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 Post subject: Re: Philco 37-38
PostPosted: Apr Fri 12, 2019 11:51 pm 
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Joined: Nov Sun 20, 2011 1:10 am
Posts: 388
Location: South Carolina
I isolated the 50k pot by clipping all the wires to it. I connected to D15 (2x15k in series=30k)then a 10k and a 3k=13k in series and a 6k8 to c+. I jumpered c+ and b-. Now I am getting -3v anywhere I Connect to in the resistor chain.
What is wrong? I also removed the 900ohm from the radio.


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 Post subject: Re: Philco 37-38
PostPosted: Apr Sat 13, 2019 4:47 am 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 3388
Location: Lexington, KY USA
Is the power supply connected to the radio? Get it working first, then connect to the radio.

The only way to have the same low voltage at all the C voltage taps is to have multiple wiring errors and / or bad components. Things in the actual circuit do not match the schematic.

Ted


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 Post subject: Re: Philco 37-38
PostPosted: Apr Sat 13, 2019 3:04 pm 
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Joined: Nov Sun 20, 2011 1:10 am
Posts: 388
Location: South Carolina
I left a connection out. I am getting-3 and -8.5 now. I think my power is ok
I removed the 900ohm resistor (item 40). I assume I don’t need to
Replace it with a wire to still make a connection?

So far I am getting nothing from the radio. But I have not replaced the electrolytic or that potted capacitor ( item 30)
I was hoping the tubes would at least warm up.



Update: I went back and checked my voltages,
All are really close to the schematic except the plate on 1J6G is .2 and
It should be 135. On 1E5G the plate is 104.6 and should be 50. The SG on
1C7G and 1D5G are a little low at 62 and should be 70.

Thanks for any ideas


Last edited by ken/sc on Apr Sat 13, 2019 8:48 pm, edited 1 time in total.

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 Post subject: Re: Philco 37-38
PostPosted: Apr Sat 13, 2019 6:38 pm 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 11445
Location: Mountains of Mourne. Ireland.
Image

It's best to replace all wax and paper capacitors first... :)

Here is your Bakelite Block capacitor - part No. 30
6287-SG
Image
The Working Voltage for your capacitors can be found via this link, by looking-up their part numbers... viewtopic.php?p=2848857#p2848857
also see... Bakelite blocks rebuilding link.

or google - example: Philco 30-4444
https://philcoradio.com/phorum/archive/ ... -2655.html

:) Greg.
oh... Do not rotate any Domino capacitors on their axis!


Schematic pages... Rider 1937
7-17 http://americanradiohistory.com/hd2/IDX ... e-0038.pdf
7-18 http://americanradiohistory.com/hd2/IDX ... e-0039.pdf

Changes 1938
http://americanradiohistory.com/hd2/IDX ... e-0013.pdf

Changes 1939 I. F. Transformer (preventing oscillation).
http://americanradiohistory.com/hd2/IDX ... e-0010.pdf


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 Post subject: Re: Philco 37-38
PostPosted: Apr Thu 18, 2019 9:57 pm 
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Joined: Nov Sun 20, 2011 1:10 am
Posts: 388
Location: South Carolina
It’s alive... at least getting static. No stations though. Not
Sure it’s picking up anything. I replaced all caps except that Bakelite filled one.
Any ideas from here?

Does this radio have to have a ground wire attached?


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 Post subject: Re: Philco 37-38
PostPosted: Apr Thu 18, 2019 10:31 pm 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 11445
Location: Mountains of Mourne. Ireland.
There looks to be a ton of switching going on in your radio!


The contacts on the the wafer-switch (and others) will have oxidized with the passage of time.

Clean them with some IPA (isopropyl alcohol) or Zippo lighter fuel (naphtha) using a business-card or a folded-up dollar bill.

Strips cut from a dollar bill are very robust for cleaning oxidized contacts.
75% cotton and 25% linen... :)

------------

Replace the bakelite block capacitor - just cut the wires and solder in your capacitor.
.15μF 200V


Greg.

