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Old 4th June 2015, 12:52 AM   #1
drizzle is offline drizzle  Singapore
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Default R601P Tube Radio

Hi All,

I have a R601P Tube Radio that works well for about 40mins and then it will distort and goes into humming and scratchy noise, If I switch it off and cool down for a short while it will works again,

Before I go and buy the tube replacement, I would like to have some opinion first. I have ruled out the tuner fault as when I turn to Aux position and listen to my iPod, it did the same thing after 40mins. Potentially it could be the output amp capacitors that is faulty or a faulty tube.

Any advice would be very much appreciated. Below is a review of the R601P that was reviewed by 6Moons. 6moons audio reviews: Quest for Sound R601P tube radio

Thanks
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Old 4th June 2015, 01:12 AM   #2
kevinkr is offline kevinkr  United States
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Why not contact the manufacturer for assistance rather than guessing?
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Old 4th June 2015, 04:30 AM   #3
drizzle is offline drizzle  Singapore
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Quote:
Originally Posted by kevinkr View Post
Why not contact the manufacturer for assistance rather than guessing?
Yup did email to the manufacturer but no reply since.
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Old 4th June 2015, 08:50 AM   #4
DF96 is offline DF96  England
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The pictures suggest it is not a tube radio, but a solid-state radio with (perhaps) a tube output stage. It could sound as bad as any 1950s radio.

The symptoms you describe are consistent with the output valves going into thermal runaway. Possible reasons:
1. poor design, running them too hot
2. gassy valves - these may settle down or may get worse with age
3. leaky coupling capacitor to the valve grid - unlikely in something new (but it is Chinese!)
4. grid leak resistor too high in value

Keep an eye on the valve voltages, especially grid and cathode.
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Old 4th June 2015, 11:55 PM   #5
drizzle is offline drizzle  Singapore
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Quote:
Originally Posted by DF96 View Post
The pictures suggest it is not a tube radio, but a solid-state radio with (perhaps) a tube output stage. It could sound as bad as any 1950s radio.

The symptoms you describe are consistent with the output valves going into thermal runaway. Possible reasons:
1. poor design, running them too hot
2. gassy valves - these may settle down or may get worse with age
3. leaky coupling capacitor to the valve grid - unlikely in something new (but it is Chinese!)
4. grid leak resistor too high in value

Keep an eye on the valve voltages, especially grid and cathode.
Thanks DF96. Yes, the radio itself is not tube but just the output stage is tube. I have ordered new replacement tube and waiting for it to arrive.
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Old 8th January 2016, 03:41 PM   #6
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Hi Drizzle,

Did you ever get the issue sorted? Sounds like there's a bad design in the output section. I heard a few other people having the same complaint. Probably the output tube is not properly biased.
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