I will never be off the
steep part of the learning cure, I think...
More work on the 184. This being my first one, I don't really know what a "good" unit should look like. And, sometimes with stuff like this, there have been ECOs that aren't documented in the available documentation, so I can't always tell whether a change is a "supposed to be there" or is just what it looks like, a bodge. Turns out there's more likelihood of a bodge than an ECO on this one. Someone did a really bad job repairing the part of the circuit (lifted traces, solder blobs, etc) that generates the 1 and 5 microsecond trigger/mark outputs and includes this mysterious delay line. Here's just a partial list.
There are supposed to be ferrites (wound as chokes) on the entrance and export ports of the delay lines, which have been removed.
When the ferrites were removed, all that extra wire was crumbled up and stuck under the board, holes drilled in the board and the wire fed up through and tacked down to the end of resistors. ![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/facepalm.gif)
At least six transistors were changed out and the substitutes require different biasing. At one place a diode was subbed for a collector bias resistor, moving the bias point from 9.5V to 12V and eliminating half of the signal swing.
The variable capacitor that adjusts the "bucket size" for a countdown counter was jammed to one end, so there are sometimes six pulses counted rather than five (for the 1us to 5us conversion). This was done to account for the change caused by the diode sub listed above, I think. ![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/facepalm.gif)
I am sure that the repair effort was aimed at getting this gear working in one particular situation and once it was working that way, the buttons were taped over so no one could f**k with it. It probably even worked.
![WTF? :wtf:](https://www.eevblog.com/forum/Smileys/default/wtf2.gif)
Now that I have reached an appropriate level of being offended by the damage done to this fine piece of gear, I am afraid it has become a quest: can I return this 184 to its pristine, well-engineered and built pre-bodge condition? And how much money with I have to expend acquiring no-longer-made diodes, transistors, and ferrites in order to do so ?
![Grin ;D](https://www.eevblog.com/forum/Smileys/default/grin.gif)