I posted this over at 18Watt.com but if you guys wouldn't mind taking a look as well I'd be much obliged.
Read the 18Watt post for the details, but basically, I built an 18Watt Trem, it sounded AMAZING for a half hour or so, then it got real quiet. Take a look?
Ben
Hammond AO-43 to 18W conversion
Moderators: pompeiisneaks, Colossal
Hammond AO-43 to 18W conversion
"I never practice my guitar. From time to time I just open the case and throw in a piece of raw meat." --Wes Montgomery
Re: Hammond AO-43 to 18W conversion
Ben,
In my Hammond organ iron i got locally like you did the OT was bad so I replacd that and the amp (Allen Hot Fudge w/Nuts) sounds fantastic. The vibrato is fun to hear, haven't had an amp with that for years.
In the 18w post there is no mention of the OT and it may have taken a dump on you just like it probably did with the previous owner that through it out on curbside clean up day. Which is coming soon, see you out there!
Mark
In my Hammond organ iron i got locally like you did the OT was bad so I replacd that and the amp (Allen Hot Fudge w/Nuts) sounds fantastic. The vibrato is fun to hear, haven't had an amp with that for years.
In the 18w post there is no mention of the OT and it may have taken a dump on you just like it probably did with the previous owner that through it out on curbside clean up day. Which is coming soon, see you out there!
Mark
Last edited by M Fowler on Mon Apr 25, 2011 2:53 am, edited 1 time in total.
Re: Hammond AO-43 to 18W conversion
Mark, how would I go about checking the OT? Measure DC resistances? Put a small AC voltage on one side and see what comes out the other?
"I never practice my guitar. From time to time I just open the case and throw in a piece of raw meat." --Wes Montgomery
Re: Hammond AO-43 to 18W conversion
If the amp is up and running you will here it low powered and strange sounding.
Testing by Dynaco:
1. With your multimeter measure the resistance from ALL the primary wires (GREEN, BLUE, GREEN/WHITE, BLUE/WHITE and RED) to ALL the secondary wires (YELLOW, ORANGE, BROWN, BLACK). You should get no continuity or an infinite resistance from any of the primary wires to any of the secondary wires. If you get a low resistance from any combination of ONE primary and ONE secondary wire there is a short in the windings somewhere and that transformer is bad and must be replaced.
2. Measure the resistance from your primary RED wire hanging in the air to the other four PRIMARY wires. You should get readings of about 15 ohms to maybe 200 ohms. If you get an "open" on any measurement the transformer is bad and must be replaced.
3. Measure the resistance from the BLACK secondary wire to each of the other secondary terminals (BROWN, ORANGE and YELLOW). In all cases you should get a very low resistance maybe between .5 ohm and 2 ohms or so. If you get an open and measure nothing then one of the windings is bad. If it is just the 8 ohm tap you might still be able to use your 8 ohm speaker on the 4 ohm tap but IMHO you should replace the transformer.
Testing by Dynaco:
1. With your multimeter measure the resistance from ALL the primary wires (GREEN, BLUE, GREEN/WHITE, BLUE/WHITE and RED) to ALL the secondary wires (YELLOW, ORANGE, BROWN, BLACK). You should get no continuity or an infinite resistance from any of the primary wires to any of the secondary wires. If you get a low resistance from any combination of ONE primary and ONE secondary wire there is a short in the windings somewhere and that transformer is bad and must be replaced.
2. Measure the resistance from your primary RED wire hanging in the air to the other four PRIMARY wires. You should get readings of about 15 ohms to maybe 200 ohms. If you get an "open" on any measurement the transformer is bad and must be replaced.
3. Measure the resistance from the BLACK secondary wire to each of the other secondary terminals (BROWN, ORANGE and YELLOW). In all cases you should get a very low resistance maybe between .5 ohm and 2 ohms or so. If you get an open and measure nothing then one of the windings is bad. If it is just the 8 ohm tap you might still be able to use your 8 ohm speaker on the 4 ohm tap but IMHO you should replace the transformer.
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guitardude57
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Re: Hammond AO-43 to 18W conversion
Benoit,
Of course when testing the OT, do it UN-Powered........... and disconnected from everything to be safe from circuit related influence and Bar-B-Que....................
Of course when testing the OT, do it UN-Powered........... and disconnected from everything to be safe from circuit related influence and Bar-B-Que....................
Mike
I am never surprised and always amazed
I am never surprised and always amazed
Re: Hammond AO-43 to 18W conversion
Don't worry, my hands don't go anywhere near the amp til I've got a bleeder resistor clipped in place and I've measured like 5 times to make sure she's not going to bite meguitardude57 wrote:Benoit,
Of course when testing the OT, do it UN-Powered........... and disconnected from everything to be safe from circuit related influence and Bar-B-Que....................
"I never practice my guitar. From time to time I just open the case and throw in a piece of raw meat." --Wes Montgomery