11-25-2009, 09:00 PM
Hi Jim
Answers inline...
Now that is very unusual...and you are VERY lucky! I've never seen one of those chassis that wasn't loaded with rubber-covered wires...unless it was a Canadian model. I have a Canadian version of a 39-25 (39-330AT) that has cloth covered wiring. The USA version is full of rotten rubber. UGH.
This time I have the schematic in front of me.
Yes, the 84/6Z4 is correct for the rectifier tube. The output tubes should both be 41.
Okay, now we're getting somewhere. You say you replaced the input filter capacitor (62), Philco part number 30-2474, with a 10 uF, 160 volt unit. Big mistake! 160 volts is much too low a voltage rating for this capacitor! According to the schematic, 265 volts is being applied across this capacitor when in operation. And, keep in mind that those voltages were measured with 1941 or older vintage test equipment which is not as accurate as today's high impedance multimeters; so that 265 volts is probably more like 280 or 290, given today's more sensitive meters and higher line voltages.
I would bet that this capacitor shorted since it was only rated at 160 volts, and the short took out the power transformer since this is the input filter.
Replace it with a new electrolytic rated at 10 uF, 450 volts.
It will not matter if you replaced electrolytic (27) with 22 uF, although 10 uF would have been a better choice. Replacing the 16 uF (27A) with a 22 uF was the right thing to do. You say the new ones were rated at 450 volts, so all should be OK there.
You will have to replace the power transformer.
Before applying power again, test that 84/6Z4 to make sure it was not harned by the failure of that new 10 uF, 160 volt cap.
Also, be absolutely sure those electrolytics are connected properly! Positive leads to B+, negative leads to B-. In the case of cap (62), the negative lead goes to the left end of the 146 ohm section of resistor (61) as shown on the schematic. This is the multi-section Candohm (resistor with metal folded over it, mounted to the chassis). The positive lead goes to the left end of the field coil (as looking at the schematic) and the cathode of the 84/6Z4 rectifier. This is important! Hook up that electrolytic backwards, and it will go BOOM, and might take out your replacement power transformer. Double-check your work to be sure before applying power.
Answers inline...
jjbuzard Wrote:I have already replaced all of the rubber coated wire, knew it was bad, FORTUNATELY most of the wire in the chassis is cloth covered, less than 10% is rubber.
Now that is very unusual...and you are VERY lucky! I've never seen one of those chassis that wasn't loaded with rubber-covered wires...unless it was a Canadian model. I have a Canadian version of a 39-25 (39-330AT) that has cloth covered wiring. The USA version is full of rotten rubber. UGH.
Quote:The rectifier tube is an 84/6Z4 that Radiodaze told me to use, I relied on them as I didn't have any of the original tubes, this tube is marked Sylvania Made in the USA - no other markings. The other two tube there was a choice on were the 41's they said the Tube Jan CHS 41 - VT-48 was the original style to use in the socket marked 41 on the diagram on the inside of the cabinate. See attached tube diagram picture.
This time I have the schematic in front of me.
Yes, the 84/6Z4 is correct for the rectifier tube. The output tubes should both be 41. Quote:I replaced the electrolytic (filter) capacitors one was a 12 MFD Philco 30-2474-X. single lead, replaced with a C-EA10-160 - 10 MFD@160v Axial-Elec., the other was a double lead - Blue 8 MFD, the other Red 16 MFD Philco 30-2475-X, replaced with 2- C-EA22-450 - 22MFD@450v Axial-Elec Cap.
Is that my error? I should have replaced the double lead (8MFD & 16 MFD) with the 22MFD and 10MFD and the single lead (12MFD) with a 22MFD?
Again these are the ones Radio Daze told me to use, I may have made the mistake of using the 22MFD to replace the 8 MFD, that would be my mistake.
Okay, now we're getting somewhere. You say you replaced the input filter capacitor (62), Philco part number 30-2474, with a 10 uF, 160 volt unit. Big mistake! 160 volts is much too low a voltage rating for this capacitor! According to the schematic, 265 volts is being applied across this capacitor when in operation. And, keep in mind that those voltages were measured with 1941 or older vintage test equipment which is not as accurate as today's high impedance multimeters; so that 265 volts is probably more like 280 or 290, given today's more sensitive meters and higher line voltages.
I would bet that this capacitor shorted since it was only rated at 160 volts, and the short took out the power transformer since this is the input filter.
Replace it with a new electrolytic rated at 10 uF, 450 volts.
It will not matter if you replaced electrolytic (27) with 22 uF, although 10 uF would have been a better choice. Replacing the 16 uF (27A) with a 22 uF was the right thing to do. You say the new ones were rated at 450 volts, so all should be OK there.
You will have to replace the power transformer.
Before applying power again, test that 84/6Z4 to make sure it was not harned by the failure of that new 10 uF, 160 volt cap.
Also, be absolutely sure those electrolytics are connected properly! Positive leads to B+, negative leads to B-. In the case of cap (62), the negative lead goes to the left end of the 146 ohm section of resistor (61) as shown on the schematic. This is the multi-section Candohm (resistor with metal folded over it, mounted to the chassis). The positive lead goes to the left end of the field coil (as looking at the schematic) and the cathode of the 84/6Z4 rectifier. This is important! Hook up that electrolytic backwards, and it will go BOOM, and might take out your replacement power transformer. Double-check your work to be sure before applying power.
--
Ron Ramirez
Ferdinand IN
