|
Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
|
Thread Tools |
7th Aug 2009, 10:25 am | #1 |
Retired Dormant Member
Join Date: Jan 2007
Location: Westbury, Wiltshire, UK.
Posts: 2,451
|
Ekco A22 cathode bypass electrolytic
The A22 is coming along nicely, I've had to go for a total rewire including the IFTs and got some terrific wire from SWB18 which really looks the part and I decided to stuff the wax caps to try and preserve what I could of its internal looks.
I'm a bit stuck on the cathode cap' of the EBL31 (goes throught the chassis). Are these reliable enough to chance leaving in circuit? If not is it possible to restuff it? All I can see is a black cylindrical blob with no way in. I don't have a capacitance meter to test it with. Dave |
7th Aug 2009, 3:15 pm | #2 |
Retired Dormant Member
Join Date: Jun 2006
Posts: 1,798
|
Re: Ekco A22 cathode bypass electrolytic
Hello Dave, if the EBL31 is in a similar output stage as my Philips EBL1 then the cathode bypass is 25uF at around 25V and not likely to be to reliable any more but any up to 100uF will be ok. You could put one in place anywhere close after disconnecting the original.
Geof |
7th Aug 2009, 3:20 pm | #3 |
Retired Dormant Member
Join Date: Jan 2007
Location: Westbury, Wiltshire, UK.
Posts: 2,451
|
Re: Ekco A22 cathode bypass electrolytic
Thanks for reply Geof. I took a chance and put a 1/4" drill straight through the middle of it. The case survived and is now back in the radio stuffed with a nice new cap'.
Dave |
7th Aug 2009, 9:00 pm | #4 | |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,737
|
Re: Ekco A22 cathode bypass electrolytic
Quote:
Modern capacitors are puny in size by comparison, and when you put one back into the case, it's as well to secure it in place with a glue gun. Tie a knot in some 22 gauge wire connecting at each end and solder the wires to the capacitor leaving some slack in the capacitor wires, so that when the connections are made, you don't put a strain on the capacitor. Make really certain you remember which end is which when you seal the case ends back on! As has been said many times before, it's hopeless to simply test old electrolytics with a capacitance meter - they must be checked on an ESR meter. In the three A22s I've restored the cathode by-pass capacitors all measured 25uF, but all were infinity on an ESR meter. (It doesn't cost much to knock up a DIY ESR meter) (Best to check the cathode voltage too of course, and the two resistors associated with the cathode (150/220R). It's also not a useful guide to the condition of waxy caps on any old radio to simply check them for leakage on say a 20M Ohm range of a multimeter and assume they're OK. They're certainly not ok with 240V up 'em! They're as leaky as a runcible spoon. Never mind about just changing "THAT" capacitor, which has rightly achieved notoriety on this forum, unless they're very difficult to get at, change the lot! Glad to hear you're A22 restoration is all but complete Dave! David, G4EBT |
|