Gave the Fender MX 5216 a quick run through, cleaning switches, as they were acting dodgy and this unit may be rotating out into a new home.

Working surface, after I'd dropped the PCB off each sub-section. While I had open metal, I took the opportunity to wipe it off.

Original buildup.

Each sub-section houses a horizontal circuit board with duplicate circuits, lots of ribbon cable.

Everything is pretty easy to get at, and through hole construction. Built in the mid 1990s, when miniaturization was really getting a toehold.

I'm guessing this could benefit from a recap. I'm not tackling that one right now, but at 10 caps a channel it doesn't look too terrible even if the pots outline an obstacle course.

Per channel breakdown: first stage is a SSM2017, TL072 is seated in the EQ section, NE5532 in the Aux send section, MC14053B in the output routing section and an NE5532 acts as post fader recovery. The summing section is populated almost entirely with NE5532.

When I bought this in ~2007, two of the input channels were non functional. As it happens, the input trim control pots had popped apart, it was a matter of realigning and tensioning the metal legs to hold it together.

One of the ribbon connectors popped free unlabelled, and since several of the header connectors at the board are not populated, I had to reverse engineer the connection. Reading continuity at Aux send 1 & 2, it became reasonable to conclude it belonged at the Aux send 1 & 2 block.

Still not as far along on the wiring process as I would like, but, if I had my way I'd be able to invest all day on my projects as opposed to nibbles in the pre & post job moments. Here's a half way update to meet my self imposed 48 hour cycle...

The Autogram AC-8 base sits flush to the desk/shelf on which it's set, the idea is the wiring passes through a hole routed in the desk, which isn't an option for me. The answer? Feet. Beautiful scrap from my good friends at One Drop Design makes for serviceable elevation required to pass a loom of cables underneath the mixer.

Unfortunately, the base is bent metal, so only the front of the mixer offers the screw in option (unmodified)..

..as a result, I simply placed more yo-yo halves to the rear of the mixer loose. Yes, I deployed the pink ones in that application.

Moving on to my 1/4" input bank, I'm installing a hard wired rear patch bay of aged Switchcraft jacks. While the holes depicted are not from the panel I'm installing, they do pose a concern over using older gear.

Never one to bow to the newer is better philosophy let's show those jacks who's boss. Pictured here is a 22 gauge cleaning brush chocked into the bit of my cordless drill.

Improvement. I will probably have to give it another pass with contact cleaner (this one was done dry)..

..but first I may need to rethink my choice of tools.

Dymo labelling, giving the appearance of completion (only the lower panel is actually soldered up). Onward and upward...

Bought a Zoom H4 in "doesn't power on" condition at auction. It arrived yesterday, loose in a small priority mail box. I guess a demonstration on how robust these things are was in order.

I cracked the compartment lid and had a peek at the battery terminals; sure enough, this thing was stored with batteries installed and a chemical reaction had taken place.

First item of business is to crack the shell. Removed the two visible screws (the lower one was behind a press fit rubber plug) and felt a screw sized indention behind the product label. In punching through the label to investigate, I can report that indention is a casting mark and can be left alone, there are only two screws on the back half of the shell.

The front & rear halves of the enclosure are snap fit together. Pictured are the three major points: above "LINE" (which is easy as you can slide your finger into the battery compartment and pull that one right out, I saved it for last), above "USB" and at the halfway point of the bottom silver case halves. Once the bottom was freed, the USB connection followed, allowing me to ease the LINE connect open from the battery compartment. Other side is similar, but only one side needs to be unlocked to separate the case halves.

The corrosion here effectively insulated the battery stack, rendering the unit inoperable. I believe the foam blocks are there to prohibit side to side movement of the contact spring, and are therefore important to retain.

Removal of the contact is easy: pliers on the elbow at the base of the spring will allow you to pull this part out when the solder is liquified. Referring to the image of the corroded contact in place, the solder pad is the entire joint as seen at upper right of the image.

I used a little universal solvent and these cleaned right up. I did pick at the spring a little to free larger chunks of the crystalline build up, but for the most part minimal agitation was required.

While the parts were out to wash I did a quick pass on the battery compartment with a wet rag.

Battery door flap back in place just before snapping the rear case half back into place & returning the hardware to its original position.

I'm happy to report the unit works like a champ now. All in all I think the entire span of time spent on this was about a half hour, including stopping to take pictures or reprimand my two year old assistant.

This sort of thing bothers me.


I recently cracked the case on a console radio to be met with a musty wave of air and chalky white controls in similar condition. Internet searches for "plastic mold", "chalky white film knob" and similar are largely useless. Though after wading a bit I found this thread:

http://www.antiqueradios.com/forums/viewtopic.php?t=114454

Which offers up some solutions to the problem. I think I'll avoid the dishwasher one, as, if this is indeed a byproduct of early plastic decomposition I doubt I'll want it anywhere near my food. Just a quick share, mainly secure the thread without another half hour of aimless searching for myself (while avoiding the creation of yet another topic specific forum bookmark in my browser).