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Old 11th Nov 2021, 8:28 pm   #1
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Default Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

I have just restored a 1936 Cossor model 378 T.R.F. "Super-Ferrodyne" receiver. This type of receiver was made in A.C. mains, universal mains, and battery versions.

This set is an A.C. Mains only set with full isolation double-wound mains transformer. The Valve line-up should be :- 'MVS/PEN', 'MS/PEN', 'PT41', '442BU'. Basically it is three Pentode valves + Rectifier. The 'MVS/PEN' is a variable-mu Pentode, tuned R.F. Amplifier, with gain controlled by altering the cathode bias (i.e. the negative grid voltage). The 'MS/PEN' is a leaky grid detector, 'straight' Pentode. 'Reaction' is provided in this stage which makes it very sensitive & selective. There is no reaction 'back-lash', (back-lash can be a nuisance in some T.R.F. sets). The output valve is a directly heated Pentode which provide plenty of volume.

This set has been in my possession for nearly two years, waiting for restoration. It was in a filthy condition, covered in a black 'soot' like substance. this needed cleaning off before considering restoration.
The Mains Transformer was tested and found to be good (much to my relief).
However, the Output Transformer had an open circuit primary and the loudspeaker was out of centre and the air-gap full of 'crud'. The speech coil, hum bucking coil, and energising coil were all OK, but the cone paper had a small tear in it, but this was easily repaired.

The speaker was completely dismantled and and cleaned, and the Output Transformer replaced with a 'multi-tapped, pri. & sec.' type which made matching the recommended 8,000 Ohm Anode load to the 3 Ohm speaker load easy. Rebuilding & re-centring is quite easy with the energised type speaker, and it now moves freely. Unfortunately the 'dust-bag' fitted over the speaker, had totally disintegrated into a 'rag' full of holes ! I have not as yet replaced this.

The chassis top was stripped down and repainted as seen in the pictures, the underside was cleaned, Electrolytics & Paper Capacitors were replaced. All the paper caps., were electrically leaky, and the Electrolytics 'dried up'. None of the Mica capacitors needed changing, and only one Resistor needed changing, R6, a 200 Ohm resistor had gone O/C, I replaced this with a 220 Ohm resistor (the value is not critical in that position). The rest of the Resistors were well within tolerance - which surprised me and pleased me simultaneously

The set was gradually run up on my variac, checking for smoke, flashovers etc. whilst monitoring the H.T.
Then I heard a voice in the loudspeaker ! Everything was working....

This receiver is very sensitive and the reaction control is very smooth with no back-lash. The selectivity is good too. Not quite as good as the "Philips Superinductance" range of T.R.F. sets, but never-the less it gives very credible results.

The cabinet has not been tackled yet (apart from re-gluing it back together). I will seek advice on the cabinet restoration. It is not in bad condition, but will need re-finishing.

I'm going to try and upload some pictures of the renovated chassis....
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Old 11th Nov 2021, 9:06 pm   #2
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

A few more pictures showing the chassis with valves fitted. The two metallised valves are Mazda equivalents, but I hope to get the proper "Cossor" valves in due course.

The renovated speaker and new O/P Transformer fitted.

Plus the repaired cone.
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Old 11th Nov 2021, 9:17 pm   #3
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

I forgot to mention the discretely fitted H.T. Fuse and Holder fitted on the back of the Mains Transformer (for added protection) There is a piece of paxolin fitted at the bottom of the Mains Transformer (by the manufacturer) which has various holes in. I utilised one of the spare holes to fit the Fuse Holder.

The Fuse is wired between the centre tap connection to the H.T. winding, and the Chassis; in the traditional way.
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Old 13th Nov 2021, 12:32 am   #4
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

A few more pictures of the unrestored chassis with a filthy dial back plate. This has been cleaned, rubbed down and repainted. Pictures in due course.

All perished rubber covered wiring and Grommets has been replaced with modern silicon types and a new 'period type' Mains lead fitted.

Should be good for another 80+ years service.... Trouble is, will there be any broadcasters on Medium & Longwave ?
I can see the day, when the medium wave band will only have "Pantry" senders of a few milliwatts on it !
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Old 17th Nov 2021, 5:06 pm   #5
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

My restored Cossor 378 "Super-Ferrodyne" Radio Chassis, complete with the correct Cossor 'MVS/PEN' & 'MS/PEN', N.O.S. Valves - kindly supplied by a member on here.

