I have been working on an early Philco model 90 Baby Grand cathedral (two 45 output tubes and a local/long distance switch) and have a question about an unmarked capacitor on the schematic. On the schematic there is a capacitor off the primary of the first IF transformer (see number 13) going to ground. This capacitor is not listed in the parts list. Actually, the capacitor does not even have a number by it on the schematic. There is no sign of this capacitor ever having been on the chassis and it is not drawn in on the location of parts under the chassis. Does anyone know where it was located or why is it on the schematic but not the parts list? Thank you for your help, I have attached the schematic for reference. Also, if anyone has a high resolution photo of the chassis of an early 90 It would really help. There was a fair amount of change to the chassis before I received it and I am trying to get it back to the original appearance and layout.
Here's a schematic that Ron has marked up (found on the online schematics on philcoradio.com) that should be more accurate and clearer than the Riders copy you have. Hope it helps. Other's who have actually worked on this version of 90 may chime in as well.
(03-31-2016, 12:40 PM)morzh Wrote: There was a thread here about 2-3 years ago about that cap. It is nowhere to be found. It was removed from the sch on Ron's site.
Thank you for the schematic. I guess I will just power up the set and see how it goes. May play around with a few different values for the mystery cap and see how it sounds.
By the way if there is a high Res photo of the underside of an early 90 chassis out there that would be helpful too.
It's interesting to note that this cap is missing on Ron's drawing. It looks like an rf bypass cap for the b+ voltage on the plate circuits. (the D circuit) With the poor drawing quality it's hard to be sure . It probably is not critical and was added as a precaution to keep rf off that line. I would think a value of .1 to .47uf was used.
!!!!!!!!!!!!!!!!!!!RESISTANCE IS FUTILE!!!!!!!!!!!!!!!!!!!!!!
/\/\/\/\/\/\/\/\/\
(04-01-2016, 03:03 PM)Tmorzh Wrote: Well....it might be agood cap (shown with an error of not in fact connectingto the B+, no tiedot) but it is immaterial - it is missing in the chassis.
I suppose I should clarify. There was no cap where it seems like it should be but there was extensive prior work with multiple non stock caps so it is a little hard to tell. I restuffed the metal cap blocks and scavenged bakelite blocks from a parts set and reatuffed them too to try to get back to factory appearance.
Sounds like it will not burn down the house to power up the set without the mystery cap. Thanks again to everyone for their help. I will post a pic of the chassis when I get a minute.
