CR100 to Restore,

[Skywave]

Alan: late reply? What late reply? I don't detect a problem . . . .

These days, the CR.100 is one of those comms. radios that doesn't seem to fetch the price on the S/H market that you would expect it to: why, I'm not sure. However this does mean that it gives people like you and I a bit of elbow room to make modifications (and thus possibly reduce the potential value) that would be frowned upon by some others, e.g. replacing old Octals with B9A / B7G valves. Mods. and improvements, in fact, just like the Good Ol' Days

It could be quite some time before I get around to mine (so many things to do, so little time, etc,. etc.). We'll see who gets started first: no doubt one of use will put out a shout - especially if a problem arises!

Al.

[pwdrive]

Hello Al, I am still in the market for a decent example of the CR1OO, a decent looking CR150 went on Ebay not to long ago for reasonable money but it was to far for me to have driven at that time if I had bid and won it. Personally I think the CR100 is underated, from all accounts if up to spec then they are a good receiver.
The CR300 is a pretty basic beast but seems to pull 'em in ok though it's primary function was CW I think.
I briefly went through what's what on the component side on mine and in a nutshell
virtually all caps are leaking to some extent so for the moment they are are disconected at one end and a new nearest value tacked in as temp. until I have time to do a neat job, in its favour is the wiring, it's almost mint which has to be a first. The logging scale is in dire straits though print and paint wise, to that extent I have a dial artwork on the PC for it when I get round to doing some transfers.
Good luck with yours.

Lawrence.

[Shaman]

Hi Lawrence, its not that the set should be altered, just to get it going better, its a need to find a good source of the KTW,s, tho remaining valves i have plenty, a few KTW,s, its finding a balance and the EF89 just mi
ght tip the balance, some of the valves i would gess came perhaps with the set. I think the set is circa 1942, the upgrade would give it a few more years, or at least till every thing goes digital alas, will shout Al as soon as i start.......Alan.

[pwdrive]

Hi Alan, I didn't mention altering it...my CR300 is still on it's KTW's but by substitution with near equivilents I have come to the conclusion that a couple of the KTW's are low emission.

Lawrence.

[pwdrive]

Here's one for the Marconi buffs regarding the CR300, the receiver I have is a CR300/1 the enamelled badge on top of the inspection lid says that's what it is as does the ID plate on the front, both the badge and the plate are original and close inspection shows that they have never been removed, the badge has a space on it for the stamped serial number....there is no serial number, the space for it is unstamped.
The CR300/1 is supposed to have a 500 kc/s xtal marker and the CR300/2 a 690 kc/s marker...my CR300/1 has a 690 kc/s xtal fitted, again it looks like an original fitment.
Any ideas?
Also does the CR100 have the board of trade emergency crystal detector fitted so that basic reception is still theoretically possible (A la crystal set) in the case of a ships power outage, and what's the local osc. temp. compensating device in a CR100...just interested to compare.

Lawrence.

[Shaman]

Hi Lawrence, its the same for me all ktw, exept the other set it has 3 could be EF89,s, fitted by a previous owner, l know there are other octal valves but they are lower gain eg 6K7 near Equivalent i suspect lower gain. The KTW61 is a variable μ amplifier pentode for use in RF or IF stages within an AGC controlled superhet receiver. So a valve having the same or above would be ok. I would leave all alone if the set disd not need a big overhaul, but iuts looming, even the output stage could be changed for an EL84, this sounds horrid to do toi a set like this, but if its hard or very expensive to get replacement valves, its the only option, i did substitute some valves as they were so low on emission the set was geting less and less selective...regards....Alan

[Shaman]

Hi Lawrence, your CR300, is a copact set, i just realised it has 8 valves, i would have thought it would be ok to restore, as long as you have or can get newish valves.

