[TV MAN]

I always thought those Zenith radios had a lot better sound than others I had heard. They seemed to play forever without problems. I have one with dead FM that I am going to try to get running for a 'test' radio. Glad you get yours running.

[jcassity]

well, this thread is not over.

taking a study on the prints to figure out how to inject a smart phone jack so the wife can use spotify for other things on the web like audio books, music and such.

i found a vid where Terry (D-Labs) got this to work but.............. his set has a power trasformer,,,, i dont!,,, and perhaps i am reading to much into a simple mod.
I searched the site here and am still reading up on others experiences.
maybe there is a link here already on "how to" for transformerless and transformer sets.



in the below link,, i get how its simple and 2$ in parts.

https://www.youtube.com/watch?v=j8YeJ0T3DpI

[jcassity]

well darn...

someone said dont use 160v rated filter caps on this beasty!

turns out i should have listened.

what i used fit really well into the original multi section can.

i will see what i can do to remedy the situation.

this would be a 150v 80/40/40 & a 40uf 25v.,,, so maybe i will install the 25v free air under the chassis to save room.

i am going to use 250v rated caps for the first three, the 80/40/40.

[jcassity]

ordered up caps and since Gary at play things sent them out so quick, i dove into the cap can today.

my prior mods made it easy as pie.
pics below of the mod.
i have a ground conductor making a ring around the interior of the can for all the cap negatives to tie to per the schematic.

each individual terminal post 4 total was given a solid #12 pigtail to land the caps pos side.  this #12 continues down the bottom to the original solder tab where the other bits tie to.

my zenith was playing yesterday evening then it started to crackle and pop until no station could be heard and all that you could hear was the crackle and pop.  going up or down with the volume did not change the audibility of the crackle or pop.  It really sounded like silver mica disease inside some of those small IF's with slug tuning.  i powered down and took it out to the shop, measuring the caps they all were reading high,, like my 47uf were reading like 160,,, my 100uf was reading around 180.

thinking this is the issue i ordered up caps first then today i opened up the can.  i undid the 100uf cap and measured it.. its reading around 95uf.  all the other 47uf caps are reading fine as well.  maybe i had a lead touching somewhere underneath ,,, who knows.
All i know is that i soldered everything back and the set is playing now.  i ran a heat gun on top of the set while playing to simulate something over heating to make it fail quicker but its not.
right now i have it pushed up into the case and letting it play and get warm in its case.

so here are the pics of my rendition of the filter caps and how i did it.

[jcassity]

ok,, i went ahead and after about an hour of running it hard, i brought it back in the house thinking all was well but its not.

so apparently after some amount of time, this thing starts to do this......
the crackle and poping is common to both AM and FM bands,,

click on the link and play the vid.
crackle and poping
this is gonna be a hard one to troubleshoot unless someone knows a trick.
i am going to have to find a way to get the volume down while its failing in order to work on it otherwise its going to drive me crazy listening to all that crap.
the only way to figure this out is to troubleshoot during it failing i guess,,, right?
or....... let it finish cooking off whatever it wants to break so that the speaker hopefully then goes quiet??

https://www.dropbox.com/s/20nwkjef2d3cbp...1.mp4?dl=0

the selenium rectifier has good ac in and good DC out,, and i dont have any odd smells.... but it could be the fault as well and its just not done cooking itself to death yet.

[Paul Philco322]

Silver migration? 

Paul

[David]

Try cleaning the tube sockets, look real close at the sockets for the 35B5 and the 19T8. If you have a set of tip cleaners for a torch try them. David

[Radioroslyn]

Ok so try disconnecting one end of R-21 (330 ohm) resistor and see if that stops the noise.

[jcassity]

will do but first
i have to warm up the set till it starts to fail.

i want to kill that noise but still have the set failing to take test point measurements... so can i put a 3 ohm resistor in place of the speaker? or can it continue its free fall without a speaker attached?
i know in the past you've said its not good to power some of these sets up without a speaker.


is it risky to keep it powered on while its failing?

[Ed Locker]

Check C-18 ( 500 pf ) by disconnecting it and see if the crackle stops.

[jcassity]

will do,,,
still awaiting it to fail,, itts been out of its cabinet on the workbench for about an hour now and not failing,, although i am starting to hear hints of slight "gargle" noises just ever so barely.

[jcassity]

here is a better schematic of this chassis

[Ed Locker]

Might try blowing some heat ( from a hair dryer ) on the bottom of the chassis to see if that speeds the intermittent up.

Ed

[jcassity]

10 15 am- extracted chassis and ran the set which in all respect seems its working fine yet im in the garage and the ambient room temp is 55deg,,,, wood heat is fixing that issue.
11 15 am- still not failing
12pm - added heat gun air to top and bottom about 12'' away for about 5min ,  still no fail

12 01 pm - i use a non-conductive screw driver and start poking at all the parts and wires underneath attempting to check for intermittent connections,, none of my prodding produces any bad noises out of the speaker.

12 30 pm - still no fail.
12 45 pm - put radio back inside the case to let it build up heat  on its own kinda trapping it like normal

1 30pm - still not failing

1 45 pm - i check the operation of the outlet in the house i am using,, it passes,, radio still not failing

2pm - i phone  a friend... update him on the radio... we have no clues other than dont bring the radio in the house. the idea is to set the radio on the porch, open a window and let the wife enjoy it since she's taken ownership of it as soon as she saw it. ,, LOL (winter time). The radio is still not failing

2 15 pm - i give up and start putting my knobs on and chassis to cabinet bolting hardware all while the radio is still playing.

2 17 pm - i get to the third chassis mounting screw and the set starts to fail

i observe whats happening as the screw is tightened down,,,,, the Bakelite cabinet iitself is not level along the bottom where the chassis sits,  its slightly warped or tweaked,, and thus as i tighten down my bolts, the chassis "twists" so to speak.

i back off on all my chassis to cabinet hold down hardware and the noise starts to dissipate and go away and the station i am on becomes clear again.

so.... on the cardboard back i put a piece of tape on there and wrote this :

"Finger tighten *only* the chassis to cabinet hardware on the bottom or the radio will start to crackle and pop.  suspect a cold solder joint or cracked tube socket somewhere"

this will be my fix to the problem because the last thing i want to be doing is chasing down something that is probably microscopic especially with the set is playing just fine now.

so..... another odd ball problem i encounter.