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Post subject: pro reverb vibrato problem
Posted: Sat Feb 28, 2015 6:07 pm
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now that i've got the reverb working, i find that when i raise the vibrato intensity pot it lowers the volume!!?? i can hear the ticking so that may mean that the bulb and resistor are ok. could this be the 3 small .01 and .02 caps, the attached resistors or the pot itself?

thanks,
mikeB.


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Post subject: Re: pro reverb vibrato problem
Posted: Sat Feb 28, 2015 7:35 pm
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What was the status of the 12AT7 reverb driver tube?


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Post subject: Re: pro reverb vibrato problem
Posted: Sat Feb 28, 2015 8:08 pm
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BMW2002Ti wrote:
What was the status of the 12AT7 reverb driver tube?


it was the one of the reverb pan connections was partially out. i made mention of that in the other thread so that others may know.
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mikeB


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Post subject: Re: pro reverb vibrato problem
Posted: Sat Feb 28, 2015 9:26 pm
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Please don't start a new thread about each and every little problem with your amp. :roll:

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Post subject: Re: pro reverb vibrato problem
Posted: Sat Feb 28, 2015 9:31 pm
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shimmilou wrote:
Please don't start a new thread about each and every little problem with your amp. :roll:

pourque?
isn't that what this is for? how else are we to learn?
thanks,
mikeB


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Post subject: Re: pro reverb vibrato problem
Posted: Sat Feb 28, 2015 11:15 pm
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No, it means that if you have one junk amp with multiple problems, or if you have multiple questions about one amp, then one thread would be plenty to deal with one amp. It seems that lately we've had a bunch of newbies join and start multiple threads about the same amp, and it's really stupid and annoying. :roll:

So far you have two threads, what's next?

Pro Reverb Broken Knob?
Pro Reverb Scratchy pots?
Where can I get parts for my Pro Reverb?
Yet another thread about my Pro Reverb?
Hey, did I mention that I have a Pro Reverb?

You get it yet? :wink:

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Post subject: Re: pro reverb vibrato problem
Posted: Sat Feb 28, 2015 11:22 pm
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shimmilou wrote:
No, it means that if you have one junk amp with multiple problems, or if you have multiple questions about one amp, then one thread would be plenty to deal with one amp. It seems that lately we've had a bunch of newbies join and start multiple threads about the same amp, and it's really stupid and annoying. :roll:


+1

Often, an amp may manifest seemingly unrelated issues that are in fact symptomatic of a larger, singular problem. It's generally easier to develop a plan for troubleshooting if all the malfunctions are categorized and prioritized within a single post.

Arjay

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Post subject: Re: pro reverb vibrato problem
Posted: Sun Mar 01, 2015 12:40 am
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Retroverbial wrote:
shimmilou wrote:
No, it means that if you have one junk amp with multiple problems, or if you have multiple questions about one amp, then one thread would be plenty to deal with one amp. It seems that lately we've had a bunch of newbies join and start multiple threads about the same amp, and it's really stupid and annoying. :roll:


+1

Often, an amp may manifest seemingly unrelated issues that are in fact symptomatic of a larger, singular problem. It's generally easier to develop a plan for troubleshooting if all the malfunctions are categorized and prioritized within a single post.

Arjay

well, a huge thanks to all who have helped me! that's all i'm going to say. i'm sure sorry if i offended people who know more than me. i won't try to learn from this forum again.
thanks all,
mikeB


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Post subject: Re: pro reverb vibrato problem
Posted: Sun Mar 01, 2015 1:34 am
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I think you did pretty good overall, Mike.

But solving amp issues is much akin to the protocols a physician uses to diagnose and a treat a patient. The more information forthcoming, the quicker the problem(s) can be resolved. Both time and money are saved.

Arjay

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Post subject: Re: pro reverb vibrato problem
Posted: Sun Mar 01, 2015 2:22 am
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Just in case the OP is still around... :mrgreen:

A weak reverb driver (12AT7) or recovery 12AX7 can exhibit change in noise and overall gain when twisting the reverb knob.

FWIW.


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Post subject: Re: pro reverb vibrato problem
Posted: Sun Mar 01, 2015 11:55 am
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MikeB Thanks for posting.
That's an interesting problem with the vibrato.
I'll review that in a moment, but now a word from our sponsors...

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Now back to our regularly scheduled free-for-all.
I recollect that the pro reverb has a couple of different vibrato circuits. Most of the have a total of 6 preamp tubes. The other has more. I'm not coming up with the schematic, but it uses 2 or 3 tubes for the vibrato instead of just one.
It would be helpful to know what chassis number and description you own. BF/SF/master
On the commonest 6 preamp model, the vibrato circuit works by grounding out the signal, so some loss of volume might be normal. Does the volume drop off like that when the vibrato is turned off?
From your previous post about the reverb, you indicated that the amp is new to you. Could this be a normal function of the Vibrato, or does it drop way off?
The other thing you noted was that there are capacitors soldered to the vibrato control. On the 6 tube version, there are no capacitors connected to the control. Do these look stock? Could they be a mod to reduce ticking?
The commonest failures on the vibrato circuit are that the optoisolator pins break loose from the light dependent resistor under the heatshrink tubing. This gives an unstable operation or ticking. The other failure involves the three disk capacitors, .01/.01/.02. They get leaky and generally quit oscillating. But if they leave the output stage of the vibrato turned on, it could affect the volume when the vibrato is turned up.


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Post subject: Re: pro reverb vibrato problem
Posted: Sun Mar 01, 2015 12:19 pm
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TimsAudio wrote:
I recollect that the pro reverb has a couple of different vibrato circuits. Most of the have a total of 6 preamp tubes. The other has more. I'm not coming up with the schematic, but it uses 2 or 3 tubes for the vibrato instead of just one.


The AA165 (and follow-on revisions) Pro Reverb has but ONE tremolo circuit -- a photo-electric oscillator (ie: an opto-isolator) driven by a single tube.

It's the non-reverb 6G5 Pro Amp (a brownface) that uses the 2- or 3-tube tremolo, which is beyond the purview of the OP's original question.

Arjay

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Post subject: Re: pro reverb vibrato problem
Posted: Sun Mar 01, 2015 4:21 pm
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Edited for being completely off base, see below. :oops:

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Last edited by shimmilou on Sun Mar 01, 2015 6:40 pm, edited 1 time in total.

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Post subject: Re: pro reverb vibrato problem
Posted: Sun Mar 01, 2015 5:05 pm
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shimmilou wrote:
The "vibrato" circuit in the Pro Reverb amp works by wiggling the bias to the output tubes, not by "grounding the signal".


Uh...... :shock:

Arjay

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Post subject: Re: pro reverb vibrato problem
Posted: Sun Mar 01, 2015 6:37 pm
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Oh no! I feel like such an arse, and apparently I know nothing and can't even read a schematic. :oops:

The vibrato in the Pro Reverb wiggles the signal, and NOT the output tube bias. My apologies for being such a jerk! :oops:

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