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Old 23rd April 2011, 04:11 AM   #1
diblet is offline diblet  United States
diyAudio Member
Join Date: May 2010
Default seeking help proof-reading reel to reel schematic modifications

i posted over at audiokarma, but didn't get any bites.. thought i would try hear to see if anyone had any thoughts...

i use a pair of akai gx-4000d reel to reel decks as music tools to record tape loops in real time and do long tape echos - in order to really put them to good use i would like to defeat the erase head (in order to record/layer over already recorded material) and also modify the unit to always play back both channels (there are times when i want to play back what is on one channel, while recording on another - the standard behavior for the unit is to mute the channel that is not selected)...

here is a link to the unaltered schematic:
Click the image to open in full size.


here are my initial thoughts for the modifications. i just wanted to get some proof-reading from more experienced folks before i carry it out on my pair of decks.


1. defeat the erase head, regardless of the track selection switch position, in a way that does not inappropriately load the bias oscillation circuit. i chose to integrate into the circuit at the wires leading to the erase head to avoid lifting components / modifying the pcb.

*it would be great to come up with a way to disable only one channel or the other on the erase head, but i can't come up with a way to do it where it would work regardless of the channel selection switch's position...

Click the image to open in full size.


2. remove the behavior of muting playback of the channel not currently selected on the channel selection switch. seems to me simply removing the resistor should keep both channels playing back at all times by leaving that connection floating regardless of the channel selection switch orientation.

Click the image to open in full size.


thanks in advance!
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