70w Fender OT

[two tone]

Hello everybody,
I´m planning to build a #40 clone soon.
I have this OT from an 80´s Fender 75 combo,
the prim. impedance is 8k8 ,
so I could use the 16 ohm tap with my 8 ohm Altec
for 4k4.I wonder if anyone of you has experience
with this model.
Regards Hanno

[two tone]

anyone?

[txbluesboy]

8.8K seems awfully high for a seventy watt amp. What output tubes did that amp use?

[two tone]

6L6,500v plates,UL taps

[txbluesboy]

Wow, 139 people have looked at this, but no ones saying anything. I think maybe everyone is scratching their heads, like I am, about that primary impedence. However, if your specs are correct, I think when you use an 8 ohm load on a 16 ohm tap as a permanent connection you should derate the transformer by 50%. It is done all the time though.

[two tone]

Well thanks,I know it can be done.
I was hoping someone might have tried
these OT´s with a Dumble Clone.
I know this series of late 70´s Fenders
(70w UL) was never really popular,
it sure is some heavy iron though..

[Bob-I]

Your best bet is to cap off the UL taps and run a regular screen supply with 1k 5w resistors on the screens. The output impedance as already discussed is quite high, so just use the 16 ohm tap.

I've had really good success with older iron, but I've never used one of these. I'll bet it'll sould great.

[ukulele]

Hello
I totally rebuilt my Fender 75 to a D-clone and didn't like how that OT sounded so I changed it to 50W fender replacement OT and liked it better. But if you have one you should try it!

[selloutrr]

8K8 seems really high how does it meter to the center tap or ground?

[Jackie Treehorn]

I did the same thing, converted a Fender 75 to HRM/skyline. Except, I kept it ultralinear, without any global negative feedback, no choke, 100k plate loads on both sides of the Long Tail Pair. I really like the sound of the amp and that iron. However, I think the transformer has 8 and 4 ohm outputs, only, and is likely a 4.4k, although I haven't tried to measure it.

[jelle]

Build a 70's ODS with iron from a UL bandmaster. I liked the UL with NFB but the guitar player liked no UL with NFB better. I did not determine the primary though.

Decent iron, IMHO. Have fun!

[novosibir]

the prim. impedance is 8k8 ,
so I could use the 16 ohm tap with my 8 ohm Altec
for 4k4.I wonder if anyone of you has experience
with this model.

Just seen your post.

No prob to use the OT w/ 2*6L6 as a 4.4K prim w/ 8 ohms load on the 16 ohms secondary, but it might be, that it saturates earlier as usual, because you can regard it as an 'overwound' 4.4K

Larry

[two tone]

Thank you all,looks like I´ll give it a try,
however it will take some time, I´m going on a
2 month vacation .
I noticed all early Dumble combos came with
an 8 ohm speaker being driven from a 4 ohm tap,
so this mismatch is part of the famous tone...