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An Introduction and a Philco 90 issue.
#46

Doesn't the wire from terminal 3 go to ground through cap 35 or is my schematic reading inexperience on full display here?
#47

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.

M R Radios   C M Tubes
#48

OK that's the schematic I have.
#49

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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#50

Chris, when you recapped the chassis, did you replace the caps in the tone control?

M R Radios   C M Tubes
#51

No I did not...I just sprayed contact cleaner on the 3 tabs and worked the controls
#52

OK, with the speaker plugged in, repeat the resistance check on wire 4. This time, turn the tone control to each position while checking.

M R Radios   C M Tubes
#53

Steve...it is 3200 ohms in all 3 positions on the tone control
#54

The tone control should have four positions. When the control is fully counter clock-wise you still get 32K?

M R Radios   C M Tubes
#55

Yes 3.2k...3200 ohms...not 32k
#56

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

M R Radios   C M Tubes
#57

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
#58

The B+ line (speaker socket terminal 4) is shorted. You will need to trace that line all the way through.

Steve

M R Radios   C M Tubes
#59

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?
#60

Yes, the one reads 20 ohms

M R Radios   C M Tubes




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