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RESISTOR ID 38-15 philco help - Printable Version

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RESISTOR ID 38-15 philco help - Bradley Rush - 12-13-2013

The resistor is attached the volume control #20 and a terminal lug. It might be the 51 k I have to get a better look at the wire on the other side.

http://s1289.photobucket.com/user/TROG999/media/38-15%20Philco/DSC_0019_zpsf556d977.jpg.html?sort=3&o=0

in this pic it is the green red brown red with silver on one end center of pic

Brad

RE: RESISTOR ID 38-15 philco help - vinzer - 12-13-2013

looks like resistor-17 to me should be 2 megs.

RE: RESISTOR ID 38-15 philco help - Bradley Rush - 12-13-2013

Thx

The color coding threw me off its banded. Not dots but that would make the color code correct for 17

thx Vinzer

RE: RESISTOR ID 38-15 philco help - Mondial - 12-13-2013

To me, it looks like the 250 ohm (body red, end green, band brown) bias resistor #33, which connects to the low end of the volume control. There should be a 70 ohm resistor #34 connected there also, with the opposite end to chassis ground.

[Image: http://i1289.photobucket.com/albums/b509/TROG999/38-15%20Philco/DSC_0014_zps722425b9.jpg]

RE: RESISTOR ID 38-15 philco help - morzh - 12-13-2013

I do not know what to make of the colors but it is either 250 or 70 Ohms bias resistors.
It is easy to determine - measure the other end of the resistor to the Chassis: if it is a short then it is the 70 Ohm, if not - then 250.

I think it is not 2M resistors as it is soldered to the "left" hence the lower (on the sch) pin of the pot, which goes to the 0-Chassis 250-70 Ohm divider. The 2M goes to the right pot's pin.

PS. You can look at my 38-15 post (about last spring), there is possible detector (dual diode) circuit mod that may or may not be there. In case you find the discrepancy - Ron pointed me to the document that describes it.

RE: RESISTOR ID 38-15 philco help - vinzer - 12-13-2013

I think Mondial is right I thought it was the agc resistor but after looking again its on the wrong end of the volume control for that.

RE: RESISTOR ID 38-15 philco help - BrendaAnnD - 12-13-2013

Definately looks like a 250 ohm 10% resistor to me. Apparently a replacement, since the other resistors are dogbones. 10% tolerance would be overkill in that set.

RE: RESISTOR ID 38-15 philco help - Mondial - 12-13-2013

Actually there are quite a few early molded carbon comps in his chassis. Whether they are original or replacements is a good question.

I believe it also has the diode detector mod for delayed AVC as Morzh mentioned. It separates the two diode plates and uses one for audio detector and the other for delayed AVC, as evidenced by the two 1 Meg resistors and the mica coupling cap.

The detector circuit certainly does not agree with the schematic he is using.

[Image: http://i1289.photobucket.com/albums/b509/TROG999/38-15%20Philco/100_6621_zps2306af7f.jpg]

RE: RESISTOR ID 38-15 philco help - Bradley Rush - 12-13-2013

I have done testing as requested. I should have measured it first Icon_e_ugeekDUHHH. The color thru me to a bad place. It is 245 ohms one side to the volume on/off #20 the other to what I have assigned as TB3 PN A. That point after the 245 ohm is TB3 A is 340 ohms to ground, TB3 A is shorted to TB1 B where the Blk wire went from #30. the 70 ohm will be the one shown in the new pic I put up with a white arrow blk outline. Trying not to move anything til I do get my wire so if it breaks will replace. This pic is with most of the caps replaced. I'm awaiting wire and the resistors before finishing this one off.

http://s1289.photobucket.com/user/TROG999/media/38-15%20Philco/pHILCO_38_15_CAPS_zps4b386313.jpg.html

All the notes are great. After looking at all the schematic's the AVC is modified. As you have shown Mr. Mondial.

RE: RESISTOR ID 38-15 philco help - Mondial - 12-13-2013

I am not sure of the resistor with the arrow, but the 70 ohm resistor is the violet one with the two black bands labeled #12.

It might be helpful for you to learn the color code for these molded resistors. They use the same body-end-dot code as the dogbones except the dot is replaced by the center band. So for example, the 70 ohm resistor has a violet body with black end and black band (7, 0 with no multiplier).

Another example would be #14 which is yellow body, black end and green band. Value is 4 Meg, (4, 0 and 5 zeros). The original mystery resistor is red body, green end and brown band for 250 ohms (2, 5, and one 0)

Since there are so many differences from the schematic, and some incorrectly identified resistors, I would try and get the set working with the original resistors before attempting to replace them. You can also check them in circuit to get a general idea of their value and see if they correspond with their markings.

RE: RESISTOR ID 38-15 philco help - Ron Ramirez - 12-13-2013

http://www.philcoradio.com/tech/resistor.htm

RE: RESISTOR ID 38-15 philco help - Bradley Rush - 12-14-2013

Thx

The color coding threw me off its banded. Not dots but that would make the color code correct for 17

thx Vinzer

RE: RESISTOR ID 38-15 philco help - Bradley Rush - 12-14-2013

Thx Ron and all!! That list will help I will get the resistors clearly ID before lighting the fuse. Once its cleaned up I too want to here it with the Mods and with out. There are a few broken and shorted wires in the way too. As soon as I get the Ecaps and wiring done and clean up of the soldering. I could let the power go. I have been just replacing both caps and resistors before putting fuel on the fire. This is a MOD that is in here I want to have a very clear pic of. Let me make sure no other lil surprises are in this RADIO.

RE: RESISTOR ID 38-15 philco help - Ron Ramirez - 12-14-2013

Yes - the changes to the 38-15 2nd detector circuit are documented, and you can find this plus all known production changes to 1933-1938 Philco sets here:

http://www.philcoradio.com/phorum/showthread.php?tid=215

Look for the file changes.zip .

RE: RESISTOR ID 38-15 philco help - Bradley Rush - 12-30-2013

http://s1289.photobucket.com/user/TROG999/media/38-15%20Philco/38_15_DETAILED_bOTTOM_NUMBERED_zps3865ab8c.jpg.html

I have had some time to look at the 38_15. What I have found is #22 the 4 Meg is gone. A 7Meg to ground is on the cap side to Tube 75 that #22 the 4 Meg went to.

Further # 17 2Meg is gone. It looks like they split into two 1 Meg and attached a Cap in between.

Above picture is of the bottom side again. I went thru and I identified each component. I have a small idea of what they did. Just a lil foggy the 2 1 Meg connect. It was late so I have only tried to get a picture have changed nothing.

The 1 Meg attached to the TB reads 975K. It then attaches to the Switch #3 position A5-A7. This is where the switch is setting did not move it.

The other reads 1.1 Meg goes from Tube 75 pin 3 the junction point of the three components to pin 5.

The 7 Meg attaches to #21 Cap the side not attache to the 500k variable resistor #20 then goes to ground.

I am making a schematic to show were they attach. After looking at the 38-10 it does appear close to that configuration.

I have assumed that #3 is the A5-A7 because I did not see that on the electronic schematic just on the Bottom view.

I would like to make sure I'm not sitting near the bleachers in left field. I will at this point replace them one for one.