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Post subject: Performer (Roc/Pro) 1000 Pops on shutoff
Posted: Sun Jul 03, 2011 4:07 am
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Picked up one of these combos at a good price. Overall it is a great amp, and well designed.
Has one potentially huge problem.
If you shut it off with a cable in the input jack you get a loud "Bang" on shut off.
With the jack empty the grounding seems to work and you get a slight thump.
A look on the schematic shows the input jack is doing a couple of things, but the shut off Bang is very loud.
Was this usual or is something not quite right?
The culprit might be the reverb inhibit circuit - jack switches from -16vdc to +16vdc.
http://support.fender.com/schematics/gu ... ematic.pdf
(This might also be why these amps hum - 16vdc near the input)

Any ideas or experiences are welcomed
Mike


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Post subject: Re: Performer (Roc/Pro) 1000 Pops on shutoff
Posted: Sun Jul 03, 2011 6:36 pm
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Never noticed that with the Performer 650

Art


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Post subject: Re: Performer (Roc/Pro) 1000 Pops on shutoff
Posted: Mon Jul 04, 2011 4:43 am
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The inibit (Q7 signal in U58) is not wotking with the jack "in". 8)

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Post subject: Re: Performer (Roc/Pro) 1000 Pops on shutoff
Posted: Wed Jul 06, 2011 5:57 am
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I have 650 that pops when turned off as well. I never noticed the pop/bump without a cable pluged in. I'll have to check. I like the amp though. I bought it new back in about '97.

Tis-san, I haven't clue as to what you said...
"The inibit (Q7 signal in U58) is not working with the jack "in".
What the hell does that mean?


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Post subject: Re: Performer (Roc/Pro) 1000 Pops on shutoff
Posted: Wed Jul 06, 2011 2:26 pm
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Sorry, there is a kind of mute circuit.
http://support.fender.com/schematics/gu ... ematic.pdf
When the jack is not connected the -16V is driver off the "INHIBIT" Transistor JFET named Q7 close to The Operational Amplifier named U5B. Then no signal can be amplified.

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Post subject: Re: Performer (Roc/Pro) 1000 Pops on shutoff
Posted: Wed Jul 06, 2011 5:05 pm
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Interesting. I just checked mine(Performer 650) and it pops when turned off with nothing plugged into it as well. I never noticed as there was always a guitar plugged into it.
Is worth trying to fix?


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Post subject: Re: Performer (Roc/Pro) 1000 Pops on shutoff
Posted: Thu Jul 07, 2011 10:10 am
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Is it the same schematic ? 8)

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Post subject: Re: Performer (Roc/Pro) 1000 Pops on shutoff
Posted: Thu Jul 07, 2011 11:42 am
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I found the service manual an another forum.
http://music-electronics-forum.com/t19550/
They are similar but not exact.


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Post subject: Re: Performer (Roc/Pro) 1000 Pops on shutoff
Posted: Thu Jul 07, 2011 1:42 pm
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Agree, similar, may be you could check carefully with a voltmeter if the voltage is applied to the mute circuit. 8)

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Post subject: Re: Performer (Roc/Pro) 1000 Pops on shutoff
Posted: Thu Jul 07, 2011 2:58 pm
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I'm not clear on where I need to test.


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Post subject: Re: Performer (Roc/Pro) 1000 Pops on shutoff
Posted: Fri Jul 08, 2011 1:04 pm
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On C1 or R2 it's the "hinibit" node, measurement should be rougly -6V jack "out" and 0V Jack "in". The Transistor Q2 is driven by CR9. 8)

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Post subject: Re: Performer (Roc/Pro) 1000 Pops on shutoff
Posted: Fri Jul 08, 2011 3:57 pm
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I'm getting -7.79 jack "out" and 0 jack "in" across c-1 and r2
When turned off jack "in" there is reverb pop.


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Post subject: Re: Performer (Roc/Pro) 1000 Pops on shutoff
Posted: Sat Jul 09, 2011 3:38 am
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Great it works !

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Post subject: Re: Performer (Roc/Pro) 1000 Pops on shutoff
Posted: Sat Jul 09, 2011 5:28 am
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Yup. But what about the pop the OP asked about and I got myself into some how?


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Post subject: Re: Performer (Roc/Pro) 1000 Pops on shutoff
Posted: Sat Jul 09, 2011 8:58 am
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About the pops:
there are some that are abnormal --> when mute circuit is not working
There are some that are ... sometimes--> due to opening circuit that creates a voltage drop transmited to the Power Amplifer (PA) and poping in the loudspeaker.

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