ETI 3600 Owner Paul Read's Page

 
    Paul Read      
 
 

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Paul Read
Present Owner
ETI 3600


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  Hi Guys,

My story goes like this, I was always interested in electronics and it was in the early '70s that I built an (awful) electronic organ (Practical Wireless I think !), and I played it in a band. The base player also had some keyboards so I played them as well. I think it was him (or the lead guitarist) who gave me the Maplin 4600 manual and a couple of negatives for PCBs.
At my first job, there was a PCB department and, as you do, I got friendly with the manager. He made me some boards, controller and transient I think, I will be able to identify them when I open the machine up for photographing. I do remember that I made the VCF PCB using the "nail varnish and etch it in the kitchen sink" method!

These boards languished partly built for a few years when I found a 3800 cabinet on offer at the Southampton branch of Maplins, so now the game was on. I got hold of the 5600 manual and purchased the remainder of the PCBs! I had decided on a few modifications so I got the sheet metal supplier to make me a front panel using full size artwork that I had prepared. I think I spent a fortune on collet style knobs, but they are the "Dogs doodahs". I finally got it finished during the mid '80s, during my second job. By this time I had been able to arm myself with a Tek 465 'scope - a definite bonus when setting up. I never played it in a band but have had many hours of fun playing with the sounds that it can make. A while after I had finished, I decided that the keyboard controller needed to be upgraded to the digital one in the 3800, it deals with fast fingering better than the original.
While I had it apart I replaced the reverb driver transistors, they had blown.

Recently I was playing it and noticed that again the reverb was not working, so I had a proper hunt for the problem. I found that the 2 transistors where getting very hot almost as soon as the synth was switch on, look at the circuit again, spot the 2 diodes near the bases, these are supposed to be in thermal contact with the output pair for stability !. Put new transistors and longer legged diodes in, now they run slightly warm and the reverb has not failed since. I will generate a technical note if you like.

Most recently I came across a guy on the O'Reilly forum looking for info on the 3800 he was building and it turns out that he lives 25 minute away! He now has a set of shiny PCBs generated from one of the 4600 manuals on the WEB and many hours cleaning up and re-scaling.

My synth gets used at school now and then and has now been joined by a DX7. The current thoughts on my 3600e, as I called it, are to add a PIC to the computer input and allow the thing to be sequenced by MIDI.

Paul
 

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