Hi all,
I just discovered this site after toying with the idea of building my own Trainwreck clone. I've decided to use schematic Version A4 for my build. I have been ordering parts and I have a question regarding the Power Transformer: Version A4 calls for a PT with a bias tap. Would a Fender Super Reverb PT (022798) work for this application or do I need to look elsewhere?
Thanks in advance for your help. It seems like the wealth of knowledge here is pretty huge and I look forward to building this amp and sharing my findings.
Rick
Newbie has PT question
Moderators: pompeiisneaks, Colossal
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ricks57custom
- Posts: 32
- Joined: Tue May 10, 2005 6:27 pm
- Location: Scottsdale, AZ
Re: Newbie has PT question
The highest tap (there are two HV taps on the heyboers) is 300-0-300 -- so anything in that range plus or minus a few volts should be copacetic. I don't know the specific ratings of the tranny you listed, but I'm sure they're out there someplace. I hadn't even realized Fender trannies had a bias tap.
Also, don't be scared of using one of the other schematics' bias methods. The voltage is what matters, not where it all starts out. I'm sure more than a few of us can post examples of how we chose to bias our amps if you want to get in the ballpark.
Also, don't be scared of using one of the other schematics' bias methods. The voltage is what matters, not where it all starts out. I'm sure more than a few of us can post examples of how we chose to bias our amps if you want to get in the ballpark.
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ricks57custom
- Posts: 32
- Joined: Tue May 10, 2005 6:27 pm
- Location: Scottsdale, AZ
Re: Newbie has PT question
Moose,
I just checked the specs on the Super PT and they're too high (460-470V across secondaries). Heyboer offers a PT with a bias tap for $5 more. I will probably go that route.
Could you give me examples of how you (or someone else) has wired your bias that would put me in the same zone without changing out too many parts? In case I want to save money on transformers.
Thanks,
Rick
I just checked the specs on the Super PT and they're too high (460-470V across secondaries). Heyboer offers a PT with a bias tap for $5 more. I will probably go that route.
Could you give me examples of how you (or someone else) has wired your bias that would put me in the same zone without changing out too many parts? In case I want to save money on transformers.
Thanks,
Rick
Re: Newbie has PT question
I actually used the A4 schematic to start with and I think I snagged my bias supply off of one of the other jobbers. Mine's almost identical to A1A, except I used a 50K pot, and I recall having to change the value of the R in the middle of the Pi filter to get me the range I needed.
I've since gone to a dual bias supply, but don't have a copy on the computer.
If heyboer will custom wind you a PT, you can stick to that and everything will be easy. I sell the dual primary OTs alone, or heyboer can probably wind you one of the old style HTS-5200s.
If you're enterprising, a VERY simple method of generating bias voltage is to use the back biasing method. Randall Aiken has an example here: http://www.aikenamps.com/BackBiasing.html
Since some transformers you were looking at is too high in voltage, you can drop some voltage off the centertap with this method, and utilize that difference at the same time. The method also works with zeners, not unlike the multi-voltage variants of the Blues Express.
I've since gone to a dual bias supply, but don't have a copy on the computer.
If heyboer will custom wind you a PT, you can stick to that and everything will be easy. I sell the dual primary OTs alone, or heyboer can probably wind you one of the old style HTS-5200s.
If you're enterprising, a VERY simple method of generating bias voltage is to use the back biasing method. Randall Aiken has an example here: http://www.aikenamps.com/BackBiasing.html
Since some transformers you were looking at is too high in voltage, you can drop some voltage off the centertap with this method, and utilize that difference at the same time. The method also works with zeners, not unlike the multi-voltage variants of the Blues Express.