Friday, May 8, 2009

The Magnum Dynalab FT 11

This FT 11 arrived working but without stereo. This very well built, compact, and stylish tuner from '88 or so had a list price of $495. It was the bottom of the Magnum Dynalab line with the FT 101 ($885) and the Etude ($1295) above it.

Popping the top revealed... not much. I discovered (according to the wonderful FMTunerInfo.com) that this was the original version of the FT 11 based on the board color. No tuning capacitor, just some chips, a few discrete components and some air. Given the vintage it was time for a cap job.



Unfortunately, the FT 11 is pan built. No bottom cover, bummer. You need to pull the main board after desoldering the antenna leads, unscrewing the rca jack plate and detaching the face. The cap count was a very modest 20 or so, replaced with Panasonic FMs, FCs and a few metallized stacked films. I replaced the 4.7 mfd output coupling caps with 22 mfd Elna Silmics. The board was easy to follow with stout traces:



I stitched the FT 11 mostly back together and fired it up. Weird. It would not tune properly, it was seemingly stuck on a crazy, out of range station. Mike took a look and said: 'Bridge.' I checked all my solder work and it looked good, but dutifully started scraping resin. Yowza! Underneath a small puddle of resin was a thin flash of solder bridging a circuit. A touch of the iron healed the bridge and the FT 11 fired up in stereo.

FMTunerInfo had suggested switching op-amps to improve the sound. I did a bit of research and discovered the installed NE5532 was a 50 cent part these days and that decent upgrades could be had for $2 to $12. Not exactly breaking the bank. I ordered a few TI bifet op-amps from Mouser: OPA2604AP ($4.27) and OPA2134PA ($2.42). And also the Analog Devices OP275GPZ from Digi-key. I should have gotten savvy and soldered in a chip caddy so I could swap them out, but that will have to wait for next time. I soldered in the OPA2604AP and fired it up. Note the brown Silmic at the lower right corner.


All was well, except now the stereo had vanished. Why, I have not a clue. I whined a bit and Mike took a twirl at the adjustments with the little plastic screw drivers and the stereo returned. I gotta get a set of those screw drivers. Whenever I ask for them Mike insists on doing it himself.

The modified FT 11 is a nice sounding tuner. It must have narrower filters than the '70s receivers I work on because KMFA, 89.5, sounded good. No hiss so Mike deemed it 'digital ready'.

I recently exchanged a few emails with an old friend and tuner guru who has been published on FMTunerInfo.com, and he has provided some excellent guidance on resolving the digital hiss issues in vintage tuners. More on that in the (hopefully) near future.

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