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Old 23rd Jul 2017, 7:43 pm   #1
poppydog
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Default KB Cavalier TP41

I have a not so wonderful KB Cavalier TP41, although its a nice colour , and I am in need of a tuner dial scan in grey if anybody has one please, or knows where there is one, mines not good. I also have some questions:

There is a cardboard tube on one of the transformers, is this supposed to be there or is it holding something together perhaps?

There is also some polystyrene where the batteries go, is this original/supposed to be there or is it someone's afterthought?

What's missing off the centre of the tuner wheel, is it brass, chrome etc.?

I ask these questions as there are not many pictures or much info on this particular radio on the internet. Please see pics.

Regards
Poppydog
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Old 23rd Jul 2017, 7:57 pm   #2
Cobaltblue
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Default Re: KB Cavalier TP41

Crackle of this parish may be able to help you.

http://kbmuseum.org.uk/

The example in the Radiomuseum doesnt have a cardboard tube.

http://www.radiomuseum.org/r/kolster..._tp41tp_4.html

Cheers

Mike T
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Old 24th Jul 2017, 7:08 am   #3
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Default Re: KB Cavalier TP41

Hi
I will try to answer your questions with regard to my 2 examples.
Not sure what the cardboard tube is for or if it is original, my radios dont have it.
The polystyrene is original, it is there to stop the batteries rattling around and from fouling on the speaker basket.
There is a concave brite on the centre of the tuner dial, it appears to be a more dull nickel finish rather than a very shiny chrome.
There should also be a nickel ring around the front edge of the dial, not sure from your photo if yours has that. The plastic dial and brites appear to be the same as the one used on the KB WP21 "Lyric".
It is very common for the printing on the aluminium covered paper dial to be faded and washed out. I was photo of the dial from a guy in Australia (I think it was some time ago) of the dial on his radio, which was very clear.
One other peculilar thing with this model of radio is, there always seems to be a staining on the bottom half of the front cloth/vinyl covering.

I will get some photos together and upload them for you.

Mike

Last edited by crackle; 24th Jul 2017 at 7:18 am.
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Old 24th Jul 2017, 9:18 am   #4
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Default Re: KB Cavalier TP41

Ok, I have taken some photos to try and show the dial and updated the KB Museum website.
It would seem that in the earlier Cavaliers the dial plate with the station markings was made of aluminium plate and painted. In the later model I have the dial is an aluminised paper dial and these types do seem to suffer from spots of corrosion and fading of the print.
http://kbmuseum.org.uk/kb_images/tp41/tp41.htm

I hope this helps.
Mike

p.s.
I must say that it was very difficult to take a photo of the dial with out too much glare and reflection.

Last edited by crackle; 24th Jul 2017 at 9:25 am.
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Old 25th Jul 2017, 9:37 pm   #5
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Default Re: KB Cavalier TP41

Quote:
Originally Posted by Cobaltblue View Post
Crackle of this parish may be able to help you.

http://kbmuseum.org.uk/

The example in the Radiomuseum doesnt have a cardboard tube.

http://www.radiomuseum.org/r/kolster..._tp41tp_4.html

Cheers

Mike T
Thanks for taking the time to reply, I did see the radio museum examples, when I typed in google the radio museum and Crackle's site was all that really came up of any interest.
Quote:
Originally Posted by crackle View Post
Ok, I have taken some photos to try and show the dial and updated the KB Museum website.
It would seem that in the earlier Cavaliers the dial plate with the station markings was made of aluminium plate and painted. In the later model I have the dial is an aluminised paper dial and these types do seem to suffer from spots of corrosion and fading of the print.
Quote:
Originally Posted by crackle View Post
I will try to answer your questions with regard to my 2 examples.
Not sure what the cardboard tube is for or if it is original, my radios dont have it.
The polystyrene is original, it is there to stop the batteries rattling around and from fouling on the speaker basket.
There is a concave brite on the centre of the tuner dial, it appears to be a more dull nickel finish rather than a very shiny chrome.
There should also be a nickel ring around the front edge of the dial, not sure from your photo if yours has that. The plastic dial and brites appear to be the same as the one used on the KB WP21 "Lyric".
It is very common for the printing on the aluminium covered paper dial to be faded and washed out. I was photo of the dial from a guy in Australia (I think it was some time ago) of the dial on his radio, which was very clear.
One other peculilar thing with this model of radio is, there always seems to be a staining on the bottom half of the front cloth/vinyl covering.

I will get some photos together and upload them for you.
Thank you Crackle for putting the extra pics up for me, my photo with the dial on it looks better in the picture than it does in reality. I really could do with a scan of one that is identical to mine. It's the aluminium paper sticker.

With regards to the cardboard tube, in the picture on the radio museum there is a rubber buffer on the tuning cap , I am wondering if on mine this is an earlier attempt (or cheaper) to stop the rear cover bottoming out or to reduce drumming? So I think I will leave it in place.

With regards to the staining, I thought it might have been the adhesive coming through. I have tried to remove it, the most aggressive I have used so far is meths and it is still there. I may try a little cellulose thinner on a cotton bud in the bottom corner.

