Repair Restoration Toys In The Attic

Turkey and Solder –or– Busy Busy!

After a whirlwind of activity, a lot of which I need to document here, I’m back online!

First of all, I wish you a Merry New Year and for those that took time off this season. Hopefully you’re back with renewed vigor to tackle that project you’ve had on your mind, or an old project that’s on your workbench.

Me? I couldn’t stop working away. Time off feels is nice; I put my toys aside while working on projects at work, and having time off gives me the time to work on my personal projects. I can only describe it as a runner’s high.

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Restoration

The Scott 222C Restoration, Part 2

Welcome back! You can find Part 1 here.

When I left off, the chassis had been gussied-up and the transformers were re-painted. Before I reassembled it all back together I thought that having the bare-chassis, free from the all weight added by the transformers, would be the best time to electrically refurbish the amp. Charles Hansen ran some excellent articles about completely-redoing a 222C in AudioXpress, and Craig Ostby of NOS Valves was always willing to lend his knowledge.

 

Clean!

Clean!

 

And here it is! All I have to do is test everything…

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Construction Toys In The Attic

A PCOXO Calibration Source

I have a 1GHz universal counter and a 5MHz function generator as well as an ancient RF generator, but I don’t really do a lot of super accurate frequency stuff to warrant a Rubidium standard (yet). In early 2012 I threw down an offer of $10 on a Bulova PCOXO-HP02 oscillator, and accepted the counteroffer of $12.50.

The Bulova PCOXO-HP02 oscillator

The Bulova PCOXO-HP02 oscillator

Now I needed to figure out how I could use the thing.

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Repair Restoration

The Mono Pioneer TX-8100 Problem

A couple years back my then-girlfriend said ‘hey, you fix stereos–I want a stereo!’ And so a Christmas gift was born.

I found a Pioneer QA-800A quad amplifier with a bad channel and lots of DC offset as well as a matching tuner, a Pioneer TX-8100 with a few bulbs out. Both were sold as-is and that was fine with me! I picked them up from the post office and set to work.

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A Mystery!

My HP oscilloscope has a curve tracer function… ?!

This is a ‘built for Amdahl’ HP 1725A oscilloscope.

I bought this ‘scope maybe six+ years ago but just last year I noticed that there’s a curve tracer function tied to the intensity knob. The back states it’s an option ‘H01,’ which does not exist in any HP literature, and I couldn’t get any info from HP / Agilent. As far as I can tell there are no curve tracer specific inputs (option 101 includes the 1607A logic-state analyzer inputs), but if you look at the first photo, this was a unit built for amdahl.

 

Front of my oscilloscope, showing the 'pull for curve tracer' text

Front of my oscilloscope; ‘pull for curve tracer’ text on topmost knob, in the centre

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Construction

A Dual-Mono AKAI M8 SE EL84 Amplifier, Part 1

This project really picked up steam in October 2012.

A couple years before this project came about, I built a box as the base for my second RH84 amplifier (design can be found here [opens in a new tab]) since my first build was based on the chassis of an unremarkable Claritone console amp (I assure you, no Project G stereos [opens in a new tab] were harmed in development of that project). The box was put together using red oak sourced from the clearance pile at Rona, cut on a not-quite-square compound mitre saw, and a table saw was used to rip the 6061 aluminum plate down to size. In the end the openings were not quite regular and I had to file the plates into fitment, but it turned out well.

 

Made form Red Oak

Made from red oak and 6061

 

Right, so I’ve got the box.

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Restoration

The Scott 222C Restoration, Part 1

I bought it in early 2010 described as a fixer-upper, with no photos, and a low price. I was egged on by those more knowledgeable than I, and I’m not one to turn down a challenge.

 

Bought based on this image.

Bought based on this image.

 

Plus, it was my birthday.

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