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|27th June 2009, 12:23 AM||#1|
Join Date: Jun 2009
Marantz SR5200 immediate shut-off
Hello. Hopefully one of you has some knowledge of this unit. I did find another thread (and many others on the net) about the 5200 but none apply to my problem. I bought the unit new in 2002.
The unit turns on but before engaging it shuts off again. There is nothing connected to the back and I've checked for wire tailings or other shorts. I opened the case and checked for dust/shorts but to no avail.
I'm pretty sure the output stage is fine. It's always been well ventilated and never overworked. Seems to me it's a power supply issue but I'm by no means an expert. So the question is where should I look first? Solder joints? Caps? Overloaded diodes/regulators?
Your help is greatly appreciated.
|30th July 2013, 11:00 AM||#2|
Join Date: Jul 2013
I have acquired the SR5200 recently for 15€ in a second hand shop. No remote and according to the shop not functioning.
I got the unit functioning under manual control and encountered I guess all the common problems users have had with it.
1. where to find a remote -> i use the Philips Prestigo universal remote control
2. unstable behaviour when using the audio input couple to the TV input when no TV signal is present on the TV video input -> use the setup menu to disable auto off on the TV input
3. Replacement of the 10.000 microfarad elcos in the power supply -> very difficult to find the replacements and I had to dissassemble the complete unit to take the motherboard out.
4. Volume control did not function -> I had to open the volume control switch and cleaned the contacts, this involved the complete dissassembling of the front panel on the way I also cleaned the window and the display from accumulated dust.
Just recently I encountered the problem described in this thread.
The relays on the power-board and main-board did not switch on and the unit looks completely dead.
According to the user manual I checked the powercord and fuses.
I had 230 Volts on the powerboard.
I did not have 6 Volts from the 7806 only 3 Volts.
I suspected some overload or one of the elcos on the powerboard.
First I replaced the elcos, no result.
Luckely I found the service manual for the unit and with the schematics I could focus on a specific connector that has four pins: 6V, G, Power Down and Standby.
Actual status 6V -> 3 V, G OK, Power Down low, Standby low.
When I removed the connector the 6V came back, G OK, Power Down low, Standby low.
Another look in the schematic revealed that the Power Down is an active low send by the main-board that pulls down the output of the small transformer to 4V3 by means of a resistor and a zener diode.
So I supected a mal-function on the main-board especially the microprocessor that is mounted on the underside of the main-board.
At that point I almost gave up as replacing the microprocessor is too much effort and too difficult.
Looking again at the sechematics I discovered that besides powering the microprocessor the 6V is also used to power the front-board by means of a white flat cable located a the right front side of the main-board.
As a last resort to see if something on the front-board causes the problem I took the flat cable out and switched the unit on.
With the cable of the relays came on and the unit powered up.
I put the cable back and switched on again and the unit worked.
I suspect an undefined state coming from the front-panel to the microprocessor that put the unit in the power-down mode.
Until now the unit functions ok
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