Repair output transformer leads on '65 Bassman head

[fevzay]

Hi guys,

First real post here. Could use some help.

I recently picked up a '65 BF Bassman head, and I've noticed that the Brown and Blue wires going to the output transformer from the power tubes have been spliced (Brown changes to Blue, and Blue changes to Brown inside the chassis between the board and tubes). So the leads are mixed, and also reversed. The Brown (turned Blue) wire is going to the place where the Blue wire should go (incorrect as I see it on the schematic), and vice versa for the Blue wire.

Also, the PI and bias section have been changed back from AB165 to AA864, which is fine by me. I also see that the Black and Green wire going to the output jacks were not reversed. As I understand it, they should have been when the other AA864 changes took place to avoid feedback. If the amp was causing feedback due to this, would reversing the Brown and Blue wires going into the transformer "cure" this? I'm wondering what happened for the previous owner to do this. The amp sounds good as it is, but I'd like to clean up the splicing and get things how they should be going off of the schematic.

Do y'all have any advice on repairing the leads? If the length is too short when I try to fix the splicing...is it possible to replace the tail ends with new wire, or do I have to make due with what it came with?

I've heard people say not to both trying to replace the full leads on transformers (opening them up). I'm sure that's over my head.

If I can replace the tail ends of the wire, what would y'all recommend using to make it compatible in rating and looks?


kind regards,
jordan

[xtian]

Welcome to TAG.

First rule of fight club: if it ain't broke, don't fix it.

But you're OCD like me, and just want to replace wires because they're the wrong color! Haw!

The oscillation caused by reversing OT primaries (e.g., blue and brown) happens on amps with negative feedback. If you swap the OT leads, you will also have to swap the wires from the PT to the tube grids.

You can add length to OT wires by splicing, soldering and shrink tubing the wires.

[billyz]

When you convert an ab165 to aa864 or other ab763 circuit you will need to reverse the OT primary leads . Otherwise the amp will howl . If you want it to look pretty then remove the transformer , take off the end cover to reveal the original splice connection. Make your new wire splice there, color as you prefer. I would not return to the ab165 circuit , it was
Not great.

[fevzay]

Thanks guys. I think that's what happened....they did the AA864 mod, and didn't reverse the OT leads (Black/Green). They must've then spliced into the leads going from the output tubes to the OT to "fix" it.

So, what gauge and type of wire should I buy to fix the spliced ends?

- Gauge
- Stranded / Solid
- etc.

[billyz]

Stranded, 18g

[fevzay]

Awesome, thanks so much.

While I'm at it....where can I order Brown and Blue PVC 18 AWG stranded wire? Looks like Mojotone has discontinued it, and AES doesn't carry it.

[gldtp99]

Oops---- post removed--

[M Fowler]

Awesome, thanks so much.

While I'm at it....where can I order Brown and Blue PVC 18 AWG stranded wire? Looks like Mojotone has discontinued it, and AES doesn't carry it.

www.Apexjr.com

[cbass]

I think all of apex' wire is teflon

[M Fowler]

http://turretboards.com/

[fevzay]

Thanks for all of your replies. I'll get this ole' Bassman looking good soon!

[fevzay]

Sorry for the newbie question again, but I'm having trouble finding the exact wire I'm looking for....

Brown (and Blue) UL-1015 PVC 18 gauge stranded hook-up wire.

I've checked out the references above, and none of the places had quite what I'm looking for. Any ideas?

Is this something I could find at a local place (hardware, electrical, etc.)???

[Firestorm]

If the splices are good, why not leave it be. It's been blackfaced; the leads are SUPPOSED to be swapped (primary or secondary, either one).

[fevzay]

Fair question, but it IS a Blackface Bassman so I'd like to get it looking "right." Just want things to make sense (to me, at least) as it should follow the AA864 schem.

Also, the splices look poor. They're taped together only appear to be twisted (not soldered). So, since they need to be addressed I figured I'd make it match typical BF AA864.