Here are a few more pictures of the finished Chassis :-
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Old 17th Nov 2021, 5:34 pm   #6
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

I have kept the chassis to the original design except for four minor modifications....

An H.T. Fuse to protect the Mains Transformer and Rectifier Valve in case of an H.T. short or excessive current.
A 150k Ohm Resistor across the Aerial & Earth connections, for Aerial static discharge if an outside long-wire Aerial is used (makes no difference to signal pickup strength).
A 0.01uF H.V. Disc Ceramic capacitor in series with the Detector Tuning Condenser, as it actually tunes the Anode coil of the 'MVS/PEN' Valve, and would therefore have H.T. on the Tuning Condenser. If the fixed and rotary veins should touch, it could cause the coil to burn out. I found that a 0.01uF condenser in series, made no difference to the tuner 'tracking'.
Finally, the Mains Lead was replaced with a modern three core (period style) type, replacing the old perished two core original. The Chassis is now Earthed for safety reasons.
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Old 17th Nov 2021, 6:53 pm   #7
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

Excellent job, well done.
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Old 17th Nov 2021, 10:24 pm   #8
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

Quote:
Originally Posted by stevehertz View Post
Excellent job, well done.
Thanks !

A simple set to restore electrically, but it really was in a filthy, derelict state.

I now have to tackle the Cabinet, which has a few scratches and wear marks around the controls and needs refinishing. The metal trim & speaker cloth also needs attention. The Tuning scale cleaned up nicely !
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Old 18th Nov 2021, 1:35 pm   #9
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

A comprehensive write up Mr V! I've just had a look at it on the Radio Museum site. The metal trim has that distinctive 30's look but the overall shape sort of leans towards the next decade [in my view anyway]. Pre-war sets have that engaging look internally because of the sometimes slightly "Heath Robinson" technology at the time. Well worth all the effort you in put in to this rescue mission. It will be interesting to see how it looks when the cabinet is sorted

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Old 19th Nov 2021, 2:03 am   #10
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

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Originally Posted by dave walsh View Post
A comprehensive write up Mr V! I've just had a look at it on the Radio Museum site. The metal trim has that distinctive 30's look but the overall shape sort of leans towards the next decade [in my view anyway]. Pre-war sets have that engaging look internally because of the sometimes slightly "Heath Robinson" technology at the time. Well worth all the effort you in put in to this rescue mission. It will be interesting to see how it looks when the cabinet is sorted

Dave W
Yes, there were various "Cossor" models (both T.R.F. & Superhet), that had that type of metal trim, in the mid to late 1930's but with completely different shaped wooden cabinets & metal trim to suit.

I personally, think the metal trim would look very nice in chrome, but as it was not like that originally, it would be wrong of me to get it chromed. I want the set to look cosmetically, original.

I'm not absolutely sure, what colour the trim was when new. The only pictures I've seen of this model when new, have been in 'Black & White' (monochrome) - which is not very helpful. The service sheet states that the cabinet is walnut finished, but doesn't mention the trim colour finish.

When I have restored the cabinet, and fitted the chassis & speaker, I will upload the completely finished set.
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Old 19th Nov 2021, 7:40 am   #11
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

Here's a photo of a couple of Cossors I have from that era, the one on the right which is my favourite looking radio of all time, a 375, shows the original colour of the metal trim.
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Old 19th Nov 2021, 1:10 pm   #12
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

Quote:
Originally Posted by stevehertz View Post
Here's a photo of a couple of Cossors I have from that era, the one on the right which is my favourite looking radio of all time, a 375, shows the original colour of the metal trim.
"stevehertz", many thanks for uploading those colour photographs of your Cossor Radio's....

I presume the trim was basically a standard, mat Aluminium colour finish originally, which is what mine seems to be now (albeit slightly pitted).

Maybe if I gently rub the trim down with very fine emery paper, then finish it off with metal polish, it will have that smooth original finish and colour ?
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Old 19th Nov 2021, 2:21 pm   #13
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

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Quote:
Originally Posted by stevehertz View Post
Here's a photo of a couple of Cossors I have from that era, the one on the right which is my favourite looking radio of all time, a 375, shows the original colour of the metal trim.
"stevehertz", many thanks for uploading those colour photographs of your Cossor Radio's....

I presume the trim was basically a standard, mat Aluminium colour finish originally, which is what mine seems to be now (albeit slightly pitted).

