Vintage Engineering is Beautiful [’70s TV]

January 30, 2015 Leave a comment

70sTV

’70s Industrial Modern Television in Custom Enclosure

Screenshots from HP 3585A Spectrum Analyzer via GPIB?

January 24, 2015 4 comments

I’m wondering if anyone reading this might have some experience and could chime in. I’m trying to make my HP 3585A spectrum analyzer talk to my Windows XP laptop over GPIB (488.1) with a National Instruments PCMCIA-GPIB card. I’ve been trying both the Keysight IntuiLink Screen Capture software (specifically for this instrument) as well as the KE5FX GPIB Toolkit‘s plotter emulator.

The drivers for the GPIB card are installed correctly. NI’s self-test suite passes; IntuiLink scans the GPIB bus and recognizes the 3585A on address 11, and KE5FX’s toolkit recognizes the GPIB card and is configured for F8 = the 3585A on address 11.

Sadly, Keysight’s app seems to do “something” when I ask it to pull a plot from the spectrum analyzer. It pops up a progress bar that takes a few seconds to finish and spawns a new window, but the generated image is totally blank. KE5FX’s app throws an unrecognizable error that’s something about the internal state of the app and exits instantly.

Anyone have any experience getting these things to talk to each other? Let me know, I’d love some pointers!

Update: It looks like I have a hardware issue with my GPIB interface. Anyone want to sell me a USB or PCMCIA interface (or even just let me borrow one for testing for a couple weeks?)

Philco 39-45 Retrofit to 40-201 Cabinet Vintage Radio Repair

January 16, 2015 1 comment

Cross-posted from the Rain City Audio Repair Blog:

A local customer approached me with his family’s Philco 40-201 vintage radio to be restored back to working condition. It had sat for several decades, very well preserved, but ultimately needed some service after the years.

Very unfortunately, however, the original chassis had a bad case of the notorious Philco coil rot and while its audio section was fully intact and the power supply in good condition, the RF coils were rotted and couldn’t be repaired. Thus it was time to find another chassis to put into the opening.

The oscillator coil, along with most of the RF coils, were the defective components on this one. This was a particularly insidious failure: the coils tested okay with a multimeter, but failed to oscillate due to green coil rot inside the windings, shorting turns together and killing the resonance. It took quite a few hours of diagnostics to narrow this down, since it was so subtle.

There are several chassis that will fit the opening, but the one I happened to find was from a Philco 39-45. They’re identically shaped, have the same dial scale, but some circuit differences. While the 40-201 uses primarily loctal tubes with the exception of the rectifier and #42 power output tubes, the 39-45 uses a mixture of octal and pre-octal tubes. The 39-45 uses a three-gang tuner and a tuned RF amplifier stage, which actually makes it a bit better of a performer than the 40-201.

The replacement chassis came partially recapped and verified working; I replaced the remainder of the capacitors and did an alignment.

Finally, it was time for an alignment. It peaked up pretty close.

Finally, back in the case!

On the first trial run, it sounded fantastic – picking up AM stations across the dial, and very surprisingly about a half-dozen shortwave stations in Arabic, Spanish, English, and several other unidentifiable languages. It’s going to be a great performer – and a wonderful family heirloom – for a long time to come.

Rain City Audio Vintage Radio Repair

Harman-Kardon Citation 12 Deluxe Professional Power Amplifier Refurbishment

January 12, 2015 Leave a comment

Cross-posted from the Rain City Audio Repair Blog:

Matching the Harman-Kardon Citation 17S professional pre-amplifier shown previously, this Citation 12 Deluxe power amplifier is its 120W per channel companion. It came to the shop for a preventive rebuild after serving for quite a few years. The owner had the original service documentation, and a shop receipt from 2003 where the four primary filter capacitors were replaced. The previous shop did a good job, but by now the rest of the capacitors were starting to show their age and it was time for a rebuild before something bad went wrong.

Following in the HK tradition, it’s very easy to service. There’s one PCB in the amplifier, with a multi-pin edge connector along the bottom. The entire board can be easily removed for service outside the chassis. New primary filter capacitors didn’t require any service, so this refurbishment focused just on the small capacitors on the amplifier PCB.

The capacitors were all going high ESR, which provides reduced filtering ability. Shown here comparing an old 50 uF capacitor (0.85 Ohms) to a new Nichicon Fine Gold 47 uF capacitor (0.09 Ohms), and a lower dissipation factor as well.

Back in the case:

After component replacement, the bias at TP1-2, TP3-4 measured within spec, so it didn’t require any further adjustments. DC offset is pretty low, about 10 mV per channel, and does not have a separate adjustment. Extremely low distortion and great performance through its power bandwidth, too!

