President Jackson without final

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rocketry23
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President Jackson without final

Post by rocketry23 »

Hello!

Can somebody help me get this Jackson back to life? :) I got this radio without the final transistor.

I checked the voltages on the driver and the final pads.

Final: Rx: 13.8V, 0V, 0V. Tx_ 13.7V, 0V, 0.91V.
Drive: Rx: 0V, 18.8V 0V. Tx 0V, 13.7V, 0.67V.
jacksonfinal.jpg
I don't see any missing components except the final transistor.

What else sould I check before installing the new one?

I have a spare SD1487 transistor what is a replacement for MRF455. Can i drop it in without any other mod?
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Re: President Jackson without final

Post by 14CS06 »

Hello

What is your PCB PB-042 A?

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Re: President Jackson without final

Post by rocketry23 »

It is a PB 042 AB
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Re: President Jackson without final

Post by 4a0026aleks »

Hello for President Jackson very well suited Soviet transistor kt920v . КТ920 В
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Re: President Jackson without final

Post by Black Spirit »

Final should be a MRF477 which are hard to find and genuine ones are expensive, A 2SC1969 will work just fine if the Collector and Emitter are crossed over [They can be crossed easily without it looking messy], What driver is that as it dont look right to me.
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Re: President Jackson without final

Post by cb4ever104 »

Black Spirit wrote: 06 Jan 2020, 12:16 What driver is that as it dont look right to me.
I was going to say that too . The screw isn't original , and the insulator looks new . To be honest the whole final stage looks to have been worked on . There's new resistors , capacitors and VRs .
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Re: President Jackson without final

Post by rocketry23 »

It is a 2sc2166 driver there. I can measure 70mA bias on that, but cannot get it lower. Is it safe to put in a new final or should I check something else?
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Re: President Jackson without final

Post by cb4ever104 »

rocketry23 wrote: 06 Jan 2020, 13:23 or should I check something else?
You should be checking that whole bias circuit .

Check R239 , VR10 , and R241 . Also . Remove the MV1Y and stick a 1N4001 diode across the 2166 , at least for testing purposes in case that's faulty .

Sammy
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Last edited by cb4ever104 on 06 Jan 2020, 13:49, edited 1 time in total.
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Re: President Jackson without final

Post by 4a0026aleks »

here YOU have instructions on how I put the transistor кт920в President Jackson. unscrewed the black radiator. then he drilled a hole under the transistor leg. screwed it down ... two output Emitter connected and soldered to the middle of the PCB and the legs and base leg of the reservoir cut and short copper wire SEPA respectively in its place. then the black radiator drilled with a thick drill bit place the nut of the transistor ( but not through)
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Re: President Jackson without final

Post by Black Spirit »

The driver to me does not look like a genuine Mitsibushi it looks like a fake [To me it does, I am not saying it is, The MV1Y appears to be missing which is probably why you cant get the bias right, As mentioned above use an 1N4001 [banded end to ground] and then see if bias will set correctly, You will also need to install a 1N4001 for the final too, It does look really messed up in there.
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Re: President Jackson without final

Post by 14CS06 »

Hello

From https://spectrum26.pagesperso-orange.fr/

1. CHECKING and REPLACING MRF 477 GRILLE and setting the JACKSON quiescent current
1) Check that your transistor driver type 2SC 2166 is not HS because it is quite fragile and it would be silly to replace an MRF 477 for nothing
For that you have several solutions, check the presence of HF on its collector with an HF probe or check its junctions with a simple ohmmeter (not very reliable).

2) If your driver is OK we continue (no need to go further if you are not sure!).
3) The destruction of the PA transistor on a JACKSON often leads to the destruction of other components (do not forget that the PA works in class A = that is to say in linear).
4) Before replacing this one, check the following points:
5) Check the adjustable resistor VR9 (100 ohms) = OFTEN CUT
- Check the resistance R237 (10 ohms) = OFTEN CUT
- Check the capacitor C183 (10 PF)
- Check the capacitor C184 (270 PF)
- Check the special diode (probe) which is stuck on the MRF477 and replace it if necessary with a 1N4148 (this is not ideal but you have no choice because for a private individual find a temperature probe c ' is almost impossible).
Now you have the choice or replace the original MRF 477 if you are lucky enough to have a spare (NOT FOUND to date or at a price approaching the price of TX!). (
The other solution is to put a 1969 2SC transistor in its place:
Many things have been written on this subject such as the crossing of the legs; no need if you follow my advice!
ATTENTION VERY IMPORTANT (it has never been said on other sites!).
Please put an isolation mica behind your 1969 2SC.
Why ?
Simply because the old transistor had its transmitter (center leg) connected to the radiator = no risk because a class A transmitter is connected to the ground of the TX. Here are the two micas insulators (washer & rectangle):

The new one (2SC 1969) has its collector (center leg) connected to the radiator = now it is the collector (powered by + 12 volts) which is connected to the chassis (you now understand the IMPORTANCE of the insulation of that -this ).

