05-17-2020, 09:56 AM
Welcome to the Phroum Neo6425,
>I'd like to bench test this speaker. How would I go about doing that?
Testing the fc and the primary of the output transformer is good. If the fc is open it's time to find a replacement spkr. Opt can be replaced separately.
One other important test is to GENTLY press on the paper cone on either sides of the spider (the round thingy @ the center). The cone should move in and out freely with any roughness. If there is roughness this can be the cause of distortion @ low volume.
In terms of caps I took a few minutes to peruse the parts list and this is what I came up with. All values are in Mfd unless otherwise noted. Ecaps are 450v, mylars 630v, and mica 500v. The mylars and micas may not need to be this high of a voltage rating depending on the circuit but this is the common rating.
1 .25
1 .3 (this is not a standard value so it will take a couple of caps in parallel to equal .3)
1 .003
2 10 eletrolytics
1 22 eletrolytic
2 .015 (X-Y type if you like)
2 .15
5 .02
5 .1
2 .05
3 110mmfd (100 is fine)
I would make the suggestion that it would be more simplistic to go stage by stage and would start at the lower right end of the schematic. That would be the power supply section. There's about 6 caps that need to replaced in that section. Tip there are three cardboard covers on the two eletrolytic cap (cans) don't lose or destroy them you'll need them latter.
Thank to Nathan here's a little bonus for your 620. https://philcoradio.com/phorum/showthread.php?tid=17820
GL on you new adventure!
ps you said you liked to read!
>I'd like to bench test this speaker. How would I go about doing that?
Testing the fc and the primary of the output transformer is good. If the fc is open it's time to find a replacement spkr. Opt can be replaced separately.
One other important test is to GENTLY press on the paper cone on either sides of the spider (the round thingy @ the center). The cone should move in and out freely with any roughness. If there is roughness this can be the cause of distortion @ low volume.
In terms of caps I took a few minutes to peruse the parts list and this is what I came up with. All values are in Mfd unless otherwise noted. Ecaps are 450v, mylars 630v, and mica 500v. The mylars and micas may not need to be this high of a voltage rating depending on the circuit but this is the common rating.
1 .25
1 .3 (this is not a standard value so it will take a couple of caps in parallel to equal .3)
1 .003
2 10 eletrolytics
1 22 eletrolytic
2 .015 (X-Y type if you like)
2 .15
5 .02
5 .1
2 .05
3 110mmfd (100 is fine)
I would make the suggestion that it would be more simplistic to go stage by stage and would start at the lower right end of the schematic. That would be the power supply section. There's about 6 caps that need to replaced in that section. Tip there are three cardboard covers on the two eletrolytic cap (cans) don't lose or destroy them you'll need them latter.
Thank to Nathan here's a little bonus for your 620. https://philcoradio.com/phorum/showthread.php?tid=17820
GL on you new adventure!
ps you said you liked to read!
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
