06-26-2018, 08:13 AM
all is not well.
lesson- dont turn your back on this set,,,
when you look into this ones eyes, you can see it working things out!!
--tubes---
i have two spares of all tubes that all checked out fine during which time the set was playing for over 4hrs just fine.
exception is i have only one spare 25L6 rect since one out of the box seemed to have failed.
most all the tubes i got from play things of the past were metal type RCA tubes ,, yet all were installed as a group and in various stages individually while i was troubleshooting.
I set up the set in its home , go in the house leaving it play and return to nothing but crackle noise.
all caps replaced to this point.
i take it apart again and back to the bench.
symptoms:
tubes light up
in about 10 sec speaker comes to life with crackle -static - crackle -pop.
the volume out of the speaker seems to default to a simulated 30% of max vol
rotation of band switch offers no speaker noise.
rotation of vol ctl knob offers no increase or decrease in speaker output.
rotation of the tone does affect the speaker noise i hear going from treble to a base / muffled sound.
tests i have done so far during this particular event............
Grounded the center tap of the vol control to chassis and the noise remained.
bench tested each tube to dongle off to the side jumper wiring only the filiment. see picture(s
--this was done to establish when the noise went away compared to which tube i had out of the ckt.
--after all tubes were dongle bench isolated & tested, the noise remained still!
----two of my tubes have the filliment on pins 7 & 8, the rest are 2 & 7.
--the above dongle test excludes the 25L6 and the 2) 50L6's.
replaced filter caps from 450v 47uf to 160v 47uf
-- i did the above because during my prior steps to geti it working one of my rectifier tubes finally set off a light show so i figured the filter caps might have taken a hit.
up above i mentioned i grounded the center tap vol ctl of the 6sq7 and the noise remained which i consider the "input" side.
I lifted off pin 6 of the 6sq7 the .01uf cap and the 220kohm Resistor and the noise goes away.
---with the above lifted leads, i am barely able to now tune to a station and i can hear things but very little vol is avail at max.
I used a plastic tool to jiggle connections around while the set was on doing a wiggle test to see if i could affect the noise in the speaker one way or the other. each connection on the bottom was wiggled and no change is speaker output
i examined the band switch under a magnifying glass to verify contacts were being picked up as the BS switch was rotated, i even bent all of them slightly down and watched them make contact.
i started shot gunning resistors and replacing all of them working my way though the 50L's to the end of the set. there are 2) 2.2mg, 1) 10mg and another that i did not replace due to access difficulty and they looked good and read within acceptable specs. so... nearly all resistors are also replaced.
****When i install all 3 of my 6sq7's, the set still has noise , the odds of all three tubes being bad is questionable.
when you ground the vol ctrl input to the 6sq7-2 and the noise remains, then lift all leads on the output of the 6sq7-6 and the noise goes away, your supposed to say you have a bad tube,, but all three are bad?????????????
*******************What makes less sense is that when i dongle bench tested and got to the 6sq7 where i only had filliment power to the pins 7 & 8,, my noise should have gone away...... yet the noise remained!!!!!!!!!!!!!!!!!
to be real honest, it sounds like something bad in one of the IF's , with all the poping and cracking going on. There is one single mica cap on the bottom ,, if this type of cap is inside my IF's, then i might have silver mica disease again? like what happened to the IF on my hallicrafters s53.
I do own a signal gen capable up to 150MC with bnc to gator clip leads and a frequency counter with bnc to gator clip leads that i purchased to do alignments with.
today....... i will.......
pull up the print, zoom in on the voltage and resistance tables ,, copy / paste to paint, then save as a jpg then print and jot down my readings.
lesson- dont turn your back on this set,,,
when you look into this ones eyes, you can see it working things out!!
--tubes---
i have two spares of all tubes that all checked out fine during which time the set was playing for over 4hrs just fine.
exception is i have only one spare 25L6 rect since one out of the box seemed to have failed.
most all the tubes i got from play things of the past were metal type RCA tubes ,, yet all were installed as a group and in various stages individually while i was troubleshooting.
I set up the set in its home , go in the house leaving it play and return to nothing but crackle noise.
all caps replaced to this point.
i take it apart again and back to the bench.
symptoms:
tubes light up
in about 10 sec speaker comes to life with crackle -static - crackle -pop.
the volume out of the speaker seems to default to a simulated 30% of max vol
rotation of band switch offers no speaker noise.
rotation of vol ctl knob offers no increase or decrease in speaker output.
rotation of the tone does affect the speaker noise i hear going from treble to a base / muffled sound.
tests i have done so far during this particular event............
Grounded the center tap of the vol control to chassis and the noise remained.
bench tested each tube to dongle off to the side jumper wiring only the filiment. see picture(s
--this was done to establish when the noise went away compared to which tube i had out of the ckt.
--after all tubes were dongle bench isolated & tested, the noise remained still!
----two of my tubes have the filliment on pins 7 & 8, the rest are 2 & 7.
--the above dongle test excludes the 25L6 and the 2) 50L6's.
replaced filter caps from 450v 47uf to 160v 47uf
-- i did the above because during my prior steps to geti it working one of my rectifier tubes finally set off a light show so i figured the filter caps might have taken a hit.
up above i mentioned i grounded the center tap vol ctl of the 6sq7 and the noise remained which i consider the "input" side.
I lifted off pin 6 of the 6sq7 the .01uf cap and the 220kohm Resistor and the noise goes away.
---with the above lifted leads, i am barely able to now tune to a station and i can hear things but very little vol is avail at max.
I used a plastic tool to jiggle connections around while the set was on doing a wiggle test to see if i could affect the noise in the speaker one way or the other. each connection on the bottom was wiggled and no change is speaker output
i examined the band switch under a magnifying glass to verify contacts were being picked up as the BS switch was rotated, i even bent all of them slightly down and watched them make contact.
i started shot gunning resistors and replacing all of them working my way though the 50L's to the end of the set. there are 2) 2.2mg, 1) 10mg and another that i did not replace due to access difficulty and they looked good and read within acceptable specs. so... nearly all resistors are also replaced.
****When i install all 3 of my 6sq7's, the set still has noise , the odds of all three tubes being bad is questionable.
when you ground the vol ctrl input to the 6sq7-2 and the noise remains, then lift all leads on the output of the 6sq7-6 and the noise goes away, your supposed to say you have a bad tube,, but all three are bad?????????????
*******************What makes less sense is that when i dongle bench tested and got to the 6sq7 where i only had filliment power to the pins 7 & 8,, my noise should have gone away...... yet the noise remained!!!!!!!!!!!!!!!!!
to be real honest, it sounds like something bad in one of the IF's , with all the poping and cracking going on. There is one single mica cap on the bottom ,, if this type of cap is inside my IF's, then i might have silver mica disease again? like what happened to the IF on my hallicrafters s53.
I do own a signal gen capable up to 150MC with bnc to gator clip leads and a frequency counter with bnc to gator clip leads that i purchased to do alignments with.
today....... i will.......
pull up the print, zoom in on the voltage and resistance tables ,, copy / paste to paint, then save as a jpg then print and jot down my readings.
