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"ODEP" crown macrotech |
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Bigbassguy 
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Joined: 22 August 2022 Location: Caribbean Status: Offline Points: 6 |
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 Topic: "ODEP" crown macrotechPosted: 19 September 2022 at 9:21pm |
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I've adjusted odep to spec and the protect issue stopped.
The bridge mode not also work but channel A seems to have 12v under ratings. I've tested some FETS removed and the C8187-4 reads well one time and at another time it reads invalid. Discharged them and reads well on and off so I'm guessing the others are playing games also.
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kedwardsleisure
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Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4947 |
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Posted: 19 September 2022 at 8:34pm |
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it should always be under 10, it's servo controlled, not adjustable. So, there's a fault somewhere. If the ODEP voltages cannot be adjusted (the adjustment is quite sensitive and should only need a touch on the pot, if the pot is hard-over then there's definitely a fault), then a faulty odep circuit itself can cause an offset, because the circuit controls the ultimate output stage drive current.
Make sure the output modules are 100% ok before digging into the control & power boards.Even the little board on the back of the output terminals (MA5000VZ) forms part of the feedback loop as the output is sensed right there. |
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Kevin
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Bigbassguy
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Posted: 19 September 2022 at 8:21pm |
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What's the cause and should it be under 10 at start-up?
How can it be adjusted?
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Bigbassguy
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Posted: 19 September 2022 at 8:04pm |
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Strange enough it dropped to under 10 when warmed up.
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kedwardsleisure
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Posted: 19 September 2022 at 7:52pm |
Thats too high, must be under 10mV and in reality is usually less than 5. |
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Kevin
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Bigbassguy
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Posted: 17 September 2022 at 12:29pm |
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Channel A reads 03.5Mv and the good Channel (B) reads 34.5Mv volumes 0 no input. All 12 transistors were removed and checked and are you. ODEP comes on slowly when amp is cold and occasionally this occurs on channel 2 at times also. All resistors (white ones) along the NPN and PNP transistors were lifted and checked All diodes checked The IOC lights up at clip at low volume There is non audible crosstalk to channel B when A alone is connected( B IOC flashes but no audio) Voltage at output on channel A does not exceed 33 Volts and if volume is exceeded amp goes into protection. Voltage at output B swings up to 70-80VAC at the point of clip which looks and sounds normal and knocks the dust off my roof  Edited by Bigbassguy - 17 September 2022 at 3:50pm |
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opacheco
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Posted: 23 August 2022 at 4:06am |
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I think you must check for the output devises (output power transistor) this the initial task in this kind of failure!.
Second, you must try to adjust the ODEP following the calibration procedure in the service manual; if this doesn’t work and you can’t get the voltages suggested for the manufacture for this adjustment procedure, you must check for the differential BJTs in the ODEP section. Have you measure for DC voltage in the output terminals? opacheco
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Bigbassguy
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Posted: 22 August 2022 at 12:32pm |
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Good news I'm happy you got it sorted out.
However I'm having a similar problem with ODEP on my 3600 however I turned the +ODEP all the way up and the light is now steady on. BTW someone made repairs to this aml before.
It plays better but if driven hard the ODEP light starts slowly dimming and power drops. Edited by Bigbassguy - 22 August 2022 at 12:39pm |
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opacheco
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Posted: 11 August 2022 at 6:13pm |
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Here a couple of little videos showing the result.
I will need to check for bias but with the 120 Vac no limited by incandescent lamp. Thanks opacheco
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opacheco
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Posted: 11 August 2022 at 6:03pm |
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Of course!!…🤣🤣
Thanks to you EmPro again! opacheco
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EmPro
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Posted: 11 August 2022 at 6:02pm |
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Is time to play some hard music on it mate
cheers
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EmPro Audio
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opacheco
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Posted: 11 August 2022 at 6:00pm |
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Well me again but with good news!!…
I changed all the parts mentioned in the switching PSU and in the last time I had to change the D17 zener Diode in the same board and the the U104 IC too(the comparator and responsible for we get 0 Vdc in the output terminales, according to the service Manual mention!) and the amp is working normally (I have this amp with a incandescent series lamp for precaution only!). The problem was I got a -2.0 Vdc in the output terminal of the amp and this created a unbalance of the rails voltages in the comparators LM339, LM393, 555 Timer, the voltages that I got were -37 Vdc and -54 Vdc for this control switching boards respect to amp ground!!!….for comparation, the another amp channel (channel 2) in good condition show a -13 Vdc and -29 Vdc aprox. respect to ground of to amp for these voltages.(remember I have limited the outlet voltage by the series incandecent lamp to 80 Vac! for precaution only! during the tests). Now, the channel 1 is working at the same voltages like the channel 2 and I tested it whit sound music signal and everything is ok now 🤞. Thanks to everyone helped me whit this multiple failure Macrotech 3600VZ Crown Amp. opacheco Edited by opacheco - 11 August 2022 at 6:02pm |
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the good Channel (B) reads 34.5Mv