Need some help with a 1934 model 84. Been 50yrs +- since playing with tubes radio or tv. Trying to get this beauty running for my son. Any advice is welcomed.
Turns on ,humms loud as you bring vol up. Checked resistors,some grounds,looks like a few changes,vol control has 2 black plastic leads now attached to ant term and if transformer,and not shure why. Looks like someone lifted a resistor an reconnected it to where it was but with 7 strands of silver wire about 5/16 long! Otherwise im going to continue checking thigs as i can. Found some weird mods any ideas? Then hunt for some needed parts original cord types,grill cloth,grid cap, hopefully finding
(This post was last modified: 08-04-2024, 10:45 PM by Bruce.)
Welcome to the Phorum, Bruce! I would recommend not powering it up again until necessary restoration is done to the chassis. Replace all paper and electrolytic capacitors. Then check resistors for drift and replace any out of spec. Inspect all wiring for cracking or missing insulation. Post some pictures of the chassis and cabinet, if you would. Lots of 'pholks' here to help you along the way. Take care and BE HEALTHY! Gary
"Don't pity the dead, pity the living, above all, those living without love."
Professor Albus Dumbledore
Gary - Westland Michigan
Did you work on this chassis, or is this the way you received the set? It has the appearance that the Bakelite blocks have been rebuilt (new looking Solder blobs). If this is someone else's work, start retracing for possible issues. Either way, good luck! You can access information for your radio in our Philco Radio Library at the bottom of this page under service info. Take care and BE HEALTHY! Gary
"Don't pity the dead, pity the living, above all, those living without love."
Professor Albus Dumbledore
Gary - Westland Michigan
You can replace #29 w/2 10mfd 450v caps. Cut the bottom off of the original cap about 3/4" from the bottom and remove the innards. Fit the new ones inside and wire them in. There's pics around if you need help. Get rid of the large blue cap and the Malory too.
Volume control has been replaced, no big surprise. On #28 you can replace the line bypass cap w/a .015 as stated but the other cap is a filter for the bias voltage. What I do is use a 10mfd 35 or 50v cap +side goes to the chassis - to the ct of the pt. This is what the early model 80 sets used and it provides better filtering in the - leg of the p/s.
The common issues are resistor around the 2nd det being out of spec, If you need to get at #18 you might find it better to drill out the three rivets and lift the covers off. You can get them a good cleaning w/a soft scotch brite/wd-40. The 3 come off as 1. Use 3 sets of 6-32 machine screws,nuts, and lock washers. Pri on #2 and 10. When measuring #2 have the vc full up. When you get there we can talk about rewinding it's easy. Get some 36G magnet wire. Measure the resistance from one of the fat pins on the 80 to pin 2 of the 42 and then pin 3 of the 42 (and 80). Should read 2 or 3K if a lot higher it's bad news.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 08-07-2024, 06:06 AM by Radioroslyn.)
Thank you for sharing your expertise. I will be starting on this beauty later today an will keep you posted on progress. Where's the best folks to get caps from. I haven't ordered that kind of stuff in years used to visit radio shack for things! Thank you again for the advise ill being using it on the road to recovery for this project.
Regards
Bruce
Tony's used to be Sal's Capacitor Corner. He passed the business on due to medical issues. I haven't ordered through Tony, but Sal's was my go-to source.
Hope this helps. Take care and BE HEALTHY! Gary
"Don't pity the dead, pity the living, above all, those living without love."
Professor Albus Dumbledore
Gary - Westland Michigan
That's interesting it shouldn't matter much as the "volume control" doesn't really control the volume it controls the rf signal coming into the set. I have seen some sets that been modified so that the rf gain is fixed (w/a resistor) and an audio gain control replaced the original. If you trace the wiring around the original will go over to #2. Also the resistance of the pot would be much high if in the audio circuit like 1/2 to 1 meg.
Oh also spec on the resistors is 20%.
Just something to look for when you are replacing parts.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 08-07-2024, 02:37 PM by Radioroslyn.)
+1 on what the others said. This is an interesting radio, very similar to the 80Jr. These are gutless wonders using only an autodyne convertor (oscillator / mixer) and a regenerative grid leak detector. this is much more primitive than sets using a pentagrid oscillator mixer, an IF amp, diode detector, 1st audio and output tube. However, the performance of this thing is amazing, and they sold these really cheap.
