I normally don’t review products here, but I’ve had a recent experience with the Global Specialties PB-503 that’s left a particularly bad taste in my mouth. Since many of the vendors who sell it don’t post product reviews, I’ll write mine here.
On the plus side, this unit is a compact and convenient way to combine several DC power supplies and a function generator with a conveniently large breadboard area. The design is well-suited to my introductory electronics course, for instance.
However, I have been unimpressed with the durability of these units. Used in a classroom setting, I have had to repair several of these that failed over a semester. (By contrast, the multimeters I have used in the classroom have gone through many fuses, but have never been damaged.) Repairs have included blown regulators in the DC power supplies and damaged voltage adjustment knobs (trim pots). Another had a bad solder joint.
Worse yet, these units have a known design flaw which the company seems uninterested in addressing. The TTL output on the function generator does not work when the unit is in sine wave or triangle wave mode (which, after all, is when the TTL output is actually needed). According to Global Specialties, this is due to a forced redesign of the unit when one of their parts became obsolete and unavailable. I notified Global Specialties of the TTL issue in January 2010. Initially, they assured me they would inform me of a fix for this problem within a few weeks. Almost one year later, I have heard no news of a resolution to this design issue, and the company has not responded to my latest inquiries.
As it stands, this product does not do what it is supposed to do; if the company has plans to fix it, they have kept those plans from me. I recommend against purchasing these units until this defect is addressed.