I have just finished putting back together this PRE BMX III console.
PRE BMXIII analog audio console reassembled
We basically ripped the guts out of this unit and in doing so, I was reminded of how well these things are built. The PRE BMX series consoles were truly wonders of audio engineering. It is a testament to their ruggedness and serviceability that so many of these units are still in use twenty to thirty years after they were manufactured.
This console suffered some pretty bad water damage to the backplane:
PRE BMXIII module backplane
Which was replace, along with many switches and buttons. The Mic2, Mic3 and CD1 modules seemed to have taken most of the damage, there were several logic ICs and IC sockets that needed to be replaced on those modules. Of course, this was not inexpensive; the parts were somewhere north of $3K plus about 40 man hours of labor… that adds up fast.
The good news, I think that the studio was back in service last night.
We are starting to work at a new client’s studios. It is a bit like stepping into a 1980s time machine, as the newest console seems to be the Broadcast Audio console in the FM studio. I feel I should wear a wide colorful tie and part my hair in the middle when working there. There is also an older UMC console in the second production room.
A what?
Exactly.
It seems the UMC console (UMC was a Connecticut-based console manufacturer that was later sold to Broadcast Audio) was having an intermittent hum problem on all the audio buses.
After poking around under the hood for a few minutes, I decided I should begin with the basics. Checking the power supply for ripple seemed like as good a place to start as any. This console has a 30-volt and a 12-volt power supply. The 30-volt supply checked out good, but the 12-volt supply, not so much:
12 volts DC, 2.7 volts AC12 Volt power supply
2.7 volts AC on the 12-volt DC power supply. That will put some hum on the audio, all right. I tried to replace the power supply main filter capacitor, but it had no effect. The regulator must also be bad and it is a Motorola part number which is likely not made anymore.
12 volt linear power supply
This is a pretty standard off the shelf power supply, I should be able to get one from Mouser for about $60.00 or so for a linear unit, which will be cheaper than us trying to trouble shoot and repair the old one. In the meantime, I took the 10 amp 0-30 volt bench supply and pressed it into temporary service. The console is working again, for now.
At some point, all this old, um, stuff needs to be replaced.
I received a great email from Michael “Catfish” Dosch, console designer for Telos / Axia Audio Systems. The email was sent in response to a comment I posted on the WEBE WICC Studio Build Out post. I thought the email was very interesting and informative, presenting a perspective that most broadcast engineers do not often see or appreciate. I asked Mike if I could use it as the basis for a blog post and he agreed. I am not going to blockquote the entire thing, but here are the unedited email and pictures.
Quote:
“Ken said you had a concern about the ruggedness of our consoles as compared to the old PR&E boards. You might not know this, but I was with PR&E before joining Telos. In fact, I designed many of those old PR&E boards. I guess that makes me an old console designer. Ahem.
The Element design is more modern in construction and styling, but it is no less rugged than those old PR&E boards. In fact, you could stand on it if you wish. The top is a 1/4-inch machined aluminum plate supported by structural aluminum ribs on the backside. The chassis itself is made of custom extruded aluminum structural pieces and machined aluminum side panels. The flat sheet metal on the bottom is not structural, it’s only a cosmetic cover. You’ll see a lot of folded sheet metal in other consoles because it’s cheap and easy. But it’s not as rugged as the Element approach which is why we chose to go with a more complex and expensive mechanical design.
One very visible difference between Element and PR&E consoles is the use of Lexan on the front panels (PR&E would use aluminum or steel on the top panel). This might seem less rugged, but it is actually chosen because it is a more durable surface than painted and silkscreened metal. It is more scratch resistant and it is rear-printed so that the markings never wear out. Silkscreens would wear off under heavy use — particularly next to faders and monitor controls — and look horrible over time. These Lexan panels will look just as good after 15 years as they do now.
