Blaupunkt Frankfurt Deluxe valve car radio questions - UK Vintage Radio Repair and Restoration Discussion Forum

chris wright · 12th Dec 2006, 4:31 pm

Hi I'm new to this list, and read the thread on connecting an MP3 to an old Blaupunkt car radio with interest as I have just bought one and am about to do this. However, I have found the transistor Blaupunkt car radio standard pinouts quoted are different to the valve/transistor older versions. On the 1963 (codeT) Frankfurt Deluxe valve/TR model I have just bought, looking at the socket from the outside, reading clockwise, the connections are
1 = power (6v on mine don't know if its 12v when radio is switched that way)
2 = Amp input
3 = ground
4 = Tuner out (I've just disconnected the original internal link to pin 2 and externalised it in a DIN plug ready for a remote connection)
5 = not connected
My questions:

The centre pin has a wire going to it but I don't know what it does.
Can anyone tell me?

I also want to know if there is any internal aerial trimming for FM sensitivity other than the AM trimmer accessible through the side of the case. I get some engine related background crackle/fizz on FM unless it's exactly tuned in to a strong station. I'm currently working to suppress the car as much as possible but wonder if there is something else I can do to tweak up the FM on the radio?

Does anyone have a schematic or data that might help me?

Chris

GJR 11L · 12th Dec 2006, 10:07 pm

Cannot help with a schematic, but if there's interference on FM, I'd substitute your ignition leads for silicon or carbon string ones, then if the interference is still there there may be something you've missed, but sadly the copper ones that are so much more reliable can cause symptoms similar to those you describe, even when you've suppressed everything.
In fact, if this were a suppression issue, I'd be surprised if it manifested itself on FM, LW on AM is where you'll get most symptoms of that.

Is your dynamo in good physical condition? I once found a strange buzzing on all bands and with tapes on an old Becker machine fitted into one of my '60s motors. The dynamo had a little cap fitted between (positive) ground and the output to the control box, also between the control box to the instrument regulator and (+ive) ground, yet still it caused a problem. Replacing the brushes, re-cutting the commutator and fitting fresh bearings (the last admittedly not due to any electrical fault) got rid of the problem.

One last thing, is there a decent connection from the outer (screen) of the coaxial lead for the aerial to ground? Again, this would be a more noticeable problem with AM, but it's worth checking even on a steel-bodied car where it has been assumed that there must be a good connection.

If a problem on FM only remains, then check the fm tuner head in the set, I take it that the fm head is the valve part of this hybrid? Checking the caps in the fm stages of the set and values of resistors wouldn't be a bad plan while you're in there.

'LIVEWIRE?' · 12th Dec 2006, 11:04 pm

Quote:

Originally Posted by chris wright

Does anyone have a schematic or data that might help me?

I don't have a schematic handy, Chris, but, in answer to the question re Pin 1 of the DIN Socket, the voltage and polarity here is almost certainly the same as that for which the radio is set. Most Blaupunkts of that era had voltage and polarity changeover switches, often in the form of two PCB strips inserted in slots.
As to the centre pin, it MAY be the signal ground(In the later all transistor sets, pin 1 is Chassis-i.e. Battery Negative, and pin 3 is SIGNAL ground)
Another possibility is that it is a switched 'live' (i.e. 6/12v +/- according to the radio voltage & polarity setting). If I can find out I will post the details on the forum. Best not to connect anything to it, without first checking it with a meter.

Regarding FM trimming, in common with just about all radios there is no seperate FM aerial trimmer. The internal alignment of the FM front end is best left alone unless you (a) have the alignment instructions and suitable instruments, and (b) are certain that the tuner is out of alignment. I would basically follow the advice given by GJR11L regarding improving (FM) Reception

Biggles · 13th Dec 2006, 1:34 pm

The noise isn't alternator whine is it? This can be improved by an in line filter on the power supply input to the radio. I would expect this to occur on AM and FM though. It is unusual in my experience to have problems with FM only, as AM is much more susceptible to interference. I remember once that I made the mistake of looking for ignition interference with the bonnet up. It disappeared with the bonnet down, obviously as the earth-bonded bonnet screened the engine compartment. You live and learn.

