KB 333 Restoration

[Crackle]

Which radio shall I restore next.

KB 429      
KB 830     
KB 333     

[Geordie McBoyne]

The 333.

Geordie McBoyne.

[tiv48]

I will also go with the 333 as i have never seen one before.
Rob t

[Crackle]

Sam, it looks like you and me have been outvoted, 8 to 2.
I am a bit relieved really as the 333 (without batteries) is at least half the weight of the 830, so much easier to carry upstairs to my little room.
I dont see much point in waiting any longer, it seems fairly conclusive that the KB 333 is the one people want to see.

Mike

[Crackle]

The cabinet of this radio is in reasonable condition, I am not so sure the speaker cloth is original, and a replacement back panel has been fitted at some time in the past.
Here is a before and after photo showing the change to the dried and cracked old lacquer, it responded well to just a clean with Liberon wax and polish remover, (still slightly wet in photo) and will look even better when it gets a final treatment of furniture restorer type oil.    

After a lot of struggling I finally managed to pull the 2 knobs off the shafts at the front of the radio. The side knob decided to be a lot more difficult though, it was recessed into the side of the cabinet and slippery. I couldn't do my usual trick of sliding the hem of a piece of material under the knob, pulling it around and twisting around the shaft under the knob, then pulling hard, because it was recessed.
I squirted WD40 in as best I could then had another go, this time being a bit more brutal with 2 screwdrivers either side into the recess.
A small mark on the edge of the hole making the recess would not matter too much as there was an escutcheon to cover the hole.

Anyway the chassis is now out of the cabinet.    
It looks like a few of the battery wires may have been changed at some time.

It looks rather empty underneath.         
I just love these simple to see switches, but they can be problematic with the phosphor bronze springs breaking off so be careful     

I wonder if the speaker is original, it has a seal on the chord tying the cloth around it.    

Here is the schematic, I have added in the various voltages.    
The full service information is on my website here; http://kbmuseum.org.uk/kb_service_manuals/KB_333_kb.pdf

Anyway off to do a bit of preliminary testing, I was very lucky with the 279 I just restored, on UKVRRR, all of the transformers ware OK, lets hope I am as lucky with this radio.

Mike

[pwdrive]

I like the cabinet style, I also like the chassis layout and the band pass input, should make a nice restore.

Lawrence.

[Mark Hennessy]

Thread title changed, as requested, to reflect the outcome of the poll.

[Crackle]

I finished the changing of all the wax paper capacitors this morning, there were only 6 in total, even the 100pF and 200pF were wax paper and copper rolled into a cylinder, and showed a small leakage. It is surprising how much the wax sizzles when you heat it with a soldering iron, it must have absorbed quite a lot of water over the years.
This is the underside of the chassis now all the components have been checked and changed.
       

I seem to have got a bit low on yellow axial capacitors, they are the best type for re-stuffing, making it very easy once you have extracted the old wax mess. I open up the rolled over end of the capacitor by running a screwdriver around the rim then a soldering iron bit. Then pull the end of the capacitor out they normally break away easily, once the capacitor has been warmed and the wax softened enough the rest of the capacitor can be pushed out from the other end. I sometimes keep and reuse the end connections to the capacitor to act as stoppers on the new capacitors leads to support the end plugs.
             

I was puzzled by a contact designed to make with the tip of the tuning knob spindle. It had come loose from its mounting, the wire from it goes to the dial lamp. Its purpose was clear when I looked for the dial lamp on the schematic. The tuning knob spindle is on a spring and it can push in and makes contact to switch on the dial lamp, but normally it is disconnected to save battery.
   

2 of the resistors were way of their tolerance. One listed as 50k was reading almost 100k so I tacked another 100k to it and hid the small additional resistor under the original dogbone. Another 250k resistor was reading in excess of 700k, I managed to find another small dogbone type which measured about 300k and fitted that.

The reaction condenser is rather unusual, it is mounted on the back and ganged to a 10k potentiometer which also acts as the volume control. The pot shows no continuity so it is going to have to come out to be dismantled to see what is going on. Unfortunately I will also have to remove the wave change switch in order to be able to remove the reaction control.
   

I may be a little while.

Mike

[tiv48]

Great work so far .
also fantastic pictures i look forward to rest of restore .
Rob t

[jimmc101]

Looking good, excellent pictures.

Just noticed the picture of the yellow cap,  100nF (104) in a 0.01uF case?

Jim