But Lexan for all of its durability has its own limitations. The edges can crack under abuse. This is why you see many older Wheatstone consoles (they have used Lexan overlays for many years) with cracks and tears at the very edges of the plastic. This is particularly troublesome in the fader slot. A frayed edge on a faders slot can cut your fingers. That is mighty unpleasant! So when we decided to use Lexan, we wanted to have all the benefits and none of the drawbacks.
So we designed a machined recess on each channel that allows the Lexan insert to have its outside edges protected by the aluminum. More obvious are the bezels around each button and even the fader slot. Look carefully and you will notice that all of the control bezel edges are above the lexan. The edges of the lexan are not exposed and therefore not prone to cracking, chipping, or splintering.
Axia Audio console control surface, Courtesy of Axia Audio / TLS corp
In this drawing, you can see the panel without the lexan. The machined pocket to protect the outer edges of the Lexan, plus the raised edges of the button and fader bezels to protect the edges around the holes. These button guards are also designed to prevent accidental actuation of the buttons. And while the guards are designed to protect accidental actuation, they never hinder deliberate activation. Notice the guards at the sides of the ON/OFF buttons and not on the top and bottom. Even operators with long fingernails will have no problems with these controls. The small round keys are engaged with a light touch of the fleshy pad of the fingertip.
Yes, I think we built great consoles at PR&E. But Axia was a fresh start, a chance to raise the bar even higher, by retaining many of PR&E’s better attributes and improving upon some of the weaker areas. DIPswitch configuration has been replaced with the convenience of the web browser. Spill-prone motherboards and electronics have been eliminated from the control surface. Unreliable monitor pots have been replaced with optical rotary encoders rated for 5,000,000 rotations.
And you asked about the faders. This is a particularly important component in a broadcast console. PR&E used Penny & Giles faders for many years. We used their Series-4000 faders in the X-Class consoles (BMXIII, AMX, ABX and STX). This was their top-of-the-line fader at the time and performed beautifully… for a year or two. Then our clients started experiencing field failures at a very high rate. We worked with P&G on a return/rework/replace program that took years to clean up. Our clients were disappointed and we spent a fortune making things right. It was that experience that caused us to begin searching for alternatives.
The market for high-end faders is quite small. There are tons of consoles out there for live sound, home recording, etc., but these products are sensitive to costs and generally use very cheap faders. There just aren’t enough high-end recording consoles or broadcast consoles being built to attract a lot of fader vendors. After a lengthy search, I disqualified all but two fader companies: P&G and a Japanese firm by the name of Tokyo Ko-on Denpa (TKD). I assigned one of our engineers to create a set of environmental and life-cycle tests to see if the TKD faders could keep up with the P&G faders. We were all shocked by the results.
Out of 100 of each type tested in various environmental conditions and physically cycled for the accelerated equivalent of 10 years of heavy use, we had only one TKD fader failure, compared to more than half of the P&G Series 4000 faders! We defined “failure” as any deterioration to specifications or any discontinuities. All the failed units had discontinuities (audio dropouts). We were able to clean the failed TKD fader and it passed the retest. About half of the failed P&G units were cleaned and passed the retest. So in the end, the practical results were TKD 100% good and P&G 75% good. Not what I expected at all.
We then designed a TKD fader into the Radiomixer. We watched the customer support logs carefully for problems. Out of the first 1,000 console channels shipped, we saw one TKD fader failure during the first year. Warranty replacement of course. The failure rate did not increase with use as you would normally expect. We were seeing consoles with 3 or 4 or 5 years of heavy use with no fader problems at all. I have heard of 20 year old Radiomixers with original faders still working great.
One particularly elegant feature of the TKD fader used in Element is a side loaded wiper arm. This prevents liquids or other foreign matter from spilling into the fader slot and directly into the fader element. This feature alone is probably responsible for extending the useful life of the faders by a considerable amount. Of course, these can be disassembled and cleaned just like a professional fader from P&G, they just don’t need it so often.
