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Old 2nd Jul 2020, 4:46 pm   #1
chipbutty
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Default ITT Schaub-Lorenz Tiny Super - sounds horrid!

I've recently aquired an absolutely mint condition Tiny Super from 1971. It came in the original box complete with foam inserts. The chap who sold it to me suspects it was never used and kept in the box. Maybe for almost fifty years! All works well except the sound. It sounds very thin and harsh. When the volume is turned up it actually hurts my ears. Especially on FM.

I have a very limited knowledge of electronics but strangely enough I can solder quite well and own a multimeter. I've fixed up a few radios over the past couple of years. Usually where the fault was obvious.

I'm assuming this radio is not supposed to sound like this so is there any way I can fault trace what the problem could be?

Thanks for any help.
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Old 2nd Jul 2020, 5:14 pm   #2
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

This was made for the German market. ITT radios for the UK market were branded 'ITT-KB'.

It may have left the factory with a fault. Sometimes the quiescent current hasn't been set properly, but there are many possibilities. It would have been returned to the dealer who would have put it on a shelf in the back room and forgotten about it.

The output transistors seem to be prone to failure in ITT radios of this era.

There is almost certainly an electrolytic capacitor between the output transistor pair and the speaker. If this has failed (and it may well have done after almost 50 years without power) the sound will be faint and tinny.
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Old 2nd Jul 2020, 5:17 pm   #3
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

Well, a bit non-descriptive but you will resolve it on here. The music my kids play hurts my ears. In all seriousness it could be a rubbing speaker cone. Tagging another one across will promptly eliminate that. If not feed an external input across the volume control to isolate the audio stage.
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Old 2nd Jul 2020, 5:23 pm   #4
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

Quote:
Originally Posted by paulsherwin View Post
There is almost certainly an electrolytic capacitor between the output transistor pair and the speaker. If this has failed (and it may well have done after almost 50 years without power) the sound will be faint and tinny.
Thanks. The sound is actually pretty loud. It's just thin and tinny with it.

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Originally Posted by toshiba tony View Post
Well, a bit non-descriptive but you will resolve it on here. The music my kids play hurts my ears. In all seriousness it could be a rubbing speaker cone. Tagging another one across will promptly eliminate that. If not feed an external input across the volume control to isolate the audio stage.
Thanks Tony. I'm a bit confused though. I'm really pretty clueless when it comes to these things! If it's possible to explain any of that in layman's terms it would be much appreciated. Though I realise it's not always easy to do that. I'll certainly give it a shot once I know what I'm doing.
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Old 2nd Jul 2020, 5:31 pm   #5
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

That could happen, depending on how much capacitance the electrolytic has lost. That's just one possible explanation amongst many though. These ITT radios sound perfectly decent and are generally underrated compared to the Grundig and Roberts models of the same era.
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Old 2nd Jul 2020, 9:38 pm   #6
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

Quote:
Originally Posted by paulsherwin View Post
The output transistors seem to be prone to failure in ITT radios of this era.
Hi I used to have one of these but sold it recently.
But I just thought I would mention I have had over 60 ITT-KB radios and so far none have suffered from faulty transistors on the OP stage. But there can always be a first.

There is a headphone socket on the radio, try listening on headphones to see if it still sounds poor. This should help tell if it is likely to be the speaker or not.

Apart from the addition of SW instead of LW this radio looks like it has an identical circuit to the ITT-KB Tiny Super sold here in the UK.

These radios are known for their good quality sound and reliability so if it sounds poor there must be a problem.
But dont forget that this a small radio and it probably will sound a little distorted if the volume is turned up much more than 3/4s.

The service information is available on the Radio Museum, https://www.radiomuseum.org/r/itt_tiny_super.html

Mike

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Old 3rd Jul 2020, 7:07 am   #7
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

If the audio sounds in in headphones then suspect the speaker is faulty, I have known this when the radio has been stored in damp conditions.

If the sound is poor also in the headphones then check the voltage between the 2 points shown on this diagram. You should measure exactly half the battery voltage, so if the battery measures 9.5v then the voltage at the point at the end of the blue arrow should be -4.75v.
This is a view looking at the copper track side of the printed circuit.
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Old 3rd Jul 2020, 10:56 am   #8
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

Thanks Mike. Some great suggestions. I will investigate. Will using 1.2v rechargeable batteries affect the audio? I have some 1.5v AA alkalines on the way to see if they make a difference. Probably not.

I don't know whether it's just my ears getting used to the sound signature of the radio or there is some burn in of components (if you believe in that sort of thing) but after leaving it playing for several hours it didn't sound as harsh. The sound is reminiscent of my Grado headphones. A very bright and clear sound. I was also getting some sibilance yesterday and that appears to have gone. I've noticed the volume quickly ramps up and I don't have to turn the volume much at all until it's pretty loud.

