Philco 37-650 Plate voltage

[Rick D]

Hi Steve
The voltage meters I have are #1= Velleman DVM-890 LCD Standard Digital Multimeter
#2= Mastercraft Auto Ranging Digital Multimeter
Now some things I have done to the set,I checked #46 resistor and got 4.25K ohms
and I checked #52 resistor and got 405K,at first thought #46 resistor was way off so
I changed it ,put in a 330K resistor and powered up the set,loud motor boating so
I shut it down and put a 3.5K resistor back in.Tried the set for about two hours
and it seemed to work fine,but talking to a friend of mine he told me this is
wrong,#52 resistor should be 3.5K and #46 resistor should be 330K,I agree so
I changed both,I powered up the set and got loud motor boating,so now I changed
the set back to #46 resistor as 3.5K and #52 backed to 330K.I have run the set for
only 1 hour after the last change had to go to bed,but at least that one hour
the set ran fine.Steve as I look at the schematic this hook up is wrong,I
look at the parts list drawing more than the schematic,it is easier for
me to follow and those two resistors should be reversed,but when I do it
the set won,t work right,this Philco set is so hard to work on,I have
refinished the cabinet put in new grill cloth,replaced the output
transformer,replaced 5 tubes changed several resistors and all of
the caps,and those black bath tub ones are no fun to work on,I have
spent so many hours trying to get this set to work right,even
my Wife tells me to take a break get away from that radio,but
I don,t like to give up,the Lady that owns this set wants to
get it working it belonged to her Father who has passed away,
even in her house that the family lived no one can sit a the
end of the table that her father sat,so I hate to give up on
this set,but you know you can only do so much and some times you
have to say enough is enough,I think I am getting to that part,
hey if one of you fellows have a chassis for a 37-650 that you
would like to sell please let me know,all the best Rick

[Steve Dow]

Rick,
Agree with the idea to step back for a while.

The motor boating can be dealt with once
voltages and wiring is correct.

Questions about motor boating:
Is it affected by turning the volume control ?

Does it make the cone move excessively ?

The screen grid pin number of the 6F6 is 4.
A 3500 ohm resistor is connected between
pin 4 of each 6F6.

The grid pin number of the 6F6 is 5. A 330,000
(330K) is connected between the grid pin 5 of the 6F6
closest to the word OUTPUT, and the wire going
to the 190 ohm end of the Candohm.

The Philco schematic is tricky. No pin numbers on
sockets and they are drawn functionally.

Radios techs read the schematics functionally
so know what resistor values are appropriate.

Also radio benches will have a tube manual
handy to translate functional tube drawings into
physical pin location and numbers.

Attachments:

1. 

   6F6.jpg
   

[Rick D]

Hello Steve
I have hand drawn the way the wires are hooked up in this set,when I
look at it I am sure the 3.5K and the 330K #46 and #52 should be switched.
So I switched them and only got a loud hum from the set,so I switched them
back again,after that I ran the set for 1&1/2 hours,seemed to be ok,could
be the resistor that was in the #46 spot was 4.25K,I put in a new one at 3.5K.
I wanted to run it for about three hours today,but I dropped a screw driver
and put a small tear in the speaker cone,so I am waiting for the glue to
dry on the repair,this set is killing me.If I can,t get the drawing I made
in an attachment on this post or if you need a better one ,is there any
way I could email it to you,my email is ,Steve
again thanks so much for the help,all the very best Rick

Attachments:

1. 

   Drawing-1.jpg
   

[Steve Dow]

Rick,
I looked at your drawing, but the only drawings that would make any sense to me are schematics. This is
because I do not have your chassis to look at directly. Without seeing the overall picture, things missed
in-plain-sight, could result in errors.

The best way to draw these schematics is to include the tube sockets, with the pin numbers. Looking at the tube
socket from the bottom, the numbers start to the left of the locating key for octal tubes. The numbers go clockwise.
The 6K6 in the last message is an example. You don’t have to draw the tube elements within the circle.

One end of a 0.01 uFd capacitor connects to pin 4 (screen grid) of the 6F6 closest to the word OUTPUT.
The other end of this 0.01uFd capacitor connects to pin 5,(grid) of the other 6F6.

[Peter Heembrock]

Hi Rick,

I have been looking back at the previous posts and I am curious about one thing…you mentioned that you replaced the output transformer with a Hammond 124D…is this correct?…The 124D is an interstage transformer and not an output transformer.

This would not work properly in the output stage and may cause other issues such as oscillation and higher than normal DC supply voltages.

Peter H

[Rick D]

Hello Steve
Thanks very much, hello Peter that 125D Hammond is listed as a Push Pull output
transformer,I did switch it for another push pull output transformer that the ohms reading were a lot
closer ,I had three so I took the one that was the closest to what the schematics
listed,I got in touch with Hammond and the 125D was the one they said to use.When
I think back I have listed so many things I must have told you it was a 124D
but it was really a 125D,sorry,thanks again all the best Rick
Link to the 125D- https://www.radiodaze.com/universal-push-pull-tube-output/

[Rick D]

Hello Fellows
After I changed the Candohm resistor and also changed the #46 resistor that was 405K and not 330K
and also the #52 resistor that was 4.25K and not 3.5K,with new resistors of the proper value I ran
the set tonight for three hours without a problem,as I look at the schematic and the hook up in the
radio I know there are some changes around the two 6F6 tubes made long befor I got this set that
are not right,but these things are hard to follow,if it was mine I would rewire this thing to the schematics this is
not my radio and I would like to get it back to the Lady who owns it so I will run it for a few times
for about three hours,then send it home.The voltage on the 6F6 plates is now 297 volts,it was as
high as 358 volts,maybe I have fixed this set with all your help,as I said I will run it again
and will let you know how I make out,I can,t thank you fellows enough for all your help,I wish
all of you the very best,thanks so much Rick

[Peter Heembrock]

Sounds like you have tamed the beast…it is always a challenge when previous changes are made by someone for whatever reason…makes things a bit confusing. Philco sets are a challenging due to their capacitor blocks and assembly techniques ( the 37-650 has those .05uF caps stuffed up under the tuning capacitor assembly…quite a bit or work to replace them due the lack of wiggle room ).

