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RE: Dynaco FM3 hum

68.108.173.65

ltman

In Reply to: RE: Dynaco FM3 hum posted by fredtr on November 26, 2023 at 12:37:59

10-4, thanks!

Follow Ups:

RE: Dynaco FM3 hum - 6bq5 10:48:21 11/27/23 (0)
The old electrolytic PS caps are notorious for going south!
if you want to keep the appearance, disconnect the can and place the individual caps under the chassis-
I have even seen detailed instructions for inserting them into the can so it looks 'original' -
Not worth it in my opinion, but...
Have fun!
Happy Listening
RE: Dynaco FM3 hum - fredtr 15:29:54 11/26/23 (1)
You're welcome. Tube equipment is very forgiving. I'm guessing you don't have a variac. As an alternative, when you bring it back up, add a light socket in series with one of the ac lines going in. With a 100 watt bulb in series, the maximum the tuner will draw is less than an amp, low enough that you can observe, measure voltages if you have volt meter, before running it at full voltage. How intense the bulb glows will also tell you if you have a problem. If it looks like 100 watts, you have a short. It should be about 1/3 as bright as normal.
- RE: Dynaco FM3 hum - ltman 22:53:22 11/27/23 (0)
  that's helpful info, thanks.
  
  I do have a variac and used it to slowly bring up the voltage for the first couple hours.
  
  And a "load lamp" which I will use as testing proceeds. Aside from the big quad cap, I have a "restore" kit from the bay with a number of small caps and components.
  
  I will not do the voltage tests described in the tuner manual though. Not going to mess with 400+ volts. I have to put a kid through college the next few years so I can't take the risk of doing something stupid yet...

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