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January 25, 2021, 05:46:04 PM

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Author Topic: Mike700 transistor and mje800 transistor  (Read 3150 times)

Green leaf

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Re: Mike700 transistor and mje800 transistor
« Reply #15 on: December 18, 2020, 09:17:00 AM »
Ok. With my negative lead on chassis ground I take positive lead and check and all the voltage readings say positive. I think my prospective from working on auto and truck dc is the problem because your dc comes from a battery there and not a rectifier bridge. How would I see a negative on one side? Or dose this mean I have some bad diodes? And we’re should I put my negative lead?

Jazz P Bass

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Re: Mike700 transistor and mje800 transistor
« Reply #16 on: December 18, 2020, 12:23:59 PM »
Leave the Black Lead attached to chassis when taking voltage measurements.
The negative voltage can be read at R 63. (Red Lead)
The rectifier side should read -46Vdc and the other side has a zener diode (CR30) attached which will drop the voltage to -15Vdc.

Green leaf

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Re: Mike700 transistor and mje800 transistor
« Reply #17 on: December 18, 2020, 01:44:58 PM »
Ok thanks Jazz! The voltage is reading properly correct polarity where it should be and the 77volts I claimed on out put of the op-amp were actually my. It%u2019s actually reading 205milly volts at pin 7. I%u2019m about to finish replacing the diodes and the two transistors I was talking about and then I will update on what happens after that. (Je800 and je700 with the four diodes around them)

Green leaf

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Re: Mike700 transistor and mje800 transistor
« Reply #18 on: December 18, 2020, 03:01:38 PM »
Ok hum on speaker is not so loud but is still present. The speaker pulls in when kicked on. I’m not getting all the heat at the transistors or at r58 and r57.

Green leaf

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Re: Mike700 transistor and mje800 transistor
« Reply #19 on: December 18, 2020, 04:30:56 PM »
Ok I have 46v+ between r49 and r47 but 37v+ between r47 and c25. It should be 23v positive. Dose this indicate c25 being a bad? Or were would I want to go with that? Thanks for all the help so far I’m having fun learning.

Green leaf

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Re: Mike700 transistor and mje800 transistor
« Reply #20 on: December 18, 2020, 10:50:16 PM »
Ok this was fun looking at schematic and figuring out. You all probably all know but don’t replace a mje800 with a mje700. When I followed the schematic it explains why I didn’t get the 24volts.

Green leaf

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Re: Mike700 transistor and mje800 transistor
« Reply #21 on: January 20, 2021, 09:47:57 PM »
Omg so finally got my transistors from China and soldered the correct pair in. Now I have signal coming out but it is not very loud and gets quieter longer it’s on. I noticed one capacitor getting just a little warm. Thanks for all the in put. I am very happy to have gotten this far with everyone helping. What should I check now that I have signal coming out? Thanks to everyone in advance.