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  #1  
Old 05-04-2012, 08:55 PM
tapeup tapeup is offline
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Bassman Output Transformer Replacement questions

Hello, I've searched for this, and haven't quite found the information I'm looking for yet. Maybe some people here can help.

I have a '66 Bassman head that was acting up, and upon taking it to a tech, I found out it had a replacement output transformer in it that was not the correct replacement for this amp, which was causing the amp to run improperly, and needs to be replaced.

My question is, which company and which model transformer is ideal? I've read lots of back and forth debate over whether or not it's worth it to spend extra money on Mercury Magnetics transformers, and I don't know what to believe. Can anybody steer me in the right direction so I can get this amp back in playing condition again?

Thanks for any and all help, I appreciate it! Cheers!
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  #2  
Old 05-04-2012, 09:18 PM
wyatt wyatt is offline
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Normally, I would go for an Allen, but they don't make offer anything above 40 watts. So I recommend ClassicTone...they offer a straight Bassman Head replacement...model 40-18011. Otherwise, Mojotone.

Mercury makes a great product, but you get nothing extra for the extra cost versus ClassicTone, Allen, Mojo, etc.
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  #3  
Old 05-04-2012, 09:28 PM
Hwoltage Hwoltage is online now
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Quote:
Originally Posted by tapeup View Post
Hello, I've searched for this, and haven't quite found the information I'm looking for yet. Maybe some people here can help.

I have a '66 Bassman head that was acting up, and upon taking it to a tech, I found out it had a replacement output transformer in it that was not the correct replacement for this amp, which was causing the amp to run improperly, and needs to be replaced.

My question is, which company and which model transformer is ideal? I've read lots of back and forth debate over whether or not it's worth it to spend extra money on Mercury Magnetics transformers, and I don't know what to believe. Can anybody steer me in the right direction so I can get this amp back in playing condition again?

Thanks for any and all help, I appreciate it! Cheers!
You should also engage your tech in this conversation. All the different transformer makers vary a few things here and there, but aside from having a transformer with enough sheer bulk (iron dimensions) to support the low end without crapping out, the most important thing is to have the correct impedance ratio for the amp's particular speaker load, tube configuration, and *desired* bias setting.

If your tech knows why the transformer is "wrong" he should know what is "right" and will be capable of steering you in the right direction.
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  #4  
Old 05-04-2012, 09:55 PM
3th3r 3th3r is offline
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The Mojotone 774 OT is made by Heyboer, which IMO are a great value -- great sound at a reasonable price.
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Old 05-05-2012, 03:34 AM
gldtp99 gldtp99 is offline
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I'd use the Classic Tone upgrade BF Bassman-type OT: http://www.classictone.net/40-18001.html
I've used this OT in many builds and replacements---a superior sounding OT at a great price--- my own BF Bassman runs one of these--- 4/8/16 ohm output taps make running almost any speaker cab a breeze..............gldtp99
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  #6  
Old 05-05-2012, 11:10 AM
zzmoore zzmoore is offline
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I am just curious.
Almost nothing in a tube guitar amp follows spec.
What OT is/was in your amp that was causing these problems.? Or was it more than just the OT.?
Best
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Old 05-05-2012, 03:16 PM
guiltless guiltless is offline
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Quote:
Originally Posted by gldtp99 View Post
I'd use the Classic Tone upgrade BF Bassman-type OT: http://www.classictone.net/40-18001.html
I've used this OT in many builds and replacements---a superior sounding OT at a great price--- my own BF Bassman runs one of these--- 4/8/16 ohm output taps make running almost any speaker cab a breeze..............gldtp99
+100

Using this one as well. Sounds great!!!
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Old 05-06-2012, 04:49 PM
tapeup tapeup is offline
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Thanks for all of the replies so far guys. I appreciate the help!


Quote:
Originally Posted by zzmoore View Post
I am just curious.
Almost nothing in a tube guitar amp follows spec.
What OT is/was in your amp that was causing these problems.? Or was it more than just the OT.?
Best
I don't have the notepad in front of me from where I wrote down all the information from the conversation I had with the tech, but from what I remember, the transformer that was in the amp was a tweed bassman replacement, and it was causing the plate voltage to be way too high. Does this sound like a possibility?
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  #9  
Old 05-06-2012, 05:44 PM
Hwoltage Hwoltage is online now
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Quote:
Originally Posted by tapeup View Post
Thanks for all of the replies so far guys. I appreciate the help!




I don't have the notepad in front of me from where I wrote down all the information from the conversation I had with the tech, but from what I remember, the transformer that was in the amp was a tweed bassman replacement, and it was causing the plate voltage to be way too high. Does this sound like a possibility?
You need to know thew exact make and model of the transformer that is in your amp. From that you will be able to find the impedance specifics and determine if it is in fact the wrong transformer.l

Does the secondary have multiple taps (4, 8 16 ohm etc)? If so make sure the correct tap is being used for the particular speaker load you are using.

Assuming both Bassman versions are two tube 6L6 push pull-amps the transformers *shouldn't* differ much. For example, the Hammond Tweed replacement has an impedance of 4200, the '59 has 4150 and the "Bassman" is 4000.

http://www.hammondmfg.com/guitarLineOT.htm

This impedance coupled with the speaker load is what reduces the voltage (although very slightly) through the transformer, which is why I say to check that the proper tap is being used as this will either lower or raise the impedance from the proper specs.
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Quote:
Originally Posted by DustyRhodesJr View Post
One person was faced with the daunting proposition of
choosing between hair plugs and a nice tube amp.

Luckily, thru this forum he found out about the Bosley
Medical pay plan, so he was able to do both.
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  #10  
Old 05-07-2012, 01:23 AM
walterw walterw is online now
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not an amp tech here, but wouldn't the "tweed" version want to see a 2Ω speaker load?

maybe that's the problem.

anyway, +1 to classictone trannys; i had the Magnetic Components blackface bassman OT installed in my early '70s pro reverb (the straight-up 4Ω one, not the one with multiple taps) and it turned that amp into a monster.
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  #11  
Old 05-30-2012, 03:47 PM
tapeup tapeup is offline
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I have a slight update to the situation, but an important piece of information nonetheless.

It is the power transformer that had been replaced with an improper unit at some point, not the output transformer.
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  #12  
Old 05-30-2012, 05:17 PM
Chris Scott Chris Scott is offline
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Quote:
Originally Posted by tapeup View Post
I have a slight update to the situation, but an important piece of information nonetheless.

It is the power transformer that had been replaced with an improper unit at some point, not the output transformer.
Mojo 762

...about $69. last time I checked. It's a Heyboer as well...
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  #13  
Old 05-30-2012, 05:25 PM
tapeup tapeup is offline
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Okay awesome, thanks for the quick reply Chris! I appreciate the help!

I see you're in Jaco, how's the surf been lately? I haven't been to Costa Rica in way too long!
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