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5e3 troubleshooting assistance needed
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vulture



Joined: 01 Mar 2008
Posts: 4503
Location: Chicago

PostPosted: Sat Jul 15, 2017 8:51 pm    Post subject: Reply with quote

Shocked Found it.

Determined to find out the problem after all this, went back in with chopstick method and prodded around again. I discovered that the wire off pin1 of the 12ax7 had weakened, not the solder, the wire. I guess the 6th time is a charm. Rolling Eyes

Thanks for helping me out. I guess the good thing was that I tweaked everything and ran some needed tests. Still have to address those areas where the voltages are off.
Cheers
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vulture



Joined: 01 Mar 2008
Posts: 4503
Location: Chicago

PostPosted: Sat Jul 15, 2017 9:10 pm    Post subject: Reply with quote

statorvane wrote:

The dropping resistor there should measure around 22K Ohms.


So its an 8.2k in there now. The cathode resistor is at 330ohms. I replaced it with a 250ohm and it helped drop the voltages off the secondary's on the 6V6's to 364V as opposed to the 380V. I have to get a 22k dropping resistor in there.
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statorvane



Joined: 21 Aug 2003
Posts: 1949
Location: Upstate New York

PostPosted: Sun Jul 16, 2017 3:38 am    Post subject: Reply with quote

Glad you got this sorted out.

It seems whoever had this amplifier prior was interested in much higher preamp voltages. Not sure why.
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Johnson82



Joined: 27 Aug 2007
Posts: 1733
Location: New Castle, IN

PostPosted: Mon Jul 17, 2017 8:54 am    Post subject: Reply with quote

Excellent! Nothing like having a problem sorted out!
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vulture



Joined: 01 Mar 2008
Posts: 4503
Location: Chicago

PostPosted: Sat Aug 05, 2017 5:31 pm    Post subject: Reply with quote

Got the 22k dropping resistor in there and helped some of the voltages, while I was at it I decided to have some modding fun.

The amp was already modded with MV which is great. Decided on switching things a bit. Thanks to Rob Robbinet I modded in a NFS, and added a cascade lead channel. I had swapped out the coupler caps (.022) in the past to dump some of the bass and man does this thing shake and shine now.

The other thing I did was add a switch to the V2 cathode cap(changed to a 1uf) to switch it out for ultra clean. The 1uf cap in conjunction with the cascade channel drives it into sweet Marshall Territory.

I decided that the ultra clean wasn't what i was after so I ended up throwing a .22uf fixed cathode cap back into the V2 as to throw a little more dirt in the clean. This alone with the cascade channel delivers some good 5e3 grit. Throw on the 1uf and it parallels the .22uf for some fantastic heavy gain territory.

And last was place a DPDT switch on the bright cap with a larger cap to dump a little more 5e3 bass into this when needed. Really takes well to pedals as well

Everything else is stock. It is a very very versatile amp.
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