Wet 1969 ITT-KB junior battery radio

[crackle]

I take my hat of to you for attempting to restore this little ITT-KB Junior.
If I can take any photos of my little Junior ML2 for you let me know.
Service manual here http://www.kbmuseum.org.uk/itt_servi...L1&ML2_ITT.pdf
Oh that's interesting its the same one as on the Elektrotanya site, at least they are not charging for my work.
Looking at what is upstairs I appear to have an Junior ML2/1 and a ML2/2
Mike

[audion_1908]

The IFTs the model Junior 21 look like they are a 100% match as they have the same schematic part number, and internal diagram, thanks for the fuller service sheets,
And I did not know it was going to be this bad! I was expecting a little corrosion and water damage. And had planed to patch up the speaker!
The bt-1 transistor with a hole rusted in it is a pain, as I can find no data sheet or sub

crackle it's your site! with the only info on the mysterious bt-1 transistor
https://www.radiomuseum.org/tubes/tube_bt1.html

You won't want to put my itt radio on your site lol

[audion_1908]

Originally Posted by crackle

I take my hat of to you for attempting to restore this little ITT-KB Junior.
If I can take any photos of my little Junior ML2 for you let me know.
Service manual here http://www.kbmuseum.org.uk/itt_servi...L1&ML2_ITT.pdf
Oh that's interesting its the same one as on the Elektrotanya site, at least they are not charging for my work.
Looking at what is upstairs I appear to have an Junior ML2/1 and a ML2/2
Mike

Some pics of the front of the PCB of both could be useful to work out if my one is a ml1 or 2 and help in the reconstruction especially in the poor state it's in.
Thanks

[Philips210]

Originally Posted by crackle

Oh that's interesting its the same one as on the Elektrotanya site, at least they are not charging for my work.

Mike

Hi.

I didn't realise it was from your information. Sorry for any offense, I was only trying to help the OP. I won't bother posting any more links on here, it's all too easy to upset someone.

Regards,
Symon.

[audion_1908]

My radio uses a 1967 cd0000 diode it's a failed npn transistor recycled as a diode! They just cut a leg off, I have only read about this, it subs a 1n4148, I hope my one survived as it's so cool!

https://www.radiomuseum.org/tubes/tube_cd9000.html

[crackle]

Originally Posted by Philips210

Hi.
I didn't realise it was from your information. Sorry for any offense, I was only trying to help the OP. I won't bother posting any more links on here, it's all too easy to upset someone.
Regards,
Symon.

There is no need to be so sensitive or apologetic I didn't say I was upset. No offence was caused as far as I was concerned, I was just surprised I guess.

Ill take some photos and make a web page for the model on my website so you can see them in detail.

Mike

[Philips210]

Hi.

I feel better now that no offense was caused. I realise that it can be time consuming repairing technical data so it is fully presentable and all due credit should be applied. I hadn't noticed the KB Museum watermark on your data as I quickly looked through the data to provide a link to the OP.

That's a very comprehensive website you have and a great reference.

Regards,
Symon

[crackle]

Prompted by this thread I have finally got around to completing a web page in the KB Museum for the ITT-KB Junior ML2 radio.

I hope the images are useful.
The only difference I can see between the ML1 and ML2 id the ML1 has a different MW coverage and a different IF frequencies. See the service manual.

I also have a few small tuning capacitors which look about the right size for the Junior ML2, you can have one if needed for the cost of postage.

and I have marked the part numbers of the coils as far as I can make them out.

I wish you all the luck in the world in your efforts to restore this sad little radio..


Mike

[ekjdm14]

Originally Posted by audion_1908

My radio uses a 1967 cd0000 diode it's a failed npn transistor recycled as a diode! They just cut a leg off, I have only read about this, it subs a 1n4148, I hope my one survived as it's so cool!

https://www.radiomuseum.org/tubes/tube_cd9000.html

That's interesting, I recall an Ultra suitcase record player I worked on used a transistor as a temperature compensating diode between the output pair. On that though, it had 2 legs commoned together so they didn't even bother to snip one off. Fingers crossed for the diode in your set, that is a pretty neat little dodge & much more efficient than scrapping all the faulty transistors plus making/purchasing loads of diodes. Doubt you'd see ingenuity like that so much these days.

Didn't Alan Sugar buy up a load of duff chips to use in his computers, because he could make use of the section that was working for another purpose?

[audion_1908]

Originally Posted by crackle

Prompted by this thread I have finally got around to completing a web page in the KB Museum for the ITT-KB Junior ML2 radio.

