McIntosh 1900 fm tuner - no lower stations
- Thread starter pfejr
- Start date
dr*audio
Fish fingers and custard!
Clean the tuning capacitor. Here's how:
http://audiokarma.org/forums/index.php?threads/how-to-clean-a-tuner-analog.144163/
http://audiokarma.org/forums/index.php?threads/how-to-clean-a-tuner-analog.144163/
Draudio knows better than me.
That said, there are some tantalum caps that are known suspects (to go bad) usually replaced with films during rebuild.
I suspect if one crapped I out you wouldn't get any stations
That said, there are some tantalum caps that are known suspects (to go bad) usually replaced with films during rebuild.
I suspect if one crapped I out you wouldn't get any stations
Aside from this, anything that affects the local oscillator below the cutoff is suspect, a job for a tech.
dr*audio
Fish fingers and custard!
I have never, in over 40 years of servicing audio equipment, seen any component in a local oscillator fail that causes it to not work at a certain frequency. They either oscillator or they don't. Not saying it can't happen, but the likelihood of it happening is somewhere between "none" and "Get out of my office."
I've seen marginal LO tubes do it, also flakey capacitors and cold solder joints. Rare in solid state, improper cleaning with sprays by the inexperienced invite capricious behavior. Sub par voltage supply can also be troublesome.
I've an SAE Series Two tuner with a problem like this that I have yet to address, a lightning strike may have blown the voltage regulator and be putting excess voltage into the front end. It sort of works when first turned on, and gradually gets wonky and fades, LEDs stay lit.
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The time sequence certainly seems to point to a thermal issue with a semiconductor.
Certainly a interesting RF challenge that certainly does not show up very often if ever. The use of a dual gate MOSFET between the two front end RF coils could lead to speculation if it is the cause.
One of those challenges you do not know if you really want to own it if it lands on your bench.......
Certainly a interesting RF challenge that certainly does not show up very often if ever. The use of a dual gate MOSFET between the two front end RF coils could lead to speculation if it is the cause.
One of those challenges you do not know if you really want to own it if it lands on your bench.......
Based on having zero experience with this stuff, I vote for both of these issues being the problem.
Anyway, I copied the text from dr*audio's linked post and filed it in my MAC1900 file for future reference. Thanks.
