Thought I'd throw this out there to see if anyone has any ideas on any component I may have missed after the recap that could be causing me to have weak, noisy reception above 1000 on the dial. The local station in town at 1470 should be blaring and it isn't (weak and noisy like a distant station would sound), yet the other end at 620 out of Milwaukee (35 miles away) is strong and clear and loud.
It seems to be around the #58 IF tube. When I try to align the set, I just barely touch the A8 and A9 trimmers on the IF can for the tube and the set begins to squeal. If I put my finger on the grid cap of the #58 IF tube, the station goes silent. It's very sensitive / finicky around that can and that tube
I haven't checked voltages yet but just wanted to see if there's something obvious that I overlooked that could be the culprit.
So how did you get such a nice set??
I've had two of them one when I was in jr high and the second one I picked up several yrs ago on epay $$$. The 1st is long gone the 2nd is awaiting restoration.
As for your issues, got all the tube shields on?? Did you have to replace a bunch of rubber wire?? Could be a wire placement problem. Check to see if C-6 C9 and 10 are wired correctly.
You didn't mention any about the resistors it's worth checking to see if they are within tolerance. Note they use an odd color code so use the diagram for proper values.
For those following at home this is what the set in question looks like.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Thanks, Terry. I actually got the radio from one of our club members. He has a basement FILLED with radios, mostly 1920's sets. And I mean FILLED. There's just a narrow pathway through the maze. He was looking to thin the herd, and had two of these model 206's. One was a farm / battery set, and I got this one. The cabinet is pretty rough. I've been clamping and gluing the last 3 nights, trying to take care of the water damage delamination.
Alas, this one was missing its original speaker. Gary at PTOTP had an 8 1/4" RCA speaker with a 1200 ohm field and an output transformer attached that I've been using. He had an original AK 4 prong speaker plug too, which helped. The only thing this speaker doesn't have is the hum bucking coil that was attached to the original AK speaker. It's CK1 on the schematic. It that critical and if so, what could be used in place of it?
I double checked C6, C9, and C10 and they appear to be correct. The .03 mfd cap goes to #24 on T3, which is at the 7 o'clock position:
I replaced a FEW of the original fossilized rubber coated wire. I am doing my best not to disturb them, as they still look good for the most part and I'd like to avoid having to totally rewire the set. I did a more thorough resistor check tonight, some are very small value, like 1 ohm, even a .5 ohm I saw.
Tonight I tried replacing C2 (2200 mmfd, I replaced with a .0022 mfd), C3 (25 mmfd, I replaced with a 25 pf), and R3, the 65K ohm resistor. Mine was reading 109K. I had the set upside down and when I turned it on, all I got was motorboating. So I turned the set right side up, turned it back on and still got motorboating, until I pushed down on the grid cap of the #58 IF tube (the infamous culprit). Then the motorboating stopped and I started to receive the same two stations I was, although they are still very noisy and sound distant. They are strong stations, yet you have to really fish around to find them and get them to come in somewhat clear.
Something is holding back the reception from coming through loud and clear. I'm getting very little if any response on all of the grid caps when I touch them with my finger, except for the 58 IF...when I touch that grid cap, the set goes silent (station reception goes away). Going to have to do some signal tracing. Do you have any ideas on what to zero in on?
> It's CK1 on the schematic. It that critical and if so, what could be used in place of it?
Not so much w/o it you may hear a little bit of 60cy hum but that's about it.
>some are very small value, like 1 ohm, even a .5 ohm I saw.
I so one that in the dial lamp circuit but also saw a few that had the omega symbol meaning megohms. First time I've seen that.
> although they are still very noisy and sound distant.
Ok try this tune in a station up near the top of the bcb 1400-1500kc then adjust A2 and A3 and see if that helps.
Have a look at the voltages on the rf amp and mixer. Mostly the screen grid and plate.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 01-08-2019, 07:26 PM by Radioroslyn.)
Ah, the omega symbol meaning megohms! I'd never seen that either. With that knowledge I replaced a few more resistors tonight that were way off. Namely R10, R16, R8 and R12. Didn't make a whole lot of difference, though, in the noisy distant reception.
There is still something going on around that 58 IF tube. When I first turn on the set, after flipping it back rightside up, it will come on motorboating. As soon as I push down on the gridcap of that tube, the motorboating stops. I'm wondering if something could be going on inside that IF can. There's not much in it judging by the schematic.
