TinkerBox MkIII

[peter.sables]

HI

Do we have any info on this transmitter. I'm going to build one to go with my Italian RC2 and Paraset.

Anything to get mestarted.

thanks
Pete

[M0TAW Tony]

Hi Pete
There was an article in the QST Jan 08 edition which gave cct, front panel layout dimensions etc. If you have a fax I will send it to you
Tony

[Buzzkf9cm]

Or you can go here and download the pdf file

Mark III manual


73 Gary, KF9CM

[peter.sables]

Hi All

Sorry for the long time delay in getting back to you. No Fax though. This set is getting me down as there is so little on it. How come all the originals are different!!! and that's the real problem. I could be building someone ells's version of it. I'm going to Bletchley in two weeks time so hope to see one for myself. I have started to build it though, Well, a version I think could be right. Think best, not to look at this set to closely. Take the switch on the left. Is that right, well if it is, how come its lacking the lettering all the others have. I think that's been added. Yes it may well need it, but is it right..

Pete G4MRU

[Buzzkf9cm]

Hi Peter,

Before I built my Tinker Box, I did a lot of research on the Mark III. I used several drawings out of publications and pictures from the web as a guide. By getting known referance points such as the National type "R" knobs (1-5/8") on the front, I got the measurements for the front. I did the same for the chassis and case. The Tinker Box I completed is as close to the one at Bletchley Park, Station X as I could make it. The WWII Naval 5A transmitter is very close to the Mark III.

You can do what you like Pete, but I spent a lot of time putting that Mark III manual together. With that effort I put together a Tinker Box that transmits a good clean 25 watts from 160 to 17 meters.

Gary, KF9CM

[peter.sables]

hi Gary.

Ha glad to meet you. Yes I've got your manual and I'm basically building you version of the set. I think its as near as its going to get, so no real pain. So many questions though. I've all but built it. Just the box now to make. That's a pain in itself but I'll sort it. Not happy with the switch on the left. Yes I know it on the Bletchey park set, But is it right!. It dose not have the printed lettering as all the others have. So it cannot have been there when the set was built. If it was then why dose it differ.....

Pete G4MRU

[Buzzkf9cm]

Hi Pete,

The left hand switch on the Tinker Box is a bit of a quandary. It's almost as if it's an afterthought. As for being symmetrical, I think 1-7/8" from the edge instead of 5/8" from the edge would be more in tune. I think that was the only place they could have put it because of the protrusion on the case of the transformer. The switch (Standby / Operate) would not be needed if you didn't need to change the output coil. Of course if you had rubber gloves....

I built the box using a inexpensive 10" table saw without too much trouble. Of course if you have access to a complete wood working shop, it would be a snap to produce.

Fill free to ask me anything about the build.

de Gary, KF9CM

[peter.sables]

Hi Gary

Yes that sounds right. I will be putting on all the switches as it also needs to look right. I've made two coils and think only need one more. I've had the front panel. Lettered for me. So that looks really good. I do not have the same meter though. (But still looking) The one I have looks ok and is the same size so when one turns up I can swap it with no marking. Interesting about the Naval 5A ! I've not found a referance to it yet, so that will be worth a look. It was said , it was a copy from a TX out of the ARRL 1938. Now I've been all over that book and years before and after with nothing like it turning up. So think that is a "red herring". I've also asked the RSGB to take a look and they came up with nothing like it. So maybe it was not a amateur TX after all.

I'm going to look for some hard wood for the box. I really want it to look right, but in the end I'll do as you have done.

Best for now Pete G4MRU

[Buzzkf9cm]

Hi Pete,

First of all I need to apologize. It's not the 5A, it's the Transmitter 5G. I've attached the 5G Manual to make up for the blunder.

The meter is an Air Ministry device, I got mine off of eBay UK so keep looking there.

For the power supply choke I used a small filament transformer from Radio Shack. The primary comes out to about 2 Henry's and it looks like the original and works well.

As for the "original" schematic I started with that. It worked adequately on the fundamental frequencies but was chirpy and unstable when used as a doubler. I ended up with the circuit using the colpitts oscillator and the voltage dividers on the screens. These improvements were found in the 1936 Radio Amateurs Handbook and the 1936 Jones Radio Handbook. The coils I used were 1.75Mc to 2.5Mc, 2.5Mc to 4Mc, 4Mc to 8Mc and 8Mc to 20Mc.

Hope this helps

73 de Gary, KF9CM

[peter.sables]

hi Gary.

That's very useful info. It answered all my questions. Now I can build with confidants. So in the end the MkIII was not unique after all. Sad really!.

I'll let you know how I get on.

Pete G4MRU

[peter.sables]

Hi ALL

That's it, finished. I'm happy with it. All I've got to do now is tweak it up to get maximum power then put it on air...

As they say, good one....Next!

Pete

[Buzzkf9cm]

Great job Pete,

Nice layout as well. I can hardly wait to see your case.


de Gary, KF9CM

[peter.sables]

Thanks Gary.

Ha, yes the box. that will be harder to build than the set. But it will get full treatment.

Pete