Zenith 7G605 Transoceanic - the Clipper
Posts: 15,302
Threads: 532
Joined: Oct 2011
City: Jackson, NJ
I also think of putting a 15V zener across the C28.
In case of any filament going open the C28 might develop much larger voltage than the rated 25V. Not just that, if inserting a tube without letting it drain it might blow the rest of the filament.
The nominal voltage across all filaments is 9.8V, so 15V I have handy should do fine.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 15,302
Threads: 532
Joined: Oct 2011
City: Jackson, NJ
The band switches were pretty clean and moved fine, but I sprayed them with some Deoxit anyway.
Yesterday I decided to use my hand as an antenna while listening to SW bands; I was able to get some good results during the day on 49M band (before the antenna switch was in the WaveMagnet position, so when I moved it to the Rod antenna position, I got the stations there).
The noise on all bands is pretty pronounced; it is constant noise, not popping and crackling so I don't think this has to do with Silver Mica problem.
When rotating the tuning cap there is some rasping noise; BTW the same problem I am having on my Zenith 9-S-262. Could be the contacts between the rotor and the case, but the cap looks very clean.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 667
Threads: 11
Joined: Sep 2014
City: Bellmawr, NJ
YOU sure it's NOT interference from something running,,,lights , solder iron pluged in,,another radio,,,refrigerator,,,just picking your Brain,,,,,sounds like something stupid for 2 radios to have same problem,,,,,what did you clean the tuning cap with ????,,Ken
Posts: 15,302
Threads: 532
Joined: Oct 2011
City: Jackson, NJ
Ken, I have.....well over 20 radios wirking, so.....
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 1,275
Threads: 44
Joined: Nov 2017
City: Menlo Park
State, Province, Country: CA
Is the constant noise a buzzing or more like continuous white noise without a note to it?
It could be that the set is just more sensitive - a portable made to be used with a small antenna. This should be noticable when tuning in stations too.
Could the noise be something intrinsic to the battery tubes ?
I don't hold with furniture that talks.
Posts: 15,302
Threads: 532
Joined: Oct 2011
City: Jackson, NJ
It's constant white noise type. And the antenna isn't even connected.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 1,275
Threads: 44
Joined: Nov 2017
City: Menlo Park
State, Province, Country: CA
OK. Can you isolate it to any stage, or see if the noise adds up through the R.F. amp and I.F. stages?
I realise you can't pull valves, but it would be possible to kill the signal at each stage with a cap, and see how noise responds?
Just a thought.
I don't hold with furniture that talks.
Posts: 15,302
Threads: 532
Joined: Oct 2011
City: Jackson, NJ
Changing tubes doesn't change anything.
I think maybe it's normal.
But first I want to clean the tuning cap and change the grommets.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 15,302
Threads: 532
Joined: Oct 2011
City: Jackson, NJ
Changed the grommets under the cap. Should've done that before recapping, had to unsolder two caps and then solder them back as they blocked one of the nuts.
This changed nothing, but then I blew, then sprayed with Blue Shower cleaner the tuning cap, then blew again to dry, and the rasping noise during tuning is gone now. Somehow it was more pronounced on BC and not so much on SW bands.
The white noise is still there but it is not huge. In fact it might be normal. I will compare it to other radios when fully assembled.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 1,275
Threads: 44
Joined: Nov 2017
City: Menlo Park
State, Province, Country: CA
Good progress I'd say 
The noise while tuning woukd have bugged me too. The constant noise might be normal... a sign of a design with more gain for small antennas.
I don't hold with furniture that talks.
Posts: 15,302
Threads: 532
Joined: Oct 2011
City: Jackson, NJ
Ed
They warn about many gain-related quirks in the manual.
As someone said, 7G605 are turds. Rare, sought after, etc, but turds nevertheless 
Well, it was the first ever portable multi-band SW receiver, it was a learning curve for Zenith.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 15,302
Threads: 532
Joined: Oct 2011
City: Jackson, NJ
The tuning cord came today.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 619
Threads: 42
Joined: Mar 2017
City: Gap Mills Wv 24941
i think it was here on this thread you suspected something along the silver mica disease.
ive been running now 5 different sets in the garage and even my trans oceanic transistor radio was poping.
it went away often,, it also simply came back often.
i started to watch weather underground web for storms.
apparently if i dont have any storms near me then i wont have pops and cracks.
if there is a storm like a state away then i will.
i think this might have to do with the exceptionally tall and long antenna i have up.
when i was experimenting with a beverage antenna.. all this pop and crackle was not present. i am not able to apply a proper beverage because of my land,, not flat... so i really never was able to get the proper layout done.
so with a random wire up high at about 30' and 250' long using tin coated electric fence wire & insulators,,, i am considering going to something smaller in awg and lighter so i an go higher and longer.
if i get above my oak trees, i can easily span 1000 feet
back to you... sorry....
maybe you have an issue with the antenna being too good of an attraction for near by weather related instances.
example.....
today i expect you and i will have crackle / pops ,, i am under a rainy day,, and you have storms off long island and some to your west around Scranton Pa... all this heading your way from us to the west.
after this eve,, or maybe tomorrow i am going to see if all the cracks & pops go away.
we all remember as kids when these sets were fairly common while on AM, you could have early warning of storms coming.
Posts: 619
Threads: 42
Joined: Mar 2017
City: Gap Mills Wv 24941
which brings me to a particular question of curiosity....
you have to wonder how the factory tuned and aligned sets when bad weather was near.. it should have had an effect on calibrating things i would think.. perhaps not...dono, i wasnt there.
Posts: 15,302
Threads: 532
Joined: Oct 2011
City: Jackson, NJ
I don't have any antenna hooked up.
Was working with the plate to which the rod is attached, without the rod.
Not really popping....just noisier than I'd like to.
I alined the IF. I did not put the IF to the converter grid via cap, I simply coupled into the antenna and then aligned.
I am not sure what the initial position of the dial pointer is: is it the black-white divide, is it something else? If I use the divide (the pointer horizontal) I can't get the oscillator to span at 1600. Just a smidge. Moving the poiner just a tad closer to the 1600 gets it.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Users browsing this thread: 2 Guest(s)
|
