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View Full Version : Pics of my JTM45 and 1986 clones

samwheat
12-26-2007, 06:16 PM
I just need to bias both.

Board is Hoffman amps style and both have a PPIMV.

I finished the JTM45 today and I'd say I have 16 hours in it. Tubes are GEC and Brimar CV4004's. Iron is Marstran.

The 1986 is less because the chassis is a Laney Pro Tube 50.

Anyway, here they are:

http://s49.photobucket.com/albums/f252/samwheat/Marshall%201986%20Clone/ (http://s49.photobucket.com/albums/f252/samwheat/Marshall%201986%20Clone/)

http://s49.photobucket.com/albums/f252/samwheat/Marshall%20JTM45%20Clone/ (http://s49.photobucket.com/albums/f252/samwheat/Marshall%20JTM45%20Clone/)
TheAmpNerd
12-27-2007, 01:54 AM
Looking good.

The only thing I would start to do is make some of the leads
from the pots longer, etc. You want to make sure of two things,

1. There is no stress on them.
2. That is enought service room to move and clip an end
point or two down the road a piece.

Have fun, learn, and make good tone.
HCStraub
12-27-2007, 07:30 AM
Looks good.
My only advise would be to put the grid stop resistors RIGHT ON THE TUBE SOCKET. Between pins 5/6 on the power tubes. Those are there to reduce oscillations, being up on the board doesn't achieve that. It will help keep the amp quieter and more stable.
If you haven't fired them up yet, make sure to use a current limiter the first time....may save you some blowups.
Good luck with them.
donnyjaguar
12-27-2007, 10:47 AM
Nice! Sounds bytes required when complete. :)
samwheat
12-27-2007, 12:21 PM
what should the neg voltage be on the bias for the initial setup?

after that i'll measure plate current
HCStraub
12-27-2007, 05:05 PM
what should the neg voltage be on the bias for the initial setup?

after that i'll measure plate current

Should be around -45v with tubes in it.......good starting point assuming it is a stock 45.

Be careful if you haven't fired it up yet........