow and fiiddly work ... and care needs to be taken when re- gluing the two parts. Most of the DF circuitry had been removed before I acquired this radio ... lots of snipped, hanging loose wires, cracked wires, wires rubbing on other components etc etc.. Much of this is sorted out, but I'm sure there will be more surprises. I have got the Main Tuning knob/dial working correctly. All tuning adjustors (L's, C's, Filter, BFO) are free, except for the IF which I haven't tackled as yet. Still a heap to do ... Cheers, Ian Last edited by tinkera123; 26th Sep 2021 at 12:51 am. |