[jcassity]

i already reconnected all that other stuff back up. i see what your doing thought,, gotta start early tomorrow ,

[jcassity]

nevermind my previous post , has nothing to do with what you asked.
Although i have reconnected things,  i believe this is the junction you mention.
this junction would be the only terminal on my filter cap section i show in my previous pic where there are 2 wires.

doing this now

[jcassity]

update for others reading this.
when i power up, at the + side of C57c filter cap & 1kohm resistor R38 i experience this.....
radio warms up and meter shows voltage ramp up to about 325v, quickly the voltage ramps down to only 55 or 60vdc.
radio has no output.
if i leave the set on for more than 20 seconds the 1kohm resistor will overheat.

terry,
I disconnected the two wires at C57c.
my voltage settles in at around 230vdc when i leave this branch open that feeds pin 5 of the 6c4.


I do notice now that what i thought were dog bone resistors are actually CAPS!!

[jcassity]

same problem,, all day messing with it.

my 240vdc output of my rectifier tube quickly drops down to 60 or so vdc after about 20 seconds. the 1kohm resistor down along the filter caps gets wayyyyy toooooo hot so i have to shut down.

when i isolate out the circuit i show in the diagram above, my 240vdc stays steady after warm up.

when i reconnect this branch, i then cut the terminal on C40 100pf cap on pin 1 of the OSC 6c4 , this isolates out the tuning cap and this one C40 cap..... same problem. my rectifier output voltage dives down to about 60vdc during warm up.

[Radioroslyn]

For those of you who are watching at home after several phone calls and digging into the schematic we found that this HV distribution is wired slightly differently than the schematic. There was another wire connected to C-37C feeding the 1st and 2nd IF amp's plate voltage. Schematic shows this wire connected to C-37B.

The problem ended up being a low resistance path across T-10 the 1st IF transformer. From pri to sec was about 1.5K this applied + 200vdc to the control grid 1st IF amp tube V-2. It didn't like that! Caused the tube to draw excessive plate current pulling the HV down.

I'm thinking that the two fixed caps in the IF can are shorted from silver migration, but that is yet to be seen. We do know that the IF transformer has resistance from pri to sec which it shouldn't and there is a high + voltage on the control grid of the IF amp.

[jcassity]

well, this radio did not make it to the christmas gift pile,

it just occured to me (sunk in) that the only way the IF can have resistivity between pin 3 and pin 1 is through the caps.
by design, its a single mounting pad but 45% of the pad on the left and right are allocated to each separate cap. the gap in between is getting full of crud that bridges the pri and sec coils.

I know i have to remove the rivit.

i will take the first IF apart again.
I will see if i can rake a dental tool along the gap to remove anything that bridges these two caps.
basially hoe out any debris to separate the two sections.

i was so confussed becuase i found it nearly impossible for the pri coil to be touching the sec coil, now that i see the flaw in the cap design, two caps under one roof, i get it now.

i want to re-assemble and see what happens.
if anyone has already done this and it fails, then i wont waste my time coming up with what i think is an original idea yet its already been done and doesnt work.

so.... let me know.

the purpose is to see if this can be done with little affect on the alignment.


one interesting troubleshooting method was revealed to me by a vid where the gent had poping noises like i had during the time the radio was working. His symptom was some speaker volume but no stations come in. he flipped the chassis over to show the bottome of the IF. He turned out the lights and operated the volume control and other widgets. with lights out and when poping noises happened, you could "SEE" bright flashes of light at the base of the IF.
Key indicator early on that the IF could be the root problem.

[Radioroslyn]

You need to remove brass rivet and remove the thin mica sheet. Cut the metal tabs that are on top of and below the mica sheet so they can not short together. The issue is that the mica becomes contaminated from the metal tabs. This changes the mica from an insulator to a CONDUCTOR. So the mica has to go as do the tabs that make up the fixed capacitor. Once you get that done measure the resistance from pri to sec, should see no resistance between the two coils. Then reinstall.

[jcassity]

got gifted with a new project from the wife,, a Nixie clock straight from scottland! should be interesting to put together since its all in pieces now.

to this radio, i should have the new 100pf caps swapped in tomorrow.

[jcassity]

I have 3 IF cans with what i assume is the automatic radio number first and the confirmed Hallicrafters pn second.

IF1  T10
119-3-18-inkstamp on can
50C241-inkstamp on can
47A086= the manual says this is the manuf pn


IF2  T11
119-3-18-inkstamp on can
50C241-inkstamp on can
47A086= the manual says this is the manuf pn

IF3  T12
119-3-28-inkstamp on can
50C242-inkstamp on can
44B388= the manual says this is the manuf pn


In this vid ..
https://www.youtube.com/watch?v=zCy69oYq5wc

He notices that it appears T11 and 12 are the same and T10 is different with respect to the caps.

he says T10 should be around 100pf,  he says T11 and 12 are going to need 47pf caps.

so............
does anyone have a resource link to these IF's where perhaps the OEM specs for the caps is posted in a document somwhere?

I want to make sure that i dump back in a cap that is relatively close to the original but as you can see i have two different setups for IF's,, so its pretty clear to me that 100pf on all the IF's pri and sec wont work in my case as a baseline to get these silver mica's replaced.

I figured i would replace all three,, although i plan to only take care of T10 for now, then listen to the set.  If its poping then i will move on to T11 and 12 mods.

[jcassity]

i guess what i am saying is ,,
is there any way to reverse eng the pn, or perhaps look for a number on the silver mica caps to determin a valuse,, perhaps a number stamped on the dual section cap itself?

[jcassity]

took a lot of time today going through my domino type caps, not a single 100pf around.  I could have rigged something up with what i had to test it but.......... why not just wait for the right pieces parts.

T10 IF transformer based was stamped with Automatic Corp.
sure wish  had info on any spec sheets by them to determine if i am using the right guess here on the 100pf caps.

not only is there signs of strikes and deterioration, there is a hole blown right through from one mica cap to the other passing through the clear spacer.

came apart really easily, I am thinking of using very tiny caps to bridge the tabs.  I would like to install the caps right inside the can and space the tabs so that i dong cut away any lead length that may have contributed towards the alignment.  .. otherwise i will just mount the caps down under the can.

[jcassity]

I really dont like these caps!

[jcassity]

any thoughts on hand making a gimick capacitor for this applicatioin? I have some very tiny wire if it is acceptable?

[vinzer]

I don't think you could get more a few pf out of gimmick cap.

[Radioroslyn]

Roughly it's about 1mmfd per turn.