HammondWiki - Diff: PercussionTroubleshooting

Differences between current version and predecessor to the previous major change of PercussionTroubleshooting.

Other diffs: Previous Revision, Previous Author

Newer page: version 5 Last edited on April 19, 2007 7:38 pm. by 65.57.245.11
Older page: version 4 Last edited on October 19, 2004 6:45 pm. by JeffDairiki
@@ -14,31 +14,37 @@
 * Now press any upper key and the reading should go to 0. 
  
 If the voltage on the K terminal seems to be behaving itself, skip the remainder of this section, and see the ''Trouble in the Preamp'' section below. 
  
-If little or no voltage appears at K with no keys pressed, you probably have a short (see ZincDendrites) most likely located either in the percussion switch assembly, or in the upper manual. 
+If little (less than 20 volts or so) or no voltage appears at K with  
+ no keys pressed, you probably have a short (see ZincDendrites) most  
+ likely located either in the percussion switch assembly, or in the  
+ upper manual. 
  
 * Cancel the upper manual presets (but leave the percussion switch in the on position). 
  
-If that gives you volts on the K terminal, you (probably) have a short in the upper manual. Skip the rest of this section. 
+If that gives you 25 to 30 volts on the K terminal, you (probably) have a short in the upper manual. Skip the rest of this section. 
  
 * Turn the percussion ON/OFF switch to OFF. 
  
-* If you still have 0 volts on the K terminal: Turn the organ off. Unsolder the blue wire from the K terminal, and the red wire from the M terminal of the [AO-28]. Turn the organ back on. 
+* If you still have too low a voltage on the K terminal: Turn the organ off. Unsolder the blue wire from the K terminal, and the red wire from the M terminal of the [AO-28]. Turn the organ back on. 
  
-If you still have no volts on K, you have a strange problem in the preamp. 
+If you still have too low a voltage on K, you have a strange problem in the preamp. 
  
-Otherwise, you have a short most likely in the percussion switches, but also possibly in the upper manual (associated with the B preset). To further narrow down the location of the short: 
+Otherwise, you have a short most likely in the percussion switches,  
+ but also possibly in the upper manual (associated with the B preset).  
+ To further narrow down the location of the short: 
  
 * Turn percussion back on. Reconnect the wires to the K and M terminals (if you had disconnected them). 
-;: (Sanity check: you should be back to having 0 volts on K.) 
+;: (Sanity check: you should be back to having low voltage on K.) 
  
 * Unsolder one of the white wires going to the left-most terminal of the ResistorPanel. 
  
 If you still have 0 volts on K, there is a short in the percussion switches. Otherwise the short is in the upper manual. 
  
 --------- 
 ! To Clean the Percussion Switch Assembly 
+See ''Zapping'' below for an easier (but not 100% reliable) alternative to physically cleaning the percussion switches.  
  
 * Remove the music rack, the two large screws and two wood screws which secure the drawbar base, place heavy paper (or thin carboard) at either end to avoid scratches and raise the drawbar base 4 to 5 inches. (See also HowToRaiseTheManuals.) 
  
 * Remove the two screws from the percussion switch cover and remove it. Spray the interior of the percussion switch housing and contacts with a good non-residual cleaner and retest to see if it works. 
@@ -54,24 +60,47 @@
  
 -------- 
 __Zapping__: 
  
-The quick fix (which also may or may not work) is ''flashing'' or ManualZapping. 
+The quick fix (which also may or may not work) is ''flashing'' or  
+ ManualZapping. You can zap either the manual or the percussion  
+switches, or both
  
-__Warning__: Improper (or even proper) zapping can do permanent damage to your organ! Make sure you completely understand what you are doing before proceding. Also, please read ManualZapping for further comments. 
+__Warning__: Improper (or even proper) zapping can do permanent damage  
+ to your organ! Make sure you completely understand what you are doing  
+ before proceding. Also, please read ManualZapping for further  
+ comments. 
  
 You have several choices of where to zap: 
  
-# Unsolder the white wire from the B preset bundle at the ResistorPanel. Select the B preset, and zap between the white wire and the manual chassis.  
-;: (Other's can elaborate here on the other choices ). 
+# To zap the upper manual assembly, unsolder the white wire from the B preset bundle at the ResistorPanel. Select the B preset, and zap between the white wire and the manual chassis (ground ). This will flash away dendrites only in the manual assembly and will not affect any dendrites that might be in the percussion switches
  
-Before you zap, you may want to check with a (good-quality ) ohm-meter to make sure there is indeed a dendrite short. (The [ZincDendrite|ZincDendrites] shorts typically have resistances a few hundreds of ohms. ) If you see a short of very low resistance , you may want to rethink your decision to zap until you've figured out more about what's causing the short
+# Unsolder the blue wire from the K terminal on the preamp. Rock the percussion switches (all four ) toward the player and flash between the blue wire and ground (the preamp chassis ). Rock the percussion switches away from the player , and flash again between the blue wire and ground
  
-After you've checked the resistance of the short , take a nine volt "transistor radio " battery , and hook it up across the short for a couple of seconds. Check the resistance again . If you now see a open circuit, rejoice!  
+# It can also be beneficial to flash the other percussion-related wires on the preamp terminals. In particular , in one case where the percussion disappeared only when the decay was set to "slow, " flashing the H, J, M , and N wires (unsoldered) with the switches in both positions solved the problem
  
-If the short is still there, but the resistance has changed (either higher or lower ) that's a good sign . Zap again (and again and again, if need be.)  
+;: (Others can elaborate here on more choices ). 
  
-If the resistance of the short isn't changing, I'd try zapping one or two more times, but your prospects are less promising. 
+Before you zap, you may want to check with a (good-quality) ohmmeter  
+to make sure there is indeed a dendrite short. (The  
+[ZincDendrite|ZincDendrites] shorts typically have resistances a few  
+hundreds of ohms.) If you see a short of very low resistance, you may  
+want to rethink your decision to zap until you've figured out more  
+about what's causing the short.  
+  
+After you've checked the resistance of the short, take a nine volt  
+"transistor radio" battery (or two, in series), and hook it up across  
+the short for a couple of seconds. Check the resistance again. If  
+you now see a open circuit, rejoice!  
+  
+If the short is still there, but the resistance has changed (either  
+higher or lower) that's a good sign. Zap again (and again and again,  
+if need be.)  
+  
+ If the resistance of the short isn't changing, I'd try zapping one or  
+ two more times, but your prospects are less promising. If you have  
+used only one battery, try two, in series. Sometimes one is not enough, but two  
+are
  
 -------- 
 ! Trouble in the Preamp 
  

The content of this page is Copyright (C) 2000, 2001, 2002 Geoffrey T. Dairiki and the other authors of the content, whoever they may be.
This is free information and you are welcome redistribute it under certain conditions; see http://www.dairiki.org/HammondWiki/opl.html for details.
Absolutely no warrantee is made as to the correctness of the information on this page.