Seventh Circle Audio

I'm getting 27v for J2 pin 1,2 AND pin 3,4. Is this correct? I thought one was supposed to be 27, the other 48. Also my jewel light isn't coming on, no voltage reading for J1. This was preassembled in the CH01, so all I did was connect the power switch and do the 110V jumper.

What do I do?

The voltages at J2 should be +27V, 0V, -27V, 0V, +48V, 0V. Put the negative probe of your meter on pin 2, 4, or 6 and keep it there while you measure pins 1, 3, and 5. Pin 1 is toward the front of the chassis.

At J1, you should measure 27V with no load. If you measure 0V, R1 may be missing. It's marked as 750 ohms on the schematic and PCB, but that's only a suggested value if you're using an LED without an internal resistor. If you bought a complete kit, R1 should be something around 100 or 120 ohms. It's not critical, however, and you can simply install a jumper if you don't have a 100 ohm resistor handy. Your panel lamp will just be a bit brighter than usual.

Tim, sorry to correct you, but wouldn't that be +27v and -27v?

You're absolutely right!

Excellent! Now can I have an A12?

Now I don't get any voltage readings for J2. I'll worry about the lamp later, I do see R1 is empty.

When I first set up the jumper for 110V I did it like the picture on the website (for the PS01). The picture on the site (off to the side) makes it seem like you jumper 1 & 4, 2 & 3. But if you look at the board picture it is different. Confusing! Well, when I plugged it in it blew the fuse. In schematic it is 1 & 3, 2 & 4 so I corrected it, changed the fuse. That is when I was getting the 27v voltages across the J2 pins. Now i'm getting nothing. 0's using the testing method you described. Did I screw something up? I don't see how, because it was already assembled and mounted.

Thanks for your help.

So, you were getting a voltage reading, and now you're not? The thing to do is to proceed systematically. Are you absolutely sure your AC outlet is working? Is your power switch definitely in the "ON" position? Are you sure the batteries in your meter are OK? Can you measure the voltage of a known source, like a 9V battery? Do you measure anything at J2 using the method you first tried? Let us know what you find.

Something weird is going on. The fuse I just put in didn't appear to be blown but I replaced it anyway with a new fuse. It is 500mA Fast Acting F-type. Also disconnected the lamp.

Now I get 27v, 0, -27v, 0, 0, 0. This is where I'm at, will not do anthing else so we can troubleshoot systematically now.

You need to use a 500mA Slo-Blo type. You can also use up to a 1A T (time delay) type. Linear supplies with capacitive filters and toroidal transformers have high inrush current, which will blow a fast acting fuse.

Once you get the fuse squared away, carefully measure the voltage at U3, pin 3. This is the regulator at the bottom, with its own heat sink. Pin 3 is at the bottom. You should see something in the neighborhood of 70V. If that's OK, carefully measure the voltage at U3, pin 2. Pin 2 is in the middle. You should see something very close to 48V. Let us know what you find.[/b]

I have the correct fuse now.

At U3 pin 3 I get 72v. At pin 2 I get 0 where I should have 48v.

What does C3 look like? Has it turned black or appear damaged in any way? With the power turned off, measure the resistance between J2 pins 5 and 6. Put the positive lead on pin 5 when you make the measurement. You probably have a shorted C3, a blown up U3, or both. Send me an e-mail if you need parts, or if you want to send it in for repair.

C3 looks fine. I'm getting 9K ohm between J2 5 & 6.

It looks like you'll have to replace the LM317HVT. Here's a tip: instead of trying to remove the solder from all three leads so you can remove the part in one piece, snip the leads at the base of the component. Then heat each lead individually and remove it from the the board. Clear the solder from the holes with solder wick, and install the new regulator. Doing it this way, you're much less likely to damage the circuit board.

Cool. Thanks for the tip Tim. I'll report my results after I swap out the defective part (that I probably blew up) tonight.

One other thing...On the schematic I received it has U3 labeled LM317T. Should that be a LM317HVT?