Repaired: 1960 Hornyphon Attache 61 German Antique Radio

Posted on September 30, 2011 by retrovoltage

I’ve been working on this Hornyphon Attache 61 model W 360 A radio for a co-worker this month. He brought the radio over from his mother’s estate in the 1970s and it’s been sitting ever since, and came to me to have it reconditioned. German radio sets from this era are nice and elegant, this one has a blonde finish that looks like it’s nearly new especially for the age:

The radio uses 7 tubes, ECC85 (6AQ8), ECH81 (6AJ8), EF89 (6DA6), EABC80 (6AK8), EM84 (6FG6), EL84 (6BQ5), EZ80 (6V4). European tubes use a different numbering system, but fortunately there were US-equivalent tubes – identified by the parenthetical numbers – which I was able to find for substitutes as well. The transformer has multiple taps on the primary, so it can be used anywhere by just changing the tap setting – perfect for when it moved from Europe to the U.S.:

On the left side we see a “slug” (inductance) tuner and the output transformer; the power transformer and rectifier are on the left. This model uses a single medium-sized speaker. There’s also some evidence of physical damage in the past:

This EL84’s tip is broken off, vacuum lost, and the getter inside has turned white. There was an incorrect substitute for the EZ80, too. This radio uses an early PC board, instead of point to point wiring:

that seems to show evidence of repair to the electrolytic filter capacitor at some point in the past – most likely the ’70s.

This 22uF 350V capacitor was placed across a section of the defective can capacitor up top, but without removing the defective part from the circuit. It probably worked okay for a time, but when the failed original capacitor finally went full short, it would’ve had minimal effect. This is a “hack” repair – it probably got the radio playing again, at the time, but it wasn’t made with much attention to best practices or correctness. I removed it and returned the power supply to its original configuration during the repair.

Early PC boards are extremely fragile – both due to their construction, and the fact that they’re now over 50 years old and have become brittle. I wouldn’t have accepted this radio for work without my Hakko rework tool, which handles PCB repair quite nicely:

Fortunately, there are good schematics available and the top side of the PC board is marked with the component values and shows trace locations and ground points, even:

My colleague assisted translating some of the German instructions for me, which clarified a few points. I begin by using the re-work tool on the bottom of the board:

then feed the leads through the top side of the board and re-solder to the solder pad and trace on the bottom:

Looking good!

There’s a few replaced components – but not as many on earlier radios:

Also replaced the can capacitor with two single capacitors above the chassis, routed through the holes the can used go into.

With all the defective parts replaced, it came time to power it up. It comes online okay – but no audio at all! Signal tracing produced a click when I’d tap the grid of the EL84 output tube, but the 1st AF (one section of the EABC80) tube produced no click like it should have. Turns out there were several cold solder joints – probably decades old – on the bottom side of the board around the output section. It’s possible they cracked from heat, even. The problem was fixed by a quick reflow on the joints, causing them to properly conduct electricity again.

That problem sorted, the radio roared to life crystal clear on the FM broadcast band – but on the AM band, it suffers nagging crackles that override the audio and sound bad. Unfortunately, this is a symptom of a very bad problem called Silver Mica Disease and it happens due to electromigration of the silver under a strong electric field. Silver migrates out of position and when a sufficient charge builds up it arcs across the gap, resulting in a static crash in the audio. It’s repairable if you have a lot of time, or a lot of money to pay for someone else’s time, but is widely considered not worth it. In this case, my customer decided AM radio isn’t that big of a deal to him and is comfortable keeping the radio FM-only. Take a look at the link to see what’s involved in an IF transformer repair, it’s not a simple procedure.

This radio has a neat tuning indicator, a magnetic deflection tube similar to a television CRT:

As the station gets stronger, the gap in the center narrows; when it closes fully you’re locked on station.

Reassembly is quite easy:

Reassembled, running, with the replaced tubes and replaced capacitors in a parts bag. A closer view:

The backlit dial has beautiful markings, originally for the cities in Germany and around Europe where it was located. German FM radios from this time period used a shortened FM band, so this one only tunes ~88-101MHz, instead of the full 88-108MHz used in the US.

The dials are marked in German, naturally. UKW is short for Ultrakurzwelle, Ultra Shortwave, which is the FM band. MW is short for Mittelwelle, Medium Wave, the AM Broadcast Band.

And here’s some photos of the finished product, lit up:

Now that it’s repaired, I expect the radio to give many more years of faithful service receiving music and brightening up the room it lives in.

