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Black Cat JB 75A Transistor Replace

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Black Cat JB 75A Transistor Replace

Post by 102 » Saturday, 15 June 2013, 10:01 AM

I have an old Black Cat JB 75A that I bought new way back in the 70's, It has been in a box for 30 years, a good place for it I'm sure but I enjoy throwing good money after bad so they say, the reason I say that is, when I first wanted to get it going again for a mobile, I thought it needed a new tube, well $50 later, (12 years ago) It still doesn't work and I am told the transistors are gone, back In the box because I was told they no longer make the 2n1522, and if you can find them they are around $40, not worth it. Well now I find a replacement (2n4048) for $14.50, worth it just to get it running for a back-up driver, (especially since I now have the new tube and the old one is also good, so I have $150.00 worth of tubes for a $10.00 amplifier) hopefully the new transistors won't squeal like the originals. My question is, is there any mystery to changing them? it looks like 2 solder joints and a bolt on connection. I am a truck driver by trade so electrical expertize is not my strong point. Do I try it my self or pay the tech to do it?


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Re: Black Cat JB 75A Transistor Replace

Post by silvereagle1 » Saturday, 14 September 2013, 11:13 AM

My dad had one of those amps back in the 70's. I remember it like it was yesterday. I wish I could find a picture of it.
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Re: Black Cat JB 75A Transistor Replace

Post by magikarp727 » Wednesday, 06 September 2017, 9:09 AM

You can also use the 2N1511 silicon one as mine has them. They were in it when I got it. They are about $5USD ea. Hope this helps. Oh and by the way the squeal is normal for the push pull type transistors, even my silicon ones do it when transmitting... Got another JB75A that the 2n1511's are shot in so I'm debating the 2n1511 vs the 2n4048. From what I hear the germanium last much longer and probably make the amp perform better from what I hear but like u said They are $15 each versus $5 each...

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Re: Black Cat JB 75A Transistor Replace

Post by MDYoungblood » Saturday, 09 September 2017, 5:56 AM

The 2n4048 is the replacement for the discontinued 2n1522 but have seen the 2n1511 used as well. Wawasee amplifiers all squealed as you put it, they were really known as a "modulator", it could be eliminated by moving the amp farther away from the radio/mic and some changed out the 2 wire power cord to a grounded cord with some success, I prefer to ground the amp's to a cold water pipe or ground rod outside.

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