Sidebar Sidebar
  • You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

A couple of questions on Transistor amplifiers

J

jtrouter

Well-Known Member
Jul 7, 2015
253
143
53
64
Hello,
I am attempting to repair a amp of a friend, He ad a mic that would key up by itself. I did repair the mic as it had a loose wire
and would go into transit mode if the floor was bumped. Anyways while he was away from the room the mic keyed and leftIMG_20220718_231810.jpgIMG_20220718_232121.jpgIMG_20220718_232112.jpg
the radio WITH the amp engaged for a long time and it was blazing hot. So My question is has anyone seen this amp or a
similar layout for a schematic to look at? And a unrelated question I have read that "some people" have said that the HG transistors
leave a lot to desire, But i would like t know how the MAcom transistors compare to the original Motorola's? They have the same data sheets
i mean identical! So fr any of you how do they compare in use? Are they the same?
Thank you and i look forward to here form you informed guys.
 

I am unsure, but what little I have read on the Macom’s has not been good overall. But, that could be coming from people abusing them and expecting them to put up with it. Who knows for sure unless someone here has used them.
 
MA/Com is a legit USA outfit. Their stuff should be real. They did legitimately license Motorola transistors.

If it's not a chinesium counterfeit, anyway.

So, if it was still hot when he came home and found it, was it still showing power on the wattmeter? Gotta wonder why it was hot if it wasn't still delivering power?

And if there's no power output, that's a pretty clear-cut symptom.

73
 
Well there was 2 caps that got so hot they melted the solder and fell off.
They are ok test wise, I just wanted a find a schematic for it or one that is
using the same design. It looks like one i have seen before but I do not have to have it as its pretty much a simple design. I just like to have one to compare it
with. And No i doo not know if it still works as it was turned off and put outside to
cool off. I have not tested it yet.
 
Wire Weasel said:
You're charging your friend extra for being an idiot right?
Click to expand...
It happens.
I put a meter in a old dx500 that got so hot it melted the plastic, other than that it was fine.
All of these amps need a fan wired to come on with the power switch.
Nomad has pictures here somewhere of a amp that melted parts off the board.

73
Jeff
 
I would start by replacing the silver-mica capacitor that melted its own solder. If you have a tester, check to see that a measurement agrees with the capacitance value marked on the capacitor.

And if you can't test it, a replacement from RF Parts is the next best thing.

40 years ago you could tell a guy to get that capacitor from is local repair-shop parts supplier.

Those guys no longer exist, and sources for a simple thing like a silver-mica capacitor are far between.

Does it do anything with the capacitor out of the circuit? If you can't get any RF power at all from it now, the capacitor won't fix anything by itself.

73
 
nomadradio said:
Those guys no longer exist, and sources for a simple thing like a silver-mica capacitor are far between.
Click to expand...
I have driven by our local radioshack every day for 4 months and the thought never crossed my mind to stop. A few years ago half of their component bins were empty and the owner said everything had been on order for months. He didn't seem confident that he could ever fill them.

I'll have to stop in next week and see how bad it is.
 

dxChat
Help Users
  • No one is chatting at the moment.


      Top Bottom
      Back