View Full Version : Sherwood Micro CPU 100 Tuner -- Pics!

SoCal Sam
11-05-2009, 12:40 AM
Check out my new to me Sherwood Micro CPU 100 tuner. It sold for $2,000 in 1977!

11-05-2009, 04:41 AM
gimme that tuner before radio sees it! :D

11-05-2009, 06:57 AM
gimme that tuner before radio sees it! :D

no fair,you get up too early :D

nice tuner socal :thmbsp: i've lusted after one of those for years but you dont see too many around.i would like to hear your impressions of it once you've had a chance to listen to it.

11-05-2009, 10:38 AM
The Micro was a grand experiment and it showed that Sherwood was still first an engineering company that made audio equipment. I remember seeing it in prototye form at CES and remarking something like, they may sell 2-3 IF it actually ever came out. Considering the price and technology they were actually very successful.

Interestingly enough most of them that become available seem to still be working, an amazing feat for such new technology.

Yes, do give some feedback and congrats on getting a rare and very very nice tuner.

SoCal Sam
11-05-2009, 11:42 AM
I'm not a tuner aficionado so here goes. This example works reasonably well and sounds good enough although I don't listen to enough FM tuners to say it sounds like this model or that. The most interesting feature has to be the digital counter and the alpha-numeric display that can store the station call sign. This feature would be super useful today and why it appeared in on of the first digital tuners only to be disregarded is a mystery. The dial scale is an attempt to give it an analog look and the LED's do light up one by one as you tune across the scale. The touch pads are similar to the Philips AH673 and have a light behind it. This tuner has variable output and a few other fine tuning controls behind the door, which reminds me of the Toshiba SA-7150, also a first gen digital tuner/receiver. The circuit boards really do look like an early computer and are secured by metal tapping screws and not machine screws. It's definitely not production honed like a Japanese tuner but that's the fun of this beast.

11-05-2009, 02:27 PM
This tuner was a joint effort of Sherwood Electronic Laboratories and Draco Labs. All of these tuners were made by Draco Labs. Later on, Draco and Sherwood had a falling out and this tuner continued on as a Draco tuner. Back in it's day it was one of the best available in sensitivity, selectivity and audio performance.

SoCal Sam
11-05-2009, 03:40 PM
Was the Micro CPU 100 the earliest digital tuner. I think there is a Dick Sequierra model that may pre-date the Micro CPU. Anyone know?

11-05-2009, 03:56 PM
Absolutely gorgeous Tuner. One that I have had my eyes on for a while.

Particularly rare with amazing sonics (from what I've read).

That would look great in my system . . . no fair!!

I use a Sanyo Plus Series T-55 tuner, which is no slouch either, and a Cayin TU-220, modern tuner with remote and 99 presets.

Cheers with that beautiful piece of audio history. :smoke:


speaker dave
11-06-2009, 06:40 AM
Was the Micro CPU 100 the earliest digital tuner. I think there is a Dick Sequierra model that may pre-date the Micro CPU. Anyone know?

I had a Micro CPU 100 for a number of years but sold it to a good home a couple of years back. Lots of early digital chips in it scared me for its longevity, but it was generally reliable. I'd recommend you change the backup battery to avoid any memory issues. A cool feature was that you could store any any station name and with a very full font (#$%&, etc.) Nice early implementation of dual bandwidth too.

Wasn't Larry Shotz associated with this one? I think I remember calling him and getting a schematic sent over (but the old memory battery is getting a bit weak!)

Earlier digital tuners? At least the Heathkit AJ1510 and the Scott (433?) unit with plug in station cards were a little earlier.

Enjoy your special tuner.


Damon Hill
11-06-2009, 02:02 PM
I'm using a Heathkit AJ1510 here; I make the station cards out of old business cards since the material is stiff enough to reliably insert into their respective slots and make/break the contacts. Except for a twitchy squelch circuit, it appears to work well. Kind of clunky by modern standards, but I think it just looks retro-cool.

Bought the unit off Ebay and had to do some power supply troubleshooting, then did a round of replacing a number of carbon film resistors and tantalum bead coupling caps. I was always intrigued by the digital FM detector and it does sound very clean compared to my Sony XDR-F1HD, which has occupied my attention for the past year. The two make quite the contrast in what 30 years of technological progress hath wrought...

There's a 709-type opamp in the demodulator I'd like to replace with a more modern unit, too.

