ARP 2600 Broken Resistor

Hi there, just wondering if anyone can help with this, I have an original grey arp 2600, not used it for a while but it just didn’t sound right. I opened it up to see if there was anything obviously wrong with it and noticed one of the resistors looked a bit black,( Bottom Left in pic ) when i touched it, it just split in half. Is this a standard resistor I can get from anywhere ? Also there seems to be a spare black wire attached to the power supply that wasn’t connected to anywhere.

Hope its an easy fix, Thanks Ian

R15 1Ohm 1/2W (same as R6) - nothing special - should be able to get from any decent electronics store - if it burns up again straight away then Q5 may by shorted out. If it works OK you can replace with 1 Ohm 1W because that 1/2W may have been just a little too close to its load tolerances

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Thank you for replying so quick, I’ve ordered some resistors and I’ll see how I get on. what about that loose wire, should it be connected to anything, it’s only about an inch long so couldn’t have been connected to anything to far away
Thanks Ian

That resistor burned because too much current went through it. The next resistor will just burn up too.
This is a sign that your capacitors in the power supply have time expired and allowing too much current through. If not properly serviced, it can smoke other components, like the bridge rectifiers, then power regulators, they too must be running very hot.

If Syntaur doesn’t have a parts kit for this I believe Synthchaser does.

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See the schematic posted by wernersaurus above, which shows 3 wires on the secondary used and attached to the circuit. That’s a typical standard center tapped winding and application, I believe. You should have those 3 attached on the secondary side. If you do, and you confirm you have the proper voltages out of the power supply circuit, shown as +/- 15 V and 35 V (common) then I wouldn’t worry about any additional wire from a possible additional winding on the transformer secondary side. That is a possibility too, but not ideal design.