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jbl_man View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jbl_man Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 12:13pm
"Anyway, in the process of repairing a badly looked after Crown Micro-Tech 1200. Saved this one a few years ago.  It works, gives a clean output but the Fanformer has seized.  Even after trying to oil the shaft and bushes its very weak and runs hot.  So I'll replace it with a small 18V transformer and 240V fan instead. "

Yup, common fault this, same with the macrotechs. Usually the coil windings are burnt/discoloured. The fan is no longer available, and used ones are hard to come by, so yes, some sort of subsitute + additional transformer should do the trick. Thumbs Up
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Post Options Post Options   Thanks (0) Thanks(0)   Quote EmPro Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 12:50pm
,,Anyway, in the process of repairing a badly looked after Crown Micro-Tech 1200. Saved this one a few years ago.  It works, gives a clean output but the Fanformer has seized.  Even after trying to oil the shaft and bushes its very weak and runs hot.  So I'll replace it with a small 18V transformer and 240V fan instead.  

Also, pulled out a BK Electronics MXF 600 to test.  MOSFET based and has very good distortion figures far exceeding many other amps but labours a bit when testing under load.  Getting a drop of output voltage in low frequencies,,

The fan in crown amps are going due to poor meinteinance,no one lubricates them untill is far too late,i have 8 MT's and no problems at all,i found them the best amps Crown ever made.
I remember 6 years ago i bought an Microtech 600 faulty,the seller mentioned as the amplifier working but only for short period of time then it cuts off....when i got it open...dear god.... 5kg of dirt all over the place..and the fan was like welded...i cannot move it even by hand...i needed to even sand the rotor to get it back in working order as the crap was so stick to it that became part of it Ouch ,so new rings,lubricated and the fan is working great even today,as i still own the amp.

Regarding to BK amplifiers,i still own two BK MXF400 and one BK MXF900 in perfect working order,and yes,they exceed the specs easly and almost bulletproof in any application you use them,best for Mid-Tops,not that kind of amps to kill them with 18inch bass bins,however loads of people useing them for bass applications.
The best modds for these amps is to fit heatsinks on the driver To126 transistors as they run hot as hell (not a good thing),replace the stupid bias trimpot with a proper trimpot (as the one fitted is a bad joke and always drifting) and if more time is available...add a different led vu-meters power supply as the one in them formed with a zenner,a resistor and a TIP29c as driver straight from the +vcc side is also a bad joke and will go kabum frying the vu-meters to death Cry


Edited by EmPro - 10 June 2022 at 1:27pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote EmPro Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 1:02pm
I love Micro-Macrotech-Powertech's  a lot,the only downside is that are hungry for current as hell....so in areas with low network power supply there kinda useless...no matter you use the 600w one or the 5kw one...so when i know i'm going somewhere with low power supply and i dont need 5kw of power i get one or two of my HH M900 (60.000uf per amp) and it does the job flawless on high quality sound,ofcourse i have three phase power generator as well,but for 100-150ppl doesn't worth the effort of getting it with me,unless the situation is critical LOL

Edited by EmPro - 10 June 2022 at 1:08pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shaun1264 Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 1:25pm
I was once given a Power-Tech 1 to repair.  The owner said one channel was badly distorted.  Checked outputs, very low mV DC offset.  Opened up, checked bias on high side and low side. Checked all output bipolars, drivers and small signals, bias adjusted (should be around 300-310mV). and checked ODEP voltages.  No issues running under load.  Told the owner there was nothing wrong with it.  I later discovered the problem was in a speaker cable.  Some how shorted by a few strands of copper in the speakon connector!  He later told me he already had blown to other amps.  That Powertech 1 must have been in ODEP hard at when driven hard.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shaun1264 Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 1:32pm
Originally posted by EmPro EmPro wrote:

I love Micro-Macrotech-Powertech's  a lot,the only downside is that are hungry for current as hell....so in areas with low network power supply there kinda useless...no matter you use the 600w one or the 5kw one...so when i know i'm going somewhere with low power supply and i dont need 5kw of power i get one or two of my HH M900 (60.000uf per amp) and it does the job flawless on high quality sound,ofcourse i have three phase power generator as well,but for 100-150ppl doesn't worth the effort of getting it with me,unless the situation is critical LOL


On one of my JBL-Urei 6260's I changed out the old filter caps and increased their sizes to 80,000uf and added small bypass caps and uprated the bridge rectifier.  Installed the caps all nice and neat off the board using ring crimps and thick gauge cable to attach to PCB.  Plenty of room in those old amps.

Made a quite a bit of difference to the bass.  Really low distortion figures in the bass. Sounds very nice. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote EmPro Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 1:36pm
Yes...the odep had kicked in to save the outputs,the other amps will just blow up and end of story,but not the macros,if well meinteined and clean,they hold dead short on output no problem,i was running my Macro's in 2R load ch in 4inch hungry coils (2 per ch) all night long and i never even dimmed the odep lights,and the sound was demential,you only need to take of them and will take care of you.Wink

Edited by EmPro - 10 June 2022 at 1:37pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote EmPro Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 1:41pm
,,On one of my JBL-Urei 6260's I changed out the old filter caps and increased their sizes to 80,000uf and added small bypass caps and uprated the bridge rectifier.  Installed the caps all nice and neat off the board using ring crimps and thick gauge cable to attach to PCB.  Plenty of room in those old amps. 

Made a quite a bit of difference to the bass.  Really low distortion figures in the bass. Sounds very nice.,,

The best part in old amps is that is always room for more LOL you don't have only better bass now,the power reserve increased helps you a lot with peak's and overall sound is by far better then before.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shaun1264 Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 1:43pm

Currently running these at the moment. 




I also own as new Crown  Macro Studio Reference.  The best amp i've ever owned.  A highly refined Grounded Bridge with more nested NFB.  The bass on that is truly astounding. From the very high damping factor or phase correction in the feedback error amp circuit? who knows but its a killer amp.




Edited by shaun1264 - 10 June 2022 at 1:45pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jbl_man Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 2:09pm
Hate to think what your home electricty bill is with that turned on. LOL
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Post Options Post Options   Thanks (0) Thanks(0)   Quote EmPro Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 2:24pm
That Macro Reference is a beast...just look at it Clap you are lucky to have one,also they go for crazy money,you have any internal pics of it? i think the bass is comeing from its massive psu plus loads of silica dies on the heatsinks LOLLOL the damping factor helps a lot as well...but more on long cables.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shaun1264 Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 2:40pm
Originally posted by jbl_man jbl_man wrote:

Hate to think what your home electricty bill is with that turned on. LOL


Fortunately I don't push them hard.  They have quite an easy life. Those 6260's and DSC260 are drawing 180watts from mains (They were drawing 200watts before I lowered the bias a bit)LOL

I did take some pics of the inside of the Macro Reference a few years back, I'll have a dig and find them at some point.  I purchased it about 10 years ago from a young man who had several complete with manual.   I wished I bought the other 3 he had at the time! He had a large collection of Crown amps.  Most seemed brand new. Later I purchased a Crown D150A II  of him, another spotless amp but I sold it three years ago, another one I wished I kept.

Cable size sure does has an effect of damping factor that's why I run the bass speakers through 8mm cables (2x4mm running cables in parallel) A bit mad, yes, but it works for me. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote EmPro Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 3:50pm
And i thought my 6mm cable is overkill for bass duties LOLLOL
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