speed calibration when two pots exist.

[MetalFisher]

The deck is a Pioneer CT-W900R.
Dual cassette, auto reverse on both wells, also both wells record-capable.
One well has only one speed adjusting pot but the other has two of them.

Using a speed calibration tape, I adjusted the speed. They both play and record at accurate speeds forward and reverse.High speed dubbing works well and the recorded tape sounds to be normal speed when played back on even a different deck.

So, why would one well have two pots for speed but the other only have one?

More specific -
VR305, labeled 1 - X1 controls the speed of well one. Simple enough.
However, VR306, labeled 2 - X1 and VR307, labeled 2 - X2 both effect "normal" speed on well 2.
Shouldn't "2 - X2" effect high speed dubbing instead of normal speed?

I found this thread talking about it - http://audiokarma.org/forums/index.php?threads/adjusting-tape-speed-late-80s-pioneer.534417/
Of course his is a different deck but what user "hdrobien " does not seem to apply to mine.

Everything works on this deck as it should but I would like to know if things are way off even though they "seem" alright.

Thanks

 

[hdrobien]

I was not able to find the service manual for this unit but I believe you can use those of the W950R available on elektrotanya which gives you directions..

My thoughts:
- high speed (x2) is only for high speed dubbing, not for playing or recording external signal
- you have to set precisely normal speed (x1) on both decks for correct playing or recording whatever the deck, like any other tape deck
- you don't need to precisely set high speed on both decks but only be sure than they run at the same speed for correct high speed dubbing (the seed itself is not an issue as long as both decks run at the same speed)
- that is why you don't have any pot for high speed on deck 1 but you need to set high speed on deck 2 at the same speed as what you measured on deck 1.

 

[MetalFisher]

Though that does make sense, it doesn't explain why the X2 pot effects playback speed on deck 2.

Like I said, everything seems to work. Both are at a good speed, high AND low speed dubbing work fine (not that I ever dub tapes anyways)

I do have the W950R service manual. I think for now I shall "leave well enough alone.

I appreciate the feedback, thank you

 

[hdrobien]

The X2 pot affects the playback in normal speed because of the schematic used for 2 speeds motor.

In high speed only the pot for X2 is used.

In normal speed both pots are in parallel.

That is why you have to set high speed first.