I guess that I am making some kind of mistake here??

[Tallman]

One thing I'll tell you the diode placed next to the transistors is not a varactor.
A varactor is used for frequency control. by the time the signal get to the final transistors that would be too late.

Usually a semiconductor placed on or very near a power transistor with or without heat sink grease is being used for temperature compensation.
Bipolar transistors have a negative temperature coefficient. When they get hot they conduct more current and then get even hotter and then more current. Thermal Runaway.

Increasing temperature in Figure below (a) will decrease VBE from the nominal 0.7V for silicon transistors. Decreasing VBE increases collector current in a common-emitter amplifier, further shifting the bias point. The cure for shifting VBE is a pair of transistors configured as a differential amplifier. If both transistors in Figurebelow (b) are at the same temperature, the VBE will track with changing temperature and cancel.

https://www.allaboutcircuits.com/textbook/semiconductors/chpt-4/bjt-quirks/

 

[Tallman]

P.S. And Stephanie looking over my shoulder (As she often does) is in total
agreement. . . . . . About my being a screwball I mean!

Hello Stephanie! No reason to let him have all the fun.

 

[BJ radionut]

Doc: You need to be here!
https://www.gordonwestradioschool.com/main/page_w5yi_training_resources.html

A learned man such as yourself would be welcome with the group of "Screwballs" that use this frequency most mornings on 3.865 MHz.
Let's see:
Myself: Top of the charts...BJ Radionut/W9FNB
Waverider/KJ4IIF
Firerunner/KK6USY
Hillbilly101/KE8GGC
Plus numerous others who drop by and chat from 4:00AM EST to sometimes 7 AM/8 Am EST
Sometimes we meet on other times, bands and Frequencies...
You never know whom may drop by and from where around the world
You would be welcomed.
All the Best
Gary/W9FNB
https://www.worldwidedx.com/account/personal-details
https://www.worldwidedx.com/members/bj-radionut.7026/

 

[Handy Andy]

Oh brother...

Somehow I get the feeling that you are under the misconception that I decided to change out the finals because the radio was not performing correctly,which is definitely not the case. My decision to change the finals to the Motorola's were strictly based on wanting a little more wattage than the 25 watts on am and 40 on ssb that's all?

Ok, radios don't come with loose hardware. However, if you suggest that you think we are saying you loosened the hardware yourself - please point that out in the post - I'd like to know. I was "being generalized" and considering the point of view of your response - was that you FOUND the hardware to be able to be loosened by hand, makes it appear that you didn't do this intentionally - but - if you say so - I digress...

What I see in the posts are that you pried up a part and it broke, we're trying to help you put it back together - you're not helping by accusing those trying to help - of undoing the very things you're trying to do! OR vice-versa - something like that...

Now - to get back on track, loose hardware and no idea as to the origin of the radio - as in previous owner, we're left with the aspect of a radio that's going to get new finals. But we have no true idea of the original condition of the radio.

But, did we ever check to see if the finals that are in it - even work? It may be safer and better to believe that the radio worked before the surgery is getting performed - as in - it was alive before it got killed under a hot soldering iron. Then we'd have a least a notion that we DID have a working radio - we may be able to help it recover.

Now if you haven't done anything too excessive to it, let's step back from the precipice for a moment and look a little further into this...

Ok, we don't have a spare MV-1Y - but if you have a 1N4148 or even a 1N914 - put one in there. Where the old MV-1Y went - it's doesn't have to bolt up, but it has to be soldered in - CORRECTLY ORIENTED so the part takes the proper place of the DIODE it replaces.

The DIODE is used to help the BASE lead keep the proper voltage across it so it can work. So it needs a power that has to flow properly - so the DIODE - oriented correctly, allows the power to flow across the parts in the proper direction - as in polarity.

Can you work with us here?

 

[FULL_MEDIC]

Doc: You need to be here!
https://www.gordonwestradioschool.com/main/page_w5yi_training_resources.html

A learned man such as yourself would be welcome with the group of "Screwballs" that use this frequency most mornings on 3.865 MHz.
Let's see:
Myself: Top of the charts...BJ Radionut/W9FNB
Waverider/KJ4IIF
Firerunner/KK6USY
Hillbilly101/KE8GGC
Plus numerous others who drop by and chat from 4:00AM EST to sometimes 7 AM/8 Am EST
Sometimes we meet on other times, bands and Frequencies...
You never know whom may drop by and from where around the world
You would be welcomed.
All the Best
Gary/W9FNB
https://www.worldwidedx.com/account/personal-details
https://www.worldwidedx.com/members/bj-radionut.7026/

Yeah Bj, I can obtain plenty of stock bottles of Haldol that may be needed by some guys i've met and they know who they are that need it! LOL

 

[FULL_MEDIC]

One thing I'll tell you the diode placed next to the transistors is not a varactor.
A varactor is used for frequency control. by the time the signal get to the final transistors that would be too late.

