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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!

<blockquote data-quote="ExitThirteen" data-source="post: 268371" data-attributes="member: 6878">After doing some research, and a lot of testing, I have successfully done conversions on the upD858 AM/SSB and MB8179 AM/SSB chassis.&nbsp;For these conversions, I used IRF520N&#039;s from International Rectifier. I&#039;m sure you could substitute ERF2030&#039;s if you wanted to do so.&nbsp;For the upD858 chassis (President Washington, Madison, Grant, Cobra 138XLR, 139XLR, etc):&nbsp;Parts you will need:IRF520 (or ERF2030)EKL companion part EN-369FN (You can build your own, too)56K ohm 1/2 watt resistor39pf disc or mica capacitor (Optional, see installation text)&nbsp;Remove old transistor at TR43Remove R179Remove L44Install IRF520 at TR43Install EN-369FN companion part across final, positive side to gate, unmarked side to sourceInstall 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 - .1VRetune TX&nbsp;That&#039;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.&nbsp;MB8719 Chassis conversion (Cobra 148 GTL (old 5 pin side mic), Uniden Grant)&nbsp;Parts you will need:IRF520 (or ERF2030)EKL companion part EN-369FN470pf disc or mica capacitor56k ohm resistorSmall jumper wire68pf disc or mica capacitor (Optional, see installation text)&nbsp;Remove old transistor at TR36Remove L40Remove C149Remove R181Install jumper wire where R181 was removedInstall IRF520 at TR36Install EN-369FN companion part across final, positive side to gate, unmarked side to sourceInstall 470pf capacitor across C152Install 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 - .1VRetune TX&nbsp;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. &nbsp;I&#039;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!</blockquote>

[QUOTE="ExitThirteen, post: 268371, member: 6878"] 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! [/QUOTE]

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