11-07-2009, 11:02 AM
Interesting tuna' you got there. The looks are reminiscent of the Yammie CT-7000. I like how it's a digital tuner, but they kept the analog knob. I have always liked the feel of the weighted knobs on vintage tuners. It might be a good idea to get that Sherwood checked over by a good tech. It would be a shame to have a cap or a resistor go, taking one of those IC's with it. I bet those things aren't easy to find.

11-07-2009, 02:43 PM
Was the Micro CPU 100 the earliest digital tuner. I think there is a Dick Sequierra model that may pre-date the Micro CPU. Anyone know?

The Sequerra is analog with a digital frequency display.

11-19-2009, 01:13 PM
I'd recommend you change the backup battery to avoid any memory issues.


I have one of these that I would like to dump.

But, it has issues, so I am wondering if a battery change will fix the issues.

Where is the battery backup?
What does it look like?
How much would it cost?
Can I find it at a local store or Radio Shack?

I have only opened it up once, but I didn't notice, or was even thinking of a battery.

It was filthy, so I don't want to open it too much, in case I really mess it up.

Thanks for any help.

search my name or my posts for pix.

I believe it was the same Brian, here, who helped me to fire it up.

03-15-2010, 06:43 PM
The Draco/Sherwood Micro CPU 100 tuner was the first to use a CPU that was originally designed for computer use. It processed the incoming signal digitally and passed it through as analogue, much like a DVD operation today. There was no var. tuning cap...the tuning knob which looked conventional on the out side was a free wheeling system that was connected to what they called a series of mirrors(early laser???) which would then determine the frequency to be tuned. The analogue dial was a concession to what people were used to in their previous audio gear. In those days, a barren front panel suggested a "cheap" piece of equipment. Also,FM had just recently exploded on the market and people were used to tuning their radios by the position of numbers printed on a face plate with a moving pointer and not by frequency. My father bought a new car in 1963 and he ordered an AM only radio because FM was a wasteland...two years later AM was the wasteland. That's how quickly things changed back then. Two thousand bucks for an FM tuner was too much for most people and the early models had filter problems. There is also two service I.C.s, ($50.00 each circa 1980) that when plugged into the unit allowed it to do a self analysis;the result of the system check was displayed on the front alphanumeric readout. The service manual was necessary to make sense of which circuits or parts were being listed on the screen. Unfortunately, many of these tuners were cannibalized for their I.C.s and other spare parts which is one reason why there are so few around today. After the split with Sherwood the tuner was marketed for a short time by Crown which led to the development of the Crown FM-1, which those who know about these things say was a close clone of the CPU 100. A great tuner that deserved a better run but was marketed by jerks. P.S. the card reading tuners were not digital, their process was a new version of the magnetic tape system. Anyway the punch card system was more of a gimmick than an innovation. There were in depth write ups on the Sherwood in Stereo Review and also by Len Feldman in Audio Magazine,Nov. 1977. Perhaps your local library will have copies available. Good catch,clean it up and take care of it and it will be worth a lot more in future. Good Luck, Bill

05-01-2010, 10:06 PM
We carried the Micro-CPU at Schaak Electronics. The list price was $2000, but in the end we were selling them for under $500. We were the wrong type of store to sell that type of high-end separates (although we did ok with H/K Citation and Phase Linear stuff).

03-24-2012, 12:16 AM
I actually worked at Draco Labs making these (they were assembled by hand) in 1979. Draco, which was Larry Shotz's first company, designed and built them, but had an agreement that they were initially distributed by Sherwood, then still in Chicago. The physical case was identical to a matching Sherwood integrated amp (which was 100 w /channel and cost something like 1/3 of the tuner, which did retail for $2000). After the falling out, we simply used mineral spirits to rub off the sherwood name, leaving
"micro CPU 100" silk screened on the front.

The tuner was a beast and weighed 36 lbs. And correct another post, it was not marketed by Crown. Draco labs designed and built Crown's FM-1 under contract. Draco was in Grafton, WI and Crown, Elkhart IN, so the Crown people drove up in a van to grab units as we made them (which I assembled as well).

I had a unit that I build after hours that larry let me buy for parts cost. The tuner required a number of hours on the test bench for calibration after assembly and the tech that did that, a guy named Mike, spent extra time tweaking mine. Supposedly it had some of the best specs of any that came off the line.