Definitely replace the electrolytic filter caps. They may have been replaced years ago but the replacements may have failed.
The Philco library discusses the Bakelite capacitors and how to hollow and rebuild them.
If you never saw radios of this vintage, volume was not controlled at the input of the 1st AF Stage. Doing so did not come around till AVC. Volume was controlled by a 3 section pot. one section shunted the antenna connection or coil. The other section was used to adjust bias on the Osc Mixer tube.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards,
MrFixr55
Thank you!
Yea seems this one is a weird one,a flea market find @$40.my son fell in love with it when i sent pic to him. It wound up being a " unkown" purchase as far as any history of where it came from an working condition ! I haven't worked on " tube" anything in 50+ years. Then luckily found this forum. 2 immediate responses from members restored my confidence in trying to get this oldie functioning again.radioroslyn an i were on the phone 2 nites ago from 930pm to almost 530am talking shop! Im still in question about a few things. Replacing caps im shure but with which " new" types? I have found diagrams an parts lists,tested resistors already, going to need a few ,my son wants me to keep ot " original" as possible. Now the fun parts, finding parts,and finding folks that can help me relearn the early tube repairs. So any guidance is absolutely greatly appreciated. It seems its been thru several repairs from things ive found. But 90 yrs old its expected. I have been taking pictures as i go pulling bad parts off.,power cord,2 "addon " caps. Pulled the dual 10mfd can . And doing some topside chasis cleaning. Hopefully i can get enough guidance to get it going. Im reading a 688 page book on tube theory an application Relearning early tube information. Book was wrote in 1933.
Thank you for responding,every little bit helps
Regards
Bruce
Hi Bruce and welcome back to tubes. I'm sure Terry filled you in on which caps to replace and which ones can be left in for now. My main resource for caps is Mouser. You can replace the paper/wax caps with 630 volt poly film. Any other voltage you'll pay a little more, 630v will cover whatever you need. Get aluminum electrolytic capacitors, preferably manufactured by Panasonic, Nichicon or Illinois. There are a few more but I can't think of them right now. That's why Mouser is so good, no knock-offs. You can get 5.00 shipping from them. I usually buy in quantities of 10 because it reduces the unit cost. But that's because I work on multiple radios. If you are just interested in fixing the one then go ahead and order the quantities you need.
RodB
Thank you!
Im try to multitask ,do phourm for info,parts search for parts, and work on cleaning up chasis ,an normal daily stuff. Any ideas where i can find a tube shield? This one's really rusty? Sn one grid cap fell apart ,was split on one side.
Thanks for the information,ill start looking them up this afternoon.
Regards
Bruce
Glad that you are reading books from 1933. As a kid, my friends used to scrounge at the town landfill. Found some amazing things (and some rather disgusting things too). One of the things that disappeared was a small wood 4 tube mantle (or is it mantel) radio, likely the oldest radio I ever found till I found a 1928 or 29 RCA Radiola 62. Couldn't carry the highboy chassis on my bicycle, so I took just the chassis. Can't remember the brand of the 4 tube mantel radio, but they were very popular during the early depression. I could not figure it out because it did not have a diode detector (the only type that that I understood because it was the only one covered in my US Navy Basic Electronics textbook, ca 1953, published by Rider). Lost the radio before I got a copy of the RCA Receiving Tube Manual which explained not only diode detectors, but grid leak detectors (the first tube detectors in post WW1 consumer radios) and biased detectors (the type used in the Radiola 60, 80, R7, R28, etc. Of course the internet and sites such as this one are a wealth of info, both documented and human. God Bless you and RadioRoslyn (Terry) for carrying on an 8 hour overnight marathon. We are all a little too old for that. The design of this radio was very unique in my book. The 80 Jr, your 84 and the later 37-84 offered superheterodyne performance in a very inexpensive radio.this was done by using an older, inexpensive "autodyne" mixer (1st detector) circuit, an IF transformer bt no IF Amp, the regenerative grid leak detector and only one stage of audio, the output tube. The radio works as well as one having a mixer, IF amp, diode detector, audio amp and audio output tube.
terms of keeping the set original, red through the library. There should be an article on how to clean out and "stuff" these blocks so they look original The large can electrolytics can be hollowed out and modern caps loaded inside the can.
Hope this all helps.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards,
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