Antique Radios Forum

This is the temporary home of the Antique Radio Forums while a new server to host it is being found. You will have to register here to post. Please Note: None of these topics will be preserved when the original forums are back.
 
HomeCalendarFAQSearchMemberlistUsergroupsRegisterLog in

Share | 
 

 Help with a Hallicafters S-20 R

View previous topic View next topic Go down 
AuthorMessage
K4YM



Posts : 2
Join date : 2010-10-21
Location : Tapppahannock, VA (Washington State Native)

PostSubject: Help with a Hallicafters S-20 R   Fri Oct 22, 2010 10:54 am

I have been restoring a Hallicrafters S-20R. The cabinet is 9/10. I have replaced all of the by-pass capacitors, filter caps and many resistors. The unit appeared to be working but needed a good alignment. I got the IF working well and the local oscillator on all the bands except the BC band. (BC has a bad trimmer on the LO coil.) The radio was receiving some shortwave broadcast stations but nothing else. By ear, I tuned the input to the 6SK7 RF amp but the output had no affect. Metering the input to the mixer I found almost no signal. It took 100k uV to see anything on the grid of the mixer. I don’t know what it should be but that looked wrong to me. After further investigation I have discovered the wiper on the band select switch for the mixer input is MISSING. No clue as to were or how it became missing. There is no evidence of it having ever been there and take may hours of work to replace it if one could even be found. The switch is buried between the chassis bottom and the RF amp plate tuning capacitors and coils for 4 bands. I had a heck of a time just seeing that it is missing.

Anyone have suggestions for a work around fix? It is a beautiful radio and it would be a shame to dump it.

I have been thinking of RC coupling between the RF plate and mixer grid. What kind of signal voltage should I have on the mixer grid? Any suggestions on component values?

Back to top Go down
View user profile
Radiosmoker

avatar

Posts : 20
Join date : 2010-10-14
Age : 73

PostSubject: Re: Help with a Hallicafters S-20 R   Fri Oct 22, 2010 12:51 pm

well since you have an unobtanium switch, finding one is an option of buying a non-working one, that price would be comparable to just buying a switch.

Being a thrifty person that I am, I would just use a toggle switch(s) wired to bandswitch connection(s). Mounted on the Case, and just make a note pasted on the lid for that band. (I also would get a LED and mount it on the switch to light when the switch is on. Depends on how fancy you want to get. A miniature switch should work fine. A DPDT type would be the most versitile. study
Back to top Go down
View user profile
47'Plymouth864

avatar

Posts : 19
Join date : 2010-10-14
Location : Laurens,SC.29360

PostSubject: Re: Help with a Hallicafters S-20 R   Fri Oct 22, 2010 12:58 pm

Hey just ask Mark Oppat,justradios.com; he might have one..if you haven't already Rolling Eyes Very Happy
Back to top Go down
View user profile
W6UN

avatar

Posts : 7
Join date : 2010-10-12
Age : 84
Location : Sparks, NV

PostSubject: Re: Help with a Hallicafters S-20 R   Fri Oct 22, 2010 4:04 pm

This guy has a couple bandswitch assemblies available.

http://tubes_tubes_tubes.tripod.com/id8.html

Good luck.

Lee, W6UN

Back to top Go down
View user profile
Sponsored content




PostSubject: Re: Help with a Hallicafters S-20 R   

Back to top Go down
 
Help with a Hallicafters S-20 R
View previous topic View next topic Back to top 
Page 1 of 1

Permissions in this forum:You cannot reply to topics in this forum
Antique Radios Forum :: Antique Radio Forums :: Antique Radio Discussions-
Jump to: