Author Topic: Roberts Radio RD70 receiver challenge  (Read 599 times)

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Offline murwilTopic starter

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Roberts Radio RD70 receiver challenge
« on: November 13, 2024, 05:54:03 pm »
I have a Roberts Radio RD70 that has a constant static sound noticeable at zero or low volume. It is NOT present at the earphone socket so I have traced it down to the small audio amp chip (IC4). I do not have a circuit diagram but I am suspecting this chip or supporting components. There are a few electrolytics close by but I’ve removed a tested them and they seem well within tollerance. The only markings I can see on the audio chip are 01311  2005. It’s a small 8 pin chip but I can’t seem to find that specific one. The earphone out seems to have its own chip amplifier and as the static can not be heard there I’m suspecting this IC4.I have had zero success of locating a schematic

I would be most appreciative if anyone can steer me to a circuit diagram or help me identify IC4. Any help would be very much appreciated. Thank you!
 

Offline FIXITNOW2003

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Re: Roberts Radio RD70 receiver challenge
« Reply #1 on: November 14, 2024, 01:06:35 pm »
as marked 2005 could it be same as RD60 which uses a TPA2005D1DRBR audio chip
 

Offline PA0PBZ

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Re: Roberts Radio RD70 receiver challenge
« Reply #2 on: November 14, 2024, 01:33:39 pm »
There are a few electrolytics close by but I’ve removed a tested them and they seem well within tolerance.
I'm not saying that it's the problem in this case but you can't really test capacitors for that kind of problem, replacing them is the only way to be sure.
Keyboard error: Press F1 to continue.
 

Offline murwilTopic starter

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Re: Roberts Radio RD70 receiver challenge
« Reply #3 on: November 14, 2024, 01:44:16 pm »
Thank you PA0PBZ. A very valid point. The caps are certainly easier to replace than the chip so I’ll follow that path.  Do wish I could find a schematic of just the audio output.
 

Offline FIXITNOW2003

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Re: Roberts Radio RD70 receiver challenge
« Reply #4 on: November 15, 2024, 07:16:09 am »
 

Offline murwilTopic starter

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Re: Roberts Radio RD70 receiver challenge
« Reply #5 on: November 15, 2024, 05:31:29 pm »
Thank you so much. While they are quite different radios these output stages are probably quite similar.
 

Offline murwilTopic starter

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Re: Roberts Radio RD70 receiver challenge
« Reply #6 on: December 09, 2024, 02:00:14 am »
After much poking around I identified it to be a dry solder joint on that output IC.
 
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