Difference in Schematic and chassis cap values? - Printable Version
+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Various and Sundry Categories (https://philcoradio.com/phorum/forumdisplay.php?fid=37)
+--- Forum: Other Radios (Non-Philco) (https://philcoradio.com/phorum/forumdisplay.php?fid=12)
+--- Thread: Difference in Schematic and chassis cap values? (/showthread.php?tid=18346)
+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Various and Sundry Categories (https://philcoradio.com/phorum/forumdisplay.php?fid=37)
+--- Forum: Other Radios (Non-Philco) (https://philcoradio.com/phorum/forumdisplay.php?fid=12)
+--- Thread: Difference in Schematic and chassis cap values? (/showthread.php?tid=18346)
Difference in Schematic and chassis cap values? - harleythatcher - 05-02-2018
First post! Been reading for quite awhile but now need a little guidance. My background: Retired Navy electronics type however that was 25 yrs ago. So it has been a relearning curve. I have retained my soldering skills thru several other hobbies over the years.
I am currently refurbing a Molorola 61-CA. I know this is a Philco forum but I have 3 Philco's on deck. I choose the Motorola as my first project mainly because I rx it first. lol
So I have found several cases where a cap in the chassis will have a different value than the schematic? Do you go by the schematic? or is it a case by case situation? On one of them the cap in place was a different manufacture so I am going to assume someone repaired and that was what they had. In that case I will go with the schematic. But for the ones that appear original but don't match is my question I guess. Thank you for your time and help in advance. I am enjoying the process so far and am looking fwd to getting to the Philco's. My favorite I think will be my 610B. I listen to SW often so this will be a treat I think.
Tt
KK4KRU
RE: Difference in Schematic and chassis cap values? - Phlogiston - 05-02-2018
I have seen an audio site that basically says that the bigger a cap is, the better. Not true, except occasionally, but in audio circuits, bypass and just about anything that ISN'T tuned, reasonably bigger is OK. It is generally advised not to go smaller. AGAIN this does not apply to tuned circuits. So if you have a choice between a .05 cap and a .047 - don't worry about it. If the bypass cap is .33 and all you have is a .5, that is OK too.
So unless it is an IF or tuned RF circuit, it isn't a big deal.
Filters in the power supply usually benefit by some increase in capacity. But never exceed the rating on your rectifier/first filter. Putting a 100uf where an 8uf was might as well be a short.
Also keep in mind that the rating on old caps is often +80%/-20%, which demonstrates the generally acceptable range. Modern caps are usually right on value (but electrolytics can change over time).
OH, before I forget - again - HI and Welcome
P.S. Don't reduce the voltage rating. If you can (especially in electrolytics) use as high a working- voltage cap as you can find/afford. It will last much longer. Also, always go with 105 deg caps if you can.
RE: Difference in Schematic and chassis cap values? - klondike98 - 05-02-2018
Welcome to the Phorum!
RE: Difference in Schematic and chassis cap values? - harleythatcher - 05-02-2018
Thank you for the guide lines Phlogiston. That info will help greatly. And cheers to you too Bob. One of my other hobbies is Homebrewing, so I will have a beer for you guys. What would you prefer? I have Stouts, Porters, Cream ALe, IRish Red, Ginger Beer (like when we were youngins but with 5% ABV), Belgians of several kinds. Anyway Cheers! Darn no beer Emoles (sp)
Tt
RE: Difference in Schematic and chassis cap values? - klondike98 - 05-02-2018
(05-02-2018, 12:58 PM)harleythatcher Wrote: Darn no beer Emoles (sp)
ah...but there is....
click on the [get more] in the "smilies" box....
RE: Difference in Schematic and chassis cap values? - Chas - 05-02-2018
Quote:So I have found several cases where a cap in the chassis will have a different value than the schematic? Do you go by the schematic?
If the cap in question is original then go by the ratings. The schematic may be an update, or not, use the schematic value when the installed cap to be replaced is clearly a replacement and not OEM...
YMMV
Chas
RE: Difference in Schematic and chassis cap values? - Phlogiston - 05-02-2018
- - or the schematic may be wrong. Just found that a few times on a McMurdo Silver V.
RE: Difference in Schematic and chassis cap values? - Electrothaumaturgist - 05-02-2018
...Or the parts list is different than what's listed on the schematics. Saw that one a few times on the last couple of radios I've done...
RE: Difference in Schematic and chassis cap values? - Arran - 05-02-2018
Schematic errors are not unusual, although some manufacturers like Philco seem to have more then others, such as places where two lines connect where they do not, or not connect on the schematic when they should. An example is the Philco model 18 or 118, the driver tube is shown connected as a pentode, but in the real sets it is a triode connected pentode driving a pair of triode connected pentodes. I think that the people in the drafting department became confused at times, too many revisions, too many code numbers, etc. On parts lists of all makes it isn't unusual to put the decimal in the wrong place, listing something like a .005 as a .05 uf or something like that.
Regards
Arran