Posted in Projects, Radios and Tubes, Vintage | Tagged , , , , , , , , , | 3 Comments

ViewSonic VP191b Computer Monitor Repair

Posted on September 24, 2011 by retrovoltage

A little while ago, I picked up a set of seven LCD monitors in various states of not working as a fun side project. The first one was quite easy – it just needed a wire reconnected internally and works perfectly. I grabbed the second one, a ViewSonic VP191b. It’s nothing hugely special, 19″ with two VGA and a DVI offering resolutions up to 1280×1024, a 16:10 aspect resolution.

Nothing I’d use as a main monitor, but a decent consumer device. And it turns out this one’s a little more complicated to repair than the last few I took care of.

Taking the case off, you can see the high voltage power supply which takes 12V DC and converts it to a thousand or so volts AC to power the backlights; in the center is the logic board and on the right the switching power supply.

The power supply is encased in a plastic insulator to keep it from shorting to the case.

Unfortunately, this one wasn’t in as good of shape as the others. In addition to having a few bad capacitors, it turns out that the resonant transformer is also bad (the yellow square to the right in the photo above.) If this supply lost regulation when a part failed as it was running, it could cause a nasty cascade taking out transistors, transformer windings, anything really and that looks like what happened.

The capacitors used in this model are:

  • 470uF 25V
  • 1000uF 16V x2
  • 470uF 16V
  • 120uF 400V
and a complete set from Mouser.com is only about $10 or so.

I don’t have a spare resonant transformer, and wasn’t able to locate another one online…maybe the end of the road? Nope! I checked the voltage ratings on some of the logic board components and they were all rated 16V…the rule of thumb for capacitors is you overrate their voltage by sqrt(2), or 1.414 times. These were rated 16V, so I estimated from this the logic board wants a 12V input. That’s handy, and pretty easy to supply.

I need a 12V bench supply for a few other projects I have coming up, so I ordered one from eBay. This one’s inexpensive and considerably bigger than I need, but it’ll be good in the future. The ViewSonic draws ~35W, and the eBay power supply can supply up to 120W. It came without connectors, so I hooked up a line cord socket that I’d scavenged out of a dead Ethernet switch. As always, when you’re working with electricity, take proper safety precautions – don’t touch power things while they’re energized and double-check your connections.

I’ve removed the power supply from the back so it doesn’t get in the way, then depopulated it to save the remaining good components for something else:

I ended up recovering 4 small signal transistors, a bridge rectifier, several misc. resistors and small capacitors, two choke coils, an unidentified standard transformer and an NTC thermistor.

Here’s a shot of the back with the power supply removed, ready for other connections:

For the first trial, I’ll just run jumper wires.

And let’s see…

Looks like it works! My estimate about the voltage proved correct. I mount up a terminal strip just like I do with a radio and wire the new power connection to that so it can be accessed from outside the case later. I’m using a computer power molex as the new connector as that’s what I have on hand, preserving the coloring.

Testing out one more time before reassembly:

Not bad!

It joins the ranks of my other spares I’m not sure what to do with yet:

Mission accomplished. I’ll just get it a power supply of its own, a power brick this time, and it’ll be finished! You can only tell it’s been worked on by the dangling wires hanging out the bottom.

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1953 Hallicrafters 8R40 Repair

Posted on September 17, 2011 by retrovoltage

This radio came from an electronics recycler, it’s the Hallicrafters 8R40. It looked like it had been stored very well, had all the tubes, the dial strings intact, no rust to speak of and not even very much dust.

This one is a bit different from the others I’ve worked on, it’s a general coverage communications receiver as opposed to being a consumer/entertainment receiver. It’s built more sturdily, designed to be serviced more easily (down to the flip-up metal top for easy access to the tubes) and was designed with an eye for sensitivity and performance to receive ham radio signals. It receives the standard AM Broadcast Band + three shortwave bands covering most of the amateur frequencies from the 160M band (1.8MHz) down to slightly longer than 8M (44MHz). It uses 8 tubes, has a tuned RF amplifier stage and two IF stages (instead of one commonly found on consumer radios) and a device called a Beat Frequency Oscillator that means it can be used to receive Morse code, not just audio signals.

An action shot of the underside, recapping in progress, starting from the right and working left. This radio was either built from bucket parts (unlikely, given it’s from a decent brand and wasn’t their cheapest model) or was repaired several times over its life, but always well. There were 6 different brands of paper capacitors: Aerovox, Micamold, Standard Condenser Co., Micamold, Cornell-Doublier, and El-Menco. I’ve replaced all paper capacitors with film capacitors with a uniform 630V rating ignoring the varying lower voltage ratings of the original capacitors. The small values were either replaced with 500V Mica or 1000V Disc capacitors of the appropriate capacitance.

