Skilled radio assistance please!

[TNC]

I have been successfully resurrecting early car radios - mostly Telefunken and Blaupunkt over the past few years. (self taught amateur!)
I’m able to deal with power supplies (vibrator and associate components) and the AF side of the radio units with good results…but the latest radio unit has me foxed.
At first I wondered whether it was frequency changer failure but I placed another AM set next to it and the FC can be heard working. (Valves have all been checked out.)

Radio performance is really poor but after careful tuning I realised that very strong signal stations are just about audible between oscillations and hash noise.
I have checked as much as I can without resorting to unsoldering the rats-nest of cap/resistor wiring which is all in a very small space…but those components that can easily tested are OK.

I am therefore wondering whether there is an experienced engineer (with better diagnostic kit) and within reasonable reach who would be prepared to take this on?  (I’m happy to double box and mail if that would be required.)

Power supply requirement would be LT 6v @ 3A and. HT 220V at <75 ma.

Obviously very happy to cover all costs…it would just be really helpful to get it sorted.

Not wanting to offed Mods. but assume a PM to me would be Ok

Many thanks,  Trevor

[Murphyv310]

Hi Trevor.
What make and model is it and what is the valve lineup?
Not saying I'd do it but perhaps can guide you in the right direction.

[TNC]

Hi Trevor,

Thanks for your response.

It’s a Telefunken IA 51 / ID 51.
The lineup is ECH42, EAF42, EAF42 and EL41.

I’ve sent you a PM.

Trevor

[Mike Watterson]

Ha, they were in VW beetles, hence 6V option. One of the last cars in UK on 6V?
https://www.radiomuseum.org/r/telefunken...a51_v.html

An amazing car radio. I guess it used a 6V vibrator for HT. Not synchronous rectifier by slave conacts in vibrator as there is metal rectifier listed. It will be on the way out if not dead. Some 1N4007s needed. For this application additional series resistors probably not needed.

[Murphyv310]

Hi.
The radio is now being sent to me for a look over. Trevor has done a fair amount to it so perhaps another pair of eyes will pinpoint the trouble.

[Kalee20]

Let us know the outcome Trevor! (Phantom twiddler upsetting alignment would be my bet, if there's background hash!)

[Murphyv310]

Hi.
Yes I'll be updating the thread in due course and most likely do some YouTube videos.
Watch this space

[PerdioPal]

Was there ever a "standard DIN" all valve car radio? I am sure I had one many years ago. I know there were transistor output ones using 12V valves, what about vibrator (proper HT) and valve output?

[Murphyv310]

Hi.
Certainly no standards back in the day. My dad had a 1951 Ford V8 Pilot with a standard fitted radio, it had switched tuning which was rather pointless if undertaking a long journey. I've come across many car radios with a vibrator like in the Pilot which was a 6 volt system, it drew around 10 amps half of what the dynamo could deliver.

[Mike Watterson]

Was there ever a "standard DIN" all valve car radio?  I am sure I had one many years ago.  I know there were transistor output ones using 12V valves, what about vibrator (proper HT) and valve output?

Actually they were regular valve run at 12 to 14HT. The "12V" ECH83 is just a rebadged ECH81 (not even specially selected) and run at about +1V bias.
https://www.radiomuseum.org/forum/ech83_qru.html#3

A number of other valve work at 12V HT with suitable bias. I think EF89, ECC82 etc.

DIN mount car radios were probably after the valve era.

Founded in 1917 as the Normenausschuß der deutschen Industrie (NADI, "Standardisation Committee of German Industry"), the NADI was renamed Deutscher Normenausschuß (DNA, "German Standardisation Committee") in 1926 to reflect that the organization now dealt with standardization issues in many fields; viz., not just for industrial products. In 1975 it was renamed again to Deutsches Institut für Normung, or 'DIN' and is recognised by the German government as the official national-standards body, representing German interests at the international and European levels.

—Wikipedia.

There were / are many DIN standards (DNA from 1926 to 1975). The 3 and 5 pin connectors on 1950s German radios etc later became DIN connectors. Later there was the mini-DIN.

So valve car radios might have referenced various DNA standards, I never heard of an overall one, or later DIN for transistor car radios. The mounting was only one DIN standard. Measurement of distortion, power etc would be a different DIN, connectors a third set of DIN standards.