[Premium-Rx] TELEFUNKEN E1500 HELP REQUESTED

[Ahmet G.]

Dear Pat,

Try to check the Tantalum and Electrolytic capacitors by simply checking the resistance accross them. I have had experience with German sets using Siemens and Evox/Rifa branded tantalums ( they are Orange or Red colored little box type tantalums ) that were shorted or almost short. Many years of operating under heat and sometimes without operation they get dry and when voltage applied they tend to short or semi-short. Some present very low impedance whereby draining the current which makes the rest of the circuitry fail.  Usually these problem ones are in the power supply.  I have seen one in the IF module of a CHR-531 also.  So a simple continuity check on these orange/red tantalums might reveal bad caps.  

Watch for low impedance components connected accross these caps, such as diodes, transistors and low impedance resistors which might make it look like a short.  Then a reverse check is needed.

If all caps check fine and  you still need the manual, I  will need to see 
if I can get some details for you. 

For German to English translation, you may want to use Alta Vista Babel Fish translation on the web.  It does help a bit.

Good luck.

Ahmet

> 
> Greetings all,
> 
> I have just got a (1974) model (R1500) Telefunken E1500 HF Receiver in  for
> repair that a friend of mine bought from a dealer in Germany last  year.
> 
> The receiver is totally deaf. It was working perfectly and suddenly just
> lost all received signals.
> 
> I have the book in German but there are no circuits/schematics at all  and
> only a simple block diagram is available. That, coupled with the fact that
> custom DIN extenders are required, makes fault finding difficult!
> 
> At first I suspected the AO1500 synthesiser.The First Local Osc  output gives
> 42.2-72.2MHz at approx -10dBm .The Second LO gives  42.00MHz at -15dBm into
> 50R. Maybe this is correct?
> 
> It would appear that neither the First or Second Mixers in the HT1500LH RF
> Front End module are working at all. I am beginning to suspect a voltage rail
> is  missing or the receiver is totally muted, however the NS1500 power  supply
> seems to be working correctly and appears to give the  correct 
> voltage outputs.
> 
> Can anyone provide a circuit/schematic of the HT1500LH RF Unit Module
> please? or point me in the direction of any further information - 
> before I  revert
> to drink!.
> 
> I just wish I had been allowed to take German at school 45 years ago  instead
> of Latin. After giving up Racals the R&S and AEG/Telefunken  receivers here
> are infinitely more challenging and, to me, represent  the peak of late
> Analogue design. (The Racal peak was the RA1779,  RA1784 and RA3701.)
> 
> All info gratefully received. Thanks,
> 
> Pat G3YFK
> 


=
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