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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 7th Jul 2019, 3:05 pm   #1
bill knox
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Default Please identify radio (Chapman)

Hi

I recently bought this radio chassis at an auction, it does not have an audio amplifier or power supply, these appear to be external to the radio, but I have powered it up and the magic eye is working.

It has 6 Band spread bands
2 Shortwave bands
And medium wave band, there is also provision to connect a non-stereo record deck, the other thing that I have noticed is that the IF and RF coils are WEYRAD I am beginning to think that this was a kit but someone may know differently

I have taken some photo's and now I will attempt to download them

If someone can identify it for me I would be most happy

Many thanks

Bill
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Old 7th Jul 2019, 3:25 pm   #2
ms660
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Default Re: Please identify radio

C.T. Chapman?:

https://www.vintage-radio.net/forum/...3&d=1396576781

Lawrence.
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Old 7th Jul 2019, 3:27 pm   #3
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Default Re: Please identify radio

It does look like a kit, but Lawrence is probably correct.
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Old 7th Jul 2019, 5:15 pm   #4
bill knox
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Default Re: Please identify radio

Hi Lawrence

I think you have hit the nail on the head, many thanks, I am probably asking for the cream but would anyone have a circuit diagram for this set.

I am considering changing the brown Hunts capacitors and checking the resistors, particularly the high value ones.

I cobbled together some components for a PSU which is supplying 240V which I did not consider to high and I put a Ma meter in series, the receiver is drawing about 30Ma, that I don't think is too excessive but there is a large WW resistor a 5K and the voltage on the receiver side is down too 157V
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Old 7th Jul 2019, 5:35 pm   #5
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Default Re: Please identify radio

Can any of the documents in this thread can be used as a guide?:

https://www.vintage-radio.net/forum/...173#post936173

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Old 7th Jul 2019, 7:13 pm   #6
bill knox
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Default Re: Please identify radio

Hi Lawrence

I have downloaded that diagram, it is for the later model but I can use it if required, My one has the EF41, ECH42, the only valve that is the same is the magic eye

Once again UKVR to the rescue

Many thanks

Bill
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Old 7th Jul 2019, 8:59 pm   #7
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Default Re: Please identify radio

I used to have a Chapman am/fm/shortwave tuner about 1962/63 vintage in a metallic gold panel finish. The general appearance was very reminiscent of the above pic's.
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Old 9th Jul 2019, 1:18 am   #8
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Default Re: Please identify radio (Chapman)

That is the Chapman S6BS tuner, second iteration I think. The earliest trace of I have of that variant is an advertisement in Wireless World (WW) 1954 September, but it might well have been released earlier than that.

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The original was announced in 1953 January, and advertised soon thereafter:

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The S6BS was a bandspread derivative of Chapman’s earlier S4 and S5 models, with the addition of a second IF stage and with three rather than two selectivity positions. A key feature of all of the Chapman valved AM tuners and the AM sections of the FM-AM tuners was the amplified and delayed AGC system, using an EBF80 pentode section as a sidechain AGC IF amplifier. This was said to avoid differential distortion and to allow application of full AGC bias to the final IF stage without running into modulation rise distortion. (The same type of AGC system was carried over to the AM section of the solid-state FM1005. Whilst germanium transistors and HF reception are probably a marriage made in hell, it does look as if Chapman made an effort to get reasonable performance; dare I say that the FM1005 AM circuit looks as if it might be a tad more sophisticated than say that of the Eddystone EB35.)

The third iteration of the S6BS was in place by 1957, and as best I can work out that was when the change was made to all-noval valves. It appears to have had dark-coloured knobs rather than the light colour of the previous iteration. By then there was a self-powered option (using the EZ80), although an outboard power supply unit was also available.

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The fourth iteration, in place by 1959, included a dimensional change (lower profile), a change in the bandspread bands from 13, 16, 19, 25, 31 and 41 metres to 11, 13, 16, 19, 25 and 31 metres, and a change in tuning indicator from the EM81 to the EM84. Also by then the S6BS/FM had been added to the range, combining the S6BS and FM91 circuits on the same chassis (with no combination except for the power supply).

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The S6BS Mk II of 1963 appears to have been simply a restyle to match the then-new FM1000 and FM1005 solid-state tuners. I don’t think that there were any significant circuit changes as compared with the immediately previous S6BS. The S6BS/FM Mk II included some changes to the FM circuitry, including a third front end gang implemented as a bandpass interstage.

The Weyrad three-gang bandspread front end appears to have been used by several manufacturers. Armstrong is known to have been a user (in its EXP119 and BS125 models) and other candidates include Dynatron (T139) and Ambassador (Viscount & Viscount II). I imagine that buying-in from a third-party was the best option for the smaller concerns. On the other hand, the major setmakers (e.g. Ekco, GEC, Murphy, Pye) were in a position to “roll their own” front ends when it came to bandspread receivers. A drawback of the Weyrad option was that it had only six bandspreads, whereas 8 were preferable, allowing full coverage from the 11 through 49 metre bands. I guess that there were mechanical and/or cost reasons for limiting the number to six. But it meant that users had to make a choice as to which bands they covered and which they left out. In contrast, for example, Murphy had 8 bandspread bands on its TA160 export receiver which had an in-house front end.

I have never seen a full review of the S6BS, but Arthur Wayne commented positively about it in Hi Fi Year Book 1962.

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There is some Chapman literature available on-line, at: http://ukhhsoc.torrens.org/makers/Chapman/index.html.

I have some service information on the S6BS 4th iteration (actually for the 3rd with handwritten amendments) – please send me a PM if you would like a copy of it.


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Old 9th Jul 2019, 8:11 am   #9
HamishBoxer
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Default Re: Please identify radio (Chapman)

The name's Hunts and it is full of them!
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Old 13th Jul 2019, 1:50 am   #10
Synchrodyne
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Default Re: Please identify radio

Quote:
Originally Posted by bill knox View Post
I cobbled together some components for a PSU which is supplying 240V which I did not consider to high and I put a Ma meter in series, the receiver is drawing about 30Ma, that I don't think is too excessive but there is a large WW resistor a 5K and the voltage on the receiver side is down too 157V
That data for the 3rd/4th iteration of the Chapman S6BS states that the HT voltage should be in the 200 to 250 V range, with 250 V also restated as the maximum.

Two HT dropping resistors are mentioned, namely 10k, 6-watt for use with 400-450 V HT (e.g. Leak amplifiers) and 5k, 4-6 watt for use with 300-350 V HT (e.g. Quad, Goodsell, etc.)


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Old 14th Aug 2019, 12:17 pm   #11
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Default Re: Please identify radio (Chapman)

Continued here: https://www.vintage-radio.net/forum/...31#post1168031
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