CR100 to Restore,

[Shaman]

Hi, i have two CR100,s both navy blue front with badge on one, the performance has been dropping off, slowly, after changing valves, its not as good as it was, so it would seem it needs a restoration, change caps, resistors which no doubt have gone high- or low, i would love to change all under the valve base components, whilst the coil pack is out, this seems a little daunting, as i have not removed one in this type of set before, i believe modern valves can be substitutes for the ktw series etc, has anyone done this before, that could give some sound advice. I would like to wire straight in the mains lead, also and do away with the plug and lead, which i would guess is as old as the radio. After all this a realighnment to get the set more responsive, awaiting your advice regards....Alan.

[Skywave]

Hi Alan,
I too have a CR.100 that is waiting for a similar sort out. The previous owner said "it worked", but I haven't powered it up yet since I can see that some of the wiring has perished insulation and that it has some strange mods. We'll have to swap notes as we progress; I'm waiting for the weather to improve.
Looking at the usual sources for these, I must say I am surprised how relatively cheaply one can obtain a CR.100 these days.

Al.

[Shaman]

Hi Al, will have to get more info, on more modern valves, for substitutes. The only thing that niggles me is the coil pack removal with waveband switch, not making any mistakes, the caps must be up for renewal as must a lot of the resistors, due to value changes leakage etc, then after all a good re-alighnment, i have several sig gen,s, even avo all wave oscillator 1930,s vintage working very well and quite accurate. I have two CR100,S both working but in need of refurbishment.....kind regards.....Alan.

[Skywave]

Hi! I've made post relevant to this topic in another Thread here, q.v.

Al.

[Shaman]

http://www.vmarsmanuals.co.uk/archive/51...1868-1.pdf Hi here is the CR100 Manual, with circuit diagram etc.....regards....Alan. ps in PDF Format.

[AlanBeckett]

I've got one as well so any info is good news
Alan

[Les G4CNH]

If the radio still has a full compliment of screening cans then stick with the KTW61's else fit adaptor plates to take B9A skirted valve holders. You can then fit EF89's and though they have their own internal screen they look better with Black screening cans in my opinion. For KTW61's the original screening cans are so important and that includes the metal top caps to give full screening. Also the receiver should have a base plate but its fitting will cause all of your hard earned re-alignment to change, more so on the upper frequency bands. It is most certain that Marconi fitted a false plate with access holes for trimming, then after alignment the base plate was replaced with a blank one. You could fit a plate with access holes already made but where does one get the proper trimming tool? I have seen them in the services, made from paxolin tube with a box spanner style fitting at the end to loosen the core lock nuts. Down the inside of the tube was a paxolin rod with an aluminium end piece containing a slot for actual core adjustment. The arrangement enabled locking of the core nut without disturbing the position of the core. I guess a suitable tool could be manufactured. Just take care sliding out the wafer switch shaft and once removed DO NOT turn any of the switches, leave them set just as they are. The large 0.1uF waxies in some of the switch compartments must be changed.

[Shaman]

    Hi, Les, i am still contemplating valve change, as KTW61,s are drying up slowly, the EF89, looks a better solution, one of my CR100,s has had some valve changes, allready, the best thing is to stick all the valves one at a time on the valve tester, and work from there, i would think quite a few caps need changing resistors as well, if out of spec, well over or under +-20%. the one CR100 has all origiional valves the other quite a few, those needing screening cans have by the looks of it alllways had them, top can included on each valve. i know the switch assy must be removed, i am dreading this, but it has to be done as one waxie,s looks bad, and the underside of the valve bases need to be exposed to change components and re-solder etc, i will get round to this, i have a few sets to catch up on, i have a pilot radio on the bench having some valve bases and components changed, please may i contact you as soon as i start stripping the set for its refurb. This one is my bedside radio at the moment....regards....Alan.

[Skywave]

Alan,
I too have a CR.100 that is waiting in the wings - and like you, there are a number of other sets that are in front of it in the queue; perhaps we can swap notes later on as things progress. In the meantime, I've a little plumbing issue to deal with . . .

Al.

[Shaman]

Hi Al, sorry for my late reply, by all means as soon as i start the set, i will pm you if you wish, as in last post i will test all my valves, see what they come out like, i am doing a pilot radio at the moment so far two valve holders were carbonised inside the two skins that make them up, the rectifier was shot, and the output valve, i have fitted octal,s, am wiring them up after the power supply is rebuilt, its an old set that deserves the work on it, it sure has had some mods on it oveer the years i guess it came to a time where it needed to be done up. Back to the CR100, i am intrigued by Les suggestion of EF89,s once the switch pack is out it could be a better option....regards...Alan.