Have you got a wire antenna attached. A ground connection if often not necessary. Lol


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 Post subject: Re: Philco 37-38
PostPosted: Apr Thu 18, 2019 11:12 pm 
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Joined: Nov Sun 20, 2011 1:10 am
Posts: 388
Location: South Carolina
If I am looking at the diagram earlier in the post all I have to do
Cut the wires for lugs 1 and 3 and solder a .15 between them. So except
For the one cap inside, this thing is just a terminal block?


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 Post subject: Re: Philco 37-38
PostPosted: Apr Fri 19, 2019 12:06 am 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 11445
Location: Mountains of Mourne. Ireland.
If I am looking at the diagram earlier in the post all I have to do
Cut the wires for lugs 1 and 3 and solder a .15 between them.
Yes

So except For the one cap inside, this thing is just a terminal block? Yes

As long as one wire is disconnected from the bakelite block - the internal capacitor will be taken out-of-circuit.

Greg.

Can you hear WSM yet - the suspense is killing me... :)


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 Post subject: Re: Philco 37-38
PostPosted: Apr Fri 19, 2019 2:06 pm 
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Joined: Nov Sun 20, 2011 1:10 am
Posts: 388
Location: South Carolina
I cut the wires loose from lugs 1 and 3 and put a .1 cap in between them.
I am still getting nothing but static.

By cutting the wire off lug 1 doesn’t that break the connection between the power
Switch and ground? Also that leaves no connection between one of the 2uf electrolytics and
Pin 4 of 1E5GP.


Thanks for your help and patience.


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 Post subject: Re: Philco 37-38
PostPosted: Apr Fri 19, 2019 3:26 pm 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 11445
Location: Mountains of Mourne. Ireland.
Ken old bean... if there are other (continuity) connections to lugs one and three, or the corresponding tabs on the opposite side, reattach them to the new capacitor.

Otherwise, dig the old one out...
• Bakelite Block Rebuilding.
https://web.archive.org/web/20170227112 ... pbuild.htm

• Recommended replacement procedure by Gary Breaux.
http://itsmegfb.tripod.com/id16.html

Watch - the sidewalls of the bakelite block are brittle!
:) Greg.


Edit: post some photos if you wish.
Posting photos to a forum thread...
The skinny: http://antiqueradios.com/forums/viewtop ... 0#p2717120


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 Post subject: Re: Philco 37-38
PostPosted: Apr Fri 19, 2019 8:15 pm 
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Joined: Nov Sun 20, 2011 1:10 am
Posts: 388
Location: South Carolina
I connected the wires to the new cap. See pic. I left the wires attached at lugs 2&4.
I am still not getting anything but static. If I play with the volume control it will squeal and motorboat.


Thanks for the help.
Ken


Attachments:
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36E9301B-9CF7-4FE5-91E8-ACAF42D93487.jpeg
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 Post subject: Re: Philco 37-38
PostPosted: Apr Fri 19, 2019 9:18 pm 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 11445
Location: Mountains of Mourne. Ireland.
Can you list your readings for these Voltage measurements.
They will be different if you are using a VTVM or multimeter!

Tell us which meter you are using.

Image
Large image→ https://a4.pbase.com/o12/56/215056/1/16 ... titled.png

1HG4 (driver).
Pin 3 plate ... ?
Pin 7 filament ... ?

1C7G
Pin 3 plate ... ?
Pin 4 grid ... ?
Pin 7 filament ... ?

1D5G
Pin 3 plate ... ?
Pin 4 screen grid ... ?
Pin 7 filament ... ?

1HG4 (2nd DET-AVC).
Pin 7 filament ... ?

1E5G
Pin 3 plate ... ?
Pin 4 screen grid ... ?
Pin 7 filament ... ?

1J6G
Pin 3 plate ... ?
Pin 4 grid 1 (1) ... ?
Pin 5 grid 1 (2) ... ?
Pin 6 plate ... ?
Pin 7 filament ... ?

Hopefully someone will interpret your readings as my tube theory is not up to snuff... :shock:

Greg.


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 Post subject: Re: Philco 37-38
PostPosted: Apr Fri 19, 2019 10:06 pm 
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Joined: Nov Sun 20, 2011 1:10 am
Posts: 388
Location: South Carolina
I am using a digital volt meter. Set on 200vdc.

