pucho812
Well-known member
Does anyone have a schematic of the 9098 preamp eq rackmount?
Amek 9098 pre/eq schematic request
- Thread starter pucho812
- Start date
Help Support GroupDIY Audio Forum:
There is a 9098i in the Technical Documents
Ricardus
WILL SOLDER FOR FOOD
This would be an interesting project. I used to work in a studio that had a 9098i. I believe I've seen discussion here or elsewhere about a hard to source transformer for these.
Sorry, it's the console, not the rackmount preamp...
pucho812
Well-known member
That is correct.
jim-analog
Member
Greetings,
I'm working on one of these 9098i rack EQs for a client; Serial # A002580a. Strange behavior with some bands working, some not, distortions and odd interactions between them. I found resistor R-12 burned open. Replacing that showed the negative 18VDC rail for the mid eq bands is shorted to ground. The board is pretty densely packed and to remove anything requires major disassembly. Why companies build these expensive devices without a removable bottom panel is beyond me. I'm guessing a shorted cap, but.........
Before going thru that and a hunt and peck process, I was hoping someone might have a print to share. I've tried everywhere I can think of with no success. I'd really appreciate it and be glad to reimburse expenses, trade docs or whatever. I'd like to get this unit off my bench and back to my client. Thanks much for any assistance/suggestions!
Regards, Jim
I'm working on one of these 9098i rack EQs for a client; Serial # A002580a. Strange behavior with some bands working, some not, distortions and odd interactions between them. I found resistor R-12 burned open. Replacing that showed the negative 18VDC rail for the mid eq bands is shorted to ground. The board is pretty densely packed and to remove anything requires major disassembly. Why companies build these expensive devices without a removable bottom panel is beyond me. I'm guessing a shorted cap, but.........
Before going thru that and a hunt and peck process, I was hoping someone might have a print to share. I've tried everywhere I can think of with no success. I'd really appreciate it and be glad to reimburse expenses, trade docs or whatever. I'd like to get this unit off my bench and back to my client. Thanks much for any assistance/suggestions!
Regards, Jim
pucho812
Well-known member
Very few companies design a chassis so that you can remove top and bottom lid and access the circuit boards
Last edited:
john12ax7
Well-known member
Chandler does this. It's super convenient and wish more did it.
Brian Roth
Well-known member
The classic UREI gear (1176 and LA-3A) also had the removable top and bottom covers for service.
Bri
pucho812
Well-known member
So does Avalon design. The pcb’s in their gear mount to chassis frame from the sides so that if I take off the bottom lid, the circuit boards are still mounted. Same with the top lid. It’s more expensive to do but it makes service much easier.
I don’t have a schematic, but I have worked on several of these. You seem to have a short, but most of he problems I encountered were mitigated by cleaning connectors, scrubbing the board- removal is a PIA- and exercising/cleaning switches and pots. The units don’t have many component failures for their age.
Didn't the Amek 9098 desk have a problem with ceramic de-coupling caps being the wrong p/n? It was something like they were 10v rated caps instead of 100v and they would fail short from being across the audio rails. I seem to remember Brian Roth having to change thousands of these caps on a desk somewhere in the last millennium...
Slenderchap
Well-known member
The 100nF ceramic caps which failed were the correct voltage... they just didn't work properly and would break down... since these caps were purchased in batches of 100000... it affected a lot of consoles.... but they were mainly the Rembrandt console and some Galileo... generally didn't happen on rack gear. More than likely to do with how the capacitors were allocated to each assembly department...
Usually just recapping the electrolytic caps gets the rack gear back to normal.
Usually just recapping the electrolytic caps gets the rack gear back to normal.
Brian Roth
Well-known member
It was an relatively early 9098 desk....split monitoring....vs the later 9098i....inline monitoring. It had more than a few random failures of 100 nF mono ceramic power rail bypass caps. The Amek USA tech folks told me that was a known problem, and originally said it was due to the caps having an incorrect voltage rating. Later, they just said it was a bad batch of caps.
The Amek design had "circuit blocks" with power rails fed to multiple opamps via a series resistor (10 Ohms??? can't recall....) for each power rail branch. Each opamp had a 100 nF cap located close to the chip for each power rail. A shorted cap would also take out the associated series resistor for that branch. The resistors were "flameproof" and would show no signs of going open circuit.
Anyway, with multiple bypass caps (six or eight???) being fed from each branch, I decided just to replace all in that section vs. trying to determine which one(s) had actually shorted. I did replace probably several hundred with that shotgun approach. The joys of determining WHICH rail bypass cap has shorted when you have multiples all in parallel...LOL.
That DID lead me to locating suitable test gear for "snooping along a PS rail" to determine which cap had shorted. My trusty Fluke DVM could only indicate that somewhere along the rail there was a short.
Bri
