Pioneer RT-707 speed issue

[cplyons]

Scored a kind of beat RT-707 at a local garage sale today for $35... (Thanks Jim!) Needs some cosmetic help (knobs for setting line and mic recording levels), but before messing with that I need to work through the main issue - playback speed.

The playback speed is about twice what it should be. The speed is the same in either playback direction. FF and Rew work fine, at a much faster speed. When I remove the case I don't see a belt or an obvious way to adjust speed on these DC motors. Does anyone know how speed is regulated on these decks and where I should start my diagnoses? I will certainly buy a service manual but I would love a shortcut to see if this is worth the time and money to get into further....

thanks!

Chris L
Austin, Texas

[stereofisher]

Are the pinch rollers engaging against the Capstain?? My TEAC's often have this problem. The arm inside the machine get dry with age and the rubber roller does not engage proberly causing your speed to run fast. You need to open it up and look for the arm that pushes the roller up against the capstain. A little oil and it should engage correctely.

Never have worked on a RT 707 deck. Always wanted one though. Great decks!! Great find! Enjoy!!! Eric :music:

[cplyons]

Tried it and no luck... Thanks Eric - I have a Teac with the same tendency, but hadn't thought to try that on this one. The Pioneer is not mechanical in the same way, appears to have a solenoid that is either 100% or 0%, pushing up on the mechanism doesn't decrease the speed.

[cplyons]

OK, here's a thought. Everything appears to work fine on this guy except the playback speed... that seems to run about double 7.5 ips. Could it be that someone rigged this machine to run at 15ips to listen to studio tapes at home? There are zillions of musicians here in Austin as well as recording studios, so there would be plenty of folks who could have done something like that...

So I still need to figure out how the speed is controlled to see if this is a crazy idea or possible, and if it can be reversed...

Anybody?
:scratch2:

[madpioneer]

My 707 intermintently will jump into 19 on a tape I recorded at 9.5
Just when it feels like it right in the middle of a song. Opened her up and sprayed the speed switch with Deoxit. Worked for about a week. Need to go back in for a second dose. Not sure if the problem is deeper than that?
May help you may not. But if it is dirty and needs cleaning thats a good place to start. For all I know the switch may have to be removed from the board to properly clean it.

[Vintage TX]

Test with a tape loaded on the machine, press play and when it takes off, turn the pitch-control back and fourth and see if the speed slows down or raise up.
If no response the power-supply can have problems, but also spray some contact-cleaner in both the speed-switch and pitch-control switch before tearing it apart. :)

[Vintage TX]

Forgot, did you check the pinch-roller ?

[raffie]

The playback speed is about twice what it should be.

playback speed... that seems to run about double 7.5 ips. Could it be that someone rigged this machine to run at 15ips
If it appears to playback too fast (double speed), it has been recorded at half the speed that you are playing it back on, I would suggest you press the 'speed' button, just next to the power button. :)

[cplyons]

Heavy dose of DeOxit and a hundred cycles of the speed switch show no effect... the pitch control doesn't work either, so I guess this a power supply issue? (Raffie I forgot to mention it, but the fast playback speed remains the same regardless of what speed is selected on the unit). Are there any voltages I can take before deciding to pull the power supply? I was kinda hoping that I could manipulate one or more of the many pots I see on the boards and not have to do major surgery... This may end up as a parts unit for somebody if the fix is too complex... a whiz with this stuff I ain't... :tears:

Chris

[raffie]

aha so the speed switch doesnt actually change the speed then? Possibly thats were the problem lies.

[jblmar]

The 707 is a DC Servo machine. If the roller and or tension adjustments are o.k., you'll need to look at the servo section. I would also look at the Pitch control as a possibility.

Ron

[wallybop]

Chris,
Did you resolve the speed problem? I have an identical problem with an RT-701. Cleaned the speed switch and pitch control, no change in the symptom.
Have any ideas?

[inductor]

its a mains operated motor, a relay changes windings over in the motor for the 2 speeds, there is no feedback for speed control as such it relies on the motor\mains frequency

[wallybop]

Vintage TX, Inductor, cplyons...Thanks for your help. The motor was the problem.

Walter

[gearhead]

Did you replace the motor, or...?

[boxoboom]

I have 2 of those 707's. Both work perfectly, however one of them (the oldest one) every so often will jump speed. (run really fast) My capstan is fine, speed switches have been sprayed with Deoxit. Turning it off and on some times will reset it, reversing the direction does the same.

I am of the opinion that there is a relay in there that gets stuck. (this is just an opinion / theory, I have not had it on the bench to find out anything yet)

Someone many years back, brought me a 701 that had the very same problem
I fixed it, but cannot remember what I did to effect it.

I will do some research on this and get back to you guys.