I hope the images are useful.
The only difference I can see between the ML1 and ML2 id the ML1 has a different MW coverage and a different IF frequencies. See the service manual.

I also have a few small tuning capacitors which look about the right size for the Junior ML2, you can have one if needed for the cost of postage.
Attachment 204312 Attachment 204313
and I have marked the part numbers of the coils as far as I can make them out.
Attachment 204314
I wish you all the luck in the world in your efforts to restore this sad little radio..


Mike

Thanks for the pics and the offer of the variable cap, but I think I have found a sub for the mitsumi pvc-2 it 60pf and 140pf with 2 inbuilt trimers, I hope it's right, I spent ages tracking down the pvc-2 data, apparently at one time it was very very common, I have also found a compatible 10k combined switch and volume control element, as mine is destroyed, I am hoping the ift are good, I need to get the tuning wheel off first, to get full access to the PCB so I can start testing and removing parts.
I think I have a ml2 as the back looks dark blue.
Are the two 20 to 50pf capacitor trimmers critical as there's lots of cheap ones on eBay

[Philips210]

Originally Posted by audion_1908

Are the two 20 to 50pf capacitor tremors critical as there's lots of cheap ones on eBay

Hi.

I'll have a look on some scrap radio boards later. I saw some with the same physical appearance recently. I'd need to check their capacitance to see if suitable.

Regards,
Symon

[TrevorG3VLF]

"That's interesting, I recall an Ultra suitcase record player I worked on used a transistor as a temperature compensating diode between the output pair. On that though, it had 2 legs commoned together so they didn't even bother to snip one off. Fingers crossed for the diode in your set, that is a pretty neat little dodge & much more efficient than scrapping all the faulty transistors plus making/purchasing loads of diodes. Doubt you'd see ingenuity like that so much these days."

There is a difference between a diode and an amplified diode. I made a power supply to drive battery valves. I made a 2V stabilised source and a diode to drop this to 1.4V when needed. Finding a diode to drop 0.6V at a substantial current was impossible and I eventually used a power transistor with base and collector connected together. I wonder what the temperature sensitivity would be.

Perhaps this will be a better arrangement than a simple diode for stabilising the current in the output pair.

[Philips210]

Originally Posted by Philips210

Hi.

I'll have a look on some scrap radio boards later. I saw some with the same physical appearance recently. I'd need to check their capacitance to see if suitable.

Regards,
Symon

Hi.

Just pulled these two trimmers (attached pic) and the measured capacitance range looks to be about 20pF to 60pF. They're not identical to the originals but should be OK. Free of charge if needed.

Regards,
Symon

[audion_1908]

Originally Posted by Philips210

Hi.

Just pulled these two trimmers (attached pic) and the measured capacitance range looks to be about 20pF to 60pF. They're not identical to the originals but should be OK. Free of charge if needed.

Regards,
Symon

They look perfect! The original ones crumbled away into rust

[Hybrid tellies]

You are a brave person tackling a job like this. Fair play to you. Keep us updated.
BTW I have a red Junior two in my workshop with a missing battery lid. I offer my services alongside Symon.

[crackle]

By the way here is a page from the 1970 ITT-KB catalogue featuring the Junior ML2
http://www.kbmuseum.org.uk/Catalogue...%20cat0005.jpg

Mike

[audion_1908]

I am filing away that rusted screw head off the tuning wheel, it's surprisingly hard metal

[audion_1908]

I tried filing a deep groove in the screw, but even when I applied enough pressure to almost crushed the PCB! it still wasn't coming out so I tried the reverse, I took the variable capacitor apart as I it was already destroyed by water, I got the tuning wheel off but it still has the variable capacitor shaft stuck in it, but atleast I can fix the PCB now and come back to the wheel later, another electrolytic capacitor fell off no loss but one of the plastic dome head transistors came off, this one has a ferrite core on one leg lucky still intact, but the transistors the legs are rotted off, the ferrite is likely criticals the circuit to stop unwanted parasitic oscillation.

[audion_1908]

Originally Posted by crackle

By the way here is a page from the 1970 ITT-KB catalogue featuring the Junior ML2
http://www.kbmuseum.org.uk/Catalogue...%20cat0005.jpg

Mike

That's a big pocket!

[audion_1908]

Originally Posted by Hybrid tellies

You are a brave person tackling a job like this. Fair play to you. Keep us updated.
BTW I have a red Junior two in my workshop with a missing battery lid. I offer my services alongside Symon.

I don't think you want my battery lid it's cracked and stained, but maybe somebody with 3D printer would like to copy it?