06-02-2024, 12:04 PM
Quote:I apologize for my confusion. The style of many of the components is foreign to me. Especially the capacitors.I understand completely...
IMHO I am sure that the RCA's desire to have a uniform radio "module" fit a number of radios/phonos is the result of the "rat's nest" that is the terminal and resistor strips. I go further to say that is the principle reason that the value of a 28 and it "brothers" is artificially low. Very difficult to understand, as well as somewhat costly tube requirements.
The 8 tube catacomb when correctly operating is extremely sensitive for a triode 8 tube radio. Even the 6 tube catacomb is nearly as sensitive but comes with "images" which can be both a liability and an asset depending on how the radio fan uses it.
Yes, the relatively large IF coils on steel lamination's and open clinched mica caps are a bit primitive. You will note that the grid leak is buried inside of a tube of varnished cambric. FWIR it is painted red and has no other color coding, before the application of the BED code.
RCA use the open clinched micas in the 16, 17, 18, 20, 21, etc up to the 66. Generally, unless these are poked, prodded twisted they are fine.
As far as the unknown values, in the AF amp these values, still relatively low are to stabilize the amp and prevent feedback via the common B & C circuits. as well as shunt any 40khz signal.
The micas in the RF are intended to resonate the IF transformers.
There should be at least one or two 1mf or 2mf large paper block bypass caps around the battery connections, being an AC set that never got the large bypass block array you will probably will need these caps. Since I do not have a complete 28 DC to reference for where these caps are physically located There may be missing brackets and such involved. As well as extension wires in the harness...
I DO have several of the caps and possibly mounting brackets but they are attached to harnesses form a Radiola 30 or a 25... I only need enough caps to provide for ARBE-III operation of the test chassis, there are three of these but only a 25 is near completion.
These caps if they are leaking can be easily stuffed with flat-pak metalized, but if they are good and I suspect, they are Stromberg-Carlson caps...
>>> the volume rheostat in an AC or even an AC (original conversion) is different for the DC version. Those series filaments... I am not sure what the correct value is but I may have the correct value, The rheostat is serviced as a cartridge. So only the resistance element cartridge is changed out. We can get to that as the last step in completing the 28 DC...
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”