It is currently Tue Mar 17, 2020 4:32 am

All times are UTC - 7 hours



Post new topic Reply to topic  [ 5 posts ] 
Author Message
Post subject: Vintage Reissue: Reissue Super Reverb Amp AB763 questions
Posted: Sun Jul 17, 2011 9:20 pm
Offline
Hobbyist
Hobbyist

Joined: Sun Jul 17, 2011 9:03 pm
Posts: 1
Hi * from Germany

May be this topic is better in the directory vintage Amps but its a reissue Amp.
So I put the post in here. May be the moderator can shift it, if its needed.

Here I have a Super Reverb RI from 09/2010 (SN CR334626) and its sounding great
with 4x10" Jensens Made in Italy inside. I only have some questions relating the
output female jacks of the loudspeakers.(2 Ohms impedance in summa)

On this Amp I have 2 Lsp outputjacks. The one nearest the standbyswitch
seems the main because it has a switch to short the Outputtransformer if
nothing is plugged in. That means the second jack (near to the footswitch jack)
is usable only if in the first jack is already used.? The circuitry seems the same
as on the old super Original from 1963.

First question:
Why do we have a switch on the main jack, which shorts the OT if nothing
is connected?? This is not good for the OT in any case?? I wonder about
the reason why? On an input it makes sense to have it shortcutted if nothing
is plugged because of the free input might be feedback or hum with the free
grid of the first 12AX7 but behind the OT its dangerous because of current flow,
is'nt it? So whats the sense of this switch?


Second question:
If the first jack with the switch is not used at all, and you plug a load into
the second jack, the OT is shorted but nevertheless to this shorted OT,
you here sound in the box during the secondary output jack. The sound
is low and distorted but there is sound coming out of the external or internal
loudspeakers (depends what you have connected) even if the main jack is
empty and the swich of the main jack shorts the OT.
Where is this sound coming from?

The questions are important for me, because on the backplane there
is nothing written than parallel input (2 Ohms ) etc. So the user has the
impression he can put in the load where he want and it makes no difference.
But If one now plugs during a gig the intermal loudspeakers in the wrong jack
(second), then he has a shorted OT but hears still little distorted sound and
believes his Amp is defective.

This was the case here and I got the Amp for repairing it but it is ok.
The owner was using the wrong jack during the stressful Gig and
may be he damadged nearly his OT on his very new Amp.

Or during a gig he wants to use an external Box only, then he has to
plug out the mains jack and plug in the external box in the mains.
After the gig, the "roady" has to take care to plug in the internal load
back into the right jack (mains jack). And all this stuff only becaus of this
strange switch which makes no sense from my point of view.

Either I should replace the mains jack with one without swich so that we
have really two jacks which are the same and really parallel or I should
write on the backpanel an especially label for the both outputs
(mainsjack vs. secondary jack) because the are not the same and its
dangerous. Or am I to stupid to understand the sense behind the switch???
In my opinion a OT with open secondary without load is safer than an OT
with shortcutted secondary without load from electrotechnical point of view??

Best regards from Stuttgart Germany
Boris Gerlach (drstrange)


Top
Profile
Fender Play Winter Sale 2020
Post subject: Re: Vintage Reissue: Reissue Super Reverb Amp AB763 questio
Posted: Sun Jul 17, 2011 11:09 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Tue Jun 29, 2010 1:20 pm
Posts: 9640
Location: Indiana
Hi Boris Gerlach,

You have to have something plugged into the main jack at all times, and you can not use the second jack by itself, because as you mentioned the output trans (OT) will be shorted when the main jack is empty.

The shorting jack is there to protect the OT if you turn on the amp with no speaker connected. The OT would go up in smoke if there were no shorting jack and the speaker was unplugged while powered on and played. The OT will be just fine when operated with a short across it, it is designed that way.

You may get a little sound out when using the second jack by itself, as the empty main jack isn't quite zero ohms. But doing this will not cause any damage, you just won't get very much sound out.

Don't replace the jack with a non-shorting jack as that is the protection for the OT.

Better to just label the jacks as you thought. :idea:

It is better to use the amp with the OT shorted rather than open. If the amp is used with an open circuit OT, it will surely smoke.

_________________
---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


Top
Profile
Post subject: Re: Vintage Reissue: Reissue Super Reverb Amp AB763 questio
Posted: Sun Jul 17, 2011 11:48 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
shimmilou wrote:
Don't replace the jack with a non-shorting jack as that is the protection for the OT.


That's why Leo put it there.

And very few know more than him.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: Vintage Reissue: Reissue Super Reverb Amp AB763 questio
Posted: Mon Jul 18, 2011 2:49 am
Offline
Hobbyist
Hobbyist

Joined: Tue Mar 15, 2011 4:22 am
Posts: 5
I thank you very much for you explanation. I learned, that my point
of view was the wrong point of view and I think I have to take another lesson in
induction and selfinduction. So I will label the jacks with coloured buttons red for the
mains and yellow for the secondary jack. This will help the musician to plug the load in the
right jack. Also if he is not familiar with the Amp because it is new for him.

Best regards
Boris Gerlach


Top
Profile
Post subject: Re: Vintage Reissue: Reissue Super Reverb Amp AB763 questio
Posted: Mon Jul 18, 2011 3:21 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14050
Location: Province de Québec, Canada
Shimmilou is right.

Shorting an output transformer is better ( it is a must ) than keep it open ; nothing connected.

Normal speaker at 2 or 4 ohms, even 8 ohms is close to a short.


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 5 posts ] 

All times are UTC - 7 hours

Fender Play Winter Sale 2020

Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to: