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 Post subject: Apex model 36....sometimes, you have to know when to stop
PostPosted: Apr Fri 03, 2020 11:39 pm 
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Joined: Dec Sun 07, 2008 7:05 am
Posts: 4262
Location: Meridian, MS 39307
A few years ago, I bought this Apex model 36 "tin can" AC set, from about 1928, from someone. I first smelled something rotten in Denmark when I noticed the power cord had been cut, the tubes had been removed, the capacitor box had blown it's guts, and there was a copy of the Rider's schematic inside the radio.

I scrounged around and found some tubes in my junk and then the radio basically sat here for a few years. The other day, I finally decided to check it out. I first discovered that the on/off switch was open; but, that can be fixed. Then, I tested the power transformer and found it to be fully functional. That's a nice start; but, things started going downhill after that.

I then removed the blown up capacitor block and before I addressed that issue, I figured I'd better check the RF coils and interstage transformers. The RF coils all measure OK; but, the two interstage transformers (one between the type 27 detector tube and 26 1st audio tube and another between the 1st audio tube and the 71A output tube) were both open. I believe I can get a couple of replacements from AES; but, there is a 3rd piece of iron in there that was disconnected and is not shown on the schematic (it has 3 wires coming out of it and it checks open). As far as the power supply filter chokes, those appear to be inside the same box that contains the power transformer.

Then, I moved to the 3-gang tuning condenser that is mostly jammed. Looking closer, there is some pot metal used in it's construction and it appears to be cracked and misshapen.

I moved on to the Utah-built speaker (that I think came with the radio) and it has an open coil. I suppose I could fit a modern PM speaker in the case, with an output transformer to match the impedance of the output tube to the VC impedance of the speaker.

Here is the schematic:
http://www.nostalgiaair.org/pagesbymode ... 040746.pdf

So, my options are.

1. Scrap it for what little parts might be usable.
2. Put it back together and find someone who wants it for a non-functional decorative piece.
3. Try to find a suitable 3-gang tuning condenser; but, the schematic does not list the value of the original.
4. Strip off enough parts from the chassis to mount the chassis out of a junk AA5 radio and rig it's tuning condenser to the original radio dial.

Sometimes, you have to realize that it's time to throw in the towel and come to grips that all of them can't be saved.


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 Post subject: Re: Apex model 36....sometimes, you have to know when to sto
PostPosted: Apr Sat 04, 2020 2:56 am 
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Joined: May Thu 26, 2011 5:58 am
Posts: 4236
Location: Capon Bridge, WV
I don't know if it'll help any but I have a chassis just like that sitting around gathering dust. It was part of a lot I got a few years ago. I have no idea of it's condition outside of the tuning condenser spinning with A LOT of help.


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 Post subject: Re: Apex model 36....sometimes, you have to know when to sto
PostPosted: Apr Sat 04, 2020 4:28 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 501
Location: Skwim WA USA
Not to be negative, but if it were me, I'd junk it and go on to something I know I'll enjoy, maybe a nice art deco console from the 30s with short wave or something. That being said, I actually had one of these from which I stripped the power supply to use on a Stewart Warner 705 with a really pretty wooden case and speaker table, with basically the same circuitry. I think I junked the Apex, but I'm not really sure. You should do what pleases you, but sometimes it's OK to say, this isn't worth my time or frustration.


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 Post subject: Re: Apex model 36....sometimes, you have to know when to sto
PostPosted: Apr Sat 04, 2020 8:22 am 
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Joined: Nov Fri 30, 2012 3:35 am
Posts: 395
Location: Phoenix, AZ
Wow, those tuning capacitor plates are quite warped. If it were mine, I think at this point I would say "too many problems," salvage the power transformer (might be useful as a donor), and move on to something else that's less troubled. But rewards of accomplishment are in the mind, so 'good on you' if you choose to tackle its restoration.
R/ John


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 Post subject: Re: Apex model 36....sometimes, you have to know when to sto
PostPosted: Apr Sat 04, 2020 1:50 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 970
Location: St. Louis, MO, USA
Hi badwaxcaps,
Your tuning capacitor looks like it doesn’t have any pot metal in it. Could be a lot of dirt and hard grease. Ref: the original post, I would think it’s worth a try if it fits in the chassis. You might try resoldering the terminals on the interstage transformers and speaker. No guarantees, but you might bet lucky. Putting a modern speaker with an audio matching transformer is a common fix and could be completely hidden in this type of speaker.

Dennis


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 Post subject: Re: Apex model 36....sometimes, you have to know when to sto
PostPosted: Apr Sat 04, 2020 5:30 pm 
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Joined: May Thu 26, 2011 5:58 am
Posts: 4236
Location: Capon Bridge, WV
I wish it didn't but alas there's pot metal holding the rotor plates on the shaft.

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 Post subject: Re: Apex model 36....sometimes, you have to know when to sto
PostPosted: Apr Sun 05, 2020 8:22 am 
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Joined: Nov Fri 30, 2012 3:35 am
Posts: 395
Location: Phoenix, AZ
This is not to hijack this thread, but on the topic of pot metal:
Many manufacturers seem to have got it wrong back in the day, but a few got it right (maybe by luck). Many years ago I restored an Ambu-5 three-dial battery set from the 1920s; pot metal disease had ruined all three tuning capacitors, but everything else in the set was in good condition. I had a donor set (different make) with a trashed cabinet, broken front panel, open audio xfmrs, missing an RF coil, generally not worth the effort ... but it had good tuning capacitors. Transplant time. The good capacitors were made by Di-Kast (now defunct) and both the entire stator plates and rotor plates assemblies were (each) cast in one piece ... a three-dimensionally deep and complex design. All the metal in them was crack-free and still had a bright finish, and they ran perfectly true. One might speculate that, due to their complexity, these plate assemblies were cast under high pressure, they likely were made using alloying metals chosen for good flow of the melt, and they may have had a controlled cool-down time to reduce the probability of warping. So even though the long-term consequences of adding certain alloying metals to the "pot melt" weren't fully appreciated in the 1920s and early 1930s, good results did sometimes happen.
R/ John


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 Post subject: Re: Apex model 36....sometimes, you have to know when to sto
PostPosted: Apr Tue 07, 2020 1:43 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1629
Location: Mt. Prospect, IL USA
I have this chassis, and had to replace the tuning cap with a 3-gang 365 pF replacement. It worked with having to fabricate some bushings for the tuning shaft added on. But the set oscillated until I shielded the 3 wires going to the stators for tuning; the wires are closer than they should be. Installing shielded wiring to the three stators solved the problem. The tuning seems to be close in relation to the dial numerals...

But seeing that the interstage transformers are shot, you might not want to get this one fixed. But, I wouldn't say it's beyond hope...


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