Sherwood Micro/CPU 100 (Draco)Schematic

[Einar72]

Hi All
Can anybody link me to a freebie or seller's site for service lit on this beastie? I'm only in for $1.99 (+tax) so far, so a few bucks more for a schematic would be worth it!

 

[mhardy6647]

now wait a minute... do you mean that you picked up a Sherwood MicroCPU-100 for a buck ninety-nine? That's just wrong...

 

[ginovino]

Why must you urinate on our heads and call it rain?
one dollar and what????

Scuse me while I get a towel to wipe the tears from my eyes.

 

[Einar72]

Well, it's one of the Draco-labeled units. Yes, dollar-ninety-nine. Think the thrift store's gone now, it was less than a quarter-mile from where Mr. Jimi is buried. Seems to have a triple power supply arrangement, and they all appear to use a TO-220 transistor instead of three-terminal regulators. That's where I think it went bad, one supply reads near zero w/ref to ground. Suppose I should read-up on the RCA CDP-1802 inside, and see if some supply voltages are referenced. I'm gonna go out on a limb here and assume the RF/IF run on a 12-15 volt supply, and the logic runs on a couple of odd (by today's standards) voltages, maybe one negative? Dunno, got a lotta things on my plate, maybe someone will eventually unearth a copy of the skizmo. Thanks for the interest, and a quick hello to all!

 

[sbaudio]

John Frieze, in Santa Barbara, had the last of the factory replacement boards for the CPU-100s. Incredibly complex inside with rechargable NiCads that always leaked on the board and shorted out the power supplies. John was the owner of the AudioVideo Clinic in SB for many years. When I asked about a schematic or service manual, he told me that the schematics were never transferred from the original blueprints. He had the original blueprints with all of the updates and changes written on them. He service my tuner and it worked great. These tuners are a lot of fun and sound wonderful when set up right. I can't imagine who could service one of these today. Have fun with yours and don't forget to check the batteries that back up the memory storage. They are NiCads and soldered on to one of the boards. Lee

 

[Einar72]

Thanks for the info!:thmbsp: Yes, the battery in mine had spilled its ooze onto the board (long before I obtained it), and I can see that setting the sorry chain of events in motion. I'll keep looking, because someone, somewhere had the "service" package for sale on the internet, maybe Manualman or someone like him, and I had the link saved. Sadly, that was lost on the wife's pc when we split up (mostly due to my collecting).

 

[eleakist]

Sherwood Micro CPU 100 - battery damage

This is a fascinating thread. I am posting in the hope that someone may have found further information on the schematic.

I have just acquired a "working" example at a premium price, only to discover that the effects of leaking battery makes operation intermittent at best. Detection of the source issue was complicated by several wire and solder breaks between the tuning module and the chassis, likely caused by shipping, this in turn stressing the related connecting wires and solder pins.

That all being solved, a careful cleaning of the battery acid revealed transistor Q02 and associated Zena diodes were rotted at the board, due to the effects of acid over time, and all but fell over once the dried acid was wiped away. This is where I am after @6 hours of tech time by someone more than capable but still left wondering re the aforementioned strange voltages.

The overall design, four presets, etc. is quite similar to the Quad FM4 - another example I have just cleaned up and recapped due to leaking batteries. Whose bright idea was this anyways? The battery cap in the Nak ST-7 fails, but mine has never leaked.

I would appreciate any insights to the voltages related to Q02 and the two Zena diodes. There is also mention of someone with blueprints and repair expertise. Any further info would be appreciated.

 

[baw333]

I understand this thread is old but ill give it a shot, has anyone found a schematic for the micro cpu 100? i could really use it!

 

[doug s.]

I understand this thread is old but ill give it a shot, has anyone found a schematic for the micro cpu 100? i could really use it!

+1. i know that rick at allegro sound in los angeles has the original blueprints, but even tho i have been wery helpful to him re: info on misc tuna related stuff, he has an attitude, and refused to make me a set, even tho i offered to pay him for his time, materials, etc... anyone in los angeles wanna pay him a wisit and se how much $$$ it will take to liberate a set? i am sure the cost could easily be ameliorated by us closet micro-cpu owners wanting a copy... :yes:

doug s.

 

[jdurbin1]

Shouldn't be that expensive... someone that needed a copy of my original blueprint-type schematics for an older a/d/s/ power amp found a printing shop that's local to me and paid to have the originals digitally scanned and hard copies printed as well. Not sure I ever heard the exact price but it couldn't have been much based on the conversations we had at the time. I bet a quick yellow pages explore for printing shops in the area would solve that - if you can convince him to give up the originals for a couple of days.

John

 

[SoCal Sam]

I've got a Sherwood Micro/CPU 100! It is loaded with boards and chips.

 

[doug s.]