Size comparison of old and new capacitors together.

All the old caps replaced, including the across-the-line cap (blue, top left) and the electrolytic filters (middle). I mounted a new terminal strip using a #6-32 screw through an existing hole in the chassis for two of the capacitors, and used an empty grounded lug from an existing terminal strip for the third. Some would remove the can capacitor, cut it open and re-stuff but I don’t find that to be a good use of my time.

A perspective shot showing the different components. It’s pretty busy down there!

All the replaced components. Four mica caps, one molded paper cap, 18 wax paper caps and two resistors.

So, flipping it back over for the first power-up:

First thing I noticed, the dial light is out. That’ll need to be replaced. The radio does crackle to life, though, and once I get the positions to life does weakly receive KIXI 880 in perfect alignment. But it has an overpowering volume-dependent hum and low sensitivity, missing many stations I know to exist there. We’re about six hours of hands-on labor to this point. Time for troubleshooting:

The hum is volume-dependent, which means it’s (almost certainly) not an issue with the power supply. Power supply wiring errors, like insufficient filtering due to a failed or missing filter cap, usually shows up as volume-independent hum. I’ll check the third filter capacitor, though, as it’s on a different ground lug. The radio has a Radio/Phono switch on the front which changes the audio source from the detector output (radio position) to the phono input on the back (phono position). When set to the phono position the hum disappears entirely. This indicates the problem lies in the RF section. I suspect the 6SG7 tuned RF amplifier has an internal heater-to-cathode short, which will put AC hum from the AC-powered tube heater into the DC cathode circuit. It could also be a short circuit to ground around one of the other RF tubes (converter, an IF amplifier or the detector) but I doubt this, a short around a functional tube would likely take it out entirely versus a leaking short internally.

Testing the tubes revealed they were all good. Several tested nearly new. All were identically branded Hallicrafters tubes to match the set which was even more interesting, I wouldn’t be surprised if they were the originals included when the set was sold. I relocated the ground from the above foreground electrolytic from the terminal strip to an unused solder lug but this didn’t correct the problem. Poking around, I discovered that the problem seemed to change with vibration and motion and the easiest place to see this effect was changing the position of the speaker. I initially suspected an intermittent in the output transformer (seen to the left of the black EPCOS capacitor):

but several tweaks around the transformer, including substituting another speaker, eliminated it from consideration. I desoldered the speaker leads and replaced with a bench speaker:

This didn’t fix the problem, so I reversed the modification and worked backwards from the output stage to discover that I’d missed a solder connection on the detector output. While there, I replaced two 200pF mica capacitors that were looking a little ragged for good measure.

With that repair made, I powered it up and it worked very nicely. AM comes on very well aligned with good tone and all the controls function. On the first shortwave band I picked up 5 stations but two of them are broadcast in Seattle. On the second, I picked up two copies of the BBC World Service and a news station in Spanish. On the highest shortwave band I picked up what I suspect are data signals and location beacons but no voice transmissions. These additional troubleshooting steps took about 2 hours, bringing the running total up to 8 hours of repairs.

I peaked up the IF transformers, but the RF alignment was “good enough” for me so I didn’t do a full RF alignment. This was built like a tank originally, and I didn’t need to replace any of the components in the RF sections, so it should be fine for quite a while. After reassembly, I put it up on my shelf:

Now I have a working general-coverage communication receiver. It’s right near my desk, so hopefully I’ll be able to spend some time cruising the dial and seeing what else is out there. Shortwave reception is heavily influenced by atmospheric conditions, it’s different every time!

Total project time for this one was about nine hours and consumed around $20 of on-hand consumable parts. For a parts list, see the service manual.

Posted in Electronics, Projects, Radios and Tubes, Vintage | Tagged , , , , , , , , , , , | 6 Comments

Westinghouse LCD Repair

Posted on August 28, 2011 by retrovoltage

After seeing the repair I made on the Samsung LCD monitor, a friend gave me a few-years-old Westinghouse LCD/TV that had quit working – it wouldn’t power on anymore. It’s a Westinghouse SK-19H210S, 19″ LCD accepting VGA or HDMI up to 1440×900 resolution (somewhat smaller than true 1080P) and can also tune ATSC and NTSC television signals to receive HDTV over the air.

It’s apparently a very known fact this one has a weak power supply – all over the web. I opened it up and grabbed the power board:

Tucked away all in the back is one capacitor that’s visibly failed, which means it’s likely several are bad or will be soon.

