• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Dynaco Mark III Classroom

Trobbins,

If the bucking or autotranformer means one of the $10 range filament transformer, it is not beyond my price scale. I am s new to this that I am still having trouble sorting out which would be the best way to go. Whether there is a best course, or are there two courses that can both be used.

On the one hand, the autotranformer seems to be the way to solve the line voltage issue between Dynaco's original 117 vac design and my 125 vac mains. It stands to reason that that extra voltage is harmful to the circuit.

On the other hand, using Retrovert's suggestion of using a timer like the 555 (bistable with an RC constant) to trigger a solid-state relay (AC relay using a TRIAC, SCR, or something similar) could be used to switch out a resistor used to temporarily limit the level of the turn-on voltage surge. I already have a new quad capacitor (30-20-20-20mf, 550 vac - 600 surge) for the Mark III.

I'm willing to use all of these, but I don't fully understand how to wire everything. That is why a sketch would be so helpful.
 
Hi all, and thanks again to all of you who have shares your knowledge and advice in the Dynaco Mark III Classroom. I've been out of the loop for a while, but I'm now ready with parts in hand to resume my endeavor to get my amp back in shape. I have (4) kfg 22mF 500v electrolytic capacitors to rebuild the can quad filter capacitor *, (2) nichicon 47mF 100v replacement bias capacitors, (1) VK3 N540H diode to replace the old selenium rectifier, (2) ic 224K 1714 630v T MPW and (1) ic 104K 2028 400v T MPW capicators to replace the three electrolytic capicators on the pc board, and (2) 10 ohm 1 watt resistors to replace the original 11.2 ohm KT88 cathode resistor.

Yeah, I went the easy (expensive) way and bought a kit, but the directions look great, and after more than 50 years between me and my last amplifier kit, I thought this was the best way to go. This will provide a soft step into the tube world. That's what the Dynaco Mark III Classroom is all about.

* I also have a German made 30mf/20mf/20mf/20mf 550v (600v surge) quad can capacitor that will fit into the original space. I am still undecided about which way to go with this.
 
You must log in or register to reply here.
Back
Top Bottom