Biggles.

chris wright · 14th Dec 2006, 5:59 pm

Many thanks to all for the replies. Walter Groer is sending me the Radio's schematic etc from Germany, he's a real star!
I've now run a dedicated feed from the battery to the radio which improves the voltage by 1 volt from the previous 'ignition switch connected' wire. I've fitted a coil suppressor, suppressed plug caps, an in-line choke with a 100mfd capacitor to ground, the aerial earth is showing no resistance to the car body and the radio chassis is earthed directly to the car body. I fitted a speaker crossover filter to attenuate the high frequencies a bit too. It's reduced the crackling to a point where it's OK as long as it's tuned in carefully to a reasonable signal but when the signal gets weaker, the noise is still there. AM is perfect, it's only FM that is a problem. Without the engine running, the radio is absolutely fine on FM too. Walter suggested that the FM alignment might be out a bit, but if it were, would there not be a problem present even when the engine isn't running?
Chris

GJR 11L · 14th Dec 2006, 10:48 pm

Try substituting (temporarily) a set of silicon or carbon leads for the ones with the suppressor caps. If that does the job, then either accept the loss of originality or live with the noise when the copper leads are in use.

I would think that an alignment issue would present, with or without the engine running, as distortion.

You have earthed the aerial to the body, but is your car unitary or on a chassis? If the latter, then it's not unknown for poor earths between the shell and the chassis especially where strips of rubber are present between.
Is the aerial mounted on an upper surface? I've encountered some older cars where the aerial was mounted horizontally underneath the floor, not the best compromise for in-car FM.

chris wright · 15th Dec 2006, 8:03 pm

Thanks for the replies, I've fitted a generator capacitor of 3.3mfd which did help slightly. Now it's really down to the singal strength. On a good strong signal it's fine, but on a weak one it's still crackly. Mostly it's OK. I guess I'm being slightly unfair on it, comparing a 43 year old radio to a moderm stereo in a new car, (even that gives some interference when the signal is weak) so I guess it's about as good as it gets now..
Rgds chris

12th Dec 2006, 4:31 pm	#1
chris wright Retired Dormant Member Join Date: Dec 2006 Location: Newbury, Berkshire, UK. Posts: 6	Blaupunkt Frankfurt Deluxe valve car radio questions Hi I'm new to this list, and read the thread on connecting an MP3 to an old Blaupunkt car radio with interest as I have just bought one and am about to do this. However, I have found the transistor Blaupunkt car radio standard pinouts quoted are different to the valve/transistor older versions. On the 1963 (codeT) Frankfurt Deluxe valve/TR model I have just bought, looking at the socket from the outside, reading clockwise, the connections are 1 = power (6v on mine don't know if its 12v when radio is switched that way) 2 = Amp input 3 = ground 4 = Tuner out (I've just disconnected the original internal link to pin 2 and externalised it in a DIN plug ready for a remote connection) 5 = not connected My questions: The centre pin has a wire going to it but I don't know what it does. Can anyone tell me? I also want to know if there is any internal aerial trimming for FM sensitivity other than the AM trimmer accessible through the side of the case. I get some engine related background crackle/fizz on FM unless it's exactly tuned in to a strong station. I'm currently working to suppress the car as much as possible but wonder if there is something else I can do to tweak up the FM on the radio? Does anyone have a schematic or data that might help me? Chris

