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Support and repair information for Marantz home theater AV receivers and older audio-only receivers.

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My sr8500 just goes on standy the sec I turn it on

I dont really know where my problem is but i have check all my 5v lines and the only 1 i have it the one that comes from the standby pcb (+5VL).

I have 0V on the ST - BY line

not sure if the AMP has blown i have ohm’ed but not really sure if i have done it right any help would be nice

forgot to add that it says check pow 5

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Hi,

Here’s the service manual for the receiver that may help. It is a direct download. Also don’t be misled by the title of the file i.e. MR7500 as the manual covers both models ;-)

Try getting into the service mode (see p.9) and see if that tells you what is happening.

If no good there are schematics in the manual. You may have to start checking at the power board and then move forward from there.

Hopefully a start.

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Hey i have the service manual but thx.

I cant get it into service mode i have tried my screens is also black(dead) but i can get it to turn on for a couple of sec if i turn on the input selector or press enter

I have also looked though most of the power board and have almost nothing there but i dont think the problem is with the power board since the T801 (relay) dosent turn on so it allows for no AC to get to the main transformer so the 2 5V lines and 15V lines that is suppoes to come from there isnt starting

and now i am a bit lost and dont really know what to do.

I have thought about shorting the relay and hope nothing startes burning so i myabe can start to measure some real things

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@ thomas nørgaard

It may be that it is going into protection mode.

A quick look at the schematic (see p.33) shows that the STANDBY lead and the P_DOWN lead going to the Standby pcb, connect directly to the CPU on the DSP board.

On p.33 cn64 there are leads marked HEAT_DET and PA_FAIL so it may be worth checking where they connect to in the Amp pcb to see if there is a signal being sent to shut the receiver down when there shouldn't be one.

Also check all the 5V supplies on the power pcb.

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@jayeff I have 5V on _PA_FAIL follow it to Q804 where i could measure it on the collector but nowhere else and got nothing on HEAT_DET

sooo where do you have any idea where to look next?

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@ thomas nørgaard

If you have +5VL then there should be voltages on pin 4 of IC 61 & IC 62 on the Power pcb

These ICs are also fed from the main AC transformer CN66/3 and it looks like the output from the ICs (+5VV & +5VV) are produced by these which I presume are some sort of voltage regulator.

I would start looking around there and maybe trace back to the main transformer circuit

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@jayeff i do have 5VL on both IC61 and IC62 but i dont have either of the other 5V line which makes sense since i have no ac on the POWER board.

I have edited my orignale question with a pic of the standby board diagram where i have written what i have measured all over it i hope it helps

and i think the big problem is that relay dosent turn on which in turn makes sure that no ac goes to the main transformer

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