Philco 76 questions - Printable Version
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Philco 76 questions - steve_mahlberg - 10-05-2020
Hi. I am pretty new to the "part swapping" hobby and am looking for some suggestions. I won't be offended by the "dummy, step by step instruction or guidance." I may need that for some parts of this project
First, The radio has no volume output.
Tubes test in useable range (even tough that may not mean they are good, I understand)
Powered slowly with a variac, I also did not see any melting or burning components. Everything looks to be original or at minimum a repair from long ago, if any.
I realize caps will have to be replaced.
I will get to checking the speaker coil (haven't done that yet)
I haven't opened up the "B" filter condenser block yet.
I was wondering what exactly is in there? I mean I understand there are three 2.0 mf and one .15 mf caps in there. Is it a "tar filled" block?
Any suggestions on ways of mounting/fitting the new caps as well as suggestions on the types of caps others have used would be awesome info.
I am also wondering the values of capacitors part numbers 3897A and 3584B They would be caps 21 and 13 on the schematic.
I am pretty sure I understand the rest of what I am looking at
Thanks for any help.
Steve
RE: Philco 76 questions - RodB - 10-05-2020
Hi Steve and welcome to the Phorum. I have taken a filter block apart and I was lucky. Mine had six caps packed in wax. Typically they are packed in the black tar and there are a couple ways to replace the caps. Take pictures and draw a diagram of the connections and mark the terminal numbers. Probably the most used removal is to heat the can and slide the old ones out after carefully opening the bottom where the terminals are. You will probably be able to mount the new caps right on the terminals. You can buy poly film caps, electrolytic caps are not recommended. I get mine from Mouser. There is a step by step to follow and it may be here on the Phorum.
I don't see a parts list but part 13 is typically 0.1 mfd and 21 is typically 0.01 mfd. All caps can be 630 volts.
RE: Philco 76 questions - chalupa13 - 10-05-2020
I just took one apart on Philco 77. I think those are identical to 76. The bottom is tar and then the rest of the block filled with paper/foil-wrapped caps. I pried them out with a screwdriver. Pull one from the middle using long tongue pliers and the rest will come out easy. I replaced 2mfd with 4mfd electrolytic caps I figured more filtering won't hurt. I believe the rectifier tube is 80 and it can handle up to 20mfd filter caps. The voltages on those caps are around 350v at least on mine, so definitely get 630v rated caps. There is so much space inside that block you can mount new caps anyway you want. The spacing between terminals is so wide that most caps won't have the wire length to reach them, so I soldered wires to the terminals and then soldered caps to those wires and used shrinkwrap tubing on the solder joints and exposed cap wires. I already tested the radio and everything seems to be working fine. Here is the diagram of your B-Cap. I marked + and - terminals for electrolytic caps, regular caps will be too expensive in those capacities.
RE: Philco 76 questions - morzh - 10-05-2020
Black tar is always a beach to take out, but some are worse than others.
And messy.
I was lucky with my 111 one, but totally failed with the 76. So I mounted the caps, but i still have not covered them, so the radio plays with the caps open.
RE: Philco 76 questions - Radioroslyn - 10-05-2020
Hi Steve and welcome,
https://philcoradio.com/library/images/schem/76.jpg
Wouldn't use electrolytic caps to replace the foil/ paper in this power supply. The ripple current will cause the input cap at least to short damaging the 80 tube. Just replaced one in my 87 w/a film. Use polyfilm caps they don't care about ripple current. Stick to the noted values of the caps. Increasing the value can cause a significant increase in the hv.
>First, The radio has no volume output.
If the speaker isn't make any noises unplug it from the chassis. Use your ohm meter and measure the resistance between two pins on it plug. Should see less than 4000 ohms any of them. If any two show no resistance then there is a problem.
GL w/your new project!
RE: Philco 76 questions - Stan the Man - 10-18-2020
Hi guys,.. Steve, I just recapped(etc) a Philco 76, (my second) This last 76 was working ok, but then I noticed one of the output tubes(45) was cool to the touch. Long story short, make sure you check your input and output transformers, and your field coil.
Stan