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 Post subject: Grunow 470
PostPosted: Aug Mon 10, 2020 1:18 am 
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Joined: Jul Wed 01, 2020 12:12 am
Posts: 87
Location: San Antonio, Texas
I hope this is the right forum.

I am working on a Grunow. The previous owner must have some work on it, specifically the E-caps. Is there a way to find out the capacitance, voltage, and number of E-caps needed in this radio?


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 Post subject: Re: Grunow 470
PostPosted: Aug Mon 10, 2020 1:25 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2143
Location: Lafayette, CO
The one nearest the 80: 22mfd., next in line: 33mfd and any more, too. 400-volt ones are fine. Enjoy! Craig


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 Post subject: Re: Grunow 470
PostPosted: Aug Mon 10, 2020 1:42 pm 
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Joined: Jul Mon 26, 2010 8:30 pm
Posts: 28911
Location: Annapolis, MD
???
This shows two 8uF electrolytics:
http://www.nostalgiaair.org/pagesbymode ... 008353.pdf
(There are actually 2 schematics there, and I can't immediately see the difference between them)

Is this the radio?
https://www.radiomuseum.org/r/general_ho_470.html

_________________
-Mark
"Voltage is fun to watch, but it's CURRENT that does the work."


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 Post subject: Re: Grunow 470
PostPosted: Aug Mon 10, 2020 3:11 pm 
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Joined: Jul Wed 01, 2020 12:12 am
Posts: 87
Location: San Antonio, Texas
This is the radio. Thanks!


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 Post subject: Re: Grunow 470
PostPosted: Aug Mon 10, 2020 3:33 pm 
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Joined: Jul Wed 01, 2020 12:12 am
Posts: 87
Location: San Antonio, Texas
pixellany wrote:
???
This shows two 8uF electrolytics:
http://www.nostalgiaair.org/pagesbymode ... 008353.pdf
(There are actually 2 schematics there, and I can't immediately see the difference between them)

Is this the radio?
https://www.radiomuseum.org/r/general_ho_470.html


The power transformer in this radio is oozing goo. My guess is that I need a new one. The old e-caps were 22 and 18. Do you think this contributed to the damaging of the power transformer?


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 Post subject: Re: Grunow 470
PostPosted: Aug Mon 10, 2020 3:51 pm 
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Joined: Jul Mon 26, 2010 8:30 pm
Posts: 28911
Location: Annapolis, MD
First, look at the schematic I linked and see if it matches your set.

Transformer:
"oozing goo" is not unusual---the key is whether it overheats. What you need is a no-load test---easily done by removing all the tubes. Ideally, hook the set up to a Variac so you can control the voltage. At the specificied input voltage, the transformer---with no load---should get only barely warm after 20 minutes or so.

_________________
-Mark
"Voltage is fun to watch, but it's CURRENT that does the work."


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 Post subject: Re: Grunow 470
PostPosted: Aug Tue 11, 2020 6:07 pm 
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Joined: Aug Thu 27, 2009 7:47 am
Posts: 2683
Location: Seattle 98125
In most cases an 80 rectifier is good for up to 32 uF input so that's unlikely to have been the cause of failure, if it is indeed bad. (Although a shorted cap would eventually cause a transformer failure.)

Terrestrial_ET wrote:
pixellany wrote:
???
This shows two 8uF electrolytics:
http://www.nostalgiaair.org/pagesbymode ... 008353.pdf
(There are actually 2 schematics there, and I can't immediately see the difference between them)

Is this the radio?
https://www.radiomuseum.org/r/general_ho_470.html


The power transformer in this radio is oozing goo. My guess is that I need a new one. The old e-caps were 22 and 18. Do you think this contributed to the damaging of the power transformer?


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 Profile  
 
 Post subject: Re: Grunow 470
PostPosted: Aug Tue 11, 2020 6:09 pm 
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Joined: Jul Mon 26, 2010 8:30 pm
Posts: 28911
Location: Annapolis, MD
pixellany wrote:
First, look at the schematic I linked and see if it matches your set.......

_________________
-Mark
"Voltage is fun to watch, but it's CURRENT that does the work."


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