Odd factory goof been eating my lunch!

[Charlie]

Quite some time ago, I recapped a 1953 Zenith AM clock radio. Like many of these Zeniths, it played when I first got it, but not too well. Signals were weak, but audio was okay. When I would plug a source into the phono jack, it sounded pretty good. Just didn't tune in stations very well.

The thing I noticed the most was there was no static. Out here in the sticks where I live, there's nothing local to hear. My best station to get during the day is KTRH out of Houston, but typically weak. Even after the recap, still couldn't get KTRH.

I did take it to Houston one day when I went to see my brother, and found it would indeed tune in stations there... good enough to listen to... but still not as good as other Zeniths like this one. I did notice I could weakly get a couple of night time stations, but not as well as it should.

After repeating the alignment multiple times and getting nowhere, I shoved it to the side to work on other things.

One of the things I was glad about was the lack of crackling in the speaker from silver mica disease. I really hate dealing with those tiny little wires. Since there was no crackling, I had figured there was no reason to open the cans up.

Last night, after TWO years since I started this, I decided to pop open the IF cans. That's where it got interesting. When I went to pull out the mica sheet on the second can, a piece of tissue paper came with it!! It was keeping the bottom contacts from touching the mica! Well son-of-a-gun! This radio came from the factory this way! So the only stations it ever picked up were strong local stations. I bet the original purchaser was pretty disappointed with it's poor performance!

I've done several IF cans in these Zeniths. That's the first time I ever found something like this. I am assuming the piece of tissue paper was likely what kept the little mica sheets separated at the assembly plant where these cans were made (kinda like the sheets of paper between cheese slices at the deli). The person putting this can together didn't notice paper when they put it in there. Musta been a Friday!

I popped some new capacitors in there and put it back together... and found the pleasant surprise of static when I first fired it up... and tuned in MANY stations all across the dial!

After aligning it again, nighttime signals and stations were strong and clear. This morning, KTRH tunes in... just like it should. I'm just glad the mystery is finally over!

[Electronic M]

Originally Posted by Charlie

Quite some time ago, I recapped a 1953 Zenith AM clock radio. Like many of these Zeniths, it played when I first got it, but not too well. Signals were weak, but audio was okay. When I would plug a source into the phono jack, it sounded pretty good. Just didn't tune in stations very well.

The thing I noticed the most was there was no static. Out here in the sticks where I live, there's nothing local to hear. My best station to get during the day is KTRH out of Houston, but typically weak. Even after the recap, still couldn't get KTRH.

I did take it to Houston one day when I went to see my brother, and found it would indeed tune in stations there... good enough to listen to... but still not as good as other Zeniths like this one. I did notice I could weakly get a couple of night time stations, but not as well as it should.

After repeating the alignment multiple times and getting nowhere, I shoved it to the side to work on other things.

One of the things I was glad about was the lack of crackling in the speaker from silver mica disease. I really hate dealing with those tiny little wires. Since there was no crackling, I had figured there was no reason to open the cans up.

Last night, after TWO years since I started this, I decided to pop open the IF cans. That's where it got interesting. When I went to pull out the mica sheet on the second can, a piece of tissue paper came with it!! It was keeping the bottom contacts from touching the mica! Well son-of-a-gun! This radio came from the factory this way! So the only stations it ever picked up were strong local stations. I bet the original purchaser was pretty disappointed with it's poor performance!

I've done several IF cans in these Zeniths. That's the first time I ever found something like this. I am assuming the piece of tissue paper was likely what kept the little mica sheets separated at the assembly plant where these cans were made (kinda like the sheets of paper between cheese slices at the deli). The person putting this can together didn't notice paper when I put it in there. Musta been a Friday!

I popped some new capacitors in there and put it back together... and found the pleasant surprise of static when I first fired it up... and tuned in MANY stations all across the dial!

After aligning it again, nighttime signals and stations were strong and clear. This morning, KTRH tunes in... just like it should. I'm just glad the mystery is finally over!

Wow! And I thought the factory unsoldered tuner harness wires I found in 2 different Zenith TVs were bad...The wire was wrapped well enough to have continuity most of the time.

[old_coot88]

Wow. And one would naively assume every radio passed a performance test after final assembly. Something similar happened with a mid-60s Zenith color console that had suddenly gone dead. Shopped the set, and it had a B+ dead short. A red B+-carrying wire had gotten pinched under the lip of the front chassis apron, and the chassis bolts tightened down on it. It had run that way for a long time before the insulation finally gave way.

[trinescope]

I have a Philco 46-1213 radio that came with a factory wiring error. The FM had a really muffled sound to it, I ended up finding a bypass capacitor was connected to the plate of the FM1000 detector tube instead of the B+ end of the plate resistor. It was acting as a low pass filter in this case. Fixing that wiring error got the radio working as it was supposed to from the beginning.

[nasadowsk]

Had an RCA tv come across my bench a while back. One of the connections for horizontal sync was crimped, but the terminal never soldered. I guess it worked well enough. Amazingly obvious when you looked under the set, no repairman ever bothered to hit it…

[dtvmcdonald]

Originally Posted by nasadowsk

Had an RCA tv come across my bench a while back. One of the connections for horizontal sync was crimped, but the terminal never soldered. I guess it worked well enough. Amazingly obvious when you looked under the set, no repairman ever bothered to hit it…

I've found those in several radios or TVs. The most egregious was my RCA
CT-100 1954 color TV. It had three unsoldered connections ... despite having been used quite a bit by one of the most famous collectors. It also had two resistors with the third band off by one. And worst of all ... one of those resistors is wrong on one of the RCA schematics! (There is an adjustment that compensates, but its all the way to one end if that's done.) All this was from the factory.