Shouldn't be that expensive... someone that needed a copy of my original blueprint-type schematics for an older a/d/s/ power amp found a printing shop that's local to me and paid to have the originals digitally scanned and hard copies printed as well. Not sure I ever heard the exact price but it couldn't have been much based on the conversations we had at the time. I bet a quick yellow pages explore for printing shops in the area would solve that - if you can convince him to give up the originals for a couple of days.

John

i agree; i had email discussions w/him regarding this very issue. as i said, rick has an attitude problem. i think he simply doesn't want anyone else to have them.

doug s.

 

[doug s.]

I've got a Sherwood Micro/CPU 100! It is loaded with boards and chips.

so, you gonna volunteer to go over to rick at allegro sound and convince him to get them printed up at a printing shop near him?

doug s.

 

[dgta]

Have I got a deal for you...

I have a set of blueprints. Unfortunately small portions of each print are washed out at the paper folds. I'm willing to share the prints with any person willing and able to reconstruct the washed-out areas. That means you must have a tuner, preferably already apart, and be able to trace the missing portions. It further means you must understand analog and digital design well and be able to verify the circuits make sense as traced, so as to avoid errors. Ideal project for a retired EE

If you're up for such a project, PM me. If no volunteers, I will eventually do it but not anytime soon, as I don't have the time.

The set is a dozen 24"x36" blueprints, they can be done one at a time. It would be best if we can find someone local to me (Detroit metro), would make logistics easier.

 

[doug s.]

Have I got a deal for you...

I have a set of blueprints. Unfortunately small portions of each print are washed out at the paper folds. I'm willing to share the prints with any person willing and able to reconstruct the washed-out areas. That means you must have a tuner, preferably already apart, and be able to trace the missing portions. It further means you must understand analog and digital design well and be able to verify the circuits make sense as traced, so as to avoid errors. Ideal project for a retired EE

If you're up for such a project, PM me. If no volunteers, I will eventually do it but not anytime soon, as I don't have the time.

The set is a dozen 24"x36" blueprints, they can be done one at a time. It would be best if we can find someone local to me (Detroit metro), would make logistics easier.

i have a tuna, but not the requisite skills or knowledge to be able to fix the drawings. but, i bet someone on the yahoo tuna forum would be able to do it. if you are not a member, i would be willing to cc your offer over there. and, i would be willing to send out my tuna, as it has some issues, and maybe they could be fixed w/proper schematics!

also, mike williams (aka radio-x tuners) who posts to the ak forums frequently (see the thread: "Who's listening to FM Tonight? What tuner?"), lives in flint, not too far from detroit. maybe he could tackle this...

mike yust posted to the thread yesterday:
http://www.audiokarma.org/forums/showpost.php?p=6299337&postcount=1758

doug s.

 

[SoCal Sam]

so, you gonna volunteer to go over to rick at allegro sound and convince him to get them printed up at a printing shop near him?

doug s.

Even though I could use the docs, I doubt an operator would simply give away his trade tools for the cost of a copy. Besides, he is in the business of selling manuals. I doubt he gets many Micro/CPU 100 service manual requests so hopefully he will be merely amused when you ask about his price.

 

[doug s.]

Even though I could use the docs, I doubt an operator would simply give away his trade tools for the cost of a copy. Besides, he is in the business of selling manuals. I doubt he gets many Micro/CPU 100 service manual requests so hopefully he will be merely amused when you ask about his price.

i don't disagree w/you even a little bit. i made it clear i was willing to pay him a reasonable fee for copies, including reimbursing him for his time/profit, etc. and this was after i had helped him out, finding for him docs for a mpx he couldn't locate, taking detailed pics of innards of a wintage m-d antenna tuna i have, etc... i think he needs a letter added to the front of his name 'rick'...

doug s.

 

[SoCal Sam]

i don't disagree w/you even a little bit. i made it clear i was willing to pay him a reasonable fee for copies, including reimbursing him for his time/profit, etc. and this was after i had helped him out, finding for him docs for a mpx he couldn't locate, taking detailed pics of innards of a wintage m-d antenna tuna i have, etc... i think he needs a letter added to the front of his name 'rick'...

doug s.

I'm on the fence on this one. A service manual will turn up...eventually. My Micro/CPU 100 was a storage shed find so I didn't get any documents or they would be yours.

 

[dgta]

I'm on the fence on this one. A service manual will turn up...eventually.

I wouldn't hold my breath. When I ordered my blueprints, in the early 80s, Draco advised me that this is as close as they came to a manual.


Doug S, I'm not actively pursuing this blueprints project. I just ran across this thread and offered my cooperation if someone else is motivated enough to pursue it.

 

[Punker X]

Dgta, Where you located. Not sure where I can find the time. But would love to borrow the prints and try to get a copy of them and possible a digital scan.