UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Amateur and Military Radio

Notices

Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

Closed Thread
 
Thread Tools
Old 18th Jul 2020, 11:45 pm   #61
mrrstrat
Pentode
 
mrrstrat's Avatar
 
Join Date: Jul 2020
Location: Rockford, Illinois, USA.
Posts: 159
Default Re: Another Hallicrafters Sky Champion S20.

Following Station X's advice: I did try to find the S20 oscillator on another radio. I have 18 or so high-quality and freshly aligned by the owner of the estate they came from. So I grabbed a strong 1932 tombstone radio that has spectacular sensitivity and volume and I could not find any trace of the signal at 955 (when the S20 was at 500 and the other radio was at around 955 - I did sweep for it as well).

The paradox, live:

This is the radio, manually tuned to a radio station (the station was found around around 1440 Khz) and I have my signal generator sending a 1400 Khz or so signal (modulated) to radio:

http://www.mrc-tech.net/1440_tone.MOV

Here is the same radio with now the signal generator taken off and then tune to the adjacent station (showing it does work - this is a local station that is 1440 Khz):

http://www.mrc-tech.net/radio_1440.MOV

And now the punchline - I hook up the signal generator to the cap of the 6L7 (after it has the cap removed) and then tune the signal generator to 455 Khz and the radio at 1800khz as the alignment instructions prescribe:

http://www.mrc-tech.net/no_455.MOV

I do have a tick mark on the dial of the signal generator that exactly locates 455 Khz.

I have used all three levels of powered output and swept the output level of the three levels out signal output. This is in the event I am overloading the signal.

I did perform the test through a BNC RMA Dummy load antenna module - the instructions say to do this through a 0.1uF cap directly to the 6L7 but I did try it with the same results as my RMA dummy antenna.

I would think that the manually tuned station coming in at about the frequency it is at and being able to spot a 1400 Mhz signal fed to it means I am in the ballpark to start alignment.

When I last tried to do this I changed all of the controls related to alignment of the medium wave band - it took me no less than an hour to find the station again by messing with the trimmers on T1 and the 4 trimmers after T1/T2 is to be set. The manual alignment method seems to only bring in 1 or 2 stations on this radio where I can usually get all of the strong ones.

Thoughts?

Last edited by mrrstrat; 19th Jul 2020 at 12:03 am.
mrrstrat is offline  
Old 19th Jul 2020, 8:51 am   #62
Station X
Moderator
 
Station X's Avatar
 
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
Default Re: Another Hallicrafters Sky Champion S20.

Regardless of anything else, the IF stages, your signal generator or perhaps both are not working at 455kHz.

Time for a different approach. What voltages do you get on all the pins of all the valves measured with respect to the chassis? There's no need to check the heater pins assuming all the valves light up.
__________________
Graham. Forum Moderator

Reach for your meter before you reach for your soldering iron.
Station X is online now  
Old 19th Jul 2020, 12:59 pm   #63
mrrstrat
Pentode
 
mrrstrat's Avatar
 
Join Date: Jul 2020
Location: Rockford, Illinois, USA.
Posts: 159
Default Re: Another Hallicrafters Sky Champion S20.

My thought exactly: todays objective is to focus on the voltages.

I did this when I first got the set up and running but dropped off when I was able to receive something on the set - figured it was an alignment exercise after that.

Very certain on the signal generator: I am certain it is in order.

Quote:
Originally Posted by Station X View Post
Regardless of anything else, the IF stages, your signal generator or perhaps both are not working at 455kHz.

Time for a different approach. What voltages do you get on all the pins of all the valves measured with respect to the chassis? There's no need to check the heater pins assuming all the valves light up.
mrrstrat is offline  
Old 19th Jul 2020, 4:54 pm   #64
mrrstrat
Pentode
 
mrrstrat's Avatar
 
Join Date: Jul 2020
Location: Rockford, Illinois, USA.
Posts: 159
Default Re: Another Hallicrafters Sky Champion S20.

I do assume you mean with the tubes in socket: I did do that exercise with the tubes out of socket as it was easy to do so and access the pins. I realize the limited utility of this but in other radio documentation (including the SX-43) there are nominals from idle and socket voltage states that give an indication of set health. I just don't have that same tube voltage nominals for the S-20.

