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 Post subject: Telefunken Dominante 5094Wk - buzzing
PostPosted: Nov Sat 16, 2019 6:30 pm 
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Joined: Nov Sat 16, 2019 6:05 pm
Posts: 4
Hi, I'm new to this forum. I'm looking for some help, please. I was lucky enough to find this lovely Hi-Fi. It worked wonderfully at first, then it developed a loud buzzing noise coming from the speakers. I turned it off for a couple of days, then when I turned it back on it worked great for a few days before the loud buzzing came back. Can anyone please tell me what might be causing the buzzing. Any help would be much appreciated. Thanks, Laurie


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 Post subject: Re: Telefunken Dominante 5094Wk - buzzing
PostPosted: Nov Sun 17, 2019 2:45 am 
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Joined: Jan Mon 16, 2012 4:15 pm
Posts: 5908
Location: Near Brandon, Iowa
Some questions:

(1) Is the "buzz" on AM radio only, or both AM and FM? Or is it only present when you are playing a record?

(2) Is the sound present when the volume control is set at minimum; or does it get louder as
you increase the volume setting?


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 Post subject: Re: Telefunken Dominante 5094Wk - buzzing
PostPosted: Nov Sun 17, 2019 4:51 pm 
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Joined: Nov Sat 16, 2019 6:05 pm
Posts: 4
Hi Lorenz200w,
Thanks for your response! It sounds like you know what you are talking about, your help is much appreciated.
The buzz is there all the time and is consistent regardless of the volume setting.
I forgot to mention the the right speaker (facing the unit)has always had a slightly lower volume than the left one as well.
If the unit is plugged in yet turned off, I can hear a very slight electrical buzzing coming from the back of the unit as well. So I always unplug between uses.
Thanks in advance for your help,
Laurie :)


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 Post subject: Re: Telefunken Dominante 5094Wk - buzzing
PostPosted: Nov Sun 17, 2019 5:56 pm 
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Joined: Jan Mon 16, 2012 4:15 pm
Posts: 5908
Location: Near Brandon, Iowa
A constant noise at all volume settings and all modes- coming out of the speakers- is a classic symptom of failed filter capacitors in the B+ supply. But in the interest of accuracy, this sound would actually be a 120 Hz "hum" (the set has a power transformer and a full wave rectifier).

It's possible for the power transformer in this model to fail in a way such that the noise emanates directly from it (not the speakers). If the transformer isn't behaving badly in other ways (i.e., overheating, dripping melted wax, producing smoke) there's a good chance it can be repaired easily. The sound this fault makes can vary from a barely-audible hum to a full-throated buzz.

It's very odd that the unit is producing noise when turned off. That might be a sign of a bad power switch in the radio, or a miswire/short in the phonograph turntable switch. Good plan to unplug it until the problem can be found and fixed.

Unless you have some test equipment and electronics service experience, you are not likely to be able to find and fix the actual problem. I recommend that you try to find a local tube electronics club that would be willing to walk you through the diagnostic steps.


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 Post subject: Re: Telefunken Dominante 5094Wk - buzzing
PostPosted: Nov Mon 18, 2019 1:07 am 
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Joined: Nov Sat 16, 2019 6:05 pm
Posts: 4
Hi again,
Great information, thank you. I have attached the schematic that I found, also, a picture of the inside, if you could take a look please?
It looks to me that the biggest transformer is dripping a bit but I'm not sure which capacitor would be the one that you mentioned. I have a friend with a soldering iron and a multimeter, who is also mechanically inclined but, he doesn't know much about electronics. He is happy to tackle changing components if you could help me a little more please? Is there a way to test the capacitor?
Thanks again for your help, Laurie.


Attachments:
telefunken inside.JPG
telefunken inside.JPG [ 437.3 KiB | Viewed 127 times ]
telefunken_dominante_5094wk_sch.pdf [2.64 MiB]
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 Post subject: Re: Telefunken Dominante 5094Wk - buzzing
PostPosted: Nov Mon 18, 2019 9:05 am 
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Joined: Mar Thu 21, 2019 3:53 pm
Posts: 86
It's a good practice to use a Dim bulb tester during tests as it will protect the radio from short or overload. Disconnect the wires from the bridge rectifier and test it with your Ohmmeter. Mark the cables where they were connected. If it reads good then reconnect it and disconnect the 2 filter caps (C161 & C162) . Mark the cables again. You may use crocodile jumpers to connect the new caps to the circuit just for the test. If you have in hand a dual cap, don't forget to ground the metal can if there is not a 3rd terminal for the ground. If the old caps are the cause of the buzz then with the new caps the buzz will go away.


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 Post subject: Re: Telefunken Dominante 5094Wk - buzzing
PostPosted: Nov Mon 18, 2019 3:00 pm 
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Joined: Jan Mon 16, 2012 4:15 pm
Posts: 5908
Location: Near Brandon, Iowa
The capacitors in question (C160 and C161) are part of a dual-cap unit. It is a cylindrical aluminum can which is at the 11 o'clock position relative to the power transformer in the photo. There is what appears to be another
electrolytic cap next to it (maroon cardboard cover) but I can't tell if that was an original part or one that was
installed in the course of a later repair.

You probably can't find an exact physical replacement for the dual cap- that's OK, though: you can wire in two axial-leaded discrete caps after disconnecting the original part. The original part can be left in place if desired, but it must be disconnected.

It's important to choose replacement capacitors with the proper capacitance rating and an adequate voltage rating. This info is printed on the original part(s).

This radio uses (by my count) a total of eight polarized electrolytic caps... it's most important to replace C160 and C161 before you power up the set again, but the remaining six caps should be replaced eventually. Also, there appear to be three nonpolarized electrolytic caps in the unit which are candidates for replacement... these are less critical.

Testing the capacitors on a device this old (60 years) is generally pointless- it takes more effort to test them than to simply replace them; and they aren't fantastically expensive, either.


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 Post subject: Re: Telefunken Dominante 5094Wk - buzzing
PostPosted: Nov Mon 18, 2019 6:36 pm 
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Joined: Nov Sat 16, 2019 6:05 pm
Posts: 4
Thanks again! I will look for someone with electronic experience and give him your wonderful information. This has been a great experience for me. Thank you, Laurie


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