Guest Join UsHello Guest,
Please feel free to join us!
Unlock sections of the Phorum that non-members cannot see.
Sign up for Phorum membership today! or Register


Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Hallicrafters S53-A
#1
Got this free a week ago.
Will be a christmas gift to my youngest boy but.........

owner said he messed up the speaker wires,, i fixed that and went over it some.  Its all original except tubes.
this is an 8 tube radio by the way. it looked so nice and nothing to worry about under the hood i opt'd not to recap or anything. it looks like its been mostly just stored and such, with some minor exterior scratches and such.

powered up and it worked fine.  Since i disagreed with the design, I took the set out of the cabinet and did a mod.  I  cut the bottom open and made a non-conductive plexi-gllass cover to go on to make it easier for future repairs plus its really neat to see all the parts.

I did notice during my power up over a few days that the radio acted like there was an intermittant connection but it seemded to go away on its own.  the speaker would sorta cut out or pop.

I installed the radio chassis into the cabinet and powered up tonight.  The left 75% of am band was absent but slowely all AM band was absent,, all gone with some slight noise from the speaker.

I dont have a scan of the schematic, just a pdf.

I have no more radio channels anywhere coming out.   If i let it cool down some i can revive the sound some but eventually the speaker for a few moments goes to high crackly tone then goes almost dead, i turn up the volume an i can hear some noise but not stations. 

Is this a symptom of a bad audio output xfrmr?  i need to act fiast to make the set work by christmas.,, shipping and all considered.

thank you,
Scott
304 772 3411 if anyone wants to talk through probable faults.

I plan to take some measurements tomorrow. I hooked my meter up to the two wires that connect to the speaker (speaker disconnected) and i was getting zero ohhms.

the speaker reads about 2.3 ohms itself.
Reply
#2
Possible when you powred up after many many years of non use that a cap went bad or some other part stressed and failed after current applied for some time. 

Maybe a recap before Christmas? Best of luck.  Icon_smile


Paul
Tubetalk1
Reply
#3
No, this is the product of a defective local oscillator, most likely a bad resistor in the circuit, but the old paper caps are likely not helping, most of those can be melted out and restuffed for looks however. As for disagreeing with the design by putting a plexiglass bottom under the chassis, there may have been a reason why the set had a metal bottom other then preventing stray fingers from getting a shock, sometimes the bottom covers acted as a shield against electrical interference, sometimes they also acted as protection in case a component shorted out and melted down, which did happen sometimes.
Regards
Arran
Reply
#4
the shielding idea i was also thinking of but that was shot down when i played the radio while it was extracted from its chassis.

All caps replaced, no change.

filter caps next.
Reply
#5
this has been frustrating, order of events.

i get the radio free
i power up and it works fine for a week, small poping noises now and again.
the normal things like switches and knobs need lube and move around a bunch with some cleaning and such.
prep for christmas and then i pull it back out to modify the bottom to add an access cover.
I extract the radio chassis and set it off to the side.
I mod the case , all went well.
I assemble the radio again and...............

upon power up the lower 75% of am bands are absent
upper parts of am band were there but fading fast.
speaker volume was drifting lower and lower until finally max volume sounded like 20% volume.
All i hear is something like "snow" noise like TV sets were there is no signal. , not AC noise.
Using a 6' aligator clip lead as a random antenna, connecting it up makes no noises
Rotating the band selector swich produces none of the normal crackle you usually get when you do this.
I measure my audio output xfrmr, its like 350ohms on the pri, about 28ohms on the sec.
I move over to my documentation and start taking readings of each tube per the instructions.
All readings were acceptable except for one particular one which said i need a negative less than a volt measurement when i vary fequency.
I never once questioned any of my readings, they all matched the Riders instructions.


I recap one at at ime until the last cap an nothing improved.
I even quickly did a simple resistor check ... Measure one side for voltage then the other side to simply "observe" on my meter a voltage drop that seemed mathmitically correct of the expected voltage drop.
I did not find a resistor that was acting in such a way that was shorted.
I did not find any resistor or thier bands obscured due to over heating.

