How are you at soldering? Do you have a voltmeter? Is there a fuse in the unit? Did you make sure no metal chips from drilling shorted anything out? The donut shaped part could be a transformer, or it could part of a filter. To get DC for the pedals, there are usually these components: a transformer (to decrease the line voltage), a rectifier bridge (turns AC to DC), a filter capacitor (to get rid of AC ripple from the rectified AC) and a voltage regulator (futher reduces ripple to eliminate hum). The filter capacitor is usually the most likely component to fail. The manual states that the maximum current draw for any pedal is 100mA. It also states that their is an 'electronic fuse, called a PTC (probably a positive temperature coefficient device. From what I've found, it uses 7809 regulator, which is one of the key components. I found a page about building an effects regulator. In the picture, the regulator is the little black square device towards the right. There is a metal tab, that should really be mounted to a heat sink. I'm including a link to the page for designing this supply. They're pretty simple, and I can find you the parts pretty cheap, if you you want to try building one. Another possibility is to find a prebuilt supply that would fit inside your case. You can get a schematic from furman if you have the serial number. In the picture the big 'can' is one of the devices I'd suspect. See if it's bulging on the end. Anywa, here's the likely culprits: the biggest capacitor (big can, voltage regulator, ptc. The ptc is probably square or rectangular, and rather small, probably about the size of the regulator, but thinner, and maybe tan or yellow, but could be some other color. Before you try any repair, if you have a voltmeter see what happens with no pedals. Then if you can read 9 volts, try the pedal with the lowest draw. The current draw will be listed on the pedal near the power supply plug. If that doesn't work, Check the voltage on the ouput pin of the regulator. It should be on the right, viewed from the front. I'm including a link to a page with a 7809 that shows the pins. There are several different versionsa I think, with different current ratings. Anything over 1 amp should have the metal tab mounted to a heat sink. The fixya format is not so conducive to solving this. You can go to ecurrencyparadise.com, and click the email me link to contact me. I'm a BSEET who has been playing with this stuff for years. There's plenty of ways to get this working, probably even better than the way they designed it.
http://www.furmanpower.com/sites/furmanpower.com/files/_/Furman-Pro-AV/spb-8_manual.pdf https://hotbottles.files.wordpress.com/2014/05/2013-12-04-21-22-59.jpg real effects pedal power supply 7809 9V Voltage Regulator
