Regarding post #18:
The male “6-Pin Connector” is only found on the cable end of the DGA and the Dual Dichro heads. The female socket is on the 24 VAC power supplies. It’s a Cinch Jones connector that carries 120 VAC current from the external power supply to the head to power the cooling fan and panel illuminators. It also carries the 24 VAC current from the external power supply to the lamp. It has nothing to do with the OP’s Dual Dichro-S.
In the following link to the Dual Dichro manual, page 7 figure 24 shows the Standard 24 VAC power supply. Figure 25 shows the 24 VAC Stabilized Power Supply.
The Dual Dichro-S uses a simple half-wave diode and power resister power supply, small and compact, built into the lamp head. This results in approximately 82 volts (pulsing DC) to the lamp. Any time you encounter an enlarger, projector, or any device that uses an 82-volt quartz-halogen lamp, you can assume that it’s powered by diode-and-resistor power supply. They're cheap to build and rarely fail. If they do, you can unsolder the bad part and replace it. It’s only when a more complex voltage stabilizing circuit is incorporated into the design that it becomes potentially unstable with aging.
The power supply of the Dual Dichro-S (disregarding the voltage-stabilizing circuit) looks like the first diagram in the following link. You must click onto "Continue Reading" to see the full diagram.
https://www.quora.com/What-is-half-wave-power-supply
The Dual Dichro-S power supply use a voltage-stabilizing circuit employing a Vactrol and other electronic components. The Vactrol tends to fail as it ages. That can make the unit unusable. Essentially the same voltage stabilizing circuit is found in the 24-volt Stabilized Power Supply for the DGA and Dual Dichro (incompatible with the Dual Dichro-S head). Most owners don’t have the resources to diagnose the problem, obtain the parts, and make the necessary repairs.
Vactrol (Resistive opto-isolator):
https://en.wikipedia.org/wiki/Resistive_opto-isolator
Some Vactrol related posts:
https://www.photrio.com/forum/threads/beseler-lamp-delay-for-printing.3703/page-2
https://www.photrio.com/forum/threads/beseler-dual-dichro-s-23-schematic.27131/
Unless you have electronics experience and can locate the necessary replacement parts, you can resolve the problem by looking for either a DGA or Dual Dichro head to replace the faulty Dual Dichro-
S head. Both the DGA and Dual Dichro heads require a 120 VAC to 24 VAC external power supply. I strongly advise avoiding the Stabilized Power Supply as it is likely to have the same problem as your Dual Dichro-S. The dichroic heads are for either B&W or color work.
If you intend on doing B&W enlarging only, then it will be much easier to simply obtain a standard lamp holder. Simply unfasten the dichroic head and lift it straight up and off of the lamp housing, set the lamp holder in place and snug the fastening knob.
The older lamp holders use the small, spherical-envelope PH-111 bayonet mount lamp. The newer version uses the larger PH-140 E26 screw base lamp. You can use either version. I prefer the later version with the PH-140 lamp. Both are 75-watt opal photo lamps and are cheap and plentiful in 2025. It’s economical to buy them in 6-lamp packs:
https://www.bhphotovideo.com/c/prod...osram_11624p_ph111a_75w_125v_lamp_6_pack.html
https://www.bhphotovideo.com/c/prod..._osram_11625p_ph140_75w_120v_lamp_6_pack.html
PH-140 lamp holder (the type I prefer)
https://www.ebay.com/itm/267056582961?_skw=Beseler+23C+lamp+head&itmmeta=01JMCH6F7M32JVAV0S932Z45K2&hash=item3e2dd01131:g:aQ0AAOSwNoJnLWuT&itmprp=enc:AQAKAAAA8FkggFvd1GGDu0w3yXCmi1eAB9pDMOxzIfFpn7Ltqpj5JBL34vlvfBxXaL2oli9NoX2k1hp5sUb38nApBAG38sK14Zps8US5skj9Cr6gklC+sIJNZljgjfdBzghk1QdaFgx02XVug2u+qXQ3it8zH8WCkHdCxZ40dQVv0apRgOZdKciVJGRM76K36c434rRr1aW9qRrw6uKOEgMqc42V8jqz50ML0nGV61G1iSNo2gYyYR3KClPbB6UEYebXOav/6t9gKFYvSAQKLOyPKEvCxN9LtFBu6mhOQSa2+MM/dtfqpiKqciHXnL9gBua/2Fdxug==|tkp:Bk9SR_zzmZGjZQ
PH-111 lamp holder
https://www.ebay.com/itm/326387924685?_skw=Beseler+23C+lamp+head&itmmeta=01JMCH6F7MQG0A5DVRK39DSACY&hash=item4bfe3c7ecd:g:UhYAAOSwlb1nYMCE&itmprp=enc:AQAKAAAA8FkggFvd1GGDu0w3yXCmi1diGExKQk74hzFxmFmgM3JjIvA9PXU0xJ5qVD+BeYqFpeFVyHvO5Y8torRtBEswV1UWYtFHvaBa67LJZ0feoRdypkxRnA2LnWMBzyCegEcOZJBpUWJ60OlaHwKjmdFsHexBI+RUqzSJ628o7BFWySYc9y0GogdERAbwJuUjNF67u9xAmgdXMP8Vjhqfxf9t1jPnWnS8ePA8atK5ZqgkyLC73fgiUdN3eAzUrvkJzcQ7clyRMnx0FXZFmKnq7TOgtfiApPbo4+6nYYLXzm1/3v/qyAnUnlUb0F9FbVi3AVxxQg==|tkp:Bk9SR_zzmZGjZQ