The Presto Pirouette T-18DC -- From the Prenco Series

[mfrench]

Sneaks in sheepishly to leave a documentary on a non-Lenco table build,....
But is it really not a Lenco?
Its allot closer than you think! :)

Presto Recording Corporation, Pirouette T-18 -- Circa 1955

Some history (I'm winging it here, and have added the real quote below my rambling):
Presto came first, out of Paramus NJ., USA. They date back a long long way in manufacturing radio broadcast consoles and record players for broadcast, and record recording lathes; back into the 20's.
Presto was bought out by David Bogen Corp in 1956.  Everything after that was labeled as Bogen-Presto, which is also the time that Lenco enters the picture, as Bogen stopped production of the Presto turntables, and Lenco began manufacturing production of the Bogen-Presto rebadged Lenco decks.
The Vintage Presto gear, pre-1956, was labeled as Presto Recording Corporation, and was manufactured by Presto in Paramus, NJ
Bogen-Presto was eventually bought out by Lear-Siegler Corp in '63, and the Bogen-Presto Corp disappeared into the corporate meat grinder, and along with it, many fine 60hz Lenco's

From a historical archive site:

PRESTO enjoyed a large success and was touted to be the world's largest manufacturers of Instantaneous sound recording equipment and discs. PRESTO was sold July 2, 1956 to Unitronics Corporation of Long Island City, NY. Six months earlier Unitronics had purchased the David Bogen Co. PRESTO was merged with the David Bogen Co., and became the Bogen-Presto division. Unitronics was the successor to Olympic Radio and Television, which also became a division of Unitronics. In September 1957 Unitronics merged with the Siegler Corp., then Siegler merged with Lear, Inc., becoming Lear-Siegler in 1962. During this time Bogen-Presto was listed as a subsidiary. In 1963 the Presto name was dropped, and Bogen shown as a subsidiary. The Moody's Industrial listed Bogen as still having disc and tape recorders along with their other hi-fi home and industrial electronics. The 1965 listing for Bogen drops the recording equipment in their product mix. Thus the "end" of PRESTO!

My project:
I bought a Presto Pirouette T-18 as a project deck in the same week that I first stumbled onto this place.
The build result, to follow,.....

The Presto T-18DC -- Prenco T-18DC


I finished this deck this past weekend. Its been a long, tedious, intense, frustrating, aggravating, dementing, uplifting, depressing, heartache, and heart full journey.
She finally made music this weekend after most of a year in trying to get her to spin quietly, without stinking, without howling, without shocking me, biting me, or otherwise trying to inflict bodily harm.
The motor was bad - so why not replace it?
Replacing it revealed design deficiencies in the OE idler drive system of three wheels - so, Why not redesign the entire drive-line?

Fortunately, I started running with this group of derelicts, here, at LH, and they got behind me, below me and above me, and somehow supported me throughout all of the many hundreds of hours of redesign efforts and build.

The results have proven, so far, to be outright amazing. So far more than worthy of every bit of effort that went into it.
It sounds fabulous.
The motor spins at half the rate of a normal table, at 900rpm, drastically reducing motor borne noise. The Lenco wheel that I installed runs on a horizontal plane, as an internal rim drive.  It runs quietly, without scrubbing, as its more inline with the driving surface, the inner platter rim.
In running this thing solid for four days now (with some sleep time here and there), I cannot find fault in it.
Its been locked on 33 rpm since I first adjusted it, and after this many hours of spinning. I don't see why it won't keep that pace as long as necessary. The precision DC motor and driver have proven to be a winner combo. Teamed up with a Lenco wheel, this thing plows though thick passages like a diesel truck, but quietly. It gets to speed, dead-on locked at 33rpm in 1/2 of a single platter rotation (90rpm in ~3 revolutions, per the KAB speed strobe/mat top scale reading).
They might not be for everybody, but, in this instance, its worked out perfectly.
 At any rate,.....
There it is, the distant evil bastard step-cousin of a Lenco, now sporting Lenco parts.
Shes likely outlived her original designers, and, has every possibility of doing that again. A Black Widow?
Hopefully she'll be spinning vinyl when she hits 100.
At 55 years old, and having just spun her first ever stereo LP's (she came on her OE plinth, with a monaural GE tonearm), she sounds spectacular.



24vdc input via Neutrik locking connector (I hate IEC type) This thing locks into place and requires effort to remove (pull back silver tab on top of connector, and twist to unlock)


exploded view of plinth, suspended motor CLD system:




Bearing clamp and thrust plate capture device:

I put a gasket into the mounting flange interface.  The ring pulls the top plate and bearing housing down, securing them, mechanically, to the plinth. The bearing flange is machined to sit flush to whatever the mounting surface is. This step just mechanically draws it down, and takes advantage of that. The bar is to recapture the thrust bearing cap, by pushing it back towards the plinth stone.

