I just brought home a 37-660 and although I've worked many radios I would like some input from anyone who has tackled one of these. It is obvious sections of the radio will need to be removed in order to access caps/resistors that need to be changed.
Any suggestions as to where to begin? Seems like one will almost have to replace most of the caps/resistors before firing the thing up (not one or two and then check operation). Also any hints/problems on removing the dial etc?
I have the schematic from NA and my quick review of things find different values for some caps. Are there different versions?
BTW, this particular radio has never been serviced except for tube replacement. All of the compnents are original. Must not have been played for a long time.
Hi Marv and welcome to The Phorum!
Changing all caps is a must and also checking and replacing any resistors that are outside the +/-20% of nominal values, as listed in the parts list for the set. A great performer when back running again.
Make sure you have a good schematic and alignment info, including Production Change Notes, many which Rider's failed to re-publish. Your set also could be a different Code version chassis. Components many times were changed in different Run numbers as well.
Hello, Marv: I just happen to be working on a 37-660 right now, which is very similar to your 665.
Caps #60 and #68 are .003mFd, 1000V rated caps. Rather than take a chance with my poly 630V caps, I ordered some .0033/1600V replacements. I don't think you need to go any higher than 1000V, but the 1600Vs were available to me so I went with them.
The rest of your paper caps should be fine replaced by the 600/630V varieties offered by many vendors. Your electrolytics should be fine replaced by 450V varieties. NOTE that in addition to the two 8mFd electrolytics located near the power transformer, you also have a small electrolytic can on the RF deck that houses 1, 2, and 3mFd caps. I strongly recommend you replace these, as all 3 are in contact with B+.
In order to replace the can and the paper caps in/on the RF deck you will have to remove the deck to get at them. This is not a simple task. Make sure you diagram and mark the wires as you de-solder them.
Thanks to all. Technically I'm a new member because it has been a long time since I logged on and had to re-registor. I used to know where to find the info on the bakelite caps but have forgotten. Can anyone direct me to it? Thanks again. Also thanks for the heads up on the high volatage caps.
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Thanks for the information. Am currently identifying/locating all of the parts so I can get my order out.
I see there is a service bulletin 257 for the 37-660. To increrase base response they changed C77 from .008 to .006 and changed resistor R36 from 51k to ??? I cannot find the value for the new part number 33-340339. Can anyone help?
(03-03-2012, 05:40 PM)marv Wrote: I cannot find the value for the new part number 33-340339.
It's right there in the part number:
340 = 40,000 ohms. The multiplier, in this case being 3 for three zeroes, followed by the first two digits of the value, 40. 339 means 1/2 watt.
Read about it here:
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Thanks for providing a quick link to the schematic.
Go with what is in the radio. Generally the best policy. In this case it appears with both resistors at 240K, it gives better filtering/removal of the RF component with a slight reduction of the audio component reaching the volume control.
Thank you Richard. Was going to mention that when stuffing one of the 8ufd lytics, when I cut into the can to my suprise it was FULL of electrolite. I never saw this before in a 75 yr radio. This can't be too common can it?