I have the COMPLETE John Riders manual set and the chapters for the S-20 are exactly what BAMA has for it and there is no additional info. The S-20R does not suffer from this deficit in information (unfortunately for me working on the S-20 w/o "R").



Quote:
Originally Posted by Station X View Post
Regardless of anything else, the IF stages, your signal generator or perhaps both are not working at 455kHz.

Time for a different approach. What voltages do you get on all the pins of all the valves measured with respect to the chassis? There's no need to check the heater pins assuming all the valves light up.
mrrstrat is offline  
Old 19th Jul 2020, 6:07 pm   #65
Station X
Moderator
 
Station X's Avatar
 
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
Default Re: Another Hallicrafters Sky Champion S20.

Measure the voltages with the set powered up.
__________________
Graham. Forum Moderator

Reach for your meter before you reach for your soldering iron.
Station X is online now  
Old 19th Jul 2020, 8:02 pm   #66
mrrstrat
Pentode
 
mrrstrat's Avatar
 
Join Date: Jul 2020
Location: Rockford, Illinois, USA.
Posts: 159
Default Re: Another Hallicrafters Sky Champion S20.

I figured that: do you mean with the tubes in or with them out?

Quote:
Originally Posted by Station X View Post
Measure the voltages with the set powered up.
mrrstrat is offline  
Old 19th Jul 2020, 8:16 pm   #67
Station X
Moderator
 
Station X's Avatar
 
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
Default Re: Another Hallicrafters Sky Champion S20.

Valves in.
__________________
Graham. Forum Moderator

Reach for your meter before you reach for your soldering iron.
Station X is online now  
Old 20th Jul 2020, 11:33 pm   #68
mrrstrat
Pentode
 
mrrstrat's Avatar
 
Join Date: Jul 2020
Location: Rockford, Illinois, USA.
Posts: 159
Default Re: Another Hallicrafters Sky Champion S20.

I did leave out the rectifier and the BFO tube - I am thinking these do not look totally what they should be but this is what I measured:

(1) 6Q7 - 2nd detector, AVC, Audio stage #1
Pin 3: 164VDC Anode
Pin 4&5: 0.912 VDC Diodes
Pin 6 1.5 VDC
Pin 8 1.51VDC Cathode

(2) 6F6 - Audio tube
Pin 3: 338 VDC Anode
Pin 4: 339 VDC Screen Grid
Pin 5: 0.01VDC Control Grid
Pin 8: 47.1VDC Cathode

(3) 6K7 - IF amplifier
Pin 3: -0.041 VDC Anode
Pin 4: 106.1 VDC Screen Grid.
Pin 5: 2.3 VDC Suppressor Grid
Pin 6: 105.6 VDC NC
Pin 8: <0 VDC Cathode

(4) 6K7 - RF stage
Pin 3: 340 VDC Anode
Pin 4: 105.4 VDC Screen Grid
Pin 5: 3.57 VDC Suppressor Grid
Pin 6: 0.261 VDC NC
Pin 8: 0-ish VDC Cathode

(5) 6L7 - 1st detector/mixer
Pin 3: 340 VDC Anode
Pin 4: 133.5 VDC Screen Grids
Pin 5: -51.2 VDC G3 (Tied to Local Oscillator Control Grid.
Pin 8: 5.63 VDC Cathode

(6) 6J5 - HF Oscillator
Pin 3: 211.4 VDC Anode
Pin 4&5: -51.2 VDC Control Grid
Pin 8: 0 VDC Cathode

All heaters were 6.58VAC

This looks odd to me and I am not a radio guy (yet) - thoughts on this?

Last edited by Station X; 21st Jul 2020 at 10:16 am. Reason: Electrode descriptions added.
mrrstrat is offline  
Old 21st Jul 2020, 9:56 am   #69
Station X
Moderator
 
Station X's Avatar
 
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
Default Re: Another Hallicrafters Sky Champion S20.

A quick glance shows no anode voltage on pin 3 of the 6K7 IF Amplifier. Open circuit primary winding in IF Transformer T2? Let's hope not.

It would also be useful to know the voltage on the various top caps.
__________________
Graham. Forum Moderator

Reach for your meter before you reach for your soldering iron.
Station X is online now  
Old 21st Jul 2020, 1:14 pm   #70
mrrstrat
Pentode
 
mrrstrat's Avatar
 
Join Date: Jul 2020
Location: Rockford, Illinois, USA.
Posts: 159
Default Re: Another Hallicrafters Sky Champion S20.