Everything parts wise on the bottom all looked very cherry, like nearly new.
I am waiting on parts to recap the filter section so the filter section is still original 4 part.

Last night i confirmed that the filter caps are drifting way out using a digi meter so maybe perhaps this is my problem.

all i know is that normally when i troubleshoot i find problems by following the test procedures.

in this case even though it passes the voltage tests, that means nothing. I have no humming noises at all typically found if a filter section is going out. This actually depends on which way the filter caps are failing. if drifting towards a short or drifting upwards in capactiance... in my case one 10uf 25v filter cap was drifting towards 3uf, while my 50uf 350vcap is drifting towards 100uf.


maybe tomorrow i will have the 47uf 450v cap to replace my 50uf 350v cap along with the others to repair my filter setion.

I do have a 6h6 tube that has something inside it that rattles. its a metal midget 8pin tube.

when i remove this tube and power up, the set still acts the same,, not change.

I guess what i am saying here is i never like it when i end up shot gunning the problem, cause thats what i am doing right now.

At this point i "know" of 3 problems.
1- the 6h6 tube should go.
2- I had no inication the filter section was going out but eventually i guess i would have...
3- my ability to accept common sense in that with sets this old, step 1 is to replace all caps,, something i should accept and make it muscle memory.
Reply
#6
here is the schematic i am using,, modified it to make it larger


Attached Files
.pdf   s53a schematic drawing.pdf (Size: 126.02 KB / Downloads: 9)
Reply
#7
update since last night ,
now things have changed.
I believe the radio is trying to tell me something more pointed now

When i power up, the radio is not safe to be on for longer than 20 seconds.

there is a 1000 ohm reisistor across the filter cap that gets hot enough to let off a certain smell we all know.

do you all think the filter caps are drawing down my speaker volume and such?
Reply
#8
a few pics of this radio

this is after i redid all the caps, excluding the filter section.


Attached Files Image(s)
           
Reply
#9
prep'ing the filter cap replacement the Radioroslyn way!


Attached Files Image(s)
           
Reply
#10
clean the muck out, drill some holes for the new leads,  then add some fish paper insulation with a note to my son he will find one day in the future,


Attached Files Image(s)
           
Reply
#11
hope to have this working tomorrow if Gary at play things of the past comes through for me.

got a box of tubes from the guy who gave me this radio, he's the same one who took all the remaining tubes i had off my hands
Reply
#12
Good luck, sometimes these things are just like holes, dig deeper, more problems.

Paul
Tubetalk1
Reply
#13
filter caps changed,
radio still doesnt work.

the 1k ohm resistor across my 6k6 is still getting hot and can not power on for more than 20 seconds.
Reply
#14
yeah,,, im pretty much lost. just knocked off the the day, hope to have this working for christmas.

i see a bunch of dog bone resistors.. since im shot gunning things.. do those generally go bad?
'
Reply
#15
Go over to C37c (last 10mf filter) and disconnect wires from the terminal except for the 1K resistor. Check the voltage at C37c w/those other wires disconnected. Should see abt 200vdc there. If so then connect the disconnected wires one by one measuring the voltage each time you reconnect one to see which wire causes the voltage drop. This will sort which section needs going over, the osc, the 6SC7 audio stage, or the mixer screen grid circuit.

GL
Terry
"Just because the microphone in front of you amplifies your voice around the world is no reason to think we have any more wisdom than we had when our voices could reach from one end of the bar to the other"     Ed Morrow

Terry
Reply




Users browsing this thread: 1 Guest(s)

About Philco Phorum

The Philco Phorum is a family-friendly place for the discussion of Philco radios and related items.

Please feel free to join us! Unlock sections of the Phorum that non-members cannot see. Sign up for Phorum membership today!

           Quick Links