Some have the misconception that if a fader is not P&G, it must be cheap. Actually, these are very expensive faders, about the same cost as P&G. But they are so well made, I think they’re worth every dollar. I know there are still some folks out there who remember P&G’s glory days when they made bullet-proof faders. I remember fondly those days as well. But in my experience, the TKD fader is superior to the equivalent P&G fader. We feel so confident, that we warrant all Axia consoles for 5 years, including all components….”
End Quote
That is a great explanation of what goes into one of these consoles right from the designer. The pictures are courtesy of Axia Audio / Telos Corporation and special thanks to Mike for taking time out to give us a glimpse into the mind of a console manufacturer.
I snapped these pictures at WICC in Bridgeport, CT. It is an older PR&E BMXII console, with 26 channels, I believe.
Pacific Recorders and Engineering BMXII 26
These were manufactured starting in 1985, I installed one in 1990. It is a testament to their durability that this one has lasted 23 years. They were expensive when purchased, and all of them were purchased directly from PR&E, Carlsbad, California. The beauty of these things is their modularity. All of the major components are replaceable, including the module face inlays.
Penny Giles conductive plastic fader, PRE BMXII console
The faders, Penny and Giles 4000 series, are fully rebuildable. The part that wears out the most is the nylon bushings that slide along the metal rails. The contact fingers sometimes also need to be replaced. These are 10 Kohm conductive plastic linear faders. P&G does not make these anymore, they have been replaced by the 8000 series, which has an edge connector instead of a wiring harness. Since the top of the fader is open, it also tends to accumulate dust, dirt, and other debris. The fader board itself should be cleaned off with warm water, light soap may be used if needed. Do not use alcohol on these because it eats into the conductive plastic and ruins the fader.
PR&E BMXII line input module
One of the great things about this console is the fact that all the modules are hot-pluggable. If one needs to be serviced, it can be pulled out of the main frame while the console is on the air and a new module plugged into it’s place. Only the line output module replacement necessitated taking the station off the air, and then only for a few seconds. It was a great concept that is now standard in almost every broadcast console.
There were several basic module configurations. On the input side, line level, mic level, and telco were standard console inputs. There was also a passive remote line select button set. Out put modules consisted of line-level output, control room monitor, and studio monitor modules.
PR&E consoles were top-of-the-line gear, but expensive. Most radio stations could not afford them and went with less expensive models like Wheatstone, BE, LPB, Autogram, Radio Systems, etc. The fact that some of these BMXII consoles are approaching 30 years of age and still in service is a testament to their construction.
In the early 1990s, PR&E began branching out into the lower priced market with their product line. They produced the Radiomixer and Productionmixer consoles, however, mid-market-sized radio stations were slow in adopting them because PR&E had the reputation of being expensive. After all, if you can only afford a Chevrolet, why bother looking at the Mercedes?
WQXR control room
This is a grainy promotions photo from the early 1990s showing what I think is the WQXR master control room, nick named “The Bridge.” I took a tour there around 1993 or so and it was a fantastic facility, of course, the New York Times spared no expense. I really felt like Willie Wonka in the Chocolate factory.
Later in that decade, they changed the name to Pacific Research and Engineering, and the went public. I think going public was the death knell, soon thereafter they sold the entire product line to Harris Broadcast. The final non-Harris console was the Airwave, which is a good medium-duty modular console, incorporating some of the traditional PR&E designs. The later consoles stopped routing audio directly through the faders, using voltage-controlled amplifiers instead. This solved some of the channel drop out problems that sometimes occurred in earlier consoles. The Airwave consoles are much less durable than the BMX series, however, with the advent of voice tracking, perhaps 24/7 durability is not that necessary anymore.
Harris has dropped support of much of the early PR&E line, but there are those that soldier on, buying up parts and rebuilding these things. Mooretronix has a good selection of BMX and ABX parts.
The WICC/WEBE installation is about to be refurbed, which means these consoles will be headed out the door. There are three of them in fair condition.
