KF7LZE's Blog

It’s the winter here in Seattle and it gets cold outside occasionally. Cold enough that I can’t vent my soldering fumes out an open window like I normally do most of the year, but I don’t want them in my apartment. Fortunately for me, my chassis stand is the same width as my stovetop and sits neatly under my externally-venting range hood so I can move it over there for ventilation.

The stand can hold the chassis up at any angle and supports a lot of weight. Every time I use it, I’m impressed with the build quality and flexibility. It’s not as nice working in the kitchen as it is on my normal workbench, but it gets the job done.

I read too much of the Internet every day, but it’s finally paid off. I happened to catch a post on Hack-a-Day about an awesome giveaway right as it was posted for a microcontroller development board. An interesting one, too – the Basic Micro ATOM Nano.

The dev boards come complete with an LCD header, a small solderless breadboard, USB connectivity, a pair of servo connectors, and more! The Nano 28 is based on the PIC16F886 microcontroller, and features an 8MHz clock,  24 I/O pins, 14K of flash memory, 368 bytes of memory, and 256 bytes of EEPROM storage.

The total value of the package is just around $50, so this is an incredible deal! Basic Micro will even ship your kit to you for free via USPS.

Not too bad. There were 55 available and I snagged one, and they’re now out of stock and won’t be replenished so I’m assuming they were clearing out these discontinued models to the community. I’ve been wanting a microcontroller board for a while, too – but the investment in an Arduino was more than I wanted to go for at once.

This changes that, and with USB connectivity and a nice looking IDE it should be pretty easy to write for. Microcontroller programming is a new thing for me and I’ll have to learn what’s possible with it. With a lot of IO pins but very little memory, this looks like it might be good for some kind of display or visualization or to send and receive data from sensors but not much more – that’s a tiny amount of memory by any standard, the equivalent of just a few sentences of text. We’ll see what’s possible. I like the integrated solderless breadboard area – this will make it easy to try out a few ideas immediately.

This might make a fun servo clock platform. I’ve had it on hand for a little while now but only just dug it out of the box I stored it in to start messing with, hopefully I’ll be able to start developing with it sooner than later.

I was cruising eBay randomly the other day and made an incredibly lucky find…a 1934 Simplex Model P Dual Band tombstone radio had just been listed. I have a pretty low maximum that I’m willing to pay for any radio, as I only buy fixer-uppers and not completed radios, so don’t buy them all that often but this one jumped out at me.

It’s dirty, as can be clearly seen in the photos. It could use some attention on the trim, but the finish is in pretty decent shape; there are some veneer issues on the bottom as well that will be a new skill to learn about fixing for me. And the knobs are wrong. Electrically, it’s your standard 1930s “Parallel AA5″ design: 6A7 6D6 75 42 80. But, it has a lot of potential once it’s cleaned up and fixed up and will display very nicely.

This one makes the cut on the display shelf, so I’ll be fixing it up sooner than later.

A client came to me with another Grunow 589 needing repair. I’ve seen this model radio before in my shop and it was pretty exciting to work on another identical one. This particular one came in excellent shape – it looks like it was stored well for most of its life. The chassis arrived with no dust, no rust, a shiny coating, and not even any cadmium flaking off under the chassis.

The radio looks like it was well loved during its time. Built in 1937, it has evidence of being repaired several times all the way up through the 1950s. The UL Reexamination Service sticker is somewhat of a testament to this as well, and the fact that it’s in nearly perfect shape.

I performed the customary intake checks – all coils, transformers, tubes and controls. This one was in pretty good electrical shape. Only two of the tubes needed to be replaced after the years, testing very weak. The volume control was in bad shape, though – same as on the other 589. Unfortunately though for this particular radio, it couldn’t be saved and needed to be replaced. The output transformer connecting the radio to the speaker was also open and needed to be replaced before the radio would run again.

I sourced a volume control identical to the original (250K with a tap for tone compensation) and a functional replacement output transformer. With these parts on hand, it was a simple matter of performing the replacements. All capacitors were replaced with brand new models, and any resistors that had drifted in value by more than 10% were also replaced. On this radio, the first audio output tube (type 76) used a bias battery to establish a control voltage. As circuitry evolved, engineers discovered this was no longer necessary; I updated the circuit design to eliminate the battery by changing the 500K grid resistor to a 10 Meg grid resistor and jumping across the battery.

I also installed interference-suppression capacitors on the incoming power line, and a 0.75A inline fuse under the chassis to protect against a tube shorting and taking out the power transformer. With these modernizations, the radio will play beautiful and should perform without maintenance for many years.

A few parts were replaced during this operation:

The radio’s owner sent me a photo of it installed back in its cabinet after he received it from service. It looks – and sounds – great!

I provide affordable antique radio repair services in the Seattle Metro area and beyond if you’re willing to ship the guts. Check out my portfolio and information page for more details!

My Hakko clogged, and the cleaning pick just wasn’t working. It was time for the teardown.

I’m not entirely sure how that shape formed, but it broke off in a clean piece; the remaining tiny plug melted away after the iron heated up. That’s annoying, though.

I’ve been needing a coat rack for a while. I live in a cold enough climate where you need a coat or jacket for at least half the year, and I have 3 or 4 that make the rounds depending on the occasion and the weather. Throwing them over the back of a chair just wasn’t cutting it anymore.

I’ve had a broken stand-up floor lamp hanging around for a while. It’s the perfect height to be a coat rack, and has the benefit of already being in my apartment. A quick Internet search showed commercial coat racks available for around $40-50. I was fairly sure I could do better, and a quick trip to Home Depot confirmed. I purchased 4 coat hangers, and 4 pipe clamps. It turned out, by luck, that the width of the pipe clamps was perfectly inside a decorative notch – so it can clamp in and not slip out.

