It very strongly seems to be nothing like that to me. The manual consistently shows different pieces of equipment connected by simple lines, suggesting that even when using the low distortion signal, it's still running through the FG-1 first. In my experiences, if you want that low distortion of a signal you would want the straightest path to where you're sending it. Funneling it through the FG-1 does what other than potentially adding distortion to the signal? When you're not using the low distortion signal and are using the functions on the FG-1, that low distortion signal is still connected to the input of the FG-1. Does it matter? I can only make out "Burst" on the FG-1's functions on the PDF, but it clearly shows in Fig. 1-6-4 VCA Symmetry Adj. the FG-1 sending a staircase wave to TP-01 on the DBX card, which is then hooked up the scope, as well as sending a triangle wave to the horizontal input of the scope. The staircase and triangle are probably linked somehow. Decoder calibration step B.1 confirms this. Step B.2 says to short J110-1 and J110-2, which are not test points but pins on the card connectors. I can't make out the text on the PDF but it definitely looks to me that step B.2 and the L and H signals are being connected directly to the pins of a removed card, as well as the + and - 12V. It doesn't look like "J" or "TP" for the DBX card to scope out, but again, I can't really make out the letters.
My test equipment is quality, no worries there. I can do the triangles and pulses no problem. I actually did just notice it looks like the width of the triangle is measured on Fig. 1-6-4 but I can't make it out really. I wish there was a high quality scan of the service manual. That being said, I really haven't encountered anything that will do a staircase wave aside from an arbitrary waveform generator, and even then most of the staircases look nothing like the one depicted in the manual. And again, it really seems to be that the triangle and staircase are somehow related on the FG-1.
It's definitely Jodrelled all over the shop, then, because although I marked where they were, they did get cleaned and turned. Only the ones on the distorted channels, though. The channels that were fine have factory DBX calibration, or wherever they were set when it was purchased by me. I can't imagine it being a make or break issue, though, especially if I plan on doing a full calibration later anyway.
That's what I was thinking, as well. The rest of the machine is calibrated. If I hook the DBX up to calibrate it and everything looks how it should, I will confirm the DBX is fine, or I will find the trouble spot and hopefully correct it.
I was never even planning on even using the DBX. I was always under the impression that most people thought it didn't sound very good on the 388 and it wasn't worth using. Then I started to read about people saying how great it works and how wonderful the 388 sounds with it. I know that some people may just not like what DBX does to the sound overall, whether it works or not, and I know some people like it as an effect. These are old pieces now, and who knows the history of the units people are making these claims about. I would like to ensure my machine is mechanically and electrically within factory specifications and come to my own conclusion.