[Eliot Ness]

......something is getting warm and distorting the whole signal.......

Do you have any Freeze Mist to spray on various components to try and isolate the problem?  A can of compressed air turned upside down will spray a freezing mist also.  In field service we used to use a mild heat gun and freeze mist to help isolate intermittent problems.

Although it sounds like you located at least one problem with too much current draw through that resistor.

[jcassity]

No I do not have freeze mist

[jcassity]

Although it sounds like you located at least one problem with too much current draw through that resistor.

no,, that was a isolated situation that was not a part of the radio working.

the set still does this.

warms up then i have no control over the crackle and poping on the speaker **WITH VOL all the way down, stations are not tuneable .
i have dongle jumper wired the filiments of each tube excluding the rect and push pulls and powered up.. the noise remains.

when i lift the 220kohm resistor on pin 6 of the 6sq7, the noise goes away.,, and if i turn vol up to max then i can tune to a station.

when i ground the input to the grid of the 6sq7,, the noise & problem remains.

when the set cools down , and all terminations connected, i power up and the set works fine for about a minute.

so far it appears there is a bad socket,,,  but ive been told its not really likely with this type of set but "could be" possible.


Three 6SQ7's were used in this socket and all three tubes have the same result.

[35Z5]

There will be a major howl, moan, groan, etc from the gallery but after popping starts, try this.

Look at top of IF cans, note slot position of screw. Adj counter clockwise approx ¼ turn any of your choice. If it makes no difference, return to orig position and go to next adjustment.

I'm thinking you may have arcing under one of the mica wafers inside can. Anyway it's a far more likely sereno than a bad tube socket.

[jcassity]

I removed the 6s Q7

I jumpered the filament
I powered the radio up and the problem remains

moving on to the next test to move the mica capacitor adjustments and see what happens

[jcassity]

I can look but I do not believe these cans are subject to Silver Mica disease

[jcassity]

I marked all the tuning capacitors on the if cans

  I exercised their position left and right a whole lot this evening

 right now it seems like something has fixed itself because the 6 SQ 7 pin number 6 now seems to maintain about 37 to 40 volts DC

however...


Eventually the set will break down and the voltage on pin 6 will begin to drop

effectively the problem Still Remains

who wants to take this on as a set to repair because I'm not Advanced enough to figure it out

I do not own a signal tracer

[jcassity]

also tom,,,

i saw a youtube that a guy found a bad IF with those silver mica caps by turning out the lights with the set upside down and he could "see" the lightning show.
i did that on my s53 and saw the same thing,, got some similar IF's from play things of the past and installed, then did an alignment ,, then it became a christmas gift for my youngest son... still going.

in this case i have no visual arching that i can see.

i think now i am at a situation where i need to use a signal tracer.

all i have is a huntron, few meters, a signal generator and a frequency counter.

[jcassity]

im now open to shipping out to someone who can take a crack at fixing this set...

scott
304 772 3411

i am stumped,,, very

[Eliot Ness]

If you're totally discouraged just put it back together, stick it on a shelf somewhere, and take on your next project.  Eventually you can come back to it with some more experience and tackle it once again. 

Taking a break from something like this lets your mind wander back to the problem now-and-then and sometimes a bright light flashes on with something else/new to try.  You'd be surprised what you see in a chassis the second time around that wasn't obvious the first time.  Like Red Green says, I'm pulling for you, we're all in this crazy hobby together:

[Video: https://www.youtube.com/watch?v=Orjbwv8H9zM]

[jcassity]

im not discouraged,,
i am saying its beyond my capable maintenance.,, !~ i am still very motivated.

I have been getting expert help and when the answers are leading towards "if you had a signal tracer then.........." or,, "I dont know what the problem is either",, that tells me i am way out of my league on this one.

all things point to a bad "something" at the 6sq7.

when the left signal input leads from the upstream IF are disconnected and tube installed , the problem remains.
when the right hand 220kohm resistor is lifted with tube installed, the problem goes away.
when i use jumper wires to pins 7 & 8 from the socket to the tube as it lay on the bench beside the set for the filament, and power up, the problem remains.
when i completely omit the 6sq7 and jumper wire from pin 7 to pin 8 on the 6sq7 tube socket, the problem remains.

I am going to change the few remaining resistors, finalize the replacement filter caps in thier perm home, re-install the 40ohm power resistor, then retest.

the one constant i have is very important.............
when the set is bone cold, 9 out of 10 times the set starts up and works pretty good.
as the set plays over an unpredictable but rather short period of time the voltage on pin6 of 6sq7 starts to degrade and eventually reaches 11vdc,, where the tech specs say i need to have 60v.

so,, two things should be my focus...
pin 6 on 6sq7 voltage degrades and only does so after "something" is loaded up with heat.
by feel, the only "thing" getting hot other than tubes is the one 40ohm power resistor.
all other things are cold as a cucumber after the set has degraded and become nothing more than a noise crackle box.

[EdHolland]

Can you substitute the 220 KOhm resistor?

If that was intermittent/bad, it would explain the low anode volts and, possibly, the crackling.

Ed

[jcassity]

I did already sub it for another and problem remains

[David]

Take a break for a day or two then go back and recheck all your work. looking at your notes and compare what you have done. When moving stuff around under the hood sometimes things get damaged such as ceramic disc caps they were good but now need replacing ask me how I know. If I lift one end of a old resistor and it test good I will go ahead and replace it just to many problems in the past when left in the radio.

[EdHolland]

Thanks for confirming the 220 K replacement.

Low HT on the anode is either a bad resistor (confirmed new) or a fault in the grid circuit causing high current draw in that valve/tube. The only DC path I see in the circuit is a 10 M to chassis.

I assume that you replaced the 0.005 uF cap between the pot and pin 2