12th Dec 2006, 10:07 pm	#2
GJR 11L Heptode Join Date: May 2004 Location: Ellington, Northumberland, UK. Posts: 815	Re: Blaupunkt Frankfurt Deluxe valve car radio questions Cannot help with a schematic, but if there's interference on FM, I'd substitute your ignition leads for silicon or carbon string ones, then if the interference is still there there may be something you've missed, but sadly the copper ones that are so much more reliable can cause symptoms similar to those you describe, even when you've suppressed everything. In fact, if this were a suppression issue, I'd be surprised if it manifested itself on FM, LW on AM is where you'll get most symptoms of that. Is your dynamo in good physical condition? I once found a strange buzzing on all bands and with tapes on an old Becker machine fitted into one of my '60s motors. The dynamo had a little cap fitted between (positive) ground and the output to the control box, also between the control box to the instrument regulator and (+ive) ground, yet still it caused a problem. Replacing the brushes, re-cutting the commutator and fitting fresh bearings (the last admittedly not due to any electrical fault) got rid of the problem. One last thing, is there a decent connection from the outer (screen) of the coaxial lead for the aerial to ground? Again, this would be a more noticeable problem with AM, but it's worth checking even on a steel-bodied car where it has been assumed that there must be a good connection. If a problem on FM only remains, then check the fm tuner head in the set, I take it that the fm head is the valve part of this hybrid? Checking the caps in the fm stages of the set and values of resistors wouldn't be a bad plan while you're in there. __________________ John.

13th Dec 2006, 1:34 pm	#4
Biggles Rest in Peace Join Date: Feb 2004 Location: Hexham, Northumberland, UK. Posts: 2,234	Re: Blaupunkt Frankfurt Deluxe valve car radio questions The noise isn't alternator whine is it? This can be improved by an in line filter on the power supply input to the radio. I would expect this to occur on AM and FM though. It is unusual in my experience to have problems with FM only, as AM is much more susceptible to interference. I remember once that I made the mistake of looking for ignition interference with the bonnet up. It disappeared with the bonnet down, obviously as the earth-bonded bonnet screened the engine compartment. You live and learn. Biggles.

14th Dec 2006, 5:59 pm	#5
chris wright Retired Dormant Member Join Date: Dec 2006 Location: Newbury, Berkshire, UK. Posts: 6	Re: Blaupunkt Frankfurt Deluxe valve car radio questions Many thanks to all for the replies. Walter Groer is sending me the Radio's schematic etc from Germany, he's a real star! I've now run a dedicated feed from the battery to the radio which improves the voltage by 1 volt from the previous 'ignition switch connected' wire. I've fitted a coil suppressor, suppressed plug caps, an in-line choke with a 100mfd capacitor to ground, the aerial earth is showing no resistance to the car body and the radio chassis is earthed directly to the car body. I fitted a speaker crossover filter to attenuate the high frequencies a bit too. It's reduced the crackling to a point where it's OK as long as it's tuned in carefully to a reasonable signal but when the signal gets weaker, the noise is still there. AM is perfect, it's only FM that is a problem. Without the engine running, the radio is absolutely fine on FM too. Walter suggested that the FM alignment might be out a bit, but if it were, would there not be a problem present even when the engine isn't running? Chris

14th Dec 2006, 10:48 pm	#6
GJR 11L Heptode Join Date: May 2004 Location: Ellington, Northumberland, UK. Posts: 815	Re: Blaupunkt Frankfurt Deluxe valve car radio questions Try substituting (temporarily) a set of silicon or carbon leads for the ones with the suppressor caps. If that does the job, then either accept the loss of originality or live with the noise when the copper leads are in use. I would think that an alignment issue would present, with or without the engine running, as distortion. You have earthed the aerial to the body, but is your car unitary or on a chassis? If the latter, then it's not unknown for poor earths between the shell and the chassis especially where strips of rubber are present between. Is the aerial mounted on an upper surface? I've encountered some older cars where the aerial was mounted horizontally underneath the floor, not the best compromise for in-car FM. __________________ John.

15th Dec 2006, 8:03 pm	#7
chris wright Retired Dormant Member Join Date: Dec 2006 Location: Newbury, Berkshire, UK. Posts: 6	Re: Blaupunkt Frankfurt Deluxe valve car radio questions Thanks for the replies, I've fitted a generator capacitor of 3.3mfd which did help slightly. Now it's really down to the singal strength. On a good strong signal it's fine, but on a weak one it's still crackly. Mostly it's OK. I guess I'm being slightly unfair on it, comparing a 43 year old radio to a moderm stereo in a new car, (even that gives some interference when the signal is weak) so I guess it's about as good as it gets now.. Rgds chris