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Old 20th Nov 2019, 12:21 pm   #1
tonymadge
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Default Marconi 297 information?

Hi and thanks for letting me join this forum.

I have been tasked with fixing a vintage radio a Marconi 297 circa early 1930's?
Apparently the tuning cord has broken and I was "volunteered" to fix it... I am 60 plus years and I once as a spotty 16 year old worked on the odd valve radio as an apprentice TV engineer. Sadly I finished working on TV's in 1987 but folk still think I can fix everything

I was wondering if anyone has done this fix before or are there any diagrams available on how the tuning cord is routed? Any help gratefully received as this is one heavy radio so I am hoping I can fix it then send it back to the owner!

I have included a pics of the radio.
Thanks again
Tony
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Old 20th Nov 2019, 12:54 pm   #2
HamishBoxer
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Default Re: Marconi 297 information?

Paul has service info for a 297. Top right of website. And welcome to our happy group.
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Old 20th Nov 2019, 1:20 pm   #3
Station X
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Default Re: Marconi 297 information?

I have checked both the service sheets on offer and neither of them contains a tuning cord threading diagram.

It shouldn't be too difficult to work out how the cord is routed. It's important that the cord goes round the tuning control shaft a couple of times so as to give a good grip.

With any luck you'll find just a single break in the existing cord and the tensioning springs etc. will be intact.
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Old 20th Nov 2019, 5:29 pm   #4
tonymadge
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Default Re: Marconi 297 information?

Thank you for the quick replies. Shame no restringing info. I will take a look anyway and see how I get on. I best get some new cord first then tackle it.
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Old 20th Nov 2019, 6:52 pm   #5
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Default Re: Marconi 297 information?

Is the broken tuning cord the only fault with this radio?

They used a "capacitor box" and I'd be surprised if the caps were any good after all this time, unless of course they've already been replaced.
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Old 21st Nov 2019, 3:13 am   #6
mickash
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Default Re: Marconi 297 information?

Hi Tony,

I've got a similar set and had to restring the cord. I'll look out the manual to see if it also covers your set.

Michael.
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Old 21st Nov 2019, 11:00 am   #7
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Default Re: Marconi 297 information?

Restringing instructions for the Marconi 297 are shown in Trader Service Sheet No 864 - EMI Cord Drives. I'm not sure if this sheet is available from www.service-data.com but it was included in the BVWS CD-ROM 2 (Winter 2000).
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Old 21st Nov 2019, 11:12 am   #8
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Default Re: Marconi 297 information?

As stated by Graham it is not (dial cording) on above data.

Wonder why some makes miss it out?Possibly not meant to fail!?
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Old 21st Nov 2019, 11:19 am   #9
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Default Re: Marconi 297 information?

I don't have Trader Service Sheet No 864 - EMI Cord Drives to check.
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Old 21st Nov 2019, 12:11 pm   #10
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Default Re: Marconi 297 information?

It isn't in the individual model data, but as Steve says, it is in 864.

Edit: Shameless plug, BVWS members get the first 1600 trader sheets as one of the member benefits.
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Old 22nd Nov 2019, 3:25 am   #11
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Default Re: Marconi 297 information?

I also used Trader sheet 864 for my HMV 470
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Old 22nd Nov 2019, 7:45 am   #12
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Default Re: Marconi 297 information?

Thank you for the help and the screen shot of the instructions. I have not tested the radio so I am not sure if any other fault is on it, thought tackle the cord then tune it in and see what happens! I have my fingers crossed
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Old 6th Dec 2019, 12:22 pm   #13
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Default Re: Marconi 297 information?

An update, after suffering a flooded kitchen bathroom the radio had to take its place in the jobs to do list! Anyway yesterday I got to stripping the chassis out and I could see that the tuning cord had broken where it goes to the rotary dial to the main "wheel". Looking at it it would seem that the spring which I found should fit onto a metal clip on the wheel, as you can see from the picture, the unbroken cord has its spring connected to a metal clip but no clip on where I would need to put the replacement cord? Also how would it fit to the spindle of the tuning knob?

I am thinking this job may be beyond me

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Old 6th Dec 2019, 5:03 pm   #14
tonymadge
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Default Re: Marconi 297 information?

Oops links seem to be not working: Here are the images
Many thanks Tony
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Old 6th Dec 2019, 5:26 pm   #15
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Default Re: Marconi 297 information?

I agree with Station X, you could be opening a can of works here if you become the maintenance technician for this set! The Marconi/HMV capacitor blocks are a nightmare to work on and the contents will all be faulty. If it's working OK it will either have been done properly and new capacitors put in the block, or more typically the replacement capacitors will be dangling from the bottom of the chassis.

The links to the pictures are not working for me, it might be best to upload them here.
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Old 6th Dec 2019, 8:55 pm   #16
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Default Re: Marconi 297 information?

Hi Tony, it looks to me that there are 2 drive cords, the first one is the gang drive (tuning capacitor) and the second one is the cursor drive.
Which one is broken? Now that you have the chassis out of the case can you turn the tuning knob and see if the tuning capacitor moves or the tuning cursor (the finger scanning the station locations) moves.
regards Brian.
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Old 7th Dec 2019, 6:23 am   #17
tonymadge
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Default Re: Marconi 297 information?

Hi Brian, yes there are two cords. The one that is broken is the one from the tuning knob, the other that drives the cursor (needle on dial display?) works fine.
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Old 8th Dec 2019, 1:24 pm   #18
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Default Re: Marconi 297 information?

Before proceeding I'd try to find out whether the radio has actually worked in the recent past. If it's faulty then the repair may be far more involved than replacing a drive cord.

You could try powering it up via a lamp limiter, but do some basic tests first.

https://www.vintage-radio.com/projec...p-limiter.html

Regarding the missing clip, it may be laying inside the set somewhere. Possibly still attached to the remains of the cord and springs.
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Old 13th Dec 2019, 4:58 pm   #19
tonymadge
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Default Re: Marconi 297 information?

Thank you for the replies, I have not yet tried to switch it on but I have looked everywhere inside the cabinet and I cannot find the missing metal clip. Is there anyone who would be happy to look at this radio, I am willing to pay them for their troubles?
Thank you
Tony
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Old 13th Dec 2019, 6:28 pm   #20
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Default Re: Marconi 297 information?

Try a post here: https://www.vintage-radio.net/forum/...play.php?f=145
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