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Old 05-24-2017, 05:18 PM
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Josef Josef is offline
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Modified Austrian Prewar Radio

Let's start one more Austrian story. To be honest this story started more than 20 years ago when I was a trainee and radio interested for a Long time of course. I received a catalog which showed many real nice radios which were offered in an auction in the first district of Vienna. I showed this catalog to my trainer and he suggested to buy the radio which I still own. I bought it for big money because of its real nice optical condition.
I also was able to make it work more or less without schematic, Internet or spare tubes. I left this radio in this condition until last summer.
Then (yes only 20 years later) I decided that something had to happen. At first I started a usual prewar radio restoration which means to remove the old tar capacitors and the electrolytics and refill them with new caps. New wires with the right diameter were soldered on before I sealed the caps again. All in all in this radio are more caps built in than in an average TV set. I had to refill about 25 caps what took me many evenings to do.
As you can see on the pictures the underside of the radio looks at least almost as it was built in 1936. Due to the fact that here in Europe are no more German AM stations prewar radios are more or less boring things. O.k. it is possible to listen radio Romania which is an absolute great station with good music program but I wanted more: Using this radio just as an amplifier is possible because it offers a record player pickup input but this is also not what I wanted and expect from a radio.
Randomly I bought a radio which was built in 1949 and had a built in FM module which was built in 1954. Due to the fact that this radio was not in great shape and also is not rare I decided to remove the FM module and built it in into my prewar radio. I know not everyone thinks that changing or adding not original in a rare prewar radio is a good thing. Honestly I also wasn't sure if I did the right thing. On the other hand it was the only way to receive Austrian radio stations and that was the thing the radio was made for.
I also decided that this modification had to be done in the absolute best quality possible. I used new cloth covered cables for example. Originally the module uses a huge power resistor which converts almost 170 Volts @ 100mA to heat what was absolutely unacceptable for me. I modified the circuits of the radio and the FM module slightly to avoid unwanted heat. To activate the FM module you just have to switch the set to Phono (record player pickup input). It is still possible to use the pickup input if a further switch on the backside of the set is activated. Never the less this radio pulls more than 100 Watts out of the mains. I also want to mention that this is an AC/DC serial heater set with one side of the power cord directly connected to the chassis. No question that 230V directly connected to the chassis can kill someone.
One the other hand the sound quality is much better than expected. Especially listening to Jazz is great fun with this set. Bass is a little weak compared to newer sets but anyway. I never will use this radio regularly. Never the less I'm looking for all built in tubes as NOS versions. I already bought most of them but I'm still looking for one or two tubes.
Please let me know your opinion if you like my restoration and modification or not.
Thank's for reading!
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Old 05-24-2017, 08:57 PM
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Sandy G Sandy G is offline
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I dunno about Austria, but here in the States, if you start working on these old sets & get good at it, you can soon have yrself a pretty decent secondary source of income-Not to mention helping to preserve a lot of interesting historic sets !
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Old 05-25-2017, 09:17 AM
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Josef,

That is a beautiful radio and you did a great job incorporating the FM tuner. What brand is your radio? I can't make it out in your photos. Does it receive shortwave?

I have a 1940 Hornyphon W455X "Potentat" that was made in Austria. I think it is one of the best looking radios in my collection. Below is a photo of it before I restored it. It is an excellent performer and has some features that are not typically found on American made radios of the same period (switchable selectivity, vernier tuning with separate logging scale).
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Old 05-25-2017, 12:07 PM
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Josef Josef is offline
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This radio is able to receive all bands like longwave, broadcast, shortwave and also FM now.
Obviously I forgot to mention that the radio and the FM tuner are both made by the same company which was called Minerva. It was sold to Grundig in the late 1960s. I also like the Hornyphon W455X which seems to be a quite big set in camparison.

Making money out of old radios seems difficult for me. If I offer stuff for sale I often have problems in getting just the worth of the parts. On the other hand I repair a lot of eletronic stuff for friends and working colleagues what also makes me not really rich

These guys modify old radios in a way I wouldn't do in most cases and ask for big money:

https://www.supersonic.at/showroom/?lang=en
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Old 05-25-2017, 12:22 PM
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maxhifi maxhifi is offline
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1. Beautiful work restoring the radio and especially the capacitors.

2. You say you don't use it often, but I think such a drastic modification only makes sense if the radio will see regular use.

3. Is the knob on the right hand side of the set connected to the FM tuner? If so you sure did a nice job making it appear original.

4. Very nice to see the inside of a European radio from this time period, thanks for sharing
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Old 05-25-2017, 02:04 PM
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Josef Josef is offline
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1. Thank you!

2. There were two reasons why I did this modification: The first was to see what is possible from technical point of view and how the redio will sound in FM mode. The second reason was to give the FM tuner module a nice home.

3. Yes exactly!

4. Thank you too!
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Old 05-26-2017, 11:49 AM
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I love the top cap connections on those tubes , they remind me of the band "Devo" , specifically the "whip it" video ....
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Old 05-28-2017, 12:52 AM
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Looks like you did a nice job on that set.


Quote:
Originally Posted by init4fun View Post
I love the top cap connections on those tubes , they remind me of the band "Devo" , specifically the "whip it" video ....
I'm sure if his Minerva is goin' wrong he'll whip it good.

That FM converter reminds me of Pilot radio's Pilotuner FM tuner....It was basically a tube FM radio sans audio amp with a phono input switch built in. The whole shebang came in a nice simple cabinet, and was a good preformer for the era. It was fairly sensitive, and could sound REALLY good if tuned up well. I used to have one that ran great, but had it's cabinet ruined in an accident. I sold that one long ago, and finally found a nice example to replace it.
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Old 05-28-2017, 05:44 AM
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Josef Josef is offline
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These top connection shieldings are nothing special. Even though the peoples receiver had one on the top of the AF7.
Pilotuners are also quite cute devices. I like the way they look!

Here you can see how my module looks if it is not built into a Radio:

http://www.radiomuseum.org/r/minerva_ukw_box.html

Here an external FM receiver from another manufacturer which can be placed under an existig AM Radio:

http://www.radiomuseum.org/r/siemens...atzgeraet.html
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Old 10-16-2018, 12:52 PM
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Unwanted Effect Occurred

Even though I tried my best to implement the FM receiver as good and as professional as possible an unwanted effect occurred: Due to the fact that the FM receiver is permanently on as soon as the radio is switched on it was possible to receive the FM IF on shortwave
I want to Point out that this was not mentioned in the instruction manual of the FM receiver so I didn't think about it earlier.
After a little bit of I decided to build in another switch which turns off the FM receiver if the radio is operated on AM. This I realized with a dial string which wraps around the band selector axle and opens the contact on AM and closes it on FM mode.
Also this modification should look as authentic as possible like the rest of the radio. I only used old components from junk devices from the early 50ies I parted out some time ago except the dial string wich is new.

I hope I can call this project finished now
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