1959 Lowrey organ amp conversion

[Cygnus X1]

See post #2 in this thread.

[gayler]

Ok, so I started a thread about 6V6 based amps so I thought I would pull this one out again. This thing has 385VAC on each leg on the trany and around 512VDC At the can cap with a Sovtek 5Y3. With the 5u4gb in it I had a snap and spark at I think the can cap that did not happen without it in place so I pulled it out and the locating tab broke off so I don't know if it somehow got put in wrong or something.

[baddog]

Test your transformer leads again to see if you did any damage. Did you have a speaker conected to the amp while you Pwhere testing it? You could always throw the tube back in and make sure it's lined uP wright. It might be ok. What's your your plan for the amp?

[gayler]

No damage done. I did't have power tubes in it because I had no speaker. Don't know what I want to build. Any suggestions?

[baddog]

I've built a matchless spitfire with a lowery organ amp and it sounded pretty good. Could build any lower watt 6v6 or el84 amp .

[gayler]

This one uses 6L6 tubes. I also have a thread on a 6V6 Gt amp Sorry for the confusion. Gayler

[gayler]

Ok, so I put in a sovtek 5y3gt two 6l6's, plugged in a p10q and warmed it up with no input. It had normal to slightly loud hum in the speaker. I forgot to try turning the hum balance. After it wrmed for about three minutes it would periodicaly get fairly loud, more like a buzz for about a second at a time. I plugged the lineout of another amp into the input and no sound when strumming. After about another minute it blew the fuse. What are your thoughts? Maybe a filter cap?

[Cygnus X1]

First wild guess is unstable bias.
Double check all of your connections.

[baddog]

All of those elecrolyitics are crap as far as I'm concerned , Including the cap can. . 512v at the first filter stage seems a lilittle high with a 5y3 hmmm. Have you built an amp yet or would this be your first one?

[gayler]

I figured the caps were crap. This 5y3 is a sovtek which i've heard gives higher voltages than a "real" 5y3. All connections are good so I don't think I have a problem there. This is an unmollested organ amp, so no changes other than adding a three wire cord and a power switch. Oh crap, I just realized I didn't have the phase inverter in when I checked this so probable why no sound although it wouldn't acount for the blown fuse. I still think it was a bad cap.

[virgilvdog]

How did you jump it from where to where. I am lost.

[baddog]

To power up your amp you need to have a speaker connected to the output transformer. The power transformer should have 2 black wires that power the amp and one should be connected to a fuse. If you connect those two wires to 120v power your amp should power up. Can you read a schematic?

The black wires on a power transformer are usually where the 120v wall power connects to the amp.

[Ran Randle]

I have the EL34 version of this same amp, its pretty cool. For the testing I installed a volume pot and wired it to the RCA input from the 6SN7 phase inverter tube. Installed a IEC socket and used two 8ohm cabinets for a 4ohm load since the OPT only has a 4ohm tap. It is low volume as is with no preamp but I tried a mesa v twin pre in front of it and it sounds pretty damn good but still not that loud but this was just for the testing to make sure it at least worked before getting into converting it into something like a 50 watt plexi. Many possibilities for HiFi use if you can find a pair of them. http://music-electronics-forum.com/t26713/