Very low output from Dynaco FM-5

[Gavijo70]

Purchased a trio of Dynaco gear at an estate sale. The pat-5 and equalizer work fantastic. However. Extremely low output from tuner. Any other components when plugged in to the tuner input on the Pat5 work great. The fm5 tuner however has the volume of a transistor radio on large speakers. Even with the volume of the tuner and preamp at maximum. I would know exactly where to look on an amp or preamp with this problem. A tuner however has me stumped. This tuner pulls in stations I cant get on my modern emotiva gear and I would like to get it up and running. Any suggestions?

 

[JRhoBurton]

Try the AUX input on the tuner. The manual says it has 28db of gain. If it is also weak, the final gain stage could be the problem and it could be bypassed if you want to tinker. (The tuner uses it also.) I have a Van Alstine modded FM-5, and they don't use the final stage. (Also a stock FM-5.)

If the AUX input is fine, you have a problem with the tuner circuit which would of course be harder to fix.

 

[Gavijo70]

Indeed there is low gain on the aux input as well. Looks like I'm after info on how to bypass that final stage. Can you point me to any instructions on how to do so?

 

[mhardy6647]

Maybe an issue with the muting circuitry?
https://www.updatemydynaco.com/documents/FM5AssemblyManual.pdf

 

[JRhoBurton]

Someone more knowledgeable should check this, but it looks to me like you could do this:

On PC26, disconnect the wires going to terminals 16 and 22, and solder them together. (Left channel.)

Also on PC26, disconnect 17 and 20, solder together. (Right channel.)

This will bypass the line level output stage. The volume pot will still be in circuit. If you turn it up all the way, you should get moderate output from FM or AUX.

Again, I am not an audio technician. Seek confirmation, do at your own risk. Good luck!