New parts arrived from Mouser.com:

Using my trusty Hakko, I replaced six capacitors. 4 caps in total showed signs of leaking from the bottom as well (discolored board below), 2 seemed okay but I replaced anyway because why not. I’m getting better at using the Hakko and doing this kind of PCB rework in general, the entire process from start to finish only took about 15 minutes this time.

100uF 400V
2200uF 10V
1000uF 10V
1000uF 25V x 2
47uF 50V

Interestingly (or maybe not), these bad caps were the same brand as the bad caps from the Samsung: CapXon. Obviously those have reliability problems, or are just the cheapest they could buy.

Reassembled and powered on. The first power-up would come online but drop off immediately and it was making a hissing noise; it turns out I hadn’t firmly connected the backlight leads. After fixing that, I snapped everything back into place. Consumer electronics these days aren’t made to be opened up, so the case doesn’t quite fit back together the way I’d like it to around the control panel on the side, but it’s not visible unless you look for it fortunately.

Another one fixed! This one was about $12 of parts. Looks like this one goes for around $80 these days, so I’m half-way to getting my money’s worth out of that rework station already.

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Testing Salvaged CCFLs

Posted on August 26, 2011 by retrovoltage

I scrounged these up a while back and just now decided to test them out as a part of another project I’m starting. They’re CCFL bulbs, cold cathode fluorescent lamps.

Each driver powers two lamps; I have 8 connected. Naturally, they’re 7 blue and 1 red instead of 8 of the same color. Each runs on 12V DC with molex connectors and are usually run off a computer power supply. (I’m interested to know the current ratings on them, which may spur another project…a multifunctional plugin-in ammeter.) These will eventually be triggered lighting inside a backlit cabinet, powered on only when it’s open.

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Dumpster Diving: Samsung 225BW LCD Repair

Posted on August 22, 2011 by retrovoltage

I found a Samsung 225BW LCD sitting on top of my apartment’s dumpster, and figured I’d drag it upstairs. It’s a few year old model but it’s better than the current older Dell LCD that I’ve been using (1680×1050 versus 1440×900). A quick check showed that it would power on, sort-of, but the power light would flicker constantly and there was no backlight.

I popped it open, suspecting a problem in the power supply – and turns out that was right. Several capacitors on the board were showing signs of failure. Capacitors are the main component I replace in the vintage radios but cost-cutting OEMs are often known to use caps that fail after only a few years when new to save a few cents on each part that goes out the door on new things as well. In this case their 330uF and 820uF @ 25V caps had failed and the logic board was no longer getting good power.

Modern electrolytic caps fail by bulging and leaking out the top and/or the bottom, it’s easy to see at a glance. The top two are bulging and leaking; the bottom ones are bulging only which is a bit difficult to make out in the photo.

This project is one of the reasons I bought a Hakko 472D desoldering tool. It’s made for reworking through-hole and point-to-point boards, and works by melting the solder and then applying a strong vacuum through the center of the nozzle sucking it out of the way and cleaning the connection. It wasn’t cheap, but I thought it’d be important to have one of these as I do more types of electronics hobby work. I tested it out on an antique radio and it works perfectly for the annoying old joints.

This board is pretty easy to work on, the components are widely spaced and marked.

Even though it’s not bad, I’m replacing the large main filter as well – just in case. It’s the same brand as the failed ones.

Here I’ve depopulated the bad components from the board and have placed the main filter back in position, with the old one above it for comparison.

The new caps are larger than the old ones – for the same ratings, a larger size capacitor is going to be a bit more durable. For example these 330uF 25V models:

Slid the components through the top, spread the leads to hold them in position while soldering and reattaching:

Bad planning on my part meant I forgot to take a photo of the board post-repair, but it only took about 30 minutes to do the entire thing – most of which was spent figuring out how to adjust the Hakko. And for the power-up:

Success! Back to life. This LCD goes for around $150 online even today and I’ve been meaning to add a second monitor to my desk anyway, so I’m about 1/3 of the way to recovering the cost of that desoldering station after the first project. One down, two to go….This project required 3x330uF 25V capacitors, 2x820uF 25V capacitors and 1x150uF 450V capacitor which came out to $9.83.

