1. Home
  2. Electronics Repair
  3. Rumbling noise from Grundig Receiver

Rumbling noise from Grundig Receiver

My trusted old Grundig R-7500 Receiver (25 years old) suddenly started emitting very loud rumbling noise on both channels from the speakers (sounds like a large lorry unloading rocks and boulders). The rumbling starts after some minutes of operation and is not affected by the volume control. Music still can be heard behind the rumbling.

Could this be some of the electrolytic capacitor finally becoming to old? Does anybody has an idea?

Thanks

Tolux

Reply to
tolux
Loading thread data ...

As rumbling is on both channels then very likely failing electrolytic, try ac voltmeter on main DC rails at the caps or a crystal earpiece.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

formatting link

Reply to
N Cook

Sounds to me like the filter caps in the power supply are dying. It would sound like a 60 cycle loud hum.

Reply to
maradcliff

On Fri, 03 Nov 2006 01:45:33 -0800, tolux Has Frothed:

Could be but it takes some diagnostics to find out for sure.

--
Pierre Salinger Memorial Hook, Line & Sinker, June 2004

COOSN-266-06-25794
Reply to
Meat Plow

snipped-for-privacy@UNLISTED.com schrieb:

No, it is not a pure 60 Hz (or 50 Hz in my part of the world ;-) sound. It is completely random rumbling noise (like I already described, like a lorry unloading rocks). Sounds more like someone scratching a needle over an old LP (yes, I am that old ;-).

Reply to
tolux

You can get that sort of noise in a failing electrolytic, i've always assumed it is a local hotspot causing bubling in the electrolyte.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

formatting link

Reply to
N Cook

these sort of noises are usually down to a bad connection somewhere

NT

Reply to
meow2222

So it's solid state? Bad resistor/transistor? Signal tracer and generator will track it down.

--
++++++++++++++++++++++++++++++++++++++++++++++++++++
+ Required crap appended to avoid restrictions imposed by brain   +
+ damaged idiots. 
+
+ Server Response: '441 Posting Failed (Rejected by POST filter)', +
+ Port: 119, Secure(SSL): No, Server Error: 441, 
+
+ Error Number: 0x800CCCA9 
+
++++++++++++++++++++++++++++++++++++++++++++++++++++
Reply to
Homer J Simpson

Thanks to everybody who answered.

I also suspected the electrolytic caps in the power supply, but could not explain the funny noises. I expected humming. The explanation with the boiling hot spots seems likely. I will replace the caps. Furthermore I will probe the PCB to look for cracks or loose connections.

Reply to
tolux

tolux spake thus:

You might also want to check for a noisy transistor. I had a similar problem with a solid-state 70s-vintage receiver; turned out one transistor was bad. I was able to easily find it since it had gone microphonic, and tapping it produced an interesting banging noise in the output.

--
Just as McDonald's is where you go when you're hungry but don't really
care about the quality of your food, Wikipedia is where you go when
you're curious but don't really care about the quality of your knowledge.

- Matthew White's WikiWatch (http://users.erols.com/mwhite28/wikiwoo.htm)
Reply to
David Nebenzahl

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.