Topics

power and mic wiring


ross ingham
 

Greetins fellow bitx users. Back in the day,1968,  I was a member of the Narrogin radio club and hung out with a bunch of old geezers,one who had a straight six saloon with a back seat that took 10 young blokes. We would build crystal sets and  hang out on the 20 and 6 meatre band. So this is an old guy has retired and getting back into hf radio. I have ordered a microbitx kit and am going through the build in my head . So here are my questions: I intend to put chassis mounted fuses in the power curcuit, do I need to put a fuse on each of the two power feed wires or can I use the same fuse and does the diode stay across from power to ground? Next , I  intend to use four pin mic socket and mic, the blue is ground but if I get the other two wires back to front it be a problem? If someone coule send me a schematic that would make eternally grreatful.
At the moment I am trying to reserect a 1930s Honeywell reciever,some of the valves are not getting hot so I  suspect they are kangeroo edward. I  put up a dipole over Christmas that is ten metres a side, works a treat for my brothers portable on 7.130 but the reciever,nothing. But oh well my othe brother is the valve guy so all good. Cheers and a happy new year. Ross 


Mike Lichtman
 

Eiclan,
On the 30’s radio, replace all the caps (especially the electrolytics) before powering up again or you may burn up the power transformer. They are usually “unobtanium”. 73 Mike KF6KXG


Bob Lunsford
 

Original caps are indeed "unobtanium" but replacement caps
are worlds ahead of the old technology. I had a Swan 350
about ten years ago that I bought at a hamfest. Plugged it in
and the power supply caps were beyond saving and one
blew up and it sounded like a shotgun shell going off.

There are some who advise putting a variable AC transformer
in the circuit and bringing it up slowly "to polarize the caps" but
while this may work, better is to do as suggested: Make a list
of the electrolytic caps and plan on replacing them.

Some have suggested putting a 100-250 W lamp i series with
the AC so the AC is limited. Might try it but it is a trial and error
situation where error is most likely and proves to be a waste of
time.

I had a Philco 650 back in the '50s that had a shorted bypase
cap on the power output tube from screen to ground. It was not
an electrolytic. This proves that it could be any cap. The electro-
lytics are polarity sensitve and putting one in backwards as far
as polarity is concerned is like inviting a short and immediate
failure.

Go slow, take your time. Some of those old radios were superb
as was the Philco I had.

Bob — KK5R

--------------------------------------------

On Tue, 1/1/19, Mike Lichtman via Groups.Io <tchrme=aol.com@groups.io> wrote:

Subject: Re: [BITX20] power and mic wiring
To: BITX20@groups.io
Date: Tuesday, January 1, 2019, 8:23 PM

Eiclan,
    On the 30’s radio,
replace all the caps (especially the electrolytics) 
before powering up again or you may burn up the power
transformer. They are usually “unobtanium”. 73 Mike
KF6KXG


ross ingham
 

Cheers for that  chaps,the replacement of valves is on the cards. Some are available on the net and my brother may have a source for others. Thanks Ross 


Richard Spohn
 

The INCANDESCENT lamp in series with the power supply may save the
radio if there is a problem with the power supply. The lamp should be
rated approximately the same as the expected wattage of the radio. -
Rich WB2GXM

On 1/1/19, Bob Lunsford via Groups.Io <nocrud222=yahoo.com@groups.io> wrote:
Original caps are indeed "unobtanium" but replacement caps
are worlds ahead of the old technology. I had a Swan 350
about ten years ago that I bought at a hamfest. Plugged it in
and the power supply caps were beyond saving and one
blew up and it sounded like a shotgun shell going off.

There are some who advise putting a variable AC transformer
in the circuit and bringing it up slowly "to polarize the caps" but
while this may work, better is to do as suggested: Make a list
of the electrolytic caps and plan on replacing them.

Some have suggested putting a 100-250 W lamp i series with
the AC so the AC is limited. Might try it but it is a trial and error
situation where error is most likely and proves to be a waste of
time.

I had a Philco 650 back in the '50s that had a shorted bypase
cap on the power output tube from screen to ground. It was not
an electrolytic. This proves that it could be any cap. The electro-
lytics are polarity sensitve and putting one in backwards as far
as polarity is concerned is like inviting a short and immediate
failure.

Go slow, take your time. Some of those old radios were superb
as was the Philco I had.

Bob — KK5R

--------------------------------------------
On Tue, 1/1/19, Mike Lichtman via Groups.Io <tchrme=aol.com@groups.io>
wrote:

Subject: Re: [BITX20] power and mic wiring
To: BITX20@groups.io
Date: Tuesday, January 1, 2019, 8:23 PM

Eiclan,
    On the 30’s radio,
replace all the caps (especially the electrolytics)
before powering up again or you may burn up the power
transformer. They are usually “unobtanium”. 73 Mike
KF6KXG