The plastic tuner wheel, I might put a request in the sets wanted section.

Thanks for all the help so far.

Regards
Poppydog
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Old 8th Aug 2017, 8:13 pm   #6
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Default Re: KB Cavalier TP41

Is it possible to replace a GET873 with a 2G302A? It's the first IF amplifier in this radio. I have had a quick look in my transistor data book and there are some similarities however I would like the more experienced members to give me the ok.

Regards
Poppydog
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Old 8th Aug 2017, 8:53 pm   #7
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Default Re: KB Cavalier TP41

I dont see why not. But I am surprised you need to change the GET873, I have only ever known these to fail due to corrosion on one or more leg.
However like many germanium transistors they can go noisy.

Mike
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Old 8th Aug 2017, 9:21 pm   #8
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Default Re: KB Cavalier TP41

This one is not good Mike, I have had to replace the output pair, there was distortion and upon investigation one of the GET113s was no good and the pair were replaced with AC128s. Oscillator/mixer GET874 had gone very low gain and this was replaced with an OC44. Numerous resistors have been replaced, they have lost a lot of their paint/lacquer and have gone very high, I think due to being stored in damp conditions. I cannot get the correct voltage readings on the first IF transistor, all the associated components have been changed, I have got low collector volts and high base/emitter volts and these tend to creep up as does the current (only a little). On all the other transistors I have managed to get the volts almost as per the sheet. Turning into a labour of love.

Regards
Poppydog
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Old 14th Aug 2017, 9:33 am   #9
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Default Re: KB Cavalier TP41

Would anybody be able to tell me what the total current draw at idle should be for this radio please ?. regards poppydog
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Old 14th Aug 2017, 9:38 am   #10
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Default Re: KB Cavalier TP41

It states in the service manual on page2, 10mA per battery at idle, 20mA per battery at 50mW output level.
Not sure how to state the "total" other than in mW, which I believe works out as 2 x 90mW at idle.
Mike

Last edited by crackle; 14th Aug 2017 at 9:46 am.
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Old 14th Aug 2017, 6:54 pm   #11
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Default Re: KB Cavalier TP41

I'm afraid we weren't singing from the same hymn sheet as the trader sheet 1560 was the one I was looking at and it doesn't state it, hence why I asked the question.

Regards
Poppydog
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Old 15th Aug 2017, 8:41 pm   #12
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Default Re: KB Cavalier TP41

Trying to measure the current from each battery is causing me problems.

Quick question, but I hope it makes sense. Crackle said it draws 10ma per battery, I have one battery clip connected to my bench power supply the other battery clip to a grundig supply. When I turn on both supplies the bench one reads 19ma(with radio turned on) the other grundig one ive connected in series with my avo and that also reads around 19ma.
When I switch(with the radio switched on) the bench supply off the grundig supply now reads around 14ma and if I turn the bench supply back on and the grundig supply off the bench supply reads around 14 ma. So does that mean when both supplies are on they are reading the combined current as they both now read around 19ma, however, that doesn't quite add up to me. Does it mean I am drawing 14ma per battery ? The same thing happens when I use a pair of 9v batteries. Is there a simple solution as its starting to drive me around the bend .

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Old 15th Aug 2017, 11:17 pm   #13
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Default Re: KB Cavalier TP41

Who knows what the tweed jacketed designer of that was smoking in his pipe!

I'd just check the standing currents in the output trannies by measuring volts across their emitter resistors and ensure that the speaker midpoint feed is somewhere close to mid rail with the speaker disconnected. About 5-10mA in each device should be OK. There's no adjustment other than fiddling with the bias resistors anyway.
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Old 16th Aug 2017, 8:59 am   #14
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Default Re: KB Cavalier TP41

The transistors TR1,2,4 are returned to the common rail so will be drawing current if the only minus power supply is connected. Tr3 will draw current with the plus side only connected, and there will be reverse leakage that is greater in germanium devices than silicon so this probably accounts for the current readings of 14mA instead of 10mA per side with the other side disconnected.
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Old 16th Aug 2017, 9:07 pm   #15
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Default Re: KB Cavalier TP41

Quote:
Originally Posted by Herald1360 View Post
Who knows what the tweed jacketed designer of that was smoking in his pipe!
Maybe somebody should have disturbed his "Condor" moment as this thing has certainly been giving me the run around .

Thanks for the reply Chris, I will measure and check the voltages and work out the currents you have suggested.

Quote:
Originally Posted by GeoffK View Post
The transistors TR1,2,4 are returned to the common rail so will be drawing current if the only minus power supply is connected. Tr3 will draw current with the plus side only connected, and there will be reverse leakage that is greater in germanium devices than silicon so this probably accounts for the current readings of 14mA instead of 10mA per side with the other side disconnected.
Thanks for your explanation Geoff, for a while there I thought it might have been a bit too technical for the technical department . However, the 2G302A, the replacement for the GET873, is working very well.

Regards
Poppydog
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