[462ron]

Well after discussing grid leak and power detectors on my Majestic 50 thread and experimenting with changing to a diode detector, I’ve decided to dig out my only other radio I have to be a candidate. It’s a TRF set with a grid leak detector. The purpose being to see if the inherent problem of distortion from a grid leak detector can be improved upon. It should have easy access to the circuitry that I need to work on. First I need to restore/repair the set to working condition. Right out of the gate, one big problem is the three tuning caps have what appears to be pot metal pulleys that are totally crumbling away and metal bands that run between them that are broken. So the research begins!

Ron            

[mbhdesign]

Ouch!

Atwater Kent started using brass pulleys in later models. I have a model 37 and a 38 that use brass pulleys.

You might be able to salvage a set of pulleys from a model 37 set. It has a very similar arrangement, if not identical to the 35.

[MrFixr55]

You can still experiment, just think of it as a fancy Model 20 3 dial set. Fortunately brass pulley and bands from later sets will work. Unfortunately they go for big bux.

These things are real simple. Similar to earlier AK sets, however, I think that the Radiola 16 competitor to this set is a better set. The things you need to check:

The pulleys and bands for the caps (Oops, you checked that already). I don't think that there is an AK35 with good ones on them. Funny, my 40 is fine. I dunno if they are pot metal or brass. I have 2 AK 35s, a Crosley 601 Bandbox and my dad's Lionels (Standard gauge NY Central, ca 1922), all with bad pot metal. I found wheels for the loco (the rest of the train set bodies are tin), but the bases for the gates and signals are all pot metal and crumbled. Funny, the streetlights are all good. Pot metal is hit or miss re quality. Attics and barn lofts are murder on it. There was an article on the internet from a guy that restored a Crosley bandbox, rebuilding all the caps, making pulleys and even carving the block for the tuning knob pinion and shaft.

The audio transformers tend to open. Ohm them.

The Grid Leak is likely bad. Just tap in a 2 Megohm resistor

The 2 caps for the RF Amps have 1K wirewound resistors that tend to open. These were meant as suppressors for oscillation instead of paying for the Hazeltine Neutrodyne patent.

I haven't found open RF coils on these sets, but it is worthwhile to clean and check them.

This is a rather flexible set as the C- for the Audio Output is separate from the C- for the 1st Audio amp. This is so the user had a choice of using an 01A, 112 or 71 for the output.

You likely know all of this. I expound incessantly in the interest of anyone else working on their first AK or similar radio.

[462ron]

Thanks guys for your input. I did a quick search for the pulleys but nada. I will do a more diligent search later but first, before I even look to order them if found, I’m going to check all the coils and audio transformers. If those transformers turn out to be bad, I might be done with this radio before going any further. The cost of those transformers if needed, plus those pulleys if found and I will probably look to buy an Arbe3 battery eliminator, all that taken into consideration, might have this project doomed. I’ll see what I come up with after further testing!

Ron

[Radioroslyn]

Egad! As all ready stated brass pulleys are the way to go. As far as I know they are interchangeable w/the pot metal ones. The issue maybe finding the brass bands to connect the 3 caps together in synchronization.

I have a 1925 Crosley set that the caps, pulleys, and gears were shot. Badly warped (pot metal ). Did a restomod job by using AK caps and pulleys. Was a tight fit but was able to get them in. Now the belts were the problem. The AK ones were too big and only had one. So I had to make them out of a three liter soda bottle cut into thin strips and perforated at the end. Worked great.

The p/s is not much of a big deal. Find a 6 or 12v transformer @ 3a or so, a bridge rectifier, 10,000mfd @25v or so, LM-317T, and 5k pot. Throw it all together and you get an adjustable power supply from 5 or 11v (what ever the input voltage is) down to 1.5vdc. there's abt a volt drop across the ic. You'll want to keep the input voltage close to max output voltage you need. Else the ic will have to dissipate a LOT of HEAT. The '317 is a cleaver ic in that it has short and over heat protection. It will come back to life after an event good as new most of the time. And there cheep at abt $3. Good for five 01A tubes. The B and C voltages can be supplied from batteries.

https://www.circuitstoday.com/few-lm317-...r-circuits

GL and get out the PB Blaster!