Maybe if I gently rub the trim down with very fine emery paper, then finish it off with metal polish, it will have that smooth original finish and colour ?
Read the bold typeface above and look at the colour of the metal moulding in the photo I uploaded - that's the original colour, like I say. No real point in me trying to 'describe' it, it is the colour that you see. So no, rubbing it down and polishing it will not give it "that smooth original finish and colour" ! If the moulding is pitted, then your only option is to prep and spray it the colour of mine using the nearest colour car spray. See zoomed in photo that may help you ID the colour better.
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Old 19th Nov 2021, 3:27 pm   #14
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

Quote:
Originally Posted by stevehertz View Post
Quote:
Originally Posted by mister valve View Post
Quote:
Originally Posted by stevehertz View Post
Here's a photo of a couple of Cossors I have from that era, the one on the right which is my favourite looking radio of all time, a 375, shows the original colour of the metal trim.
"stevehertz", many thanks for uploading those colour photographs of your Cossor Radio's....

I presume the trim was basically a standard, mat Aluminium colour finish originally, which is what mine seems to be now (albeit slightly pitted).

Maybe if I gently rub the trim down with very fine emery paper, then finish it off with metal polish, it will have that smooth original finish and colour ?
Read the bold typeface above and look at the colour of the metal moulding in the photo I uploaded - that's the original colour, like I say. No real point in me trying to 'describe' it, it is the colour that you see. So no, rubbing it down and polishing it will not give it "that smooth original finish and colour" ! If the moulding is pitted, then your only option is to prep and spray it the colour of mine using the nearest colour car spray. See zoomed in photo that may help you ID the colour better.
I have downloaded and zoomed in to the Trim and it appears to me to be a silver/grey colour. The problem is that electronics and display equipment can tint or even alter colours from the original, to that displayed on the screen.

Thanks anyway for your help.
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Old 19th Nov 2021, 10:19 pm   #15
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

I thought it was silver grey even from the Radio Museum illustration but that example is a bit grim with definitely very pitted metal work. Steve's helpful illustrations look similar [in colour] but much better overall [if you "see" what I mean?]. Clearly they never aimed for chrome so any reasonable trim should work. Either way I'd like to see a renovated cabinet along with the case Mr V.
Good luck with it.

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Old 20th Nov 2021, 8:11 am   #16
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

If I get time I'll take my 375 outside and take a close up photo of the metal trim.
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Old 20th Nov 2021, 12:27 pm   #17
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

I cleaned up the trim (which I have detached from the cabinet), it is a uniform colour all over, including the normally unexposed bits. Mine looks the colour, I can only discribe as a grey/gold !

What I think I will have to do is take the trim with me, to a motor factors shop where they sell car 'touch-up' spray paint, and get a matching paint as near as possible.

The speaker cloth has gold 'flics' in the pattern, so it is possible that the trim was sprayed to blend in with the cloth.

Speaking of "Speaker Cloth", does anyone know whether there is any, either N.O.S. or reproduction cloth of this style being made ? My cloth is O.K. but not perfect (there is some slight damage to it) I will upload a picture of the cloth (& the metal trim).
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Old 20th Nov 2021, 1:44 pm   #18
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

Ben Dijkman does a very similar cloth.

https://www.bendijkman.nl/index.php?...oduct&ipath=14

Cheers

Mike T
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Old 20th Nov 2021, 3:02 pm   #19
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

Thanks, Mike T (Cobaltblue), I'll check that out.

Regards, Kevin.
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Old 20th Nov 2021, 4:10 pm   #20
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Default Re: Cossor, 378 "Super-Ferrodyne" Receiver, Restoration

Quote:
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I cleaned up the trim (which I have detached from the cabinet), it is a uniform colour all over, including the normally unexposed bits. Mine looks the colour, I can only discribe as a grey/gold !

What I think I will have to do is take the trim with me, to a motor factors shop where they sell car 'touch-up' spray paint, and get a matching paint as near as possible.

The speaker cloth has gold 'flics' in the pattern, so it is possible that the trim was sprayed to blend in with the cloth.

Speaking of "Speaker Cloth", does anyone know whether there is any, either N.O.S. or reproduction cloth of this style being made ? My cloth is O.K. but not perfect (there is some slight damage to it) I will upload a picture of the cloth (& the metal trim).
That's the right colour, and it's in good enough condition to leave (not repaint) in my opinion.
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