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G8MNY > TECH 01.05.18 13:08l 91 Lines 4240 Bytes #999 (0) @ WW
BID : 18055_GB7CIP
Read: DK3UZ GUEST OE7FMI
Subj: Mixer Eurorack1804X/ItMix PM184X
Path: DB0FHN<OE2XZR<OE5XBR<OE1XAB<HG8LXL<N0KFQ<NS2B<N9PMO<VE3UIL<JH9YMQ<
JE7YGF<GB7CIP
Sent: 180501/0902Z @:GB7CIP.#32.GBR.EURO #:18055 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Update Jan 18)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
I have worked on both of these Behringer 10ch AF Mixers, "T Mix PM184X" has a
plastic carrying handle & a huge 375W/ch (4ê) PA amp built in underneath. The
"Eurotrack 1804X" is a mixer only & has a separate mains transformer.
ch 1 2 3 4 5 6 7 8 9 10 o/p
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
XLR³O O O O O O . . o o o o ³ 6 XLR Mic/mono Jack line +4 tone controls
Jack³o o o o o o ú ú o o o o ³
LF³ú ú ú ú ú ú o o o o o o ³ 4 Stereo 2 Jack ins +4 tone controls
Gain³ù ù ù ù ù ù o o o o o'o'o ³
³=============================³ 1 Aux Jack & 1 Phono Tape In & Out
Top2³ù ù ù ù ù ù ù ù ù ù ³
Top1³ù ù ù ù ù ù ù ù ù ù ÛÛÛÛÛ ÞÞ ³B 32 mode FX echo 24bit processor
Mid³ù ù ù ù ù ù ù ù ù ù ÛFXÛÛ ÞÞ ³a
Bas³ù ù ù ù ù ù ù ù ù ù ÛÛÛÛÛ ÞÞ ³r Aux & Separate Alt/Solo Mix functions
Aux³ù ù ù ù ù ù ù ù ù ù ³
³ ú ú ú ú ú ú ú ú ú ú||EQ|| ' ³ 7 Band Graphic EQ.
Fx³ù ù ù ù ù ù ù ù ù ù ú ú ³
Pan³ù ù ù ù ù ù ù ù ù ù ù ù :ù ú ³ All Ch have ext rear Jack effect option
³: : : : : : : : : : . . . . ³
³| | | | | | | | | | | | | ||³ XLR Bal & Jack Un O/Ps
³| | | | | | | | | | | | | ||³
³| | | | | | | | | | | | | ||³Main
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙL&R
Faders Aux Fx Alt
The 1st Mixer+Amp was not working properly, it had a broken LS screw post & a
very noisy mixer. On painstakingly opening it up, literally 100s of knobs jack
nuts & screws, (1 needed drilling out) to release the large PCB. It soon became
obvious that a CUP OF COFFEE had done it in. (Always power off/remove batts if
this happens to you!)
I photographed the PCB to show up the many small corrosion points in detail on
a PC screen & see all Surface Mount bits zoomed in to more easily check it out.
After much tinkering I found a SM dual Op amp IC with a completely corroded
away +ve pin. At this point I gave up as un-reparable for a few years.
At a Ham rally I spotted the similar 1804X "mixer only" version, for œ20, less
its external transformer & a noisy slider, so I bought it, & made up
transformer box for it. The bad slider was the 1st ch Mic, so I stripped this
mixer down too, unsoldered & removed the slider, opened it up, re-tensioned the
wipers & put it all back together. Then solder suckered the PCB holes to refit.
All tested OK.
I did not want to wreck the now "good mixer", so I went back to the PM184X
Mixer+Amp again. Removing the duff SM IC I had previously found, but the loud
crackle noise was still there! I also spotted an overload/PFL LED would not
light. Testing further I found a symular SM dual Op amp IC with no +ve rail, or
to the that chanel's LED. This faile power I traced to a tiny plated through
PCB track bridge failure under a component, (same as other ch track layouts) so
I pieced it out on the non component side with 2A fuse wire. Retesting all
noise gone.
Now to the duff SM IC, filing it's corner off, I managed to expose enough metal
(0.2mm) to tin & solder 2A fuse wire to it. Putting it back in, a steady hand
was needed for SM ICs! Hey Presto it all worked too.
Back to the last bit, the PA Amp's broken dual post LS high current screw post,
I made a replacement part from an old similar one & made it fit.
To stop this Mixer "coffee fault" in the future, to both mixers, I added felt
rings washers cur from "J Cloth" on each of the 79 pot shafts & glued a cloth
to the cover for the 15 sliders holes & slotted them.
Before closing up, I drilled out & re-tappped the seized screw thread in the
spot welded collar, that I had to drill off, & replaced the screw for a "Proper
Job". Also all the screw threads were greased up to enable easier re-assembly &
undoing next time!
Then it was just the matter of the 100s screws, nuts & washed clean the knobs,
etc. Then do a good test out. A very hot 2x 4R large dummy load with the
375W/Ch amp. :=)
It has now been used at a function quite reliably, (spare taken too) so
eventually it was well worth all the hassle in the end.
Why Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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