Usually a semiconductor placed on or very near a power transistor with or without heat sink grease is being used for temperature compensation.
Bipolar transistors have a negative temperature coefficient. When they get hot they conduct more current and then get even hotter and then more current. Thermal Runaway.

Increasing temperature in Figure below (a) will decrease VBE from the nominal 0.7V for silicon transistors. Decreasing VBE increases collector current in a common-emitter amplifier, further shifting the bias point. The cure for shifting VBE is a pair of transistors configured as a differential amplifier. If both transistors in Figurebelow (b) are at the same temperature, the VBE will track with changing temperature and cancel.

https://www.allaboutcircuits.com/textbook/semiconductors/chpt-4/bjt-quirks/

I definitely have just the tonic for your problem involving the bipolar semiconductor. All that is needed is a compound consisting of an ointment containing a base petroleum used as a vehicle mixed with powdered Lithium. Just apply liberally as a conductive paste, I am sure that you'll feel fine!

 

[FULL_MEDIC]

Hello Stephanie! No reason to let him have all the fun.

Steph sez , and I quote "anyone that sits for days on end with a giant lollipop sized mic is missing a few transistors for sure!

 

[FULL_MEDIC]

When someone has loosened the mounting hardware on those transistors. It means several things.

One, they swapped in part to "try and see if it works"

Two - the radio may work with them in, so let's push it off to someone else that can take care of this.

Three - the radio is toxic...

Toxic means it's been exposed to and worked on by other people that don't know what they are getting into - and now it's transferred over to you.

It's like a patient that was in for a simple appendectomy - has now turned into a bleeder that needs a crash cart and 2 liters of blood to replace what the darn triage trainee left for you to fix. The Anesthesiologists just went outside for a cigarette and your left with a mess and nurses that are looking for a trash can to lose their cookies in...

Good luck Doctor.

Someone once asked me . . . Are you better at putting bullets in people, or getting them out!

 

[FULL_MEDIC]

Someone once asked me . . . Are you better at putting bullets in people, or getting them out!

You see the answer is rather simple. . . . "BOTH" Now lets see who will figure out the riddle first?

 

[FULL_MEDIC]

Well in the voice of James Earl Jones, “just what is it that we still never know”?

Is it that each of those is 40w so you’re thinking together you’ll end up with 80w? Ain’t gonna happen brother, so you’re not gonna get your moneys worth. What exactly are you expecting from them, you’ve never said I don’t think?

I think what you’re gonna do is butcher a radio and in the end have one that works just about the same as it does now or won’t work at all. Is it worth that? Not to me. Been there, done that.

But in the words (more the voice) of Bobby Boucher’s momma...”you go have fun playing the foosball with ya friends”. Or in your case, putting your finals in your radio. Good luck.
I never rely on luck VADER. . . But you might be right I am far superior with a scalpel than a soldering rework station!


View attachment 26241

 

[FULL_MEDIC]

Well in the voice of James Earl Jones, “just what is it that we still never know”?

Is it that each of those is 40w so you’re thinking together you’ll end up with 80w? Ain’t gonna happen brother, so you’re not gonna get your moneys worth. What exactly are you expecting from them, you’ve never said I don’t think?

I think what you’re gonna do is butcher a radio and in the end have one that works just about the same as it does now or won’t work at all. Is it worth that? Not to me. Been there, done that.

But in the words (more the voice) of Bobby Boucher’s momma...”you go have fun playing the foosball with ya friends”. Or in your case, putting your finals in your radio. Good luck.



View attachment 26241

Besides Vader. . . . . . If I thought that way I would have bought a dozen MRF 497's

 

[FULL_MEDIC]

Time for dinner and some. . . . . . . . .

 

[Tallman]

Dag nab it! It's no fun when the O.P. hijacks his own thread. You're gonna fit right in here with the rest of the patients. Now take your meds and have a nap.

 

[loosecannon]

FULL_MEDIC,

if you got them from RF parts, then they are the real deal.
90 bucks! ouch!

Remember that the emitter and collector on your MRF497's are switched around from the way they are on the stock finals. (2SC2312's)
you will need to bend those two pins in order to accommodate the new pinout.
be sure to put some heat shrink tubing on the middle lead to prevent any accidental shorting.

you will also need to re-set the bias after your parts change.
LC

 

[SIX-SHOOTER]

ARRL = Amateur Radios Real Losers.A useless bunch of money & power hungry clowns.Stay far far away from them & hold onto the money in your pocket or they will do everything possible to get their greedy hands on it to support some other useless cause.

SIX-SHOOTER