Tuesday, 24 June 2014

TTSH - ARP 2600 Replica - 2047-1 VCO submodule

This is the second part of my TTSH (Two thousand six hundred) build.

You can see my full build thread HERE
There are two awesome TTSH threads in Muffs.
2600 clone - Two Thousand Six Hundred (TTSH)
Two Thousand Six Hundred (TTSH) Project General Build Thread
The DSL-Man site has a very good TTSH thread
And of course the official build thread is here


The 4027-1 was an improved design over the original ARP 4017/4027 VCO's

The TTSH 2047-1 module is pretty straight forward to put together except for
though those pesky SMD caps. They are tiny and one gave me a headache when it decided to fly off my tweezers onto the floor.

This is a packet of six 100n SMD caps viewed against a Australian 20 cent piece.

Pointless trying to find it. A new order from mouser beckons.

Half way there

1k87 Tempco Resistor.

One finished sub module.... two to go.

As a comparison, I'd thought it would be nice to see the TTSH 2047-1 against a original ARP 2047-1 sub module. This is a spare I have left over from a earlier restoration of a vintage 2600.

The original ARP (like the TTSH version) used three of these 2047-1 submodules. The rest of the VCO circuit is on the main PCB.
 The modern TTSH 2047 uses a 3046 IC. The vintage a CA3086 IC

The CA3046 transistor arrays consists of five general purpose silicon NPN transistors. Two of the transistors are internally connected to form a differentially connected pair.

The CA3086 transistor arrays also consists of five general-purpose silicon NPN transistors. We also have two of the transistors internally connected to form a differentially connected pair.
The pin outs of both look the same.The CA3046's probably have closer tolerances
than the older CA3086, however I wonder if CA3086’s can be used (if you can find them)?
 As in the TTSH build the 2N3904 and 2N3906 transistors are pushed together for thermal contact.

The vintage 4027-1 PCB:(It's a work of art).

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