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Old 4th July 2007, 06:29 PM   #11
anatech is offline anatech  Canada
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Hi aantunes,
C713 .... 0.01uF not critical at all (protection transistor)
C710 .... 0.047uF use 100 V or higher.
C721 .... 0.1 uF ? couldn't find it. Looks like supply decoupling.
C706 .... 0.1 uF
Your other two across the resistors .... 0.1 uF 100V Not critical, for supply.

My schematic copies for this amp are very hard to make out. Very poor scans.

-Chris
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Old 8th July 2007, 11:14 AM   #12
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HELP


After replacing all electrlytic caps on board p700 the resistor r759 always burns out!!!!!!

Anyone as any clue
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Old 8th July 2007, 11:22 AM   #13
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Another strange thing when replacin capsc717 and c718
the manual mentions 10uf but in the 2 channel the old ones that were there were of 22uf

Any clue?
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Old 9th July 2007, 03:32 PM   #14
anatech is offline anatech  Canada
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Hi aantunes,
I can't read my schematic in that area very well. Is R759 a 3R3 in series with the base of the output transistor?
Quote:
After replacing all electrlytic caps on board p700 the resistor r759 always burns out!!!!!!
Something else changed. Wire off and shorting? Solder splash shorting traces?

Quote:
Another strange thing when replacin capsc717 and c718
My manual shows those as 22uF. Depends on the market possibly. It's simply part of the filter in the protection network. No biggie, use 22uF.

-Chris
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Old 11th July 2007, 09:31 AM   #15
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hI ANATECH,


Big problems, after the burn transistor I found that I've placed the power transistor in the wrongh place, this meas instead of replacing in the original position I've switch betwwen 2 of them.

I think I may have ruined my amp !!!!!!!

Aterf replacing the burn resistence and placing the transistors in the correct place, 3 others resistors burnout!!!!

Te problem is I'm a stupid nubbie! First I don't have an external ac power, so I was just connecting the channel to the ampplifier and power it on to test...what i think is stupid!!!

so now i'm going to study http://www.kpsec.freeuk.com/index.htm
and try to learn something about electronics, try to test all the components and see if I can save this little baby...

Help needed!!!!!!!!!!!!
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Old 11th July 2007, 03:39 PM   #16
anatech is offline anatech  Canada
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Hi aantunes,
Too bad you're there and I'm here. I could rebuild it properly. Setting the idle current may be troublesome now though.

A new set of outputs for that channel. No ifs, ands or buts. This is a great little amplifier. I'm sorry to hear about the trouble. It's a bad amp to learn on too, because it's a little different to most.

Hugo may be able to help you. You should take stock of your situation and ask him how much. This is a classic little amplifier with the ability to stomp on many others for sound quality. So it's well worth what ever it reasonably costs to repair.

Hugo is "Netlist". He is a very good technician as well.

-Chris
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Old 3rd September 2007, 01:55 AM   #17
jblmar is offline jblmar  United States
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Just came across this thread.
Sounds like thermal runaway issue. Are the heat sinks (either left or right) hotter that the other? If so, the protection circuit will cut off the speaker realy. As the heat sink cools, the thermistor will allow current to flow and the relay will be switched back on.

Ron
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Old 3rd September 2007, 02:04 AM   #18
anatech is offline anatech  Canada
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Hi Ron,
This model does not have thermal cut out. It does have thermistors that people tend to break the leads on. High bias. Boom.

-Chris
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Old 3rd September 2007, 11:01 PM   #19
jblmar is offline jblmar  United States
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Hi Chris,
The thermistors are what I meant. My 300DC developed a thermal runaway condition on one channel about 4 years ago. The channel would cut out when the heat sink reached a certain temperature (resistance). The thermistor would cut the current. Took a few minutes for the HS to cool and restore function until the next cycle.

Ron
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Old 5th July 2013, 05:37 AM   #20
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After replacing a total of 11 transistors,
a number of resistors, a couple of diodes and
whatnot (there was a hole burnt in the pcb,
major disaster) in a Marantz 170DC, I need to adjust
bias as the heatsink becomes too hot (+54 Celsius).
How do I do this? (no pot present).
Very grateful for some hints...
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