We have used the 1 SPOT (as have thousands of other people) with just about all the Boss pedals and they normally work fine together. The Boss PSA adapter puts out about 9.6VDC and so does the 1 SPOT. The 1 SPOT also has circuit protection built into it so that it really can’t pass AC voltage or overly high DC voltage to pedals hooked up to it.
Having said that, we had a few customers in 2008/09 call us about a digital Boss unit getting burned out while using a 1 SPOT. Boss will not cover them on their warranty as soon as they find out that a non-Boss power supply was being used. While investigating one of these problems, a customer sent us his Boss Micro BR recorder, along with his still-working 1 SPOT. We got the schematic from Boss, opened the unit and found that an internal voltage regulator (voltage step-down device) had burned up and caused a cascade failure of other components in the BR. This voltage regulator is made by Seiko and is specified as being “without overload protection circuit”, even though Seiko also makes the same regulator “with overload protection circuit”… it probably saved Boss a few pennies by using the former regulator rather than the latter. The regulator also comes in “A” and “B” versions. “A” has a maximum input voltage of 10V. “B” has a maximum input voltage of 16V. The “B” version is specified on the Boss parts list. However, if an “A” version slipped into production by mistake, feeding it 9.6V could easily cause it to wear down over time and eventually burn up.
When we looked at the schematic, it became obvious that the 1 SPOT could not have caused this component failure. In addition, the 1 SPOT the customer sent back to us with his BR was still working perfectly. Although it’s impossible to confirm it, it seems that the burned voltage regulator was probably either defective, or an incorrect regulator was used (one that had the wrong input voltage specs but got mixed in with the batch of correct regulators during production).
Unfortunately, Boss has an easy out with warranty repairs since most people do not use a Boss PSA adapter anymore, but use a 1 SPOT or other pedalboard power supply. That cuts their warranty repair expense down considerably since most guitar players are honest when asked by Boss tech support what power supply they were using.
The only thing we can conclude thus far is that Boss was having quality control problems on some of their digital products. They all have surface mount components and run internally off of 3.3VDC typically, stepped-down from 9.6VDC input. If their surface mount step-down regulators fail, the product is ruined. The only recourse a Boss customer has is to be dishonest when talking to tech support and say that they were using a Boss PSA adapter even when they were not… and most people prefer to be honest.

UPDATE: It’s now been several years since we’ve heard from anyone about a Boss product being “damaged by a 1 SPOT”. It seems that Boss solved whatever issues may have existed in their component specifications to make them more reliable.

In general, if your 1 SPOT is still working and can still power other pedals, then it was definitely NOT the 1 SPOT that caused the problem.