Dynaco FM-3 Curcuit Boards

[denny9167]

Here are some pics of the new boards I've done for the Dynatuner FM-3,
I was able to find some newer,and better components to replace the old.

[miklos]

So this is the front end with the first IF?
Looking good.

[denny9167]

Originally Posted by miklos

So this is the front end with the first IF?
Looking good.

Yes it's the first stage,I should have the next stages w/ discriminator real soon.
One of the new components for oscillator circuit, the trimmer capacitor can be adjusted above board which really helps on the RF alignment. Thanks

[kevinkr]

That board looks really good. Perhaps there is enough interest here that you could eventually offer these as part of a group buy.

[denny9167]

Originally Posted by kevinkr

That board looks really good. Perhaps there is enough interest here that you could eventually offer these as part of a group buy.

Yes I am seriously considering it, there seems to be a huge intrest today in Dynaco gear, and the FM-3 is gaining on the other Dynaco products. I would hope enough intrest to begin manufacturing of the parts that are hard to find such as the IFT's needed for tube tuners.

[kevinkr]

You'd have no competition as far as I know so this could be a viable business. No question that these boards would make for a more stable and predictable tuner over time. Taming thermally induced local oscillator drift was a challenge in the original design, presumably you have kept the original ceramic caps or replaced them with devices with the same tempco. (Potentially some minor tweaking required here.) FR4 or G10 should be a lot less hygroscopic than the original phenolic pcbs and less lossy which hopefully result in somewhat improved overall performance. Definitely looks a lot better which is good enough justification IMHO, and the other new parts should help stability as well.

[Eli Duttman]

I would hope enough intrest to begin manufacturing of the parts that are hard to find such as the IFT's needed for tube tuners.

There's a fellow in Germany that makes IF "cans". The PCB versions look like rectangular blocks. Nothing unusual about that. The P2P versions are cylindrical, with a wedge on top that holds everything together. IIRC, the coils for the P2P versions are mounted on PCB material which sticks through a slot in the shield and an opening in the PCB material is what the wedge engages.

Yet another method for dealing with the IF interstage trafo issue is a parafeed setup, with a RF choke loading the plate and a DC blocking cap. coupling the plate to a reverse connected (step up wired) BJT IF "can". The Mouser catalog page for BJT IF trafos is here.

[kmaier]

If you make a board set for the FM-3 available I'd be interested in a few sets actually as I have a few FM-3s of my own plus some friends have some as well. It would be nice to have new modern boards for restoration.

Regards, KM

[denny9167]

Originally Posted by kmaier

If you make a board set for the FM-3 available I'd be interested in a few sets actually as I have a few FM-3s of my own plus some friends have some as well. It would be nice to have new modern boards for restoration.

Regards, KM

I will have some PC-8 boards some time at the end of next week, I have already done PC-12,so I will have a FULL set,some already populated,I could work an exchange,old for the new,which will lower the cost,plus give me the components I need to populate the new boards. I can PM you when I get those in,Thanks.

[denny9167]

Here is PC-12. When I was first working on the design,I was using the old board as a pattern,so I didn't design the new board to accomidate individual components for the PEC filters,although I know there are modern PEC modules available,I just decided to use the old. In the newer design I will make space available for the PEC components.