• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

rt-909 and rt-707 heads

F

fixinstuff

Member
Hello again. Playback heads for the RT-909 is part number RPB-65. Playback heads for RT-707 is part number RPB-41. (from the service manuals parts list) Does anyone know for fact that they are actually the same head and are interchangeable and compatible? The oaktreevintage site sort of says they are compatible, but not really clear that they are. Maybe someone has actually swaped them and can verify? Thanks
 
Register to hide this ad
I have never swapped them, but I have looked at both of these machines and the heads which I observed looked rather different. The 909 head looked very similar to a teac head with it parabolic shape. The 707 head looked significantly flatter and less parabolic in shape to my eye. Perhaps they are interchangable, but I would not have guessed so from the look of the heads which I have seen.

However I would wait for somebody who is far more knoledgable about Pioneers than I am to respond before taking my word as gospel on this.
 
Not expert advise, just my $0.02 here but none the less, they "may appear" to look identical but one should also keep in mind the actual physical dimensions of each head on different units may be slightly different? :scratch2: This must be taken into account when swapping or switching heads. :yes:
IMO, it's always best to just replace with the actual original model number head whenever possible. :D
 
I talked about wit John at JRF Magnetics. He told me the heads are interchangeable. They just look different but have same parameters.

Currently I'm trying to use Akai GX heads on the RT-909.
Will report soon if they work on the RT.

Vlad
 
Way to go Vlad! :yes:

If anyone can confirm this, only you can! :D


matrix said:
I talked about wit John at JRF Magnetics. He told me the heads are interchangeable. They just look different but have same parameters.

Currently I'm trying to use Akai GX heads on the RT-909.
Will report soon if they work on the RT.

Vlad
Click to expand...
 
Thanks, Vlad for the info. So far I haven't had any other info on the swap. Looking forward to any other info and how the Akai GX heads reproduce on the Pioneer. Have you checked the heads resistance compared with the 909?
 
fixinstuff said:
Thanks, Vlad for the info. So far I haven't had any other info on the swap. Looking forward to any other info and how the Akai GX heads reproduce on the Pioneer. Have you checked the heads resistance compared with the 909?
Click to expand...

Yes, I checked the DCR. RT-909 Heads are ~210-220 Ohm and GX heads are ~190-200 Ohm.
It should work.
But the main problem is the mounting of the GX heads. They have different size and their mounting screws are on the side. RT heads have lower height and the mounting screws on the bottom.
I did a CAD drawing for a new mounting plate and manufactured it on a CNC milling machine.
Also the shield can of the GX head had to be modified a little.
Now it looks good and the GX head is in alignement with the tape path.
I have to complete now the rework of a RT-909 which will be the deck for this experiment.

Vlad
 
matrix said:
Yes, I checked the DCR. RT-909 Heads are ~210-220 Ohm and GX heads are ~190-200 Ohm.
It should work.
But the main problem is the mounting of the GX heads. They have different size and their mounting screws are on the side. RT heads have lower height and the mounting screws on the bottom.
I did a CAD drawing for a new mounting plate and manufactured it on a CNC milling machine.
Also the shield can of the GX head had to be modified a little.
Now it looks good and the GX head is in alignement with the tape path.
I have to complete now the rework of a RT-909 which will be the deck for this experiment.

Vlad
Click to expand...
It's not the resistance which is crucial factor. From what I understand, it is the heads inductance, and possibly their Qs as well. And even if they have the same inductance, the far higher Qs of the ferrite heads might still cause some undesirable impacts upon their performance without corresponding changes to the circuitry.

This is a question for a real expert on this subject who knows more about substituting different types of heads than I do.
 
Last edited:
goldear said:
It's not the resistance which is crucial factor. From what I understand, it is the heads inductance, and possibly their Qs as well. And even if they have the same inductance, the far higher Qs of the ferrite heads might still cause some undesirable impacts upon their performance without corresponding changes to the circuitry.

This is a question for a real expert on this subject who knows more about substituting different types of heads than I do.
Click to expand...

Yes is true, but as I know this is valid for the recording head. Play heads should be not affected because they only read the information on the tape which is then simply amplified by the head pre-amplifier.
As I know Play heads are differentiators, meaning that their amplitutude increases proportional with the frequency. This increasing is then put down to a flat response with the correction according to NAB or IEC standards, better to say with the Playback EQ setting in the head pre-amp.
This is the way how I understand these things. So in my oppinion the GX playback heads should work.
The only problem I see is that maybe it would be not possible to obtain a very flat response over the freq. range.
But we will know the truth after I did the real test.

P.S. I do not want to replace also the recoding head by a GX one - here I see also the problems you talk about.

Vlad
 
You must log in or register to reply here.
Back
Top Bottom