The transistor is fixed and its insulation checked at ohmmeter we can continue!
On my two attached photos I put POINTS of colors on the legs of the different transistors and on the welding points on the printed circuit board:

GREEN = BASE
BLUE = TRANSMITTER
RED = COLLECTOR

You just have to solder the legs of the 2SC1969 on the right colors and you will quickly understand that it is not useful to cross its legs because the manufacturer has provided a transmitter output (in blue) in the center and at left of its printed circuit board!
Now (contrary to what some people claim) you have to adjust the quiescent currents of the DRIVER and PA.
To do this, go to channel 19 in USB mode
MIC gain at ZERO = important.
Remove the PA / DRIVER supply plate (the small copper bridge in front of the output stages).
Connect an ammeter between TP8 and TP6 set VR10 (left) to obtain a current of 80 MA. (Driver quiescent current).
Connect an ammeter between TP8 and TP7 set VR9 (right) to obtain a current of 35 MA (PA quiescent current).
These average values ​​can be refined if you have an oscilloscope to view the output signal:
These settings are made in BLU carrier (especially do not speak into the microphone during the tests!).
IF IMPOSSIBLE to have this range of settings = VALUE MUCH TOO HIGH (style more than 500 MA) it is that you either have the diode plated on the burned transistor or the adjustable potentiometer RV9 of value 100 ohms out of use because track cut!
Replace the power board that has gone into AM mode with the mic / gain at max.
Set the AM power by VR11 to 8 Watts max for a 2SC1969 otherwise modulation overwritten.
Same in SSB position on modulation tip (whistle) adjust with VR8 the power to 20 W PEEP max.
Set VR12 for 92% modulation rate in AM
FM deviation (modulation rate) is set by VR4.
Calibrate your S / Meter in emission with VR7 (red zone limit).
If OK we continue the alignment:
Check the CARRIER VR5 potentiometer carefully = adjust it to have the least possible emission in SSB (without microphone signal of course) = in principle it is in the middle of its travel.
This potentiometer is in the center of the TX (width direction) and just behind the integrated circuit IC3.
I give you the exact text of the manufacturer for this adjustment.
Carrier setting on Jackson (CARRIER)
Set VR5 to obtain minimum carrier wave elimination without modulation for USB and LSB modes

I REPEAT anyway that replacing a MRF 477 with a 2SC1969 greatly decreases the performance of the TX (who can do the most can the least but not the opposite!)
This is especially true in BLU this remark!

Here are photos to better explain the transformation to you:
1) difference between MRF 477 and 2SC1969
green = base
blue = transmitter
red = collector

Image

2) location on the plate without crossing the legs (just solder the legs on the right colors)

Image

And as a last resort if you can replace the MRF 477 with the new PB 335AA turntable (as on the last JACKSON)

Image

Image

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Re: President Jackson without final

Post by cb4ever104 »

Black Spirit wrote: 06 Jan 2020, 14:33 The MV1Y appears to be missing
Never noticed that Nick :) Saying that , I would have expected the current to be off the charts without it .

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Re: President Jackson without final

Post by rocketry23 »

OK, i checked everything. That c2166 was a FAKE one. I dropped in a spare original, i used a 1N4007 to replace missing MV1Y, now it can be set to 50mA.
fake2166.jpg
Great, I want to drop in my SD1487 what is a replace for MRF455, but what are that components on that PB 335AA? Is that a 220ohm resistor? And the other 2? Is there anything on the other side of that pcb?
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Re: President Jackson without final

Post by cb4ever104 »

rocketry23 wrote: 06 Jan 2020, 15:34 Great, I want to drop in my SD1487 what is a replace for MRF455, but what are that components on that PB 335AA? Is that a 220ohm resistor? And the other 2? Is there anything on the other side of that pcb?
Seems like a lot of work but just a little more power . Why don't you look for a MRF477 , or just use a 2SC1969 instead ?
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Ex GM0 , now EA5 .
Handle "Fortune Hunter" back in "the day"
Radios ....? Anything that says "TAIWAN R.O.C" on the back.
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Re: President Jackson without final

Post by rocketry23 »

cb4ever104 wrote: 06 Jan 2020, 19:03 Why don't you look for a MRF477 , or just use a 2SC1969 instead ?
It is hard to find even a 2SC1969 in Hungary.... :( Maybe if you can link me a trusted seller on ebay?
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