I have replaced all the caps with the Hayseed Hamfest kit.

The radio is working now and sounds good on AM.

Everything seems to work...but this is my first receiver so most of it is new to me.

I looked at temperatures everywhere with a Fluke temp gun.

I found some hot spots but they were fixed because of not proper grounding to chassis.

At one point a cap blew and was shorted and there was some sparking in the 80 Rectifier tube.

I checked the voltages on the tubes and they are running high. For example 310, 310, 315 and 317 Celcius on pins 3 and 4 on my 6F6 tubes.

My transformer is nice and cool but all tube voltages are high like this.

My main AC voltage is 120.

Should I run this off a Variac at 110 to see if that helps.

What about the Rectifier tube could that be an issue.

For long life of the components I want to run this at a lower voltage on the tubes.

I appreciate the feedback.

MK

I cannot claim any expertise here... but a friend helped me when I discovered my Tube rectifier was replaced with solid state, and my B+ was too high. That option is also discussed here as well as other possibilities..

https://www.philcoradio.com/phorum/show ... p?tid=1682

If the tube rectifier has been solid stated, why not use the now unused 5 volt winding to buck the input voltage and add an ICL thermistor to the transformer primary?

John

He recommended a dropping resistor, It worked very well, voltage is spot on in my receiver now...

I'm not sure what the OP needs

Mike

Yes on the variac or a bucking transformer. I run all my old gear on 110 and there is a significant reduction in power supply heat. 110 also reduces stress on 80 year old original parts. Of course in observance of original engineering standards the correct input voltage is whatever it takes to put 6.3V on the filaments but it will run very happily all day long on 110 and that's what most of them were run on back in the day.

Just wondering....to begin with...assuming that the PS was properly recapped...what is the AC voltage on the HV secondary of the power transformer (or pins 2 and 3 of the 80 rectifier)? What are you seeing on the B+ line, right after the last filter cap?

Most all of my SX-25 voltages are within 10% of spec.

Your 6F6 voltages are right where they need to be. If plate/screen voltages on the other tubes in previous stages are really high, you may have some dropping resistors specific to a particular stage or stages, way out of spec. IMHO, I would confirm that these are OK or replace vs. solid-stating the rectifier. A tube's life/performance will certainly suffer over time, if the plate/screen supply voltages are nearing or over the tube's recommended operating/max voltages.

When properly functioning, this receiver, first released 80 years ago, performs pretty well. There are no tube performance/circuit design anomalies to speak of, and the notable heat generated by these types of octal/loctal etc. tubes is typical.

Also, 117vac, today's typical line voltage, is only 7% higher than the 110vac back in the day. Hardly an issue. These radios faced sometimes wildly fluxuating line voltages (and B+), back in the '40's. Line voltage regulation in many areas of the country was not nearly what it is today.

Todd
ka8gef

All the tubes I am using came with the unit. So I am not sure of what is going on with them. I am waiting now for all new or new old stock tubes coming in the mail.

At one point I pulled in stations on all bands except band two. Now the BFO doesn't work, ANL doesn't seem to do anything and I have detached the S meter because it wasn't working. The crystal seems to work well.

I am just going to wait till the tubes come so I can see if this is the problem.

Mike.

Thanks for all the info. I will check the voltages the next time I flip it over.

I added a coaxial jack to the back and it had screwed itself loose! So now I am getting a few stations again on 3 and 4.......I await the new tubes.

MK

This thread...
→ viewtopic.php?p=3256353#p3256353
was locked by a moderator who should have explained to you, that it is forum etiquette to have one thread - for one radio.

anyhoo...
SX-42 wrote: Wow!
This was a very cool restoration to see. Thank you for posting your work!

Those are radio restoration videos from John Kopp in Arkansas, and Paul Carlson in British Columbia.


you did scroll down this page, right.
viewtopic.php?p=3206030#p3206030

Greg.

Hi to all and thanks for the feedback. I replaced about 5 of the tubes with new ones or NOS that I received in the mail this past week. Still waiting for some more tubes I ordered including the 6J5GT.