[462ron]

Thanks Terry. I watched a YT video where a guy made new metal bands by cutting a section of a tape measure lengthwise to get the right width. If I do find the pulleys, I might try and experiment with some kind of elastic bands/belts as replacements but that’s a ways off yet.

Ron

[mbhdesign]

Hi Ron,

Just PM'd you with a few possible sources for AK tuning capacitor / brass pullys. Also a Model 37 chassis, which has the same pully and belt set-up as the Model 35 - but it's an AC-powered model vs. the DC Battery Model 35 version.

Hope it helps!
Michael (mbhdesign)

[mbhdesign]

Oh, and this might help too:

Here's a chart showing interchangeability between different AK set pullys and belts:
http://www.atwaterkent.info/TechData/Ima...08_088.gif

And here's where that comes from:
http://www.atwaterkent.info/TechData/akS...Index.html

Scroll down to Model 35, pages 85 through 89.

Hope that helps!
Michael (mbhdesign)

[Radioroslyn]

Well shut my mouth.[Image: https://philcoradio.com/phorum/images/sm...on_lol.gif]

[Radioroslyn]

Edited post 5.

[MrFixr55]

Hi 462 Ron and Phriends,

I had great success powering 01As with 5V from a power supply glommed from a discarded computer. There is a standard color cod for "ATX" Power Supply. Usually the black is negative, and red is +5V. Green is +3.3V so if you have a radio with UV199s, This will work. Yellow is +12V, white is -5V, Blue is -12V, therefore, you get everything you want out of this supply except B+, which you can get from the value pack of 9V batteries, which will power the radio for several hours. The 5V and 3.3V outputs are usually 15-25A o you can power a heck of a lot of 01As or 199s with one of these. It will even power a 12V car radio. The one I have puts out 7A for +12V and 26A for +5V and +3.3V. The -5V and -12V are only about 0.5A but that is good enough for bias. The Common negative is at chassis potential.

I mounted an 8 lug terminal strip to the power supply and connected all of the outputs to this terminal strip. Cheap and handy1

[MrFixr55]

@RadioRoslyn-

Hi Terry,

I have a Crosley 601 Bandbox. This may be the same radio that you are talking about. One of my first experiences with pot metal in an antique radio. It is a total mess. Tuning caps, pulleys, bracket for tuning knob pinion and shaft, all Pot Metal, all crumbled. I will eventually get around to fixing it, in a manner similar to you- replacing the crumbled caps with AK units. I have plenty of them, but not enough pulleys.

Of course, I can't find the website or the link, but there was a guy who actually rebuilt the caps using washers and parts cut from Corian. He made the pulleys from Corian.

[Radioroslyn]

Hey John

https://philcoradio.com/phorum/showthread.php?tid=17177

[462ron]

Hi MrFixr, well I ohmed out all the coils and audio interstage transformers and it looks like it’s a go. Mbhdesigns put me onto a model 37 on eBay which is very close to my 35. It’s the whole chassis minus tubes and cabinet and has my much needed brass pulleys and bands and as an added bonus the interstage transformers and coils if ever needed. Should have it by Thursday. I do have a power supply unit kicking around from a computer I scrapped long ago. I will look into seeing what voltages it puts out. I think there are 90, 67.5 and 22.5volt requirements to run this radio. More decisions to make. Thanks for the input!

Ron

[Radioroslyn]

Ron

I'll mention in passing that if you are into the aesthetics when you have it apart you can flip the two end tuning caps around. Then the top will be on the bottom. Most of the time it's not as rusty.
That's great that your audio transformers are good. I think my favorite of the AK battery sets is the model 33/48. Great performer and and the little knob on the left adds a good bit of selectivity.
Computer p/s may not be a good choice for a power source. Most use high speed switch circuits that generate rf noise. Good ole 60cy power transformers or batteries would be a much cleaning choice.