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Author Topic: MP-1 v.2 Not editable equalizer.  (Read 2704 times)

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RVLP

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MP-1 v.2 Not editable equalizer.
« on: Time Format »

When I try to edit the equalizer, the numbers on the display change but the sound does not change at all.
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MarshallJMP

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Re: MP-1 v.2 Not editable equalizer.
« Reply #1 on: Time Format »

Does this happend on bass,mid,treble and presence ?
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RVLP

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Re: MP-1 v.2 Not editable equalizer.
« Reply #2 on: Time Format »

Does this happend on bass,mid,treble and presence ?
Yes.
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MarshallJMP

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Re: MP-1 v.2 Not editable equalizer.
« Reply #3 on: Time Format »

There are 2 TC9170AP chips near the front (they are in ic sockets); check if they get hot.
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RVLP

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Re: MP-1 v.2 Not editable equalizer.
« Reply #4 on: Time Format »

They are barely warm.
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MarshallJMP

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Re: MP-1 v.2 Not editable equalizer.
« Reply #5 on: Time Format »

Ok can you measure the voltage on pin 1 and pin 16 (to ground)?
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RVLP

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Re: MP-1 v.2 Not editable equalizer.
« Reply #6 on: Time Format »

7.18 V - Is the voltage between pin 1 and pin 16. The voltage between pin 1 and ground is -6.1 V , between pin 16 and ground is +1V.
« Last Edit: Time Format by RVLP »
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RVLP

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Re: MP-1 v.2 Not editable equalizer.
« Reply #7 on: Time Format »

I fixed the device today. Thanks to everyone who wanted to help.
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MarshallJMP

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Re: MP-1 v.2 Not editable equalizer.
« Reply #8 on: Time Format »

So what was the problem, seems to me the voltage on pin 16?
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RVLP

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Re: MP-1 v.2 Not editable equalizer.
« Reply #9 on: Time Format »

The is a  short-circuited ceramic capacitor H5M 104 ( seems a filter circuit of U19, U20). It connected in parallel with a diode and located near U20, on the left.
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MarshallJMP

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Re: MP-1 v.2 Not editable equalizer.
« Reply #10 on: Time Format »

Ah ok I see so it was the cap that made the voltage go way too low.
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RVLP

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Re: MP-1 v.2 Not editable equalizer.
« Reply #11 on: Time Format »

I think it's just old age.I already replaced the electrolytic capacitors in the power supply circuits of tubes.
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