The enormous capacitors provide a ton of power. Both channels play for several seconds after power is removed, although the left channel goes on for longer than the right due to individual variations in the components that are being used. Back in it’s case, these two are the centerpiece of a fantastic and powerful vintage system that’s going to sound amazing for a long time to come. It’s crisp, neutral and accurate sound lets the amplifiers take a back seat to the source material and deliver great sonic performance.

Rain City Audio Vintage Stereo Repair

Free Your Keurig 2.0 with the Keurig Freedom Clip

January 10, 2015 Leave a comment

I wrote about how the Keurig 2.0 single-serving coffee maker came crippled by built-in DRM, locking you into using only “authorized” coffee servings in the new version of the machine a few weeks back. Enterprising users figured out how to use some scotch tape and the top of a Keurig-branded pod over the sensor to fool it into accepting any coffee serving, but even still, that’s not the most durable fix. Water, steam and a flimsy piece of tape aren’t a great mix and the last thing you want is having to fiddle with tape and optical sensors first thing in the morning just to get your fix.

It gets even better, though: the Keurig 2.0 DRM Freedom Clip! The coffee masters over at the Rogers Family Company, manufacturers of fully biodegradable single-serving coffee pods, figured out the special color Keurig uses to authenticate the cups and produced a clip that fits over the optical sensor with that color on the top face. It clips right in, once, and stays there forever. And the best part?

keurigfreedomclip

That’s right: it costs NOTHING, not even postage.

You should probably buy some coffee from them for making this hack possible, but this is fantastic and definitely worth checking out.

Thanks, Rogers Family Gourmet Coffee!

[Keurig DRM Freedom Clip]

 

Sherwood S2000-III Tube FM Tuner Repair

January 8, 2015 Leave a comment

Cross-posted from the Rain City Audio Repair Blog:

Sherwood made some excellent hi-fi FM tuners back in the day, and this S2000-III is no exception. Unfortunately, there’s not a lot of documentation about this model available, but that didn’t stop it from getting an overhaul and alignment.

The Sherwood is marked like it’s a stereo tuner, but the stereo de-multiplexer is an add-on module on an optional separate sub-chassis which was either removed, or never fitted, to this particular model. As a result, most of the front-panel options for various stereo and blend settings don’t operate.

Most of the capacitors were ceramic but several bad paper-mylar capacitors were installed, contributing to its poor performance. The large metal plate is where the sub-chassis for MPX reception would be fitted, plugging into an octal socket above the chassis – but it’s missing, so this tuner will only receive mono.

In addition, the 6BZ7 tube, used as a cascode RF amplifier, was defective with an intermittent heater; it needed to be replaced. After sorting the tubes and capacitors which were keeping it from running at all, I proceeded on to the alignment, coupling my signal generator to the distortion analyzer and using the 300 Ohm antenna connection. It was definitely out of spec:

Alignment was fairly straightforward. First, I tuned up the oscillator to bring the dial into alignment, then adjusted the RF amplifier for strongest signal and lowest distortion. Re-tuning the RF amplifier significantly improved performance, but it had a ways to go still:

Finally, adjusting the IF chain from back to front for the point of lowest distortion at each stage really cleaned it up.

There we go! Much better. Most alignments can be completed, even without factory instructions, by aligning for lowest distortion with a distortion analyzer.

Fresh tubes, fresh capacitors and an alignment have this tuner performing very well. It’s going to be great for a long time, too.

Rain City Audio Tube Radio Repair

Harman-Kardon Citation 17S Pre-Amplifier Refurbishing

January 2, 2015 Leave a comment

Cross-posted from the Rain City Audio Repair Blog:

I recently got to work on a Harman-Kardon Citation 17S pre-amplifier. Vintage HK gear is some of my favorite to work on: it’s robust, reliable, and built to be easy to service. The Citation 17 pre-amplifier is the companion for the Citation 12 power amplifier, and has a ton of features.

This one features a total of 6 inputs with 2 phono options, two tape loop outputs, and two pre-amp outputs which could drive a pair of power amplifiers.

Inside, it’s extremely open, and all of the circuit boards are mounted on edge connectors that can be easily removed for service outside the chassis.

There are 4 circuit cards with a variety of capacitors on them. These caps were starting to show their age, but weren’t quite dead yet, but several had high leakage and high ESR and were definitely not doing their jobs. This one was the worst, where internal leakage and heat was causing the skin of the capacitor to shrink and pull back.

Lots of replaced parts from this one! Testing showed it was performing perfectly after the service. I also cleaned the balance pot as it was a bit scratchy.

This pre-amp will continue to serve faithfully with its companion power amplifier for a long time to come, and deliver the detailed, accurate sound HK is known for.

Rain City Audio Vintage Stereo Repair

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