Chapman/Derritron S6BS FM

[Synchrodyne]

Here are some various items about the Chapman S6BS/FM (and S6BS).

Cheers,

Steve


from the 1959 Chapman brochure:      

from Wireless World 1961 October:      

from Hi-Fi Year Book 1962:      

from a Chapman brochure circa 1966:      

from Wireless World 1968 February:      

[Murphyv310]

My goodness Synchrodyne you have been busy.
Many thanks for all the info.

[Synchrodyne]

Some information on the Chapman S6BS Mk II, including a schematic, came up in a recent UKVRR thread, see:  http://www.vintage-radio.net/forum/showt...p?t=135688.

As far as I know, the AM section of the S6BS/FM Mk II was quite separate to the FM section (power supply and tuning indicator apart), and was the same as the S6BS Mk II.


Cheers,

Steve

[Murphyv310]

Hi.
The next stage with the Chapman is to test the Stereo Decoder and if found to work as expected to add the Chapman to my 3-3 that is housed in our sideboard.
The Chapman works very well indeed on Caroline 648kHz and I am in the process of moving the frame aerial to the loft and having it constantly tuned to it. A new aerial cable will be run to the Chapman. I may get this completed before Santa comes if not it will be in the week between the big day and New year.

[Murphyv310]

Hi.
The Stereo Decoder needs a bit of work so in the meantime I am running the FM section on mono only. I'm swithering about using the MC1310P chip which will be an easy build.
I have been lucky in as much as the 3-3 is getting a custom made front panel and a carpenter friend is making up a second shelf above the Chapman and there will be side pieces added for both the Tuner and amp.
Here it is at the moment.
   
   

[shamwari]

Very nice, especially the night time shot!

My S6BS FM needs restringing as it came with the cord missing (other than for two bits still attached to the tension spring).  

Does the cord follow a similar arrangement as on the Chapman FM1000 (picture below - hopefully)?  That is, from the tension spring in the large pulley on the tuning capacitors to the tuning knob spindle, twice around the tuning knob spindle then up to one of the idler pulleys and straight across the top of the tuning scale to the other idler pulley then back to the spring on the large pulley.

[Alistair D]

Hii Shamwari

I see you are a member over on UKVRRR.

This thread from back in April has a few service manual pages. Perhaps the original poster has a stringing diagram as well. It would be worth dropping him an email.

https://www.vintage-radio.net/forum/show...p?t=135688

Al

[Terry]

Many cord drive systems are very simple.

A tuning gang tunes from HF to LF as it is rotated clockwise so, if the MW tuning scale runs from 200m to 550m (1600kHz to 550kHz) from left to right and there are no complicated multi-section pulleys involved, it is reasonable to assume a simple drive from tuning spindle to dial to tuning gang (in any order). As the tuning knob should rotate in the same direction as the tuning gang, that will determine the final arrangement which will simply connect all three essential elements via such pulleys and so forth which are required to complete the 'circuit'.

Multi section pulleys or evidence of a combination of cord and steel wire, on the other hand, are a definite No-No without the directions!

Anybody who has, like me, tried to work out one of these (usually Philips) abominations and found that, when every thing should work, something goes backwards or jams half way, that detailed directions are essential!

[shamwari]

Thanks, Al, I've sent him a PM. Thanks also, Terry, for the tips.

James

[Murphyv310]

Thread revival.
I've decided to build a decoder with an MC1310 chip. I have now acquired a couple and will build this in the dedicated Chapman enclosure. As the MC1310 has in input impedance of 50k I'll add a FET follower after the MPX output from the tuner.