FETRON MKI Removal

[FreeFormFunkified]

Hey guys, new guy here needs some help changing out the fetron in V1 to 12AX7, its a '77 MKI HRG and does not have a switch to change between the two like other early MKI's. THe guys at Boogie say its a simple "remove and Replace" BUT the maintenance manual says theres a few things that have to be done to make it work at top spec. Has anyone done this before? Im confident I could solder just dont know what to look for, I dont know jack about resistors, caps values etc... lol Im talking pictures of HOW TO DO, or point me the right direction. :? Thanks

 

[Boogiebabies]

If you have Microsoft Power Point, I have instructions and photos to do the upgrade.

 

[FreeFormFunkified]

Thanks for the reply Boogiebabies, I currently have microsoft office exel 2007 but not power point but ill try to post a couple pics and maybe you can explain to me what im seeing

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[FreeFormFunkified]

just discovered I DO have power point

 

[FreeFormFunkified]

Heres a couple pics of VI from the insidehttp://i1125.photohttp://i1125.photobucket.com/albums/l599/Boogsandreeds/IMG-20110430-00098.jpgbucket.com/http://i1125.photobucket.com/albums/l599/Boogsandreeds/IMG-20110430-00097.jpgalbums/l599/Boogsandreeds/IMG-20110430-00096.jpg

 

[Boogiebabies]

Please PM me your e-mail address.

 

[FreeFormFunkified]

Please PM me your e-mail address.

Thanks for the pics, well what Ive gathered so far is that at pin8 and pin3 the "IN5302" j-fet will be replaced by 1.5K 1/2 watt cathode resistors, but its unclear what to do with everything with the green arrows ie; the 33K zeners going to ground at pin3 do they need to be removed? Im still doing the research but a little confused! Im going to open up MKI reissue and do an A/B :idea:

 

[stokes]

Contact Boogiebabies,like he said.You wont be confused anymore.

 

[FreeFormFunkified]

If you have Microsoft Power Point, I have instructions and photos to do the upgrade.

Boogiebabies I did get your photos but im not pulling up any instructions or text thru the microsoft power point and IM SURE its just me not knowing how to use my own stuff

 

[FreeFormFunkified]

Contact Boogiebabies,like he said.You wont be confused anymore.

yes ive been in contact with Boogiebabies and recieved some great photos but no text or instructions but I am still a NOOB at this

 

[Boogiebabies]

I thought you had the schematic. It states to change the 62K plate resistors to 100K. Change the two 1N5302's and replace with 1.5K resistors.
On the schematic it states that the 33K B+ rail dropper resistor could be between 15K-33K. You can leave it or tune it by ear. Lastly, make sure the
100K to ground off the preamp B+ rail is good. This is where the 60uf cap on the preamp board gets drained when you turn off the amp.

 

[FreeFormFunkified]

I thought you had the schematic. It states to change the 62K plate resistors to 100K. Change the two 1N5302's and replace with 1.5K resistors.
On the schematic it states that the 33K B+ rail dropper resistor could be between 15K-33K. You can leave it or tune it by ear. Lastly, make sure the
100K to ground off the preamp B+ rail is good. This is where the 60uf cap on the preamp board gets drained when you turn off the amp.

Thanks Boogiebabies, that is a great help and I appreciate your patience bud, I have a very special MKI belonged to the late and great guitarist Tommy Crain of the "Charlie Daniels Band", so I want to do this "right" and "once" if you get my drift, Thanks again brother U THE MAN!!

 

[FreeFormFunkified]

Shipped off to Mesa for a complete service, Thanks very much for the input guys!