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Author Topic: marshall G25r  (Read 531 times)

Isidore kanerus

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marshall G25r
« on: May 30, 2017, 06:14:18 AM »

hi guys, I have a Park Marshall G25r that I need to repair but it has proved difficult to repair without the schematic. Please may anyone help me with the schematic, please. (Park Marshall G25r schematic). Thanks. :'(
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J M Fahey

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Re: marshall G25r
« Reply #1 on: May 30, 2017, 01:44:11 PM »

Hope somebody posts it but in any case search for the Marshall MG G25r or similar name, same Marshall amp is sold under different brands or models depending on the Country.

I have found the exact same one sold in Germany as Park, and here in Argentina as plain "Marshall"  , no qualifications, obviously to profit from the famous name :)
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Clyde

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Re: marshall G25r
« Reply #2 on: May 31, 2017, 10:46:06 AM »

The only help I can offer is:

G10R schematic (post#4)   http://music-electronics-forum.com/t12984/

Attachment is for G25RCD

Maybe enough info in these to get you where you want to go.
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Isidore kanerus

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Re: marshall G25r
« Reply #3 on: June 01, 2017, 04:49:37 AM »

thanks guys, Yes it's a Park Marshall G25r. the problem Im having is, it plays well for a few minutes and it starts distorting.
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DrGonz78

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Re: marshall G25r
« Reply #4 on: June 01, 2017, 04:38:47 PM »

Also, check the Marshall MG30RCD schematic attached here to see if any similarities between your amp. Such as does it have a TDA2050 chip for the output stage?
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A person who never made a mistake never tried anything new. -Albert Einstein

phatt

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Re: marshall G25r
« Reply #5 on: June 02, 2017, 08:42:01 AM »

You might first check the voltages on the main power supply (at the 2 large Electrolytics) then check the voltage on the opamps, pins 4 and 8 on the opamps.
If the Schematic that member *Clyde* kindly linked to is correct then you should read around +/- 20 for power chip and +/- 9 Volts for preamp supply.

Check the terminals on the speaker output for DC voltage it should only read a few mV, anything over 1 Volt is a sign of trouble.

Check the heatsink on the TDA**** power chip, if it's hot to touch with no signal then something is wrong?
Phil.
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