[Shaman]

Hi Lawrence, your CR300, is a compact set, i just realised it has 8 valves, i would have thought it would be ok to restore, as long as you have or can get newish valves. far as i know if the power is off the set is dead, on my CR100,s so i would say no to the crystal detector, which would perhaps be a westcore if it had one, the set is 1942 era admiralty version, the other set has its plates removed. And what's the local osc. temp. compensating device in a CR100 my answer never found out what it is. The pics above are showing the state of the set after main smoothing cap failed, no bang just dribble...regards...Alan.

           

[Yorkie]

Remember when searching for info on the CR100 to include in the search 'B28' and R1297 - same set, depending on whether used by the Army, Navy, or RAF. Such a complex set, rather like Racals, that you never quite know whther it's working right or not, without the necessary test gear. A much under-rated set in my view far superior to sets such as R1155's, which enjoy an iconic status that isn't backed up by its basic spec.

Some sites you night find helful Al are:

http://www.philipstorr.id.au/radio/sixte...s_rx11.htm

He undertook a complete restoration - a total stripdown and rebuild, which is very well illustrated on his site. Some of his comments are:

"I searched the internet for details of the B28/CR100 and I found quite a few pages devoted to restoration and I even found the original workshop manual on the Boat Anchor site. From reading the stories of peoples restorations I soon realised I would have to replace all twenty two 0.1 uF chassis mount capacitors as they were always leaky twenty years ago so what is the chance of any of them being OK today. The electrolytics had already been replaced but as that was perhaps forty years ago they all had to go also. Getting the chassis mount caps out proved to be more difficult than I thought and I soon realised whoever had replaced a lot of the wiring thirty or forty years ago had made a mess of it".

"Well in for a "penny in for a pound", take the thing apart and replace all the caps, most of the resistors and all the wiring. While ripping it apart I discovered some old pitch covered caps deep inside the coil shields. To my relief I soon discovered the receiver was made to come apart, right down to the shields around each coil assembly, making replacing the bits around the coils quite easy. Just as well I reduced to a big box of bits, the wiring in the coil assemblies left a lot to be desired. In investigating the IF coils I found the BFO coil is open circuit but as the "opening" is where it terminates on a capacitor I should be able to fix it".

End quote.

I don't know if you've downloaded Chris Parry's excellent 'e-book' on the restoration of Military radios, but if not, it can be found here:

http://www.vk2bv.org/radio/radio-files/r...050723.pdf

There's an interesting article about screen printing a new front panel for a CR100, albeit you aren't contemplating that:

http://www.jonkster.com/radio/

Hope that's of interest.

A lot of these military radios - AR88s, HROs etc, like the CR100 B28 etc, are very cheap because of the sheer size, weight, complexity, and the fact that some don't lend themselves to non-military use without considerable modification. I once stripped an 1155 back to the IFTs and coilpack and rebuilt it with modern valves, based on an article in Short Wave mag. I plated all the original valvholder holes to fit B9 valveholders, built in a PSU and audio stage, fitted an 'S' Meter, made a new front panel. It was quite an undertaking, but the end result was far superior to the 1155, which I considered only fit as a donor.

Best of luck with the restoration Al!

[Shaman]

Hi, David, you found the link i was looking for, it was on my other computer that gave up the ghost, now i can put it on my usb stick take it to my other computers, 10 out of 10 for finding this link, http://www.philipstorr.id.au/radio/sixte...s_rx11.htm i agree the 1155 is not all that brilliant, i have an AR88LF, sorry but its not all its cracked up to be, i still love my as you rightly said B28 a name i suspect used by the navy, CR100 in all its variants. I do have a printed out version of Chris Parry's book, but the
site in the link above say,s it all and shows you, its a CR100 restorer,s bible shown in lovely pictures, that take you step by step. You are right David these are naval/Military sets, that by now due to their age need drastic modification/re-build to enable them to survive, yes we could leave them as they are but they would become metal boxes and nothing more, its nice to see and hear them working, thanks for your valued reply, spot on as usual.....Alan.