1J4G.Driver Pin3=131.3vdc. Pin 7=2

1CG7. Pin 3=132.8. Pin 4=63.1. Pin 7=2

1D5G. Pin3=132.6. Pin 4=63.2. Pin 7=0

1HG4 Pin 7=2

1E5G. Pin 3=around 80 and motorboats when I touch it
Pin 4=47.7. Pin 7=2

1J6G. Pin3=130.2. Pin 4=-7 pin 5=-7 pin 6=130 pin 7=2


By tube 1D5G not having 2 volts does that mean the filament is gone?



Thanks


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 Post subject: Re: Philco 37-38
PostPosted: Apr Sat 20, 2019 12:51 am 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 11445
Location: Mountains of Mourne. Ireland.
As long as the Voltage at the tips of your multimeter probes is under 2V which it should be - pull a couple of tubes and compare resistance readings across filament pins 2 and 7 (I don't know how much over-Voltage they can take)!

Otherwise trace the 2V connection wires to your suspect tube.
I have no idea about your other discrepancies... :shock:

Image

:) Greg.


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 Post subject: Re: Philco 37-38
PostPosted: May Fri 03, 2019 12:17 am 
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Joined: Nov Sun 20, 2011 1:10 am
Posts: 388
Location: South Carolina
I checked the resistance on all tubes pins 2 and 7. They all show 0.
I traced the 2v heater circuit from pin 2 on 1H4G to the pilot light. All
are 0. So not breaks in circuit.

Not sure where to go from here.


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 Post subject: Re: Philco 37-38
PostPosted: May Fri 03, 2019 2:24 am 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 11445
Location: Mountains of Mourne. Ireland.
Ken, apart from never working on your radio, my vacuum tube theory is not up to snuff... :shock:
Hopefully someone will point you in the right direction.

Schematic: http://americanradiohistory.com/hd2/IDX ... e-0038.pdf
Layout: http://americanradiohistory.com/hd2/IDX ... e-0039.pdf
Changes: http://americanradiohistory.com/hd2/IDX ... e-0013.pdf

You really would benefit from a second pair of eyes on your chassis.
Greg.


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 Post subject: Re: Philco 37-38
PostPosted: May Fri 03, 2019 2:45 pm 
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Joined: Nov Sun 20, 2011 1:10 am
Posts: 388
Location: South Carolina
Need some more help with this radio. I think I am really close.’
Thanks for any help you can give me


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 Post subject: Re: Philco 37-38
PostPosted: May Fri 03, 2019 5:01 pm 
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Joined: Jul Mon 26, 2010 8:30 pm
Posts: 27300
Location: Annapolis, MD
One question **appears** to be resolved---you did not get the expected voltage on the 1D5 filament. All the tubes are wired in parallel, and they all have the filaments on pins 2 and 7. For any tube, those connections could be reversed. The unambiguous way to check filament voltage is from pin 2 to 7--or vice-versa.

At first glance, the tube voltages are reasonable. One tube (1EG) seems to have a low plate current---have you tested the tubes?

A standard set of steps:
--touch the grid** of the 1st audio tube--you should get some kind of noise
--repeat for the 2nd det and the IF tube
--repeat for the mixer (1st det)
--If you get a noise touching the grid of of the 1st detector), then you can do a "trial alignment"--Hook a signal generator to the mixer grid and tweak the 4 IF adjustments to verify they are responsive.

More to follow after these steps...


** "grid" means the control grid. Many of the tubes in that set have grid caps---if so, it is the control grid. Other wise, the control grid is the one closest to the cathode. On the diagram posted earlier, the control grid is labelled "G"

_________________
-Mark
"Measure voltage, but THINK current." --anon.


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 Post subject: Re: Philco 37-38
PostPosted: May Sat 04, 2019 1:52 pm 
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Joined: Nov Sun 20, 2011 1:10 am
Posts: 388
Location: South Carolina
I touched the grids on all the tubes with a screwdriver and get a electronic popping sound.
When i connected my signal generator to the grid of 1C7G through a .1 capacitor
Per the alignment instructions I am picking up stations.
So I assume all I need to do is put a alignment on it?


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 Post subject: Re: Philco 37-38
PostPosted: May Sat 04, 2019 1:55 pm 
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Joined: Nov Sun 20, 2011 1:10 am
Posts: 388
Location: South Carolina
It is cutting in and out getting stations and motorboating really bad


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