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I am looking to use two Roto-Tone Deluxes for switching between different Germanium transistors in Q3 of a Tone Bender MkIII. Seems relatively straight-forward to use three of the pad areas for the E, B, and C of the transistors. However, I wanted to also have set trim pots for each of the transistors since the bias will be different for each one. I have a second Roto-Tone, so that shouldn’t be an issue, but I didn’t want to have to change two switches every time I switched transistors. Is there a way to daisy chain the Roto-Tones together, so I use one switch and both boards will replace their part on the main PCB (Q3 for the first board and the trim pot for the second)?
Not that it necessarily matters, but I am going to socket the transistors with the Collector in D, Base in A, and Emitter in B.
I gave this some thought and I think this will work:
Mount each bias trimmer in a ROTOTONE section with pin 1 in A, and pins 2 & 3 in C.
Mount each transistor in ROTOTONE section with Collector in A, Emitter in B and Base in D.
Wire the ROTOTONE control pads:
A to collector pad of Q3, B to emitter pad of Q3, C to pin 3 of bias trimmer pad on PCB, and D to base pad of Q3.
That should give you three (or four if you wish) different transistors for Q3 with different bias pots for each.
I hope this helps.
Wilkie, thank you so much for the thoughtful reply. I’m wrapping my head around this. Some questions/comments:
– You are indicating this can be done on a single Roto-tone in this way, which is intriguing. I think I may have to forgo using sockets (circular) for the transistors in order to fit them, but I will play around with it.
– Are you saying for the Trimmer connection on the main PCB (not the Roto-tone), only one pin connection is needed?
– If I did decide to go with two separate boards, could I simply have a switch in one of the boards and then wire connect every pin from the switch to the same holes on the second board? I have never done that or even know if this is a thing, though.
Thank you so much for taking the time to respond to this. Amazing.
Jon
I am looking at things and definitely I can’t use sockets.
I am wrapping my brain around how you are having some of the direct connections on the Roto-Tone for the transistors and trimmerand that is why only pin 3 location needs to connecting on the board. I’m looking at the trace on the board and the schematic to make sure I get it.
This is an extremely complex and amazingly thought out solution. It will require me to forgo sockets as well as possibly switch to vertical/side trimpots from the ones I currently have.
UPDATE – I may be able to socket and use these trimmers on a single Roto-Tone if I mount them on opposite sides of the Roto-Tone. The soldering will be challenging, but could work.
Wilkie1,
Would the below work? I can have much more clearance on sockets and trimpots this way. I took your concept of Pins 2 and 3 on the trimpot in their own area and the Collector on the same area as Pin 1 on the trimmer.
Collector – C, Base – B, Emitter – D. Pin 1 – D, Pin 2 – A, Pin 3 – A.
A connects to main board Pin 3 for trimmer, B connects to board base Q3, C connects to board collector Q3, D connects to board emitter Q3.
The transistor is PNP in case that wasn’t clear.
It will be helpful for you to compare the connections I described for the ROTOTONE with the schematic. You will note that The trimmer connection on pad A is also connectiing to the collector on pad A. On the schematic, you can see that the PCB board makes that connection. Therefore , you only need one other trimmer connection at pad C.
You can use single sockets to mount the transistor. They can be placed where needed and the transistor leads can be bent to fit. I usually use them instead of the more expensive round sockets.
Yes, you can solder the trimmers on the back of the board. All of Barry’s boards have plated-through holes. That would give you the room to mount everything.
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