Studio Pro 50 volume loss

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The Guitar
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Studio Pro 50 volume loss

Post by The Guitar » Wed Jun 09, 2021 3:17 pm

This just happened yesterday when I fired it up. I have to turn the Pre and Post up all the way to hear it. The Saturation is kind of fizzy. Also, when I unplug the guitar cable it will squeal if I mess with the dials. I thought it could've been one of the rear jacks thatightve needed cleaned, but that didn't help. I have a Kasino Concert head that I plugged into the Power Amp In on the Pro, to use the speaker. I also have ran it into the unbalanced in. I also have 2 778 op amps and an original 4558 in it. If that info will be useful... After I turned it off, I checked to see if anything was warm/hot. I did notice one of the huge caps was warm and 2 of these white boxes were hot. Not too sure what's going on. Any help is appreciated.
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Enzo
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Re: Studio Pro 50 volume loss

Post by Enzo » Wed Jun 09, 2021 8:39 pm

The two resistors normally get hot. The cap right next to the hot resistors will get warm because it is next to them.

You may have cleaned the jacks, but did you try a cord patched from Preamp out to Power amp in?

How did you connect your Kasino to the power amp in? I sure hope you did not plug a cord from the Kasino speaker out into that jack.

Plug into this amp with guitar, then run a cord from Preamp out to the input of another amp. How does the preamp sound over there?

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The Guitar
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Re: Studio Pro 50 volume loss

Post by The Guitar » Thu Jun 10, 2021 6:50 am

The first time I hooked the Kasino up, it was from it's speaker out to the Pro's power amp in. It was loud so I switched to the line out. The last 2 times I played around on the Kasino, it's been with the line out. I'll have to get my Crate G212 out of storage to test the Pro's preamp out. I'll try patching the pre out to the power in and see what it does.

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Enzo
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Re: Studio Pro 50 volume loss

Post by Enzo » Thu Jun 10, 2021 9:42 am

Oh dear. NEVER connect the speaker out of an amp to an input. Inputs are designed to take the half a volt or less of the guitar, or even one volt from a line level source, but the speaker output of an amp can be 25-30 volts or in that area, and can damage the input amp.

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The Guitar
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Re: Studio Pro 50 volume loss

Post by The Guitar » Thu Jun 10, 2021 2:12 pm

I did jump the in/out and it restored some of the volume. When the Saturation and Pre are all the way up, it is fizzy and, if I'm using the term right, the low end is clipping. Chugging doesn't sound good at all. I can dial back the pre to about 5, 6, before the sound is clearer, but fizzy still.

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The Guitar
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Re: Studio Pro 50 volume loss

Post by The Guitar » Wed Jun 23, 2021 10:46 am

Could it possibly be one or more of the op amps? I have 2 778s and one original 4558 in.

Bah! Now it has all 778s and no change. 😬

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The Guitar
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Re: Studio Pro 50 volume loss

Post by The Guitar » Wed Aug 24, 2022 10:43 am

**UPDATE**
Months back I dropped it off at a local speaker repair shop and he had his partner look it over. Fixed the low volume output, as that was a bad cap, but could not find out the saturation issue. He even sent it to Peavey, but they could not help as they have no boards or parts. The saturation issue is the fizzy/muddy saturation that happens when that knob is turned up. Without any saturation, Pre knob all the way up, it has a decent dirty tone. There's also a squeal that comes in when the Post knob is turned up beyond a point. Have to turn it off to stop that. But yeah, that's where the 'ol 50 is at for the moment. 😋

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