The new DC motor speed control pot. Its infinitely variable between dead-stop to hundreds of RPM at the platter.
This is the left rear corner of the deck:


Bottom of deck, motor CLD facade plate:

Rear of deck, showing motor driver and compartment:

The deck is supported at the three legs via a stone pillar that passes from the feet to the plinth base, further isolating the motor layer:

Motor CLD:



I made custom Lenco spring suspended motor mount struts. The struts mount to an aluminum plate that fastens to the CLD motor layer. I know, its probably not proper CLD, but I needed the thickness -- and, it works, very well.
The motor mount layer is from top to bottom:
~ 2.5mm rubber pond liner repair tape, EPDM rubber
~ 2ea. 1/8" masonite sheets
~ epdm pond liner rubber
~ cork
~ 1/2" MDF
~ cork
~ epdm pond liner
~ 1/8" masonite
~ 1/2" polyethylene sheet that the motor mount to, and as base to the layer.
All the motor mount layers were siliconed together over 100% of the mating surfaces.
The motor CLD attaches to the plinth bottom at four points, via 1/4-20 rubber well nuts to isolate it at that last fastening stage.

Here is an early stage dry-fitting phase of the motor mount, the Lenco wheel, etc.
The motor struts are total DIY, and as mentioned, have Lenco springs as suspension. The shown capstan is not the final capstan, but the OE capstan that I was using as a stand-in.



The Prenco series, together:

The cut-away L75 was done to emulate the looks of the Presto. I bought the Presto first, but, it became such a problematic build that I almost gave up on it. I liked the cutaway Lenco look, so, I decided to make my L75 look like the Presto, and now my Presto is a Lenco - So, I present to you, The Prenco series of turntables.



If you have not followed this build, there are fourteen more pages of ramblings, here:
http://www.lencoheaven.net/forum/index.php?topic=1087.0

[mosin]

Mike, It is both beautiful and innovative. Good stuff!

[jaspert]

Hats off to you.. Wonderful build. Another showcase of the multi talents on LH.

[Basite]

Congrats

congrats

congrats

that's a beautiful very innovative turntable
I bet she sounds even better than she looks (and that's very good already )

Keep them spinning,
Bert.

[mfrench]

Thanks guys. Truly appreciated.

The one month evaluation of this thing is just pure bliss.  I'm so ultimately happy with this deck right now.
In this month, my L75 has been torn apart for maintenance and dry-fitting my next build. So, this presto has been pushed really, really hard. All day, every day, for a month. Its been more than up to the task.
Technically, it has yet to falter. In this month, I was expecting to have to deal with speed variations. In truth, there have been a few, very minor adjustments, mostly early on, as the system was first settling in.
I've since put a newly retread two hole tire on it, which slowed the platter speed down a bit, as the new wheel was just ever so slightly wider than the 35->40y.o. tire that I fitted things with (newly ground tire vs. old tire worn edge); This was beneficial to me, so that I could open up my speed pot a little.  Since that retread wheel has burned in, its been really steady, and I haven't speed checked it in a week or ten days now (the new wheel has been on for three weeks or so).  It has gotten to a point where the faith in its ability to hold speed has grown really strong. So, now its going to be a once a week check, and maybe work towards a couple of week span, then a month,.....
The motor vibration damping system has really done its job well.  If you reach under the plinth, you can feel the slightest vibration within the CLD. On top of the plinth, its been almost completely attenuated, by feel, and it takes an extended ear-on-plinth critical evaluation to just pick up the most faint of motor noise, so all of that effort has paid off far more than its time spent.
The Lenco wheel and its thin knife-edge holds massive value in our systems, and cannot be credited enough. The Prestos original tires sounded like a big offroad vehicle with mud tires on, or maybe even studded snow tires - just incredibly noisy (when the quiet motor was finally driving them). The Lenco wheel provided an equal amount of torque, and with the minimal contact patch. Its more than worthy for any turntable rim drive retrofitting project. Combined with the 100% of the torque 100% of the time DC motor driving force, this has proven to be a solid, massively torquey combo that gets to speed almost instantly, yet has kept its noise level out of the playback stream -  Lenco springs doing their thing.
The background is black between tracks. I've just been totally impressed with that. I was worried that the old bearing might be noisy, but its proven to be just fine and probably more steady, laterally, than the Lenco (but my L75 bushings might be worn a bit too).

This one's mine, and it ain't going nowhere

[ejfud]

That is a work of art. Great job.

[mfrench]

thanks, Gary!

Well, I'm proud to say that I dropped the needle yesterday afternoon, and within a few seconds of doing that, we had a 5.5 earthquake. Not a single effect or groove skip - she tracked flawlessly throughout the shaking. Ridiculously heavy plinths work.
So, its now passed the earth shaking test.

[glady86]

 Hi Mike,love your soapstone beauty!What's the name of the finish you used to get that "wet look" I would like to try some with slate.

[mfrench]

thanks, Travis!

The sealer is called Enrich-N-Seal by Custom Building Products. Its a sealer that darkens, and maintains the wet look, as you suggested. Some products don't, but this one takes you to as dark as the stone will go, and keeps you there - permanently. So test hidden samples, or get ready for a change.
For gray slate, you might end up closer to black.
Its an amazing product as far as a sealer goes,... like 15 year outdoor exposure life.
Its expensive, but goes a long way. You can get a pint of it, but don't be surprised by $35->40$ per pint. A pint will go a mile.

enrich-n-seal link:
HERE

[glady86]

 Thanks a million Mike ,the cost is not so bad,actually a drop in the bucket if I figure the total cost for my project.

[strata]

Spectacular project. Many working hours well spent I hope. It must sound fantastic. Congrats!!