The S meter is non functional but when I apply voltage to it the meter works so I will wait for the 6J5GT. I also rewound my BFO tube. It has an in and an out and a center tap. Very delicate wire. The inside of my BFO tube look ok. So I am going to wait to get my 6J5GT and take it from there. The BFO was working.

Band 2 is all BZzzz so it maybe my dipole antennae is the choke critical. I have one choke. The dipole is 15 x 2 feet so 30 feet across. I am also in the city so maybe I am picking up all sorts of interference.

I ordered a frequency generator from Ebay. So that is on it's way.

MK

Thanks Greg noted.

MK

I am watching this thread as well - I have a minty SX-25 that looks like it had a power transformer failure and have been poorly converted to a 5R4 rectifier set with the poorly mounted and wired transformer. It looks like it was assembled with someone wearing boxing gloves and soldered with one of those obnoxious 100 watt soldering guns. The retro-repair is enough that the owner dumped the set because of the cost of not only fixing it but getting it sellable despite the perfect condition.

Could you post some detailed pix of the inside? That would help to see what "the boat anchor butcher" did to this set. Closeups of the set of a nice big pic I can blow up for detail

Here is what it looked like when I first got it.

I have now rewired the dials,
copper electroplated the vents,
made my own dials and s meter graphics
replaced the cord and added a 1.5 amp fuse and holder
replaced all caps but the mica ones
replaced five of the tubes with nos ones...waiting for the rest of the tubes in the mail.
it isn't perfect yet but seems to work well on AM and 3 and 4
band 2 is just noise but I have a feeling it might be something not grounding or something simple like that
from the serial number I believe i have a version made late in 1941.
I replaced almost all the resisters as of today except the tiny dog bones on the tuners.

I am using a 30 meter dipole homemade antennae and mounted a coax receptacle on the back as well.

Looks good on the inside (the "pre-upgrade" pic, that is). I saw what looked like a big twisted pair by the alignment capacitor section and figured it was the previous owner making up modifications. Also There is a wire that looks like something not stock in this area. I am going by what I have seen in the S-20, S-20R, and the SX-24 as I have worked on all three of these (and rebuilding a S-20).

Thanks for the pic! If you can at some point a closeup view of the section around the rectifier, A/C plug, and transformer would be great as well

There are supposed to be a couple of "gimmick" twisted pairs in the RF and oscillatore areas.

One of these is supposed to increase sensitivity by nulling out oscillator coupling into the second control grid
of the convertor.

In my set I had fits getting it aligned with it there, so I finally removed it
and the set seemed to work just as well. This may well have been because removing it made the
two RF amps track the oscillator better.

Here is some pics post some of the work. I am going back in and shortening the leads on everything and generally making it look a lot cleaner now.

Thanks! This looks good - mine has a lot of nonsense around the rectifier and A/C plug. The new transformer - not sure but it looks like one the guy had laying around - has wires in excess of 6 inches long on it and is a bird nest. Also has apparently rewired the connections to the A/C plug but does not look complete.

With the number of vintage radios I have fixed that have been 'creatively repaired' I really wish people that are mildly skilled in electronic restoration would try to focus on fixing low-end Heathkit and Eico radios or common AA5 types before they butcher up a nice set.

This picture is enough for me to see there is a tad bit more work than I thought to get this set working.

I am considering on staying with the 5R4 conversion: should I convert it back to a type 80 given it does not have the original transformer? Is this a common change when replacing a transformer with a modern one? By that does it really help knock down the transformer for the set or is it more of a convenience to not use a type 80?

I have no idea what the transformer is as I have not dug in past seeing it is not the original PT. I would buy a known-to-work transformer for this to do it right.

Next time i work on the radio I will try to give you more information on where each transformer wire goes and voltage etc. It might be this week-end.

I think I might have smd. Is it a problem on the SX25. I get lots of signals but the channels come in muffled. Any advice?

Thanks in advance.

MK

On 80 tube I got 333 and 334v on pin 2 and 3.