Question about TOA Electronics P-924MK2 Amplifier

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I need a schematic for a TOA P-906, (series one, not MKII) also I wish to purchase the output transistor board assembly for a TOA Z-912MKII

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I have schematics for the old 900 series. Do you have them for the MKII? Email me at

Posted on Oct 06, 2009

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What is the number of blue output transistor.

If you wish to get some details; check the site linked here. Pull up older posts. Surf the site with patience.
It will be the same number used for Green and Red color output transistors. Surf the above site. It has schematic diagrams to many popular brand TVs. You can point this out there.

Jul 14, 2015 | Televison & Video

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Tv blows 2sc4429 transistor

Check the freewheeling capacitor, connected between its collector terminal to ground for loose solder, or damage. Repalce this capacitor, before replacing the horizontal output transistor. If this capacitor is open, the horizontal output transistor will blow off, at the time of switch-on itself. Normally, its value will be grater than 3900pF & lesser than 9800pF[2500V]
If you wish to get some details; check the site linked here. Viewing it in "Mosaic" will make surf easy. Surf the site with patience. Pull up older posts. Surf the site with patience.

Apr 09, 2014 | Televison & Video

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I have two 260X3 MK11 amps, they stopped working they are 8 years old

Check fuser, power supply filters, and all electrolytic capacitors, look at the top of these caps for swelling check for dry solder on the circuit boards, check output transistors and scorched resistors

Nov 09, 2013 | Sonance Sonamp 260 MKII 2-Channel...

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My toa a-912mk2 amp does not work and the red protect light stays on

• Check for shorted power transistors, and extract in pairs.

If it powers up, without protect..

• Check again for possible additional components before replacing

the bad ones.

A good amp never produce an over of 0.7V on its output.

Sep 06, 2012 | TOA Electronics A912MK2 Amplifier

1 Answer

I have a TOA 301 15W amp and a Bose 151 environmental speaker(40w 4 ohms). I do not have a manual for the amp and wish to connect the speaker as a small PA . My concern is that the output I think I should...

Don't worry about the 7.7 volts. Just connect between COM and 4 ohms and you'll be fine. I didn't find a 301 part number related to a 15w amplifier, but I did find a BG series (115 130) of 15 watt amps manual


May 08, 2011 | TOA Electronics Audio Players & Recorders

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Hello I have GK 1001 bass amp that stoped workirepng. I removed it from the case to get at the circuit board. Once I got down to the component level I descovered that several of the power transisors...

Yep... happens all the time. That is why I cold start an amp like this with an incandescent lamp in series to act as a current limiter. I will tell you what is wrong. You did NOT go back far enough in finding the bad parts. Also some that were not shorted MAY have been degraded. The real problem lies in the driver transistors and the bias regulating circuit and the transistors in that area. This amp has a mass number of components and there are many that if they fail they wipe out a bunch. When you think you have it repaired run it a while with a 150 Watt light bulb in series with the power input cord. Here is your schematic:

Scroll down to the link "Get Manual" and click to download. In the schematic there are over twenty transistors involved with power output and bias stability. This is one of the most complex amps I have seen. They get voltage capability by having two series banks of transistors to each voltage rail. The biasing network is a nightmare!!! Pot R28 sets the rest bias which you measure between J5-1 and J5-2 which is 1/3 of the rest current across a total of .4 ohms... whatever it is supposed to be. Q3, Q7, Q16 and Q17 are ALL real critical to the biasing as well as the smaller Q12 and Q13 and all the others. The problem when you have a feedback amplifier is if any of these components are sick, the feedback will still attempt to balance the amp even though it sloowly fries other parts. Frankly, this is going to be a miserable one to fix. Use the light bulb trick and a Variac. There are a few voltages marked n the schematic USE THEM TO CHECK the operation. When certain transistors go, they will take a bunch with them... NOTICE the FUSIBLE resistors up near the rails a couple stages back... need to check all of those and replace with IDENTICAL ones if they are blown or way off value. There are a lot of Zener diodes that ALL need to be checked as they afect the bias levels. You will need nearly full voltage during checking which really makes it tough. With the light bulb if too much current is drawn from the line the light will light absorbing the power line voltage. The light should remain off when repaired AND voltages should be near what is shown on the schematic. I would expect to see half the rail voltage across each of the sets within the banks when at idle. Good luck... from an electrical engineer with 50 years exp.

Apr 17, 2011 | GallienKrueger Gallien Krueger 800rb

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Protection light stays on even when everything is disconnected.the output transistors are turning red hot instantly and it has a 20 amp draw on it.while it is hooked up to a power supply with no sound...

there is a short somewhere one your board that is putting all the load on your output transistors follow the traces on the board both ways to find the short

Jul 05, 2009 | Power Acoustik GOTHIC OV2-1800 Car Amp

1 Answer

Connecting input & output on my TOA 900 series amp

Jan 07, 2008 | TOA Electronics P-924MK2 Amplifier

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