I recently bought an old Lowrey TLO organ from the 1960s. When I got it home
> and fired up, it worked fine and sounded decent, but then when I turned on
> the Main Chorus Reverb it quickly died. So the first place i checked was
> the fuse to the power supply / amp unit and sure enough it blew, so i
> replaced it with another fuse of the same ratings, the same make / model
> even. I turned it on and it came up for about a half a second then died
> again. I checked and it blew that fuse too. This was even with that Reverb
> switch turned off.
What is the rating of the fuse? May be someone has changed it with one under rating. For an organ made in the 60s, I presume it is fully transistorised without any IC chips. So I guess some of the transistors were getting old and leaky, and some of the capacitors might get leaky too. Check if there is any capacitor oil leakage near to the ON/OFF switch with a torch light. This is quite common in an old Yamaha Organ like A55. It has a 47nF 600V capacitor accross the switch and some capacitors directly across the AC mains.
> At this point i figured that something in the switch was messing it up, so i
> took off the plate around it and examined it. Thw way the switches work is
> that there are are these plastic rockers that have a spring connected to
> them and on each side of the spring are two conductors (SPDT). So the
> rocker moves the spring between contacting one condcutor and the other, and
> apparently the spring had come out and was laying across both conductors,
> obviously the problem that caused it to die in the first place. So I
> managed to reposition the spring back in the rocker the way it should be
> and gave it a few test rocks, without the electricity on, and it looked
> like it was doing it's job alright. So I plugged the organ back in and
> turned it back on with yet another fuse in, but it did the same thing, came
> up for a half second (this is indicated by the light on the power switch)
> and died.
If you suspect the switch is shorted, it is very to confirm with an ohm meter. Just connect the 2 mains wire from your organ to the ohm meter and switch to X 1 range. If the resistance drops very low say below 10 ohms on OFF condition, then the switch is probably faulty.
> I'm wondering if the spring coming out and shorting a path between the two
> conductors may have done damage to some components of the power supply
> before the fuse had time to kill it. I was wondering anyone could venture a
> guess at to what the problem could be. I'm open to any suggestions. Also, I
> may be taking a shot in the dark with this one, but I was wondering if
> anyone knew where i could possibly get another power supply for this organ.
> It's a Lowrey TLO from, I think, 1968. Any help would greatly be
> appreciated.
Is there a big transformer in the power supply? I dont think it is very hard to fix the PS but it would be very tough to fix the other functions of the organ made in the 1960s even with the schematics. As there are so many transistors, PCBs, and bundles of messy wires.
Regards,
Allen
> Brian Molnar