Dynatuner-Model FM-3 (tube) problem

[Fort Knox]

I recently came across a Dyna FM tuner which pulls in all stations
strong for about 3-4 min..when first turned on ...then after it warms up
alot of the stations seem to drift away or weaken..the guy I bought
the amp from said he capped and tubed it ...any thoughts

[hjames]

I recently came across a Dyna FM tuner which pulls in all stations
strong for about 3-4 min..when first turned on ...then after it warms up
a lot of the stations seem to drift away or weaken..the guy I bought
the amp from said he capped and tubed it ...any thoughts

That's a tube based tuner - and he replaced parts with, perhaps,
somewhat different values, that changes the resonant frequency of parts of the circuit.
Even if its the 'same" value, due to parts tolerances they may be different,
and that can change the circuits somewhat.

... so has anyone re-aligned it?
I'm not offering because I don't have the test gear to do so,
but there are resonant tuned circuits in receiving gear -
if the resonant freq is off, the performance is off.

There are (local to DC area) folks on Audiokarma that may be able to help with that ...
or may know a local shop that could do the work for you.

Check in the Tubes forum over there and see who responds ...
and good luck!

[audiomagnate]

That's a tube based tuner - and he replaced parts with, perhaps,
somewhat different values, that changes the resonant frequency of parts of the circuit.
Even if its the 'same" value, due to parts tolerances they may be different,
and that can change the circuits somewhat.

... so has anyone re-aligned it?
I'm not offering because I don't have the test gear to do so,
but there are resonant tuned circuits in receiving gear -
if the resonant freq is off, the performance is off.

There are (local to DC area) folks on Audiokarma that may be able to help with that ...
or may know a local shop that could do the work for you.

Check in the Tubes forum over there and see who responds ...
and good luck!


No special tools are needed to align an FM-3, just a plastic allen wrench alignment tool and a soldering iron. The tuning eye serves as your VTVM. It's all in the manual.

[kmanusa]

I recently came across a Dyna FM tuner which pulls in all stations
strong for about 3-4 min..when first turned on ...then after it warms up
alot of the stations seem to drift away or weaken..the guy I bought
the amp from said he capped and tubed it ...any thoughts

With tube gear, the first suspect is the tubes themselves (there appear to be 11 tubes including the "magic eye" tuning tube). You should check the tubes with a tube checker; if you don't have one then try substituting tubes one at a time with known good tubes. If you can't do either, ask a friend to check the tubes or take it to a technician. With RF gear, tube substitution can be problematic so use the tube types shown in the manual and don't try replacing tubes with different types (tube rolling).

If it is not the tubes causing the problem, you will have to pull the covers and get inside. One problem with gear that has been modified is that the replacement components may be different from the originals and this can be especially troublesome with RF gear as has been pointed out. You will need the manual to do troubleshooting or alignment, see here:

http://www.the-planet.org/dynaco/Tuner/FM3.pdf

There are lethal voltages inside so if you are not comfortable with that, leave it alone and take it to someone who is-- it can kill you.

Keith

[Fort Knox]

:) I did chg tubes ..and yes that does require... realignment
good thinking..