[criageek]

Hey jcassity - here is a variac on sale.

http://www.mpja.com/05-04-17.asp?r=378483&s=3

One problem though.  Based on everything I've read on here I think you should have one that's isolated...this one says it's non-isolated.

Rich

[morzh]

I use a variac and an isolation xfmr separately. My variac is pretty much the same as shown here.

[jcassity]

tore out the band selector switch again to access a resistor that needed replaced.
working on a way to make these hidden parts more accessable in the future without lengthening the leads... seems impossible.

Due to what terry taught me about testing the sockets (another thing i would not have known about) i found my V1 7AF7 loktal socket was bad,, replacing now with new.

found some shematic conflicts on 7AF7 updates as well that i am working though.
I am very very very very fortunate i primarily used the fold out diagram from chuck to work on this radio.
if i had used the pamplet technician rendition, i would have been totally wrong!!! everywhere and would probably have smoked this whole set.

question- do i calibrate R102?
On my R102 that was getting hot,  with a 500 ohm installed i have about 300v on pin 3 of my dual 6k6's.
if i install the shematic call out 300ohm resistor the 6k6' voltages will go up and i dont think i want that?
I have purchased about 12 options to solve this resistor for heat and resistance calibration including 2) mouser 300ohm chassis mount reisistors.
I do like the mouser resistors but they dont "look" right for the time on the set. I have many tubular wire wound adjustable resistors that look more in line with the era. I know that if i put two 300ohm resistors in series that will get my voltage down some, the 7AF7 code 125 update says that the normal voltages of 225v on pin 3 of the 6k6's will read about 20v higher with this update.. so a target of 250v?

What is a desired voltage at pin 3 of the push pull 6k6's in order to maintain another half centry of life?
if i have the opportunity to calibrate R102 in order to control the 6k6's voltage and heat, i want to do that now.
i will be ready to install a solution here in a few hours.

----------------------------------------------------------------
here are the resistor options i have for now

4540-012 RESISTOR 50W 400, 50W, ADJ, 4 1/2" LONG... 5 3.25
4540-014 RESISTOR 50W 500, 50W, ADJ, 4" LONG, USED. 10 2.25
4540-044 RESISTOR 50W 250, 50W, ADJ, OHMITE, 4"L, U 1 2.25
4540-062 RESISTOR 50W 250, OHMITE 0568,50W,ADJ,4",U 1 2.75
4540-065 RESISTOR 50W 300, 50W, ADJ, 4"L, USED..... 1 2.00
4540-136 RESISTOR 50W 400, 50W, ADJ., 4" LONG, NEW. 1 4.25
4540-136 RESISTOR 50W 300, 50W, ADJ., 4" LONG, NEW. 1 4.25

RH050300R0FE02 -Desc.: Wirewound Resistors - Chassis Mount 50watt 300ohm 1% qty2 5.57 ea.

[jcassity]

got everything together and radio is back up and operational including shortwave.

let me know about calibrating the R102 i mentioned earlier.

[Mondial]

250 V to 275V on the 6K6 tubes would be about right. They are rated at 285 V max.

Did you try the new 6K6 tubes? Their condition will determine how high the voltage will be.

[jcassity]

yes, all new tubes installed
i have with a 500ohm resistor kit i put togetherchassis mounted i am at 283v.

suggestions?

put dual 300 in series? the mouser ones or another solution?

i have to wonder if there isnt still a problem,,, although ive enjoyed using the radio this eve on my work bench.
i let it run for about 4 hrs straight and the 500 ohm resistor is holding steady stong, no changes to the voltage drop across it. Also my candohm is still holding down 22v.

[Mondial]

Yes, try the two 300 ohm resistors in series. Should give 270 V or so which would be about right.

[jcassity]

is there a source for these chassis mounted resistors somewhere?
what are they called, how do i hunt them, terminology and such.
Does anyone have these i can trade out for ?

of all my options, i can install my mouser gold looking chassis mount resistors but would rather pick something more vintage looking if possible.

where can i find a site that has these?
looking for about 600 ohms.
I have two 2700 ohm resistors of this type and put them in parallel but that brings my voltage too low at the 6k6's.

i believe that 750 is actually my sweet spot

even all of my new 50watt adjustable ceramic types get way too hot to touch unless i mod them to be heat sync chassis mounted.

i am starting to wonder if i should look at 100w or 75 watt.

with only 800ma here, i am starting to really scratch my head, by the numbers 50 watt should be way over kill but it seems not.