I've noticed on FM the station has to be tuned 'just so' or the audio sounds very brittle. I own a few smaller analgue radios and haven't come across this before. Certainly the audio does sound fuller when I hit the sweet spot on FM.

It's all a bit strange.
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Old 3rd Jul 2020, 12:09 pm   #9
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

Quote:
Originally Posted by crackle View Post
But I just thought I would mention I have had over 60 ITT-KB radios and so far none have suffered from faulty transistors on the OP stage. But there can always be a first.
You're right Mike, I was thinking of something else - apologies.
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Old 3rd Jul 2020, 1:02 pm   #10
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

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Originally Posted by chipbutty View Post
It's all a bit strange.
Any electrolytic capacitors will probably require reforming after such a long time. You may well find that a long run for a few hours could reform them and performance improve.
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Old 3rd Jul 2020, 4:47 pm   #11
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

This sounds like it is a case of the electrolytic capacitors reforming themselves..
On a few occasions have turned on a transistor radio I have just bought, which has probably not been used for 30 years or more and it has barely worked. Then after dismantling it all and getting my iron hot, it has started working all on its own.
These radios from the late 60's to 80's are very resilient.
It will probably continue to improve, hopefully to the point where it is again producing its normal rich and full tones. I have always thought these little ITT-KB radios can sound like a radio twice its size.

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Old 3rd Jul 2020, 8:39 pm   #12
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

I hope it does continue to improve Mike. It's not what I'd call a pleasant listen.

I'm having problems getting the chassis out of the case. I've followed the instructions in the service manual. Apparently it should now slide out from the right side. The heatsink and speaker wires prevent removal. Looks like I'll have to snip the speaker wires as I can't get to them to desolder.
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Old 4th Jul 2020, 8:37 am   #13
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

Whilst I don't have the radio in front of me, logic suggests that the radio was assembled by hand and so someone soldered the speaker wires during assembly.

There is a thread on this radio on this website and on the Kolster Brands Museum photo, it shows 3 screws holding the pc board into place RHS. The telescopic aerial and "pip" in the case securing LHS.

Having removed same, note the tuning scale are also secured by similar screws, I would have thought the chassis is removed by first lifting the bottom of the board away from the "pip."

The thread also suggests that the radio has excellent sound quality which my ITT Tiny also has. "Can't believe is not Grundig" springs to mind!!

Hope this helps.

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Old 4th Jul 2020, 9:09 am   #14
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

This series of ITT radios always had a surprisingly good bass resonse. They used the largest elliptical speaker possible (and all with generous magnets) in such small casings.
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Old 4th Jul 2020, 11:01 am   #15
chipbutty
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

Quote:
Originally Posted by simpsons View Post
Whilst I don't have the radio in front of me, logic suggests that the radio was assembled by hand and so someone soldered the speaker wires during assembly.

There is a thread on this radio on this website and on the Kolster Brands Museum photo, it shows 3 screws holding the pc board into place RHS. The telescopic aerial and "pip" in the case securing LHS.

Having removed same, note the tuning scale are also secured by similar screws, I would have thought the chassis is removed by first lifting the bottom of the board away from the "pip."
Thanks. Yes all the screws are out including the tuner. The boards is free but it can't be leveraged out. The only way to get it out is to either remove the heatsink, which has glued itself to the caps, or pull the wires from the speaker. I'll have another look in a bit. All good fun.
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Old 4th Jul 2020, 11:06 am   #16
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

Are these the electrolytic caps on the right, contained in the heatsink? Does it look like the cap on the lower right has leaked or is it some sort of glue or thermal paste?
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Old 4th Jul 2020, 11:25 am   #17
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

The items in the heatsinks are the output transistors, electrolytics are in the blue plastic wraps, as others have said I would use it a while before you go changing components.
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Old 4th Jul 2020, 11:31 am   #18
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

No I'm not changing components. I'm trying to take the board out to measure the voltage as suggested above.
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Old 4th Jul 2020, 11:45 am   #19
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

I had a similar thing with a ITT golf pre-set a while ago, it sounded like it was being throttled, it turned out to be the audio coupling cap.
The elec caps were nearly all those good quality black nippon-chemi branded ones, for some reason the audio coupler cap was a brand I had never heard of. Once removed it measured in the pf range when tested, the replacement transformed the sound.
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Old 4th Jul 2020, 11:56 am   #20
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Default Re: ITT Schaub-Lorenz Tiny Super - sounds horrid!

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No I'm not changing components. I'm trying to take the board out to measure the voltage as suggested above.
You should be able to measure the voltages on the component side of the Printed Circuit Board by probing the appropriate component leads.
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