[Jukin Jay]

Do you have a schematic or know of a URL for one?

[Jukin Jay]

I found a schematic in a dark corner of AK. The capstan motor is controlled by an oscillator and power amplifier on the servo amplifier assembly. If you've ruled out anything mechanical, it is most likely a component failure on that board. The manual has a good description of the circuit operation. I'd recommend an oscilloscope for troubleshooting.

Does it also run fast in record mode? The pitch control wiper is bypassed for a fixed tap for recording. If it runs at the proper speed recording, it could be the pitch control itself or the pitch control. Same actual speed regardless of the speed selector switch?

[wallybop]

Yes. What inductor said about a relay in the motor became very clear. The motor is socketed, I plugged a second motor in w/o mounting it in the deck, held the motor (safely) turned the deck on and changed the speed. I could feel the speed shift. The capstan axel on the original motor was running very fast with no change by the speed switch or pitch control.

[inductor]

well i was partly right, at least the problem is resolved !

[KentTeffeteller]

Hi,

With this deck, this problem is usually nothing more than a pitch pot with dirty contacts. A shot of Deoxit into this pot after taking the front panel off and you should be in business. The machine is a superb recorder and you'll enjoy it well.

[gearhead]

Hi,

With this deck, this problem is usually nothing more than a pitch pot with dirty contacts. A shot of Deoxit into this pot after taking the front panel off and you should be in business. The machine is a superb recorder and you'll enjoy it well.

This didn't fix mine, it's still running fast.

[wallybop]

gearhead,

The first attempted solutions were mechanical solutions: pinch roller, pressure and possible mis-tracking. After that contact cleaner was applied to the pitch contol and speed switch and the controls were 'exercised' with no change. The capstan was running very fast. The motor was replaced and the symptoms stopped. The speed switch and pitch control then functioned properly. It would be good if someone could explane how the feedback control circuit and speed shift circuits operate on this motor. Otherwise that is the limit of my knowledge.

[JodyBoykin]

I know this is really really late.. The speed problem with the RT-707 is in the molex style mulit pin connector .. facing the machine and on the right side .. underneath and upside down under what I am guessing is the servo control board. Pioneer , in a stroke of genius , couldn't find a happy medium between hand wire wrapping and soldering stuff, and putting a crappy connector on really important stuff. OH YEAH, they are doing it much better now! Spray the really expensive best selling all purpose ozone killing NASA approved contact cleaner on ALL removable plugs, moving contacts, switches, and pots! The white plastic multi pin connector is the culprit for the dreaded runaway capstan disorder. This from experience. There is a similar problem with the Technics SP-15 turntables. A flaky solder joint in 90% of them eventually causes the motor to run wild. This happens with these DD DC frequency controlled motors when the rotational data from the counter head on the motor does not reach the input side of the comparator ... The FG circuit sends the "go wild" to the servo amp that drives the capstan motor.. I don't know what to do!!! . Speakers are also motors. They are not DC, however. Oh yeah.. when you replaced the motor, that connector was definately disturbed.. that waswhat probably fixed the problem..???? ;)

[gearhead]

Thanks, JodyBoykin, and welcome to AK.
That was a very informative first post!
(Better info than a few put out in 500 posts...)
But, that didn't fix it, either.
:sigh:

[wallybop]

Gearhead...I second that, great post JodyBoykin. I plugged speedo back into the cleaned socket but it still ran wild.

[gearhead]

I guess I'm going to have to replace the motor.
(mumbles words not in Webster's...)

[jblmar]

You need to check the wave form(s) going to the motor with an oscilloscope. A defective relay would display the same symptoms as a defective IC so you need to check the IC voltages and waveform at the inputs and outputs referenced to those given in the service manual.

Off hand I don't know the circuit, but if an IC is used for speed functions, either the IC or its associated components may be at fault.
If someone has the service manual, it would be a great help if they can let us know if a wave form guide is included.

Ron

[lbossp29]

My RT 701 started doing this same thing suddenly tonight, total bummer. I've tried cleaning the speed switch and pitch pot. The speed is, like you said, twice what it should be. Should I be looking for a new motor? Do they exist or is this a lost cause? Thanks!

-Luke

[lbossp29]

Problem solved...I read through this posting too quickly the first time. On second reading I noticed the post about the connector inside the unit needing to be cleaned. Before I did anything else I wiggled the connector and the speed returned to normal. After cleaning the connector and soldering what appeared to be a cold solder joint on the board my RT-701 is working great...thanks to JodyBoykin for the excellent post!!!

[KentTeffeteller]

Hi,

Thanks for that superb first post. A very important commandment for RT 701/707 owners. Check thy soldering and Molex connectors. Molex connectors are a pain in der rear end. Ask anyone who ever had to maintain or service an MCI tape machine or console.