Huldra8 poor FM rec...
 
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Huldra8 poor FM reception

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jvanselm
(@jvanselm)
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Joined: 2 years ago
Posts: 4
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Gentlemen, have owned a Huldra 8 for a number of years, over time I have replaced a number of caps and the output sound is great. The unit has never worked satisfactorily on FM while FM reception on other radios in the same location is reasonable. Originally when I started unit first time, when selecting FM a regular, repeating  loud crack sound came through with the music. Selecting mono fixed the crack problem. I assumed the problem had something to do with the push button or stereo indicator light so I disconnected the blue and black cables coming from the Stereo decoder(to the push button assy) This fixed the cracking problem and the stereo indicator functioned when listening to tape or phono. The low volume output on FM remained and of course stereo detection no longer functions. As I do not use FM normally the issue ended up in the too hard basket. However I really like to get the system to work correctly so I am wondering if there is someone on the forum that could help me fault find the problem. I have the Huldra 8 wiring diagram and a copy of the service manual. Also have access to a basic Hantek scope (20mHz, 20mV) I use my laptop to generate audio frequency signals via the headphone outlet, and the scope reproduces these signals Ok ( at voltages in the 100 mV range)

AM reception OK with good volume at 25% volume, FM volume setting has to be increased to 60% to get some volume.

I have a basic understanding of the functionality of the components on the PCB no1 and the IF board no.2. In the service manual I have the diagram of how to remove the FM PCB. This diagram shows the various interconnections. I have hooked up the scope to the d contact on FM PB (no.10 in the wiring diagram) and to the connection on the AM/FM slider switch. Get 48.6V DC on both contacts. (flat trace) This while the radio is playing at 60% volume setting.

Before I remove the FM board I wonder if someone could recommend some other measuring points I could utilise to narrow down the faulty component(s) I would expect to pick up a 10.7 mHz /7-8mV coming to ECH81  but unsure where to connect the scope.  Also I am not sure if it is OK to earth the scope probe on the radio chassis or should it be grounded on the PCB.

 

Hopefully there is an expert on the forum that can help me on my way. Greetings from New Zealand


   
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