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1939-1941 Stromberg-Carlson Dial Stringing Diagrams

Posted on August 17, 2011 by retrovoltage

I’m recently the proud owner of a copy of the original dial-stringing guides for several Stromberg-Carlson radios from 1939-1941. This information is extremely hard to come by – it wasn’t included with the original engineering/service data, nor is it anywhere else on the web. Back in February when I was starting to restore a SC 520-PG for gift, I was looking for this dial-stringing information. With the help of a fellow radio collector Jody, I was able to come up with a photocopy of the original service data sheet. In six months of intensive searching and consulting every collector’s resource I know of, he was the only one able to help. Most other collectors and hobbyists, including several who were around when they were making these new, didn’t believe the data was ever published in the first place so I’m quite excited to be able to share it here.

I’m making these available free of charge to any collector or hobbyist who can use them, in the hope they’ll save someone the amount of frustration I had to go through to get my 520 dial restrung without a guide. So, without further delay, here they are:

These diagrams obviously cover the Stromberg-Carlson models 519, 520, 512, 522 and 523. If you have any other dial stringing guides to add to this page, I’d love to have them!

Posted in Radios and Tubes, Vintage | Tagged , , , , , , , , , , , , , | 1 Comment

Antique Radios in “Babylon 5”

Posted on July 20, 2011 by retrovoltage

In Season 2, Episode 7 of television program “Babylon 5” (1994-1998), you can see a few antique radios in the space station’s Earth History Exhibit.

With the help of some other radio hobbyists, I’ve identified the interesting ones. On the top shelf left to right, the wooden Tombstone radio is an unknown Wilcox-Gay model from around 1934; next is a Zenith 5G500 portable radio with Wave Magnet antenna, the Red square is an Emerson model 560, and finally the blue peaking out of the frame on the right of the top shelf is a 1960s GE radio in the C430A family. None of those are particularly special radios now, although they are nice and interesting, and in the ’90s they were probably easier to find for cheaper.

Posted in Commentary, Photos, Television, Vintage | Tagged , , , , , , , | 3 Comments

New Project Idea: Oddball Tube Hi-Fi Amplifier

Posted on July 12, 2011 by retrovoltage

I’m looking for a new summer project, and think I’m going to branch off from repairing radios to building some of my own gear. I’m interested in making a tube hi-fi stereo amplifier to go with my old speakers – and it’s something I can build. Audiophiles, guitar enthusiasts, and other people into tube audio have driven the price of most of the good audio tubes higher than I’m interested in paying, though.

The 6V6 audio tube is known and loved by enthusiasts everywhere, and came in a variety of other versions with different ratings, different glass, different power supply requirements but pretty much all produce the same output. I’m interested in making a miniature-tube amplifier, so I’ll be starting with the 6AQ5A tube – but these are pretty expensive. An alternately powered version, the 5AQ5 goes for only about $2/each so that looks like a winner.

I’ll be basing my amplifier on the Silvertone 69A, a dual-channel push-pull stereo amplifier manufcatured in 1960. This amplifier used a 5U4 rectifier tube to supply the high voltage. By replacing the tube rectifier (right, above) with a pair of 1N4007 silicon diodes (left, above) I’ll free up the 5V power supply. A set of four 5AQ5s draws 2.4A of current; a 5U4 draws 3A of current so there’s more power to spare and a guarantee of being able to find cheap hi-fi tubes for years to come without a lot of competition.

The schematic – with some bias and output mods – not showing the power supply or output tube modifications – that I’m basing the design is here (click for larger version!):

This should be a good sounding little amp if I get around to actually completing construction. I have most of the iron [transformers] in stock already, it’s just a question of buying some hardware and spending the time required to wire it. We’ll see.

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Found: Sansui SP1500 Speakers

Posted on July 9, 2011 by retrovoltage

It’s been a little while since I’ve gone on my rounds through the salvage and recycling centers nearby. There wasn’t much out there today, but I did find a very good condition pair of Sansui SP1500 speakers. I already own a pair of Sansui SP2500s and a pair of Sansui SP7500Xs, maybe I’ll find the whole set one day. These were made between 1960 and 1974. More for looks than show, but they’re solid for home use.

I found a thumbnail, but no full size, of the original spec sheet.

This particular set is a 3-way design with 5 drivers (the midrange stage uses two different sizes), 8 Ohm impedance accepting 50W of power with an efficiency of 97 dB (1W*1m) and frequency response from 40Hz-20KHz. They’re quite heavy weighing in at 47 lbs. each, give a good “thud” when rapped with their walnut and pressed board construction.

They’re in great shape, for having been found at a recycler. I noticed them in the back of the loading dock in an area that’s normally off-limits, and convinced the worker to bring them out front for me. Normally they won’t sell out of the back room, but it didn’t take much convincing. With rated power handling of 60W into 5 drivers, these should be solid performers in my system.

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