Penta Mod?

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westsider60
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Penta Mod?

Post by westsider60 » Sat Feb 05, 2022 7:52 pm

Anyone know anything about this Penta Mod? Any info would be great
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JamesPaul
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Re: Penta Mod?

Post by JamesPaul » Sat Feb 05, 2022 9:19 pm

No idea. It is something around R87, or if R87 was a circuit update, it may even be R87 on an older version of the Penta PCB, and not a mod at all. You should be able to sort it out, between your actual PCB and the PCB layout (page 2) in the attached.

Edit: I was focusing too much on mod. I did not even consider the schematic. When you factor it in, that is just R87. It probably was a circuit update. Your Penta just has an older PCB.

Edit2: Thought about it some more and now I think those 2 resistors are R86 and R87. As if the XXX output originally was off C7, and the update was the addition of R86 & R87. With both of those being 560k, just a voltage divider to attenuate output by 50%. Bottom line is the PCB layouts between yours and the schematic are different. I would shift to the schematic and trace it out on your PCB to see if this is correct. Either way, it would be great if you let us know what you find; mod or update.


Penta Head Schematic.pdf
Penta Head Schematic
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Enzo wrote:I find if the amp is working, that is a good point to stop fixing it.
James Paul's Peaveys
Decade, Classics, Ecoustic, Windsors, VYPYR, Triple XXX, XXL, VKs, Bandit, JSXs, VIP, Piranha and a Penta.

westsider60
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Re: Penta Mod?

Post by westsider60 » Tue Feb 08, 2022 7:10 am

It appears to be a voltage divider as the "Mudflap Girl Has a noticeable lack of low end volume which would require more volume to overcome the attenuation of the voltage division.

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JamesPaul
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Re: Penta Mod?

Post by JamesPaul » Tue Feb 08, 2022 8:53 am

Then it probably is the scenario I also arrived at.

If you look at your PCB pic, originally the XXX output was the end of C7. Peavey probably still had PCBs produced for this version of the circuit

When Peavey updated the circuit with the R86 & R87 voltage divider, they were able to lift the output end of C7, and solder in the voltage divider. Taking a longer look at your PCB pic, R86 is connected to R60. That should be the GND side of R60.

This is a match for the updated schematic in what I attached. However the PCB layout in what I attached has been updated to have R86 & R87 conventionally mounted on the PCB.

So yours is not a mod, just the updated circuit on a previous version of the PCB.

I have not yet had to open my Penta, but when I do I will check what PCB and circuit is in there. And next time I try to assist, I will spend more time analyzing before I post.
Enzo wrote:I find if the amp is working, that is a good point to stop fixing it.
James Paul's Peaveys
Decade, Classics, Ecoustic, Windsors, VYPYR, Triple XXX, XXL, VKs, Bandit, JSXs, VIP, Piranha and a Penta.

westsider60
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Re: Penta Mod?

Post by westsider60 » Wed Feb 09, 2022 9:35 am

Thanks for your time, This is my first round with the Penta. I'm used to dealing with the Mace 320T. The thought has crossed my mind to run an AB in to each one Just for kicks of course. Rossington seems to get the same tone with either one.

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