Now it’s holding up my coats, reusable shopping bags, umbrellas and is keeping an eye on the shoes parked under it. The cost of the materials was about $12 from Home Depot. If the pipe clamps had been copper or black, the entire thing would look very well matched…but as it is, it’s good enough for the corner behind the door.

I picked up a very nice 1937/1938 General Electric model F-135 radio from Craigslist a few weeks ago, and have been starting to dig into it. It’s one of the highest end radios they produced that year for the 1937 holiday season and 1938 production year: with 13 tubes, automatic frequency control to eliminate station drift, experimental hi-fi reception in 4 bands from 550KHz (AM) up past 40MHz (VHF) continuously, it offers a motorized tuning with 13 station presets and push-pull 6L6 tubes pushing 20W into a huge speaker. It should sound incredible when it’s all fixed up, and it’s the most complex and highest-end radio in my collection.

I found an ad mentioning my F-135, and showing the next lower model the F-96, in the Dec 1937 issue of Radio Retailing:

I used to have an F-96, actually, but sold it unrestored for the same price I paid for it without touching to free up some storage space – a decision I still regret, but have rectified by getting a new F-135. It’s a beast of a radio, stored fairly well but with some rubs, scratches, water rings and a cigar burn on the top.

I vacuumed miles of cob-webs and a 1/4″ thick layer of dust before even attempting to remove it from the back. The radio has a unique power transformer style, only GE used “bathtub” power transformers like this. Most are normally square with square cores…this one’s an oval. You can see the motor preset assembly and the pair of output tubes as well.

The chassis is enormous and has a lot going on.

Underneath, it looks like someone’s taken a crack at it in the ’80s or ’90s. There are a pair of orange drops, and a pair of modern electrolytic capacitors – and a few 1940s/1950s era replacements – but other than that it’s all original. There’s a decent amount of crumbling rubber wire that will need to be replaced, and one of the coils has a broken solder lug that I’ll have to fix, but it’s in shockingly good shape otherwise and should be easy to service. Not many things are buried.

The cabinet cleaned up very nicely after intensive scrubbing with cleaning wipes, Goop, and plain water and rags alternately. Following that, two applications of Howard’s. It brought out the shine on the finish while still leaving the patina around the corners, and blending the scratches in the original finish. I lightly sanded the rings on the top, but not all the way, and left the cigar burn – I didn’t want to remove all of the “character” in the cabinet.

The chassis doesn’t have any good mounting points, so I bit the bullet and ordered one from Steve Strong who makes custom radio chassis stands. They’re huge, high-quality, fully articulated and can support a lot of weight. Arrived some assembly required:

All assembled, it can rotate 360° including suspending the chassis upside down, locked in with the chassis retaining bolts that normally hold the radio into the cabinet.

And locked in ready to go:

Most of the coils in the radio test fine, with the exception of the output transformer which has one half of the push-pull primary open. That’s bad news, but fortunately 6L6 tubes are pretty commonly used today in guitar and hi-fi gear, so new-stock output transformers are easy to come by. The original was rated for 20W; the closest size available for the replacement is an Edcor 30W transformer. The new transformer might even improve the sound quality a bit – losses in transformers were one of the sources of poor fidelity in older radios (and even in modern hi-fi gear); the new transformer is flat from 20Hz-20KHz.

Edcor builds the transformers to order, so it won’t be here for another month or so, but I’ll be starting on the rest of the repairs before then. Stay tuned!

Just a short update to show what I’m working on right now. Other priorities have gotten in the way of actually updating this site over the last week, but things are still going on in the background!

One project up on my bench is a 1951 car radio, a Firestone 4-B-31 “Roamer”. It’s a 6V radio that uses a vibrator power supply and 6 tubes to receive the AM band, and should clean up pretty nicely once it’s finished. I’m repairing this one for a client I met locally who is building a rat rod out of 1920s-1960s car parts.

Recapping the projects I completed in the month of October. I started out with a few goals:

• GE LF-116 Radio Repair
• Sanyo Solid-State Receiver Repair
• EICO 460 Oscilloscope Overhaul and Tune-Up

I’ve had this idea for quite a few years but haven’t put much time into it, between everything else I’ve been going on. Once or twice a year for the past five or so years, I’ve posted on Craigslist seeking a broken cello to turn into an art project. Finally, the ad hit and I think I can make it happen.

Verve//Remixed 3 has an incredible album cover. You should buy their music for that reason alone.

I’m hoping to make my own version of the Cello Boombox on the cover…and this will be my starting point, a cello with a broken neck the owner wasn’t interested in repairing. The neck snapped off, the bridge is missing, and there are quite a few cracks (although they aren’t visible unless you look closely) and it needs to be re-glued.

I doubt I’ll do anything with this until next year at least, but now it’s a possibility. I’m just glad I was able to find a broken cello, I wasn’t willing to destroy a functional instrument for this. Not to mention, a working cello costs a lot of money.

There are a few things to consider:

Speaker size and placement. How many drivers will I use, and what types?

Cabinet volume and phase cancelling. If I configure this as a stereo boombox, I’d need to isolate the enclosures internally from each other or the out-of-phase parts of the left and right channels of the audio could cancel or introduce distortion.

Audio source. The Verve Remixed album cover is concept art, not a real product, so the knobs and panel meters and a floppy disk drive aren’t things I could realistically include. Do I mount a small music player in the center – maybe an iPod Touch, or a small Android tablet? Or should I just make this into an artistic speaker without its own audio source?

Power. If this is going to have its own amplifier, how am I going to power it? An outboard power pack? Rechargeable batteries inside?

If anyone has suggestions on those design topics, I’d love to hear them, or from anyone else who has attempted a project like this.