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Author Topic: Yeasu "A" gets a capendectomy  (Read 2749 times)
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N3DRB The Derb
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« on: December 16, 2008, 08:57:22 PM »

The 2 main filter caps in the FT 101's never seem to get changed out. 100uf@500 vdc - after I saw some bubbling and a small amount of drippage under the terminals on mine  I decided to test. They both were 20~22 MEG Resistors instead. Gotta go.

I had some 1" diameter 180 uf@500 volts TCI units with clamps and surgery was performed and successfull! A small amount of drillage on the chassis had to be performed to mount the smaller clamps.

that out of focus cap in the before picture was found to be a 250K!! resistor. It has since been changed out. There were 2 others almost as bad that are now changed.

The FT 101's seem to be in that area of time where not too many folks consider to think that the electrolytics need changing. A 35 year old cap is no better than a 45 year old cap if it's bad.

Early riceboxes are just as much in need of cap checking n replacement as any other BA. ( and yes, the FT101 is a BA IMO. )




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WA1GFZ
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« Reply #1 on: December 16, 2008, 09:34:52 PM »

Derb,
Danger man! Those 470K resistors are not rated for much voltage. Good chance they will open and you will never know it. Go to a resistor vendor like Dale Vishay and check the rating. I bet not over 250V.
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N3DRB The Derb
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« Reply #2 on: December 16, 2008, 11:53:48 PM »

well the voltage actually across them each would only be +300. Teh are 1% carbon film units from this place:

http://www.tubedepot.com/resistors.html

I buy from this place because they ship FED Ex and are located a few miles from the main Fed Ex hub in Memphis, TN.

so the shipping speed is like lighting. They literally just roll a van to the central FedEx hub each day.

I always use a bangstick..... I would have been dead long time ago if not. If they pop, they pop. I'll double it up, but thats what Yeasu had.


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WA1GFZ
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« Reply #3 on: December 17, 2008, 10:41:22 AM »

I would double them up with 2 in series. 300V  steady state is quite high for a film resistor.
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