Crosley 68CR restore

[DuncanIdaho]

This is my first DIY restore project involving tubes. I've done several solid state repairs but never anything this old. The unit and cabinet are in excellent condition and I was able to revive the turntable mechanics. Here is a link to the NA info.

http://www.nostalgiaair.org/PagesByModel/589/M0003589.pdf

The turntable works under it's (the 68CR) power which is a nice start IMO. The issue is that there is a hum that is instantly noticeable when switched on and gets maybe 2-3 times louder if left on. If turned off or a few moments and turned back on it starts out at a higher level the shorter period of time it's left off before switching back on.

I have temporarily removed the FW rec tube (5Y3 GT) which seems to allow the unit to stay on and operate the dial lamps and turntable. I have zero experience with tubes but this particular tube was too hot to touch after only a few moments of being on and humming so I pulled it out.

Any recommendations or suggestions of where to start would be appreciated. I have read that many suggest starting with caps and resistors... Could this tube be bad, should it get that hot?
Thanks,
-Duncan

[Chris Hornbeck]

Electronics this old will have power supply electrolytic capacitors that are half a century past their expected lifetime. If they have been brought back up to working voltage very, very slowly and if you're very lucky, they might still work, but it sounds like that isn't the case here.

Several good folks sell replacement multisection electrolytics, including Antique Electronics and possibly even our own (and wonderful) Jim McShane or Triode Electronics.

All good fortune,
Chris Hornbeck

[DuncanIdaho]

Thanks Chris,
I'm very excited to get this project started even if it may take me some time. I wanted to post some pictures of the electronics box. I removed it from the cabinet and was surprised to see that (at least to me) it is in surprisingly good shape and clean for something with and open bottom.




It sounds like most people are recommending to start by replacing the electrolytic (paper caps, looks like about 12) capacitors and go from there... is that your recommend also?

Thanks again.
-Dillon

[kevinkr]

You've got it, replace all electrolytics and paper caps. The paper types can be replaced with inexpensive polypropylene types of the closest standard (modern) value to the ones that are in there. Check all resistors as well.

Normally the rectifier and output tube will run hot enough that you will not be able to touch them in normal operation.

[DuncanIdaho]

Thanks Kevin,

I'm having trouble finding a good match for the .00025 µF paper caps online. I can find .001 µF in a close enough voltage but that seems way to high capacitance?

What do you think?

Thanks,

[Frank Berry]

.00025uF = 250pf. 270pf is a standard value and should work well for you.