best place to look for the unlock PIN
I got my spare box stuck in what sounds like the same predicament as you.
I thought about how long it would take to brute force the code. I've done it on several car stereos that had a 4 digit code, but those did not lock out after 3 tries, and mercifully, each digit only had 6 possibilities. Just a matter of hours, easily done on a cross country trip.
Anyway, realizing it would take far to long to crack in that manner, I put on my hacker hat. Anyone see Wargames? Use codes that makes sense.
Tried VOOM (8666) and HDTV etc. Then made the guess that the code might involve the serial #, so that there wouldn't be a master unlock code.
Sure enough, on my first try, I got it. There is a sticker on the back, with model #, a number, a bar code and another number.
DSR-550
######-002
BARCODE
UA:000-#####-40545-###
I've inserted the ### so as not to give out my serial # in case it matters.
Anyway. There were 3 areas with 3 digit codes. Unlikely candidates. One with 6 digits, and 2 with 5 digits. I guessed that the second of the 2 5 digit codes would be the most unique. Of that, I chose to truncate the leading digit. Tried the code 0545 and viola! The box was back to normal.
So, try finding your equivalent and give it a try.
If it works, please post results back here so we know that it wasn't just a damn lucky try on my part.
I went back to the hidden menu that I had messed with, took it out of the evil mode that I had placed it in, and then proceeded to clear all locks and PIN. That required me to enter the PIN, which was still 0545.
All is well now with that box. Which incidentally was the one that I left looking at the bird when VOOM went boom. I was recording to DVHS at the time, since I had gone to bed at midnight Eastern.
P.S. I will not be divulging the nasty menu on this forum at this time. Perhaps if we have a good workaround I will.
P.P.S. I am curious what would have happened if I had set a PIN of my own before invoking the ill-fated choice.