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Mj802 amplifiers

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WATCH RELATED VIDEO: Transistor MJ802 Original Motorola

45 Watt Class B Amplifier


By continuing to use the forum you conform your acceptance of these. If you are not happy to accept these you must stop using the forum and delete our cookies from your browser. Goodmans Model Amp Fault. I have a power amp fault on my Goodmans receiver. The previous drivers BC, BC are ON - just, the voltage across the bias voltage transistor feeding the drivers is 1.

I have uploaded a schematic Thanks. Attached Thumbnails. Last edited by Dougallh; 15th Oct at pm. Re: Goodmans Model Amp Fault. These should both be about 0. If these are wrong the bias will also be wrong. Also check the voltage across R - this should be about 0.

If the resistor is high in value or the current limiter transistor VT is faulty the current though the next stage will be too low so you will not be able to get the bias current high enough.

I presume you have checked the signal off load with a 1KHz signal and scope? Does the waveform look basically OK except for some crossover distortion kink being visible? What is the DC offset voltage at the speaker output? For this sort of amp it should be less than mV and ideally less than 50mV.

Thanks for your reply; the voltages around the resistors you mention are correct. There is just 0. I believe that there are probably 3 levels of DC feedback I have replaced both output triplets twice now; no change Last edited by Dougallh; 16th Oct at pm. Reason: addition. Focus on the DC conditions no signal. You should be able to compare the voltages with the good amplifier. Then markup the transistor voltages on a copy of the circuit noting any differences and post back here, Laborious, but the best way to diagnose the fault.

I have to ask is it possible it's a fake? I have managed to find the problem after much trouble: The most available bias current, from adusting the pot R, would only turn up the B-E voltage on VT, to 0. When the MJ blew it took out 10 transistors! Before embarking on re-ordering the triplet transistors from a different source I tried replacing the BCL with a BCL - fault fixed!

I have never had problems with these transistors apart from noise before I agree with you Tony re the pot placing. I have repaired 3 Bush SRP51 record players one of the nicest portable record players made in my view, superior deck, big speaker, big sound which have a 50 ohm pot in the top of the divider, these go high over time.

They all needed 18 ohms so I replaced the presets with a fixed resistor. I may do the same in this case if there is significant drift over time. Thread Tools. All times are GMT. The time now is pm. User Name. Remember Me? Mark Forums Read. Vintage Audio record players, hi-fi etc Amplifiers, speakers, gramophones and other audio equipment. Posts: Find More Posts by Dougallh.

Find More Posts by tony brady. Re: Goodmans Model Amp Fault Thanks for your reply; the voltages around the resistors you mention are correct. Posts: 5, Re: Goodmans Model Amp Fault I have managed to find the problem after much trouble: The most available bias current, from adusting the pot R, would only turn up the B-E voltage on VT, to 0.


MJ802 Transistors. Datasheet pdf. Equivalent

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the MJ is a silicon NPN transistor preferred for use as output device in complementary AF amplifier applications up to W per channelUce/Ucb.

MOTOROLA MJ802 Transistor TO-3 NPN 30A 100V


These goals were achieved by using a discrete-components op-amp driving a BJT complementary common-emitter output stage into Class B operation. In this way, for small output currents, the output transistors are turned off, and the op-amp provides all of the output current. At higher output currents, the power transistors conduct, and the contribution of the op-amp is limited to approximately 0. The quiescent current of the op-amp biases the external transistors, and hence greatly reduces the range of crossover. The idea sprang up from a letter published on Wireless World, December , page 65 written by N. Allinson, then at the University of Keele, Staffordshire. The discrete-components op-amp is based on a Douglas Self design. Nevertheless, his circuit featured quite obviously a Class A output stage. As for proper operation of this amplifier a Class B output stage op-amp is required, the original circuit was modified accordingly.

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mj802 amplifiers

This page was last updated on 7 November Transistor Substitutes. The semiconductors used in the original circuit are, naturally, no longer available and even some of those shown in the update article can be difficult to source in some localities. The following list of substitutes has been prepared to assist those who are having difficulties in finding the specified devices. I have also included details of the working voltage, current and power dissipation for each transistor, when used in the circuit, so that other alternative devices may be considered.

Le plus souvent, il a trois bornes. En ce qui concerne le transistor unipolaire, il se compose de la source, du drain, et de la grille qui remplit la fonction de commande.

NTE Electronics MJ802 TRANSISTOR NPN SILICON 100V 30AMP TO-3 CASE HI PWR AUD AMP


User Name Stay logged in? Find More Posts by tiefbassuebertr. GE's first true complementary power devices from or the 16th week of Originally Posted by AndrewT. Last edited by tiefbassuebertr; 29th April at PM.

Robot or human?

The MJ is a silicon NPN transistor in a TO3 type case designed for use as an output device in audio amplifiers to 00 watts music power per channel. There may be errors in the measurement of different commodity sizes. Our wide selection is elegible for free shipping and free returns, Discontinued by manufacturer: Yes. Represent your faith wherever you go with this beautiful religious cross pendant necklace, but if for some reason you are not satisfied with your purchase. Be ready for compliments and love as this will commend your decorative skills, please do not hesitate to inform us.

hFE against Ic for MJE and MJ at VCE = +25V MJE MJ 80 60 40 20 As can be seen, there is a general trend for.

MJ802 NPN Power Transistor – Datasheet

Part : MJ Allied Stock : Download Datasheet. Shopping from outside North America? My Account.

Proper transistors for SAE Mark III CM amplifier.

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Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences. No license is. Specification mentioned in this publication are. This publication supersedes and replaces all information previously supplied. STMicroelectronics products.

The MJ is a silicon PNP transistor in a TO3 type case designed for use as an output device in audio amplifiers to 00 watts music power per channel. Actopus Copper Sheet Metal Plate mm 3.

100w amplifier circuit with PCB

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Crown D60 Amplifier Problem

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