It seems to receive a few more stations since the resistor changes, more below 1000 on the dial, but that's where most of the stations are in the area. Adjusting A2 and A3 while I have the strong local station noisily playing at 1470 didn't make any difference. I even tried my SStran AM transmitter, which should blast at low volume and it too sounds distant and noisy. It broadcasts at 1450. I didn't have time tonight to check the voltages but will tomorrow. Any other ideas? There are a couple of original micas I left in place. I'm wondering if the mica-mold style C4 would make a difference?
Thanks for the video with Harlow Wilcox! The Fibber McGee & Molly announcer that they nicknamed "Waxy" because he was always doing those Johnson Wax Glo Coat commercials! I have an original Glo-Coat can circa 1946....
You said that you aligned the IF stage did the trimmers A-8 thru 11 have a definite peak @ 472 1/2kc ? Have a listen for the local oscillator @ 472 1/2kc above the dial setting. If you have a spare 2A7 (bit of an odd tube) I'd give it a try too.
As you probably know HW also was the announcer for Amos n Andy around the WWII years and later and Suspense replacing Joesph Kearns aka George Wilson on Dennis the Menace. JK died in '62 during the run of DTM and he was replaced by nun other than Gale Gordon as John Wilson George's brother. On radio he was Foggy Williams on FMandM, mayor LaTriva, Rumson Bullard, Mr Concklin, ect...
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 01-09-2019, 12:36 AM by Radioroslyn.)
Tonight's enjoyment included taking apart that #58 tube IF can...and finding nothing amiss with it. I sleeved the grid cap wire down further to make sure that it couldn't touch at all, but oddly enough all of the wires coming out of that can were nice and pliable yet...nothing crumbling. There was even a cloth covered one!
It was like trying to pull a golf ball through a garden hose to get it out of the can though!
I was able to replace another crumbling wire that may have had a bare spot touching against one of the studs from the can, and touched up a solder joint from one of the wires leading out of the can, but outside of that, no real progress. Symptoms remain the same, even after swapping out a #58 tube and the 2A7 as you suggested. I will try the local osc test tomorrow night and the voltage checks. Never got to that tonight as the can project took a lot more time than I had planned.
Yes I knew Harlow was Amos 'n Andy's announcer too. I love listening to those shows too. Gale Gordon must've been doing double duty with Lucy and DTM at the same time in the early 60's. Have you seen the Twilight Zone episode "Static" with Dean Jagger (aka General Waverly from White Christmas)? That's one of my fav's too.
One of Phil Harris's radio "daughters" is in White Christmas. I forget which one.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
I think I got it about as good as I can get it, Terry. The combination of the grid cap wire having a tiny bare spot inside the can that was touching against the metal eyelet, and a crumbling wire with a bare spot touching against the stud of the IF can seems to have been causing all of the motorboating and weird noises. I can move the chassis, bang on the workbench and it doesn't cut out, crackle or motorboat anymore. I did do the local OSC test and it passed. I had the radio at 620 and the other radio at around 1100, and I could hear the OSC. When I turned off the AK, the OSC sound stopped on the other radio.
I gave it another alignment and found it needs to be slightly off peak to eliminate a lot of the noise. It receives a lot of stations. Still a little weaker on the upper end of the dial, but I can live with that. The OSC is working, the ANT is working, IF and RF cans are doing their thing. Resistors are all good. Capacitors have all been changed, save for a couple of micas. Several tubes have been tried. Not too many more components I can change.
A.K sets are never good candidates for a quick recap, I wouldn't even think of running one of these without replacing, or sleaving, the leads on the power transformer, and maybe the hot side of the IF cans as well.
Regards
Arran
I certainly understand that good advice Arran. I gave the transformer wires a thorough examination and they looked ok. With a small brush I coated them with liquid tape at the transformer and any place where they were near the chassis. The IF can wires were surprisingly pliable. Seems like certain color wires don't harden and crack. A few were even cloth covered. The wire that was cracked and touching the if can stud was so buried I didn't find it until after the can was removed. But you're right these AK sets are not for the faint of heart. They are not easy to work on because of the poor condition of the wiring insulation.This one has an especially cramped chassis as well.
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