Problem With Transformer transplant

chazo64

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Hey guys a quick q for yall .I got a 15watt transformer for my 5f1 and after installing it my 5f1 after it warms up makes a squeal and thats it not a real loud squeal but one that doesn't seem to respond to increase or a decrease in the volume no smoke no fuse blow I haven't changed anything except the transformer . So logic tells me put back the old trans former and see what happens if it works send the new one back and replace it but mabey i am am not doing something correctly
 

thechad

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Hey guys a quick q for yall .I got a 15watt transformer for my 5f1 and after installing it my 5f1 after it warms up makes a squeal and thats it not a real loud squeal but one that doesn't seem to respond to increase or a decrease in the volume no smoke no fuse blow I haven't changed anything except the transformer . So logic tells me put back the old trans former and see what happens if it works send the new one back and replace it but mabey i am am not doing something correctly

Do you have pictures of what you did?
 

chazo64

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If it was the OT, Switch the B+ and Plate wires (usually red and blue)
Hey bro you mean reverse the red and blue so attach the blue wire to #1 b+at cap and the red to #3 pin on my 6v6 which is the opposite of how the other trans former was hooked up?? just double checking I really dont want to cook my champ!!
 

chazo64

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I mean this should just be a no brainer right I took my Classic tone 40 18115 out and installed the 18031 red wire to b+ blue wire to#3 power tube red #8 rectifire green and black 8ohm tape off remaining wires yellow and purp on the primary side I do have a left over brown wire that Dave had marked n/c i taped that off as well. So I supose I will switch the transfors and see what happens.
 

guitar_paul1

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Since the output winding is floating it should be possible to merely reverse the phase of the output by swapping wires.

Shouldn't hurt anything.
Worst it can do is squeal worse if they were phased right the first time, according to the schematic I looked at.

(In which case look elsewhere for the problem.)

Don't leave it howling too long if it's worse.
Is the feedback resistor 22k in your build?
 

Lowerleftcoast

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I mean this should just be a no brainer right I took my Classic tone 40 18115 out and installed the 18031 red wire to b+ blue wire to#3 power tube red #8 rectifire green and black 8ohm tape off remaining wires yellow and purp on the primary side
https://s3.amazonaws.com/tubedepot-com-production/spree/attached_files/40-18031.pdf?1487778103

https://s3.amazonaws.com/tubedepot-com-production/spree/attached_files/40-18115.pdf?1487778103

Have a look at the two. The dots are reversed on the transformers. Red = Blue in this case. They got you good... didn't they?
 
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chazo64

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Yep that threw me off but all better that worked just fine ...but I dont like how the amp sounds now ......so I started checking some voltages...from left to right o n a boot hill 5f1 no mods (other than the tranny) voltage as follows 401,337,292,21.2,1.5,187,198,1.48.....so as yall know all but a couple are high . How about some feed back verbal not ...ya know
 

Lowerleftcoast

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What DC resistance did you measure on the primaries of each OT?

We might assume the 40-18031 has more bass capability. It is rated for 70mA where the 40-18115 is rated for 50mA.

Just to confirm... you are using a 4 Ohm speaker? On the yellow tap?
 




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