Enquiry

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les
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Enquiry

Postby les » Fri Aug 02, 2019 12:10 am

Just out of interest, I emailed Blaupunkt car radios in Germany to ask for the correct impedance speakers to use for the old radio I have, and I got this reply.——-“because of an event in a foreign country, we are unable to work on your enquiry” ——- and that’s before we’ve left Europe! We can share security issues but presumably draw the line at speaker specifications! :o


POMMReg
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Re: Enquiry

Postby POMMReg » Fri Aug 02, 2019 1:24 am

Stockpile Blaupunkt speakers NOW!!
Further investigations uncovered it was an inside job!!

geoberni
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Re: Enquiry

Postby geoberni » Fri Aug 02, 2019 8:42 am

:lol: :lol:
it's more likely because they have no idea. I'm surprised you found any contact details.

The firm that made your old radio no longer exists: https://en.wikipedia.org/wiki/Blaupunkt
The 2011 take-over effectively left Blaupunkt as a managed brand name with all production outsourced to China, with virtually no 'Bosch era' products still under production.
Last edited by geoberni on Fri Aug 02, 2019 9:42 am, edited 1 time in total.
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minijojo
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Re: Enquiry

Postby minijojo » Fri Aug 02, 2019 9:17 am

hallo Les,
i tried to find information about your enquiry. In the forums i searched, most Blaupunkt radios are listed as 4 Ω impedance for the speakers.
hope thats helps a bit

here is a link to a classic radio seller with some technical infos to the radios
https://www.klassikerautoradio.de/www-k ... blaupunkt/

if help with translation required, feel free to pm me
regards
Joachim

les
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Re: Enquiry

Postby les » Fri Aug 02, 2019 11:12 am

Thanks for your time, it was kind of you. I agree the general consensus suggests 4 ohms but my query stems from an article I read saying 4 ohm speakers could/would cause damage over time. I have attached the page, and would be interested in your interpretation, of that paragraph. I think it might relate to specific years of that model, I’m not sure
https://www.bmw2002faq.com/forums/topic ... g-diagram/


JHarley
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Re: Enquiry

Postby JHarley » Fri Aug 02, 2019 11:55 am

POMMReg wrote:
Fri Aug 02, 2019 1:24 am
Stockpile Blaupunkt speakers NOW!!
I'll second that!, where do we get Blaupunkt speakers!!
The Moggy Minor will stand with dignity for all time :D, I'm in Northampton, UK

minijojo
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Re: Enquiry

Postby minijojo » Fri Aug 02, 2019 1:13 pm

the impedance of a speaker is a measure of the current provided by the amplifier of the radio. So safe way is using a speaker with the specified impedance. Using speakers with higher impedance, will lower the current provided by the amplifier and will cause no damage. Using a speaker with a lower impedance then specified by the amplifier, will increase the current at full load and could cause damage to the amplifier and at least damage your radio

geoberni
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Re: Enquiry

Postby geoberni » Fri Aug 02, 2019 2:22 pm

Presumably you have the ID label on the radio, giving a model name/number; but there's no Impedance value given?
It's this bit that concerns you?
Speakers should be 8 ohm through the late 1970's. Using 4 ohm speakers will damage the radio over time.
Might seem obvious, but have you tried searching for a manual online to support the model name/number?

I agree with minijojo that using 4ohm when the thing is designed for 8ohm could damage the output amp.

The alternative is to use 4 Ohm and stop yourself turning it up full, perhaps not an easy option inn a noisy Moggie! :lol:

That article makes it sound as though they only used 8ohm speakers until the 70s, but I've just found this photo https://www.classentials.com/product/bl ... eaker-box/
which says it's a 1960s yet it's 4ohm. :-?

You might try contacting this website in the USA and see if they can help with definitive info for your model http://www.vintageblau.com/
They seem to know a lot about old Blaupunkt kit.
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les
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Re: Enquiry

Postby les » Fri Aug 02, 2019 4:21 pm

I thank you both for your interest, yes the sentence you highlight was the problem. Saying through the late 70s puzzled me, I’m sure mine is early and Mono, There is a label on the set but not of the model type, it is the same as shown in the link I posted, the rear is identical, I will try the links. There seems to be ways round this but the correct values would be nice to know. Thanks again.


les
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Re: Enquiry

Postby les » Fri Aug 02, 2019 6:56 pm

Well I have received a response from Vintageblau, and have been told that from about 1974, this radio went from using an 8 ohm speaker to 4 ohm interestingly,. The guy thinks mine should be 4 ohms. Yet it the write up it said in about that year the speaker connection plug went from 2 round pins to a pin and spade, mine is 2 round pins so presumably pre 1974, and from his info the set would then be using 8 ohms. Getting there but thinking is one thing definitely is another, although I am grateful for his reply. If I can’t confirm the precise year I’ll consider using 8 ohms. There must be a test to put the radio through I’ll try to contact a technician in that field.


