Ace and Steve’s Big Vintage Summer Adventure
Update No. 2:
The Heartbreak of Vintage Gear
by Steve Graham
This was originally going to be a much different progress report. I’ll get into that later, but let’s start with the really bad news, progress to the discouraging, then end with the cautiously hopeful.
The sad case of two Fishers. (Fisher 20A Monoblocks) Ace had given me carte blanche, with the only condition being I not purloin the output transformers. The plan was to perform a major parts replacement, consisting of most resistors and all capacitors, but leave the transformers, input jacks and speaker connectors in place. But I got part way into stripping the Fishers and found that the output transformers in both monoblocks were bad, honest. I have the measurements and pictures of the measurements to prove it. Both output transformers failed on the same section of the primary winding. I’m waiting for Ace’s direction as to whether we just abandon them, set them aside in hopes that an opportunity to press forward will present itself, or wait for some divine intervention. My trusty editor finds the Fishers so repulsive-looking, that he’d be happy to see them melted down to become rebar or truck bumpers (Editor’s note: I never said that! But I do believe Fisher gear is the reason stereos were relegated to basements). Not exactly the supportive boss one needs when the chips are down. A snazzy paint job, some gold-plated jacks and connectors and a sweet-sounding circuit just might make them desirable, almost.
At this point I have to come clean. I had assumed – yes, I know, assumption is the mother of all screwups – that the Fishers’ transformers were good, so I went ahead and bought replacement capacitors and resistors. For better or worse, I’m invested in this project. I’m also a sucker for waifs, strays and hard luck cases. Sure, the Fishers are butt-ugly, but to me that’s part of their charm. I hope that a solution can be found and someday they’ll become the ugly ducklings that morph into beautiful-sounding swans.
Someone suggested that I have the output transformers rewound. My guess is that this would likely cost at least 500 dollars. Too much to sink into old amplifiers of questionable performance. Even a new pair of generic Hammonds start at around 300 dollars, all in. I’m pretty sure I could make a decent-sounding pair of amps around what’s left of these, but that’s Ace’s call and I understand his reluctance to make it.
I know all of you purists are about to burst a blood vessel. You are freaking out that I’m destroying a piece of audio heritage. Take a pill, as we used to say in the seventies. Fisher already spoiled the party with their substandard components. And don’t get me started on how Fisher was running the output tubes way over their maximum recommended voltage and at 100% of their power dissipation when sixty to seventy is more typical.
The Leak Stereo 20, so close but not quite there. As reported last time, the Leak was progressing nicely. But another assumption has come back to bite me. I finished a minimum burn-in cycle with the Leak playing streamed music into a dummy load for about seventy hours. The Leak on its own is quite quiet, but as it was playing into the dummy load, I hadn’t noticed one critical thing: the Leak doesn’t play nice with other components. To varying degrees, any component plugged into the Leak results in hum on the output that could be heard when connected to speakers. The least amount of hum was with my PS Audio DirectStream DAC plugged directly into the Leak. The PS has a digital volume control so its output is controllable. The hum was still audible but only with my ear pressed against the speaker. The PS uses transformers to couple its output to the outside world and it’s that I think was responsible for the lowest amount of hum of all the components I had available. But any other component plugged into the Leak, even ones that play nice with other amps, yielded too much hum.
The Stereo 20 was so close to perfection. (Sigh) It was sounding really promising when fed by my PS DAC. Noise issues, hum included, can be some of the nastiest to track down in a stereo component. Unfortunately, there isn’t a piece of test equipment, at least not one that I own, that will point the finger at the problem. It’s just work and dumb luck that will find and fix this gremlin. One big obstacle to troubleshooting is the construction method Leak used. I’m sure they only expected their amps to be used for ten of fifteen years, then be scrapped or traded. If the sticker on the underside of the Leak chassis is to be believed, it was built in 1960. (See one of the pictures below.) I’m sure back then no one at Leak, or any other equipment manufacturer, expected their gear still be in service sixty-two years later.
The wiring board, sometimes called a ladder board, where most of the passive components are mounted, is easily accessible. The wiring harness that connects everything together occupies the ~1/2” space between the board and the inside top of the chassis. Unfortunately, the board is held in place with three automotive style, push-on clips (picture above). Removing these would, I’m sure, destroy them.
As well, the wiring harness bundles all wiring, filament, B+, signal and grounds together (pictures above and below). Even in 1960, amplifier builders were realizing the value of twisting filament wiring (picture below shows how NOT to do it) and routing them far as possible from signal-carrying leads. In fact, any wiring carrying or susceptible to AC signals should be twisted pairs. Leak, I’m sure, knew of these practices but chose to ignore them to minimize assembly times.
I’m just too stubborn to give up on the Leak. As well, I’d like to hear for myself if David Neice’s affection for the Stereo 20 is justified. I’ll try a few more things, but if I have to get radical, I will. Vintage lovers fear not. I won’t change the circuit, but layout and wire routing might need “adjustment”.
The Mactone X-21. I haven’t quite come to terms with the Mac, but I think there’s a way forward. Though not strictly necessary, I’m going to bring the AC line wiring up to current electrical code. I’ve installed the proper tubes – I suspect that at some point sub-optimal ones were used – but now it’s adorned with NOS beauties from GE and Mullard. A little bit of tidying up and I’ll be ready to put it to the test.
I have a new-found respect for techs that work on vintage gear. If talent and a good dose of luck is on their side it will be smiles all ‘round. But the odds are stacked against them as far as I can see. Hero to zero is a tightrope they walk every day.
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