Fuck Lenny I am way cooler than you, or was...
I had me a Viking Of Mineapolis. It was not only tube, the optional record amplifiers could be removed, unplugged. Whether yuo bought into the record capability was irrelevant however, to the playback. All you needee was a pr eamp the had tape (NARTB equalized) inputs. Just so happens I had one, and for the life of me I can't reme,mber the make and model of it. It MAYT have been an H.H. Scott but don't take that to the usury.... er .. bank.
Anyway, to get back to your dilemma. At this point I suspect your tachomete r. That ia not a large error. Hoever this does not explain the much larger error in the actual tape speed.
Here is something interesting just occurred to me, you know tape does not s hrink. Is it possible that the slight error in motor speed combined with th e tape being stretched has resulted in the cumulative error you obseved ?
Really, 700 some Hz is way off of 1,000. You can REALLY hear that. You said it sounded slow, I guess it was. But why.
Ihave f***ed with a couple of reel to reels laely and I see the tape is not what it once was, n fact me and my little crew have zero good tape. The be st shit we got right now clogs up theheadss in like, half hour or something . It still plays but the level keeps dropping. I looked at the prices of ne w tape and decided, not.
These are really cool. When I hit the lottery I will send a minion to pick me one up... I have digital solution anyway, but I still think they're cool . In fact my buddy has a nice Teac he is probaably going to sell. I worked on it, it is a fucink nice deck, really. Takes the 10" reels. Four track si mulcord. Though it is a three head, it can switch the playback head to the record head in sound on sound to keep the sound in sync. Otherwise yoy owul d have to waste a generation on every overdub. Or whatever. Ask Les Paul lo l. you know whatI mean. The thing is a practical recording studio.
I oculd not get nfo on your Ampex from the usual sources. I did however sco re in the 99th percentile in mechanical reasoning in one of them thar pre S AT typee thingies when I was young. I mean before I crashed a car young, an d that means young. All those idlers and shit, unless ther eis a driven sha ft rubber wheel (whiich is not an idler) or some type of stepped thing, the size does not really matter.
An idler by definition is not driven by its shaft. If it is, it is a drive wheel, not an idler.
For example, on a record player if you were to make the idler wheel a bit b igger, the speed would not change except for maybe what the rubber drags it down or something. Ther math has not changed because the only numbers tha tmatter are those of the SFM of the motor shaft and the SFM of the driven f lywheel which is either the tunrtable or the alumin(i)um thing attched to t he capstan. Math it math.
It is usual to have that much of a speed error on something like that, but of course that explins your presence here...
Anyway, the way I see it is suspect the RPM meter about the motor, OR maybe those extra wires go to the cap to trim the speed. (???) Now that would be tripped out. But tell you what, it is very possible.
Look see if there is any rubber in that thing that is nailed down. By that I mean a driven shaft with a rubber surface driving something. There is a g ood reason they stuck with the metal motor shaft and the final dirven thing , those two diaameters make the ratio and that is that. Other designs not s o much.
hell, you might have to rewire the capacitor to give more RPMs. Seriously, that is possible.
Wish ?I oculd get a mmanual ion that thing, dammit