StillGotMy1stCar
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Re: Enquiry

Postby StillGotMy1stCar » Sat Aug 03, 2019 12:34 am

I expect the change from 8 ohm to 4 ohm coincides with the change from Germanium to Silicon output transistors in the late 60’s early 70’s. Both types of transistors suffer from thermal runaway but the earlier Germanium are far worse and are generally lower powered. Thermal runaway is where the base emitter junction voltage reduces with temperature rise which in turn makes the transistor conduct more increasing the temperature until the output transistors self-destruct. Using 8 ohm speakers on a Germanium transistor output stage will reduce the power through the transistors.
That’s the basics, it is a bit more complicated than that.
Take the top off and I think you will find two transistors screwed on to a heatsink near the speaker socket, have a look at the numbers written on them, AD161 and AD162 were a popular Germanium complimentary pair of transistors of that era, if it is then 8 ohms it is.
If not let me know the numbers and I will see if I can identify them, Blaupunkt may have used their own numbers that might make identification harder.
Take a photo if you like.
Regards John

les
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Re: Enquiry

Postby les » Sat Aug 03, 2019 9:08 am

Thanks for that John, the technical stuff lost me a bit but taking a look is a plan.


StillGotMy1stCar
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Re: Enquiry

Postby StillGotMy1stCar » Sat Aug 03, 2019 10:02 am

Yes if we can identify the output transistors I should be able work out the power they can handle.

les
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Re: Enquiry

Postby les » Sat Aug 03, 2019 10:44 am

That would be most helpful John.


les
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Re: Enquiry

Postby les » Sat Aug 03, 2019 5:35 pm

John in response to your kind offer I have identified the two transistors you refer to. I can only read the number of the top one which is AD 156, there is a small (d7) above this number. I’ve attached a picture. The speaker socket is at the far right of the image.
B4D84014-D608-4AD6-BAE8-90B6BFAA8CE6.jpeg
B4D84014-D608-4AD6-BAE8-90B6BFAA8CE6.jpeg (508.39 KiB) Viewed 433 times


StillGotMy1stCar
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Re: Enquiry

Postby StillGotMy1stCar » Sat Aug 03, 2019 6:47 pm

Thanks Les, they are indeed Germanium Transistors AD156 and AD157, better spec than AD161/162 but still not great. Play it safe and use an 8 ohm speaker or two 4 ohm speakers in series.
Regards John

les
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Re: Enquiry

Postby les » Sat Aug 03, 2019 7:56 pm

That’s the answer I needed, thanks to your knowledge John. I can now proceed. One more question, speaker wattage is that a consideration?
I want to thank all for their contribution to my post, even Chris!!


StillGotMy1stCar
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Re: Enquiry

Postby StillGotMy1stCar » Sat Aug 03, 2019 9:35 pm

Any full range speaker over 5W will be fine but don’t go too high as they can take more driving for the same volume.
One important thing is the Sensitivity or Efficiency, Measured in decibels from 1 Meter away being driven with 1 Watt.
Remember every 3dB is a doubling in sound output.
Regards John

les
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Re: Enquiry

Postby les » Sat Aug 03, 2019 9:56 pm

Ok I think I’m on the right path now, thanks to some great help :D


StillGotMy1stCar
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Re: Enquiry

Postby StillGotMy1stCar » Sun Aug 04, 2019 12:18 am

Breaking news, I’ve tracked down some circuit diagrams online, both Wolfsburg but with an output stage similar to yours, one using AD161/162 has an output impedance of 5.8 ohms most likely the 8 ohm model as 5.8 ohm speakers are not readily available, and one using the slightly better rated AD156/157 like yours has an output impedance of 4 ohms. The one scanned document looks as if it was stored inside the radio under the PCB.
Blaupunkt Wolfsburg (1024x773).jpg
Blaupunkt Wolfsburg (1024x773).jpg (582.13 KiB) Viewed 377 times
Would be amazing if yours had a schematic tucked between bottom cover and PCB.
So it looks like it is a 4 ohm speaker after all.
It won't do any harm to use an 8 ohm speaker as previously discussed just won't be as loud.
Regards Embarrassed John


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