Author Topic: Four-pin/five-pin halfbreed.  (Read 8577 times)

Offline vpalmer

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Four-pin/five-pin halfbreed.
« on: May 20, 2004, 09:22:28 PM »
Hello,

I have a 1974 model suitcase Rhodes and am trying to order a replacement cable.  All parts on the keyboard are original.  I have a problem -- the jack on the amp is a four-pin, and the jack on the piano itself requires a five-pin female end.  The person I am trying to order the cable from told me this is not normal -- can anyone help?

-Vanessa

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Four-pin/five-pin halfbreed.
« Reply #1 on: May 24, 2004, 07:09:52 AM »
Hi :-)
The fact is that you can't connect a 4-pin Cabinet to a 5-pin Piano preamp. The 5-pin version has a different power supply concept. The 4-pin uses a single 24V supply, the 5-pin version uses a dual +/-15V supply. So sadly, your problem can only be solved by searching for a 4-pin Piano top.

regards, Jens :-)

Offline vpalmer

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Problem.
« Reply #2 on: May 24, 2004, 04:10:02 PM »
I've been told that the 5-pin keyboard and 4-pin amp are "incompatible" by a number of different people.  Here's the weird part though: all of it was purchased as a set and works fine -- you can hear it in action at www.purevolume.com/ininkplease.  I have a cable with a five-pin jack on the keyboard end and a four-pin jack on the amp end -- so it is already functional.  The keyboard, amp, and connecting cable were purchased together at a music shop in Sidney, Montana in the mid-70s by my band director, who sold everything to me two years ago.  I have never had any problems with my current keyboard (abnormal though it may be); I just wanted a replacement cable for the road.  Is it possible I have the product of some kind of factory slip-up?  Ideas, anyone?

-Vanessa

Offline Jenzz

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Four-pin/five-pin halfbreed.
« Reply #3 on: May 25, 2004, 02:16:09 AM »
Have you ever checked the innards of the Piano preamp?

Seems that somebody modded the circuit to make it work at single 24V supply...this can be done, although its a bit difficult.

regards, Jens
Rhodes tech in Germany
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Offline vpalmer

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Four-pin/five-pin halfbreed.
« Reply #4 on: May 25, 2004, 12:08:16 PM »
I've only ever opened up the amp to solder some wires; never the keyboard.  What would I be looking for?

The person from whom I was originally trying to buy a cord makes them himself; maybe I'll just try a four-pin cable but with a five-pin jack on the tacked on the keyboard end.  One of the sockets won't be connected to anything in the cord, but it might work.  Suggestions?

Offline Jenzz

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Four-pin/five-pin halfbreed.
« Reply #5 on: May 26, 2004, 01:57:06 AM »
Hi :-)

Look for a circuit like this:
http://www-k.ext.ti.com/SRVS/Data/ti/KnowledgeBases/analog/document/faqs/virtual.htm

This forms a virtual ground circuit with Vcc/2 being the ground terminal.

With this circuit, you can derive a +/-12 V supply out of the single 24V supply of the 4-Pin cabinet.

regards, Jens
Rhodes tech in Germany
www.tasteundtechnik.de
www.spontaneousstorytelling.net

VintageVibe 64 ACL + DOD FX25B, EHX SmallStone, Tone City Sweet Cream, Pearl FG-01

Adams Solist 3.1 Vibraphone

Offline Jenzz

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Four-pin/five-pin halfbreed.
« Reply #6 on: May 26, 2004, 07:58:31 AM »
Hi again :-)
While searching for some other things i came over this conversion kit schematic on the Super Site:

http://www.fenderrhodes.org/rhodes/ch11/fig11-16.jpg

This one makes it possible to connect a 5-pin Piano to a 4-pin cabinet by using an external / additional power supply only for the Piano


regards, Jens
Rhodes tech in Germany
www.tasteundtechnik.de
www.spontaneousstorytelling.net

VintageVibe 64 ACL + DOD FX25B, EHX SmallStone, Tone City Sweet Cream, Pearl FG-01

Adams Solist 3.1 Vibraphone