[Mondial]

Do not be so concerned with the voltage on pin 3 of the 6K6 tubes. It can go to 315 V or more safely. What is really important is the voltage on pin 4, which is the screen grid. If the voltage on pin 4 is around 250 V or less then you are fine. 

Check this voltage on pin 4 as I believe there is a dropping resistor which reduces the voltage to it. It appears Philco ran a higher voltage on pin 3 but reduced it on pin 4 so the tubes operated within there ratings.

Any power resistor that is not heat sinked to the chassis will get too hot to touch. They will reach several hundred degrees at their rated power and is perfectly normal.

[jcassity]

ok,,
on pin 3 i have about 283vdc,,
on pin 4 of both 6k6's i have around 254vdc,, all good to the info you gave me.,, matches my print as well.
of all the resistors i ordered, this one i had laying around worked out best.  its 611ohms total.
wired it in and placed it outside among the tubes.  there were two convienent holes already waiting for me to mount this resistor right where there are no other components below it.  seemed like the radio was trying to tell me something,, like "put that resistor here!"
During long operation of radio i can still touch the resistor and not get the ouch factor till about 5 seconds so its doing its job wicking heat.
funny story last night....
we watched Dr Who around 11pm then i went out around midnight to piddle some more.  I had no shortwave!!!!!!!
im like,, what the heck happened.  due to my inexperience, the obvious was the last thing i thought of.  since my Philco has SW band of 9.3 to about 15.5KC,, after an hour of troubleshooting and worrying,  it occured to me.... humm maybe theres's nothing on right now.!  I was right.  My  hallicrafters goes from like 1.8kc to about 38kc so i compared and sure enough nothing was on.
got up this morning to let a stupid PITA cat out at 7am and decided to check again,, SW coming in strong.
now i need to buy a dial glass and a needle, then toss it back into the cabinet.  Gather my notes and diagrams and store them in the cabinet for my boys to use about a half century from now.  I might in some time in the future decide to get the turn table working as well,  would need a record for it,, i think its a 78 turntable?

[jcassity]

another thing i learned,,
when replacing loktal sockets,, the factory rivit is best because its lower profile.
the ones i show on my far right closest to you in the pic above shows a standard rivit.
it stands too tall bumps into barely the bottom of my 7AF7 tube. This tube still snaps in place fine but i sure its not ideal.
a little file work would fix it but i wont bother now,, its not broke so i wont fix it.

[jcassity]

gonna be shipping my hallicrafters and the philco off to D-Labs soon to have them both professionally aligned.
i dont have the right equipment to do this. couple hundered bux and they both should be good.

I shade tree alighned the hallicrafers by tweekingi in the WWV on the 2.5, 5, 10, & 15kc and i am very close on 75% of the dial,,, its a tad off on each end.

apparently 20kc on wwv isnt available very often

[jcassity]

dang it,, i need two light bulbs,,

[jcassity]

tech question here...
while on shortwave i hear a tiny humm,, investigated.......
i have a polarized two prong chord update.

with my VOM, from radio chassis to the third prong of my source outlet i have 54vac

should i integrage a 3prong plug on the radio?

I noticed that when i manually jump my chassis ground to the third prong of my source outlet, my reception improves slightly.

whats up with this chassiis difference of potential,, is it because the primary of the power transformer is not chassis grounded?

[Radioroslyn]

>while on shortwave i hear a tiny humm,, investigated.......
i have a polarized two prong cord update.
with my VOM, from radio chassis to the third prong of my source outlet i have 54vac

What you are seeing is some ac leakage or coupling from the .01 line bypass caps. This is normal. If you have a different earth gnd like a water pipe or hot water baseboard heat element may be a little better than the gnd on the outlet.
Grounding the chassis will eliminate this voltage.