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Why Do People Do This?

Posted: 16 Oct 2017, 10:39
by astradyne
I took delivery of a faulty Lincoln Mk1 last week and finally got round to looking at it. All is fine with the radio bar no output (although a radio sat next to it picks up great TX audio).

So, first port of call, check the driver and output transistors. Popped them out to find there's a 2166 in place of the 1969! Not sure how well that would drive an MRF477. Not sure if the 477 is genuine either as it's not the original and had been badly fitted.

Why do people do this?

Re: Why Do People Do This?

Posted: 16 Oct 2017, 11:33
by MARKASTERIX
The 2166 runs the MRF477 very well and not the 1969. the 1969 will run it but overkill.

The schematic on CBTricks shows the 2166 and 477

Re: Why Do People Do This?

Posted: 16 Oct 2017, 11:50
by ch25
Nothing wrong to use 1969 when tech knows his job.
Chris

Re: Why Do People Do This?

Posted: 16 Oct 2017, 13:27
by Black Spirit
The lincoln has a 2166 driver not 1969 ;) , My pet hate is when some remove the MRF477 and throw it away before testing it or the 2166, I have yet to come across a lincoln/2830 where the output just stops and the 477 is at fault, Most of the time the output stops working in a lincoln that i have found is the driver bias diode goes open so 2166 gets 8v and quickly fails.

I had a Lincoln not long ago with blown 2166 that was still present and yep MRF477 was missing and someone tried to fit a 1969 [Crossed legged], Luckily i found an ebay seller with x2 brand new genuine Mitsibushi 2SC1945 so grabbed them and installed one and it was doing around 15-20w which was plenty enough, And I would put money on it the missing 477 was good.

Re: Why Do People Do This?

Posted: 16 Oct 2017, 15:11
by astradyne
Sorry guys. My error.

I got confused with the driver in the later MRF455 output version of the radio... :oops:

Re: Why Do People Do This?

Posted: 16 Oct 2017, 15:52
by Black Spirit
The MRF455 doesn't have a 1969 driver either, But i see no reason why a 1969 wouldn't work and shouldn't be much difference in output.

Off topic.
The 455 was used because the 477 was discontinued, The 2166 will produce for sake of arguments 3w into the 455 to give 25-30w output, The same as the 477 did.

Re: Why Do People Do This?

Posted: 16 Oct 2017, 16:28
by astradyne
Black Spirit wrote:The MRF455 doesn't have a 1969 driver either, But i see no reason why a 1969 wouldn't work and shouldn't be much difference in output.

Off topic.
The 455 was used because the 477 was discontinued, The 2166 will produce for sake of arguments 3w into the 455 to give 25-30w output, The same as the 477 did.
Strange. I have a late Lincoln here with a 455 and it's always had a 1969 driver fitted. Obviously fitted by someone when the 2166 blew. To air on the side of caution I'll get hold of a 2166 to replace it with.