MOSFET conversions for upD858 and MB8719 boards

[psycho]

lol, to each their own. But you should just get used to it. Transistors are on their way out

Not a problem....I bought 6 new 1969s 1 year ago. It's hard to blow a 1969 unless someone running a 1000 watts keys up right next to you.

 

[Robb]

STEP-BY-STEP IRF520N MOSFET CONVERSION...CYBERNET EXPORT- PTBM059C0X. - YouTube

 

[liquidh8]

Bump just because we are still waiting on pictures! lol :redface:

 

[TIN_CAN]

Same write up to the T that RadioNut from the east coast of Canada did...so who did this???

MOSFET conversions for upD858 - UPDATED

After doing some research, and a lot of testing, I have successfully done conversions on the upD858 AM/SSB and MB8179 AM/SSB chassis.

For these conversions, I used IRF520N's from International Rectifier. I'm sure you could substitute ERF2030's if you wanted to do so.

For the upD858 chassis (President Washington, Madison, Grant, Cobra 138XLR, 139XLR, etc):

Parts you will need:
IRF520 (or ERF2030)
EKL companion part EN-369FN (You can build your own, too)
56K ohm 1/2 watt resistor
39pf disc or mica capacitor (Optional, see installation text)

Remove old transistor at TR43
Remove R179
Remove L44
Install IRF520 at TR43
Install EN-369FN companion part across final, positive side to gate, unmarked side to source
Install 56k ohm resistor from IRF520 gate to L31 (goes to far side of L31, furthest away from final, +13V)
Install 39pf capacitor across C167 (This is optional, will bump up output in some units, test radio without first)
Check voltage at gate of final, should read approx. 3.65V + or - .1V
Retune TX

That's it! Double check your work, and you should have the same output if not more than the old stock transistor. My President Washington did about 22W on SSB before, with the MOSFET in place, it now does 27W on SSB.

MB8719 Chassis conversion (Cobra 148 GTL (old 5 pin side mic), Uniden Grant)

Parts you will need:
IRF520 (or ERF2030)
EKL companion part EN-369FN
470pf disc or mica capacitor
56k ohm resistor
Small jumper wire
68pf disc or mica capacitor (Optional, see installation text)

Remove old transistor at TR36
Remove L40
Remove C149
Remove R181
Install jumper wire where R181 was removed
Install IRF520 at TR36
Install EN-369FN companion part across final, positive side to gate, unmarked side to source
Install 470pf capacitor across C152
Install 56K ohm resistor from IRF520 gate to L39 (Goes to far side of L39, furthest away from final, +13V)
Install 68pf capacitor across C146 (This is optional, will bump up output in some units, test radio without first)
Check voltage at gate of final, should read approx. 3.65V + or - .1V
Retune TX

There you have it! Again, double check your work, and you should have at least the same output as the old final, if not more. My Grant XL barely did 18W before this conversion, now it does about 24W.

I've have excellent audio reports back after doing several conversions on both these chassis, so I think I have these fine-tuned. Good luck and have fun!

 

[Zman]

Just like tubes the transistors are going the way of the dinosaur. Either get used to the new mosfets and SMT or get out of the hobby.

 

[Zman]

POO POO ON YOUR MOSFETS

Thats what you will be saying when you can no longer get ANY 1969s, 1307s, 2166, 2312, ect ect....... Youll be saying poo poo on the old finals!

 

[psycho]

lol, to each their own. But you should just get used to it. Transistors are on their way out

Mosfets are transistors.
I have 6 1307s, 6 1969s, and 7 2166s that I bought from RF parts a quite a few years ago. POO POO on mosfets.
I will try that mosfet conversion with a beat up but damn good working Cobra 148 I bought on craigslist.

 

[Zman]

This is a cool mod. I did it in my TRC 449 and im getting 25 PEP on AM and about 30 or so on SSB... Im going to do it to my TRC 458 and Cobra 139 both of which have bad finals.

 

[9C1Driver]

Just like tubes the transistors are going the way of the dinosaur. Either get used to the new mosfets and SMT or get out of the hobby.

I think it's nice to have this option for a broken radio. That said if your radio is working fine there is no point doing the mosfet conversion. Good to keep in mind if something goes wrong down the road.

 

[ExitThirteen]

I think it's nice to have this option for a broken radio. That said if your radio is working fine there is no point doing the mosfet conversion. Good to keep in mind if something goes wrong down the road.

You nailed it. That's why I posted this, it gives people another option. I did the MOSFET mod on my President Washington (D858) because at the time, I didn't have any spare C1307's. I have several C1307's now, but since the mod is still 100% functional in my Washington, I never bothered to change it back to run the C1307 final.

Tin Can, that mod that you posted came from me. Someone copied it and reposted it on a different website.


~Cheers~

 

[unit_399]

Hey Thirteen -

Did you ever get the C1306 driver to Mosfet conversion worked out ?? Just wondering.73s.

- 399

 

[ExitThirteen]

Sadly, no... I haven't had a lot of free time as of late, been working 7 days a week... it's the new work week these days in my profession.


~Cheers~

 

[unit_399]

In today's economy, it's called, "Doing what you have to do to get by." 73s.

- 399

 

[Zman]

REAL (NOT FAKE!) 1307 finals are too hard to come by so this is a great conversion!!!!

 

[Zman]

I recently tried this mod in my Cobra 148 GTL old style and immediately fried the final choke as soon as i hooked the radio to the 12 volt power cord....