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Old 3rd Apr 2018, 2:11 pm   #1
Sweetmk1dub
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Default Early 80's? Blaupunkt Hamburg car radio.

Hi guys, my first post here so be gentle.

I have myself an old Blaupunkt Hamburg radio with an aux lead out of the back.

It's a bit broken inside and smells burnt out (connecting a live cable to ground and the negative cable to the electric aerial connection will do that I guess) but I'd like to get it working again.

I've had it apart and replaced the glass fuse with no joy.

I don't really know where to go from here but I guess a forum like this is a good start. Cheers, Karl
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Old 3rd Apr 2018, 3:38 pm   #2
orbanp1
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Default Re: Early 80''s? Blaupunkt hamburg car radio

Hi Karl,

Welcome to the forum!

Here is a Hamburg radio, not the same model number, but looks similar:
https://www.radiomuseum.org/r/blaupunkt_hamburg.html
See how close it is to your radio, this could help.

First step would be to check if any of the transistors got blown.
Power up the radio, and measure voltages at the transistor terminals.
The transistors should be in their "linear operating mode", the Vbe voltages 0.1V to 0.3V for germanium devices, 0.5V to 0.7V if silicon transistors.
Vce voltages should be somewhere 2V to 12V, depending on the circuit.
(The schematics from the RM site shows voltages.)
A blown transistor would have a short (0V) or excessive voltage on it on of those measurements, depending if it is shorted or "burned out".

Good luck, Peter
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Old 3rd Apr 2018, 5:05 pm   #3
Sweetmk1dub
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Default Re: Early 80's? Blaupunkt Hamburg car radio.

Thank you Peter.
I'll be buying myself a multi meter and having a go next weekend hopefully.

Cheers, Karl
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Old 3rd Apr 2018, 5:18 pm   #4
'LIVEWIRE?'
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Default Re: Early 80's? Blaupunkt Hamburg car radio.

From late 1971 until mid 1995, I worked as I.C.E. (Car radio service engineer) for a Blaupunkt main dealer, and would have no doubt repaired examples of that model. Like all Blaupunkt car radios, these were strictly Negative Earth Only so a reversed polarity supply will have almost certainly destroyed the output transistors (or I.C.-not sure which was used in these) Just noticed that the FD number stamped on that label on the top cover is '441', which is the 41st week of 1974, so that's when it was made. Your Hamburg is earlier than that on the Radio Museum site (Theirs is a 7639xxxx, whilst yours is a 7638xxxxx model) The circuit, however, will be similar, and the output transistors, which are mounted on a heatsink, are AD`156/157. These are similar to the once ubiquitos AD161/162, and may well have failed.

Last edited by 'LIVEWIRE?'; 3rd Apr 2018 at 5:24 pm. Reason: To update & correct information)
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Old 3rd Apr 2018, 5:23 pm   #5
paulsherwin
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Default Re: Early 80's? Blaupunkt Hamburg car radio.

This will be a very challenging repair if you have no electronics knowledge or experience. It may be better to bite the bullet and pay a professional to repair it (or just scrap it). You could spend lots of time and money on it and still not have a working unit.
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Old 3rd Apr 2018, 9:18 pm   #6
Sweetmk1dub
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Default Re: Early 80's? Blaupunkt Hamburg car radio.

It's much older than the car I removed it from then! That's fantastic info there 'LIVEWIRE?'. Cheers.

You're most likely right there Paul, I'll have to attempt it though, I'm handy enough with a soldering iron so it's not like I can make it any more broken.

Cheers, Karl.
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