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An Introduction and a Philco 90 issue.
cknob
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#46

11-27-2021, 01:31 PM
Doesn't the wire from terminal 3 go to ground through cap 35 or is my schematic reading inexperience on full display here?
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Steve Davis
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#47

11-27-2021, 01:47 PM
Here is the schematic I am looking at   Early Schematics – Philco Library (philcoradio.com)    (scroll down to 90 mid version) In this schematic there is a cap number 38 but, unless the cap is shorted, it won't change the reading.
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(This post was last modified: 11-27-2021, 01:49 PM by Steve Davis.)
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cknob
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#48

11-27-2021, 01:50 PM
OK that's the schematic I have.
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#49

11-27-2021, 03:39 PM
OK I was doing something stupid.  The wire from terminal 3 is fine...it reads infinite resistance to ground.  The wire from BC resistor terminal 4 is the same readings as before...90.4k ohms with the speaker unplugged...3200 ohms with the speaker plugged in.

Pics show these 2 readings, the speaker socket and the general area around the speaker socket.  All tubes are out.  In the last pic, that small black box attachment is for a 1/4" jack input for Bluetooth and similar input.  Pretty sure it's not an issue.  Radio and it worked fine before.


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Steve Davis
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#50

11-27-2021, 05:08 PM
Chris, when you recapped the chassis, did you replace the caps in the tone control?
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cknob
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#51

11-27-2021, 05:39 PM
No I did not...I just sprayed contact cleaner on the 3 tabs and worked the controls
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Steve Davis
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#52

11-27-2021, 05:51 PM
OK, with the speaker plugged in, repeat the resistance check on wire 4. This time, turn the tone control to each position while checking.
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#53

11-27-2021, 08:13 PM
Steve...it is 3200 ohms in all 3 positions on the tone control
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Steve Davis
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#54

11-27-2021, 09:04 PM
The tone control should have four positions. When the control is fully counter clock-wise you still get 32K?
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cknob
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#55

11-27-2021, 09:49 PM
Yes 3.2k...3200 ohms...not 32k
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Steve Davis
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#56

11-27-2021, 10:27 PM
Yes, I meant 3.2K.  Take resistance measurements on all speaker plug terminals first with the speaker plugged in and again with the speaker unplugged.

Steve
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#57

11-28-2021, 12:09 AM
OK starting on speaker socket that is connected to BC terminal 4 and going clockwise.

Speaker plugged in:
1. 3200 ohms
2. Infinity
3. 98k ohms
4. 20 ohms

Speaker unplugged:
1. 90.6k ohms
2. Infinity
3. Infinity
4. 22 ohms
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Steve Davis
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#58

11-28-2021, 02:34 PM
The B+ line (speaker socket terminal 4) is shorted. You will need to trace that line all the way through.

Steve
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cknob
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#59

11-28-2021, 02:55 PM
Will do...thanks so much Steve...I'll get back to you. It's socket 4, the one that's reading 20 ohms plugged or unplugged correct?
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#60

11-28-2021, 03:22 PM
Yes, the one reads 20 ohms
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