Peter H

PS …I hate capacitor blocks.

[Jean Marcotte]

Rick,

I was wondering if there has been any change in the plate voltage after a few more sessions of 3 hours on.

Jean

[Rick D]

Hi Jean
When I first started befor I changed some of the resistors the plate voltage was
around 358 volts and now it stays around 275 to 285 ,at times after running for
a while it may be a few volts down from when I first started,I ran it seven nights
for about 4 hours non stop each time checking the voltage at the start and the finish
and also in between,very little change.Now for the bad news,two nights ago it made
a crackling noise and slowly quit,I was sick all that work,I had to leave it for a
few days,tonight I checked the voltage on all tubes,I found on the 6J5 tube no
plate voltage so I checked on my service data sheet,it has no voltage listed
for the 6J5 tube ,is there no plate voltage on that 6J5 tube ?.And to my
surprise while checking the 6J5 tube the set came back to life,a low crackling
noise but working,but still no voltage on the plate of that tube.I did not
run it more than a minute at a time because it still had a bit of low crackling
noise and I was afraid it would die and never start again.What I did was start
it and with a wooden prob tapped every joint and moved ever wire ,but found
nothing loose or a bad solder joint.I am not moving it I will leave it
on it,s end until I find the problem,Jean do you have any ideas where
I should look,I have sanded the tube pins put a small round file
down each pin hole in the tube base and used a tooth pick with
deoxit to clean the hole,anything else you could think of, I would be
happy to try and very thankful,wow this set has really given me
a hard ride,thanks in advance for any help all the very best Rick

[Peter Heembrock]

Hi Rick,

Having just finished working on this chassis model I can offer a few places to look…the 6J5 is the detector and the plate for that tube is fed through a 1 meg resistor so the plate voltage is typically 1 to 2 volts DC…and not much more.

I would recommend checking the values of item 35 and 34 ( 1 meg each I believe )…and then check item 29 and 30 which are 110pf…item 30 has these caps in a block…normally they are ok but if they have high leakage it can affect the detector stage.

Peter H

[Rick D]

Hi Peter
One of the fellows that is always there to help and I thank you so much,as you
know I have put lot effort into this set, much more than any other set I have restored.
If I ever get this set going right I should be able to write a book on
it,with a few of you fellows as the main characters.Today I have a lot
going on around the house so I may not be able to get back to it until
tonight,but I will check everything you told me to and get back to you,thanks again for
your advice and help,all the very best Rick

[Rick D]

Hello Peter
I checked the two resistors #34 was 1.35 Meg and #35 was 1.15 Meg,I then checked the two caps the # 30
wich is new checked at 120pf and the # 29 the one in the base of the 6J5 tube was 262pf,these parts
were still in the circut when checked but with the 6J5 tube out.Now when I start the set there
is still a crackling noise,the set goes off and on,when this happens the dial light stays
on it dose not flicker,I shut the set off and on until it stays on with no interruption,I still
won,t leave it on for any length , two or three minutes at a time,I am afraid
something might happen and it won,t start again,do you fellows think the caps and resistors
will be ok or should they be changed,if I have to take them out of circuit to test them
I may as well change them ,they are all around each other and hard to get at,so if I have
to I may as well replace with new,I will wait to hear from you fellows befor I do anything
just to be sure, any ideas on this problem,I am lost,thanks again all the very best Rick

[Jean Marcotte]

Rick, poor Rick!!!

That crackling can come from anywhere in the radio. But since the dial lights don’t flicker, we at least have eliminated the on/off switch. It may seem like a joke but that is quite often a problem. Now when the set goes on and off, are you just loosing radio signal or is the speaker totally dead ? Try to monitor the plate voltage of the 6F6’s to see if it falls when the set goes off. An analog meter is best for this. From there we can work backwards and eliminate the b+ as the problem. Maybe we will find the trouble before Christmas (now that’s a joke).

The reason I asked for a more recent reading of the plate voltage is that since you started this thread, the plate voltage has kept coming down fairly regularly. We started at 358V and now we have as low as 275V and nothing specific has been done to that effect. So what I think is that the radio has been stored in bad conditions for years and the power transformer accumulated humidity. The first winding on a transformer is the primary and so it is the deepest and hardest to dry. What probably happened is leaking of the primary because of humidity, giving the same symptoms as a short and as time goes on (with the radio on) it is now drying and will keep getting better I hope. But the voltages now are less a concern.

Find the cause of that crackling and then we open a bottle of champagne.

Jean

[Steve Dow]

Hi Rick,
Philco gives no plate voltage for the 6J5 because the voltage chart refers to use of a tester
with a 1000 ohms/volt rating. Using that kind of meter, no voltage would show.

Also measuring the voltage would inhibit operation of the AVC circuit.

When you touched the 6J5 plate with your meter probe, you detuned the
circuit slightly , and your DVM picked up the voltage. Was the voltage
positive or negative ?

Does the shadow meter work in the radio ?

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