I noticed that too - that was to be a point of focus today.

I did NOT take off T2 and totally checked T1 for open windings and signs of broken wires. When I saw the low/no voltage on anode (aka "Plate" in USA-speak) I became concerned that I need to pull it off and look at it. Then trace the quality of the connections.

I am pretty good about making sure my connections are solid and I do not tolerate some of the anemic connections I have seen in production work and fixes.

The behavior I noticed is that the T2 adjustments have NO effect when I am manually tuning in a station to make the radio work. So I will do this simple sanity check as T1 was a pain to get off and check. T2 looked simple.
mrrstrat is offline  
Old 21st Jul 2020, 5:53 pm   #71
mrrstrat
Pentode
 
mrrstrat's Avatar
 
Join Date: Jul 2020
Location: Rockford, Illinois, USA.
Posts: 159
Default Re: Another Hallicrafters Sky Champion S20.

I got the transformer off and carefully disassembled: this may be game over for this can.

One side measures good and the other pair measures open.

Moving the small wires around and different contacts I cannot make the pair that measures open to read any value.

I am assuming that the "top" two and the "bottom" two are pairs on the transformer. The side that measures dead (open) does not have any measurement or continuity with the other two wires that read a non-zero value.

So now what..
Attached Thumbnails
Click image for larger version

Name:	IMG-7190.jpg
Views:	58
Size:	47.5 KB
ID:	211479   Click image for larger version

Name:	IMG-7191.jpg
Views:	57
Size:	50.9 KB
ID:	211480  
mrrstrat is offline  
Old 21st Jul 2020, 5:58 pm   #72
Station X
Moderator
 
Station X's Avatar
 
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
Default Re: Another Hallicrafters Sky Champion S20.

I wouldn't lose hope. Breaks in wire generally occur near the terminations and a visual examination with a magnifier may reveal this.

Failing that you've nothing to lose by attempting a rewind. You may be able to carefully unwind the wire and reuse it. A couple of carboard cheeks may be needed to stop the new winding from spreading.
__________________
Graham. Forum Moderator

Reach for your meter before you reach for your soldering iron.
Station X is online now  
Old 21st Jul 2020, 6:26 pm   #73
mrrstrat
Pentode
 
mrrstrat's Avatar
 
Join Date: Jul 2020
Location: Rockford, Illinois, USA.
Posts: 159
Default Re: Another Hallicrafters Sky Champion S20.

One side did allow for unwinding and I did solder it to the contact. But the top one appears to NOT want to unwind. I am guessing is it not able to as I scraped the ear-wax looking wax away totally and this wire disappears deep inside of the coil and appears to have no unwind path as the other one had.

I did strip the wire on top and it does not have continuity or resistance anywhere else on the other three wires. I pulled the other wire away to get enough 'new' wire to replace what was there before. Visually looks good so the break might be in the very middle for all I know.

Quote:
Originally Posted by Station X View Post
I wouldn't lose hope. Breaks in wire generally occur near the terminations and a visual examination with a magnifier may reveal this.

Failing that you've nothing to lose by attempting a rewind. You may be able to carefully unwind the wire and reuse it. A couple of carboard cheeks may be needed to stop the new winding from spreading.
Attached Thumbnails
Click image for larger version

Name:	IMG-7192.jpg
Views:	47
Size:	39.6 KB
ID:	211484  
mrrstrat is offline  
Old 21st Jul 2020, 6:38 pm   #74
Station X
Moderator
 
Station X's Avatar
 
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
Default Re: Another Hallicrafters Sky Champion S20.

Can you slide the coil off the former to gain access to the inner end of the winding? The break may be there.

Not sure what you mean by not wanting to unwind. The wire is coated with a sticky substance (wax?) from new so that it stays in place when "wave wound". The bond is weak so it should be possible to unwind the wire onto a temporary bobbin.

As I said, the original winding was wave wound, but so called "scramble winding" by hand should be OK.
__________________
Graham. Forum Moderator

Reach for your meter before you reach for your soldering iron.
Station X is online now  
Old 21st Jul 2020, 6:51 pm   #75
mrrstrat
Pentode
 
mrrstrat's Avatar
 
Join Date: Jul 2020
Location: Rockford, Illinois, USA.
Posts: 159
Default Re: Another Hallicrafters Sky Champion S20.

