Just refinished recapping - completely - a very nice model 47-1230. As good practice I'd replace one or two and verify functionality. Got down to the last two capacitors, C-309 (on Riders black Sprague .01 mfd in the attached picture) and the strange looking C-419 (two leads to one ground) Went to turn on and now get nothing but hiss from all bands. Prior to replacing these final two capacitors radio was playing excellent on all bands. So thinking one may have been bad I replaced them again - still nothing but hiss. Re- soldered the old wax ones back in - no change. What could have happened? Thus far I've cleaned all tube sockets, tried different tubes etc. No change. Switching to phono and adding an external source through the old phono input - works - plays whatever source (happens to be my iphone through a Bluetooth receiver) loud and clear with zero hum. Rotating the band switch produces "pops" through speaker and if, with the volume set to wide open you can hear some kind of broadcast - very faint - that does not change with moving the tuning capacitor. Push buttons no longer operate either, except for the phono selector one. What to look for next? It's like the radio part has been "disconnected" from the amplifier part of the radio. [
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Hi Gcerio, had same problem with my 47 1230. Do a quick search on 47 1230,maybe there is some help there. I never got mine to work. Good Luck, Bill
A blob of solder is bridging a connection somewhere? Also carefully inspect nearby components that could have been pushed so that their leads are shorting against something.
I repaired a 47-1227 way back when (2002) that had a 3 lead capacitor like C419. I recall having the same problem (dead across all bands) because I wired in the replacement cap wrong. It sounds like when you re-installed the old cap you may have wired it in incorrectly. How did you have the replacement wired?
No offense, but this recap looks VERY BAD. This gotta be cleaned up before you work on the rest of it.
I am not advocating all the extras like restuffing an such, but reliable accurate and safe soldering is a must.
Jeremy, How did you make out with your 47 1230. I had the very same problem. Do you have any photos of your restoration ? Thanks Bill
I must agree with morzh, this recap is not done right. You have a capacitor lead going between two terminals on a terminal strip with no sleeving so the slightest movement will cause a short and another with a long lead going over several components. The soldering looks ugly but some people have adopted the view that you should not unsolder wires directly from old terminals or tube sockets, you just cut the wire a short distance from the solder lug and solder to this stub lead. This is not necessarily bad but it does need insulation.
OK. I have seen at least 4 different lug connections for the C419. Does anyone know the correct connections? I too have reception problems after replacing the C419. Thank you,Bill
willy,
treat it like any other shielded design your familiar with. treat it like the shield is an umbrella around the object you want to protect from external emi but i would not include the shield in the gnd side of the cap lead itself, i would gather the shield EMI and bring that path to an area not close to any tube pin or any trimmer cap etc ,, just find a clear open bonding point away from stuff. i use the term bonding loosely as there is a big difference between bonding and grounding.... think "tube shield"
i was under the impression the three leg cap was nothing more than a shielded cap.
i wrapped mine in a narrow band of automotive sticky back aluminum exhaust repair tape which included tinned solder wick braid hanging off to the side which starts under one of the early layers of foil. there may be some scientific reason as to why this method is not totally correct because if i used plain tin foil then the wraps of foil would touch each other making this better i think?. in my case i suspect that the automotive exhaust tape being separated by the layer of glue is creating some degree of capacitance itself, which isn't really good for a shield. my stuff's working so..............
i then added heat shrink around the cap which in my opinion only helped to friction seal up or keep pressure on the foil to solder wick connection. this would be more as a coupling shield i guess because the solder wick is not welded to the foil,, just touching.
if i had a do over,, i would have simply wrapped the cap in foil,, then wrapped the cap in solder wick and solder the wick in place but this might have damaged the poly cap.
i was looking around for copper braid you find in some coax to slip over the cap for the shield but could not find copper so i did this.
the difference here is my shield is not terminated to either end of the cap.
my Zenith 7H920 (with FM) schematic does not illustrate in print the concept that the shield is ever tied to one end of the cap so i made my shield like any other logical shield design,, just wrap the part and bond or ground this shield layer,, this way the shield acts as an antenna and shunts any EMI to chassis.