Ok - challenge accepted!

The coil popped off and I can now freely unwind both. I'll try to find a suitable connection. Before the top wire didn't want to go anywhere and I didn't know it was pressed fit on the cardboard tube.

Now getting it back on is a separate challenge, but I am hoping to unwind a small amount of wire to get to a non-break.



Quote:
Originally Posted by Station X View Post
Can you slide the coil off the former to gain access to the inner end of the winding? The break may be there.

Not sure what you mean by not wanting to unwind. The wire is coated with a sticky substance (wax?) from new so that it stays in place when "wave wound". The bond is weak so it should be possible to unwind the wire onto a temporary bobbin.

As I said, the original winding was wave wound, but so called "scramble winding" by hand should be OK.
Attached Thumbnails
Click image for larger version

Name:	IMG-7193.jpg
Views:	42
Size:	38.9 KB
ID:	211489  
mrrstrat is offline  
Old 21st Jul 2020, 7:40 pm   #76
mrrstrat
Pentode
 
mrrstrat's Avatar
 
Join Date: Jul 2020
Location: Rockford, Illinois, USA.
Posts: 159
Default Re: Another Hallicrafters Sky Champion S20.

Ok that didn't work so well - The inside I would unwind a length of wire and it would break. I must have unwound 1 mil of wire off of the coil thickness before I found where it was not broke and would measure 7.5 ohms from the 13.5 or so the other side is at. And the coil inside is basically falling out and unwinding.

Is there an aftermarket or similar IF I can use as a replacement? this one requires coupling to an anode.

50045 is the model number of the IF that is good: This one is 5004 and I cannot read the last number. It looks a little like a "1" and in certain light like its a "1A".
mrrstrat is offline  
Old 21st Jul 2020, 8:35 pm   #77
Station X
Moderator
 
Station X's Avatar
 
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
Default Re: Another Hallicrafters Sky Champion S20.

You could look for a scrapper S20, but you wouldn't know whether its IFT's were any good.

Better to rewind it with enamelled copper wire of similar diameter.

Resistance per metre tables will show how much wire to use.
__________________
Graham. Forum Moderator

Reach for your meter before you reach for your soldering iron.
Station X is online now  
Old 22nd Jul 2020, 1:54 am   #78
mrrstrat
Pentode
 
mrrstrat's Avatar
 
Join Date: Jul 2020
Location: Rockford, Illinois, USA.
Posts: 159
Default Re: Another Hallicrafters Sky Champion S20.

Is it hard to wind your own?
mrrstrat is offline  
Old 22nd Jul 2020, 4:31 am   #79
mrrstrat
Pentode
 
mrrstrat's Avatar
 
Join Date: Jul 2020
Location: Rockford, Illinois, USA.
Posts: 159
Default Re: Another Hallicrafters Sky Champion S20.

I bought a 455khz HV IF can suitable as a replacement. It is a generic high voltage IF 4-wire two variable capacitor 2nd IF position can. Its a Guthman of Chicago model from the 30s.

I think I can make it work.
Attached Thumbnails
Click image for larger version

Name:	s-l1600-7.jpg
Views:	63
Size:	54.4 KB
ID:	211503   Click image for larger version

Name:	s-l1600-8.jpg
Views:	53
Size:	56.3 KB
ID:	211504   Click image for larger version

Name:	s-l1600-9.jpg
Views:	51
Size:	96.4 KB
ID:	211505   Click image for larger version

Name:	s-l1600-10.jpg
Views:	52
Size:	87.6 KB
ID:	211506  
mrrstrat is offline  
Old 22nd Jul 2020, 1:12 pm   #80
Station X
Moderator
 
Station X's Avatar
 
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
Default Re: Another Hallicrafters Sky Champion S20.

Should work. It helps that the new transformer is wire ended, so no need to drill new holes in the chassis for tags. You may have to drill a new mounting hole/holes though.

I'd visually check that the trimmers are OK before installing it though.
__________________
Graham. Forum Moderator

Reach for your meter before you reach for your soldering iron.
Station X is online now  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 11:37 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.