Peavey Ultra-Channel Switching mod?

[JerryP]

I've driven past the Eraser Co. here in Syracuse a million times and always wondered what they did there! Looks like I'll be paying them a visit. Thanks!
Jerry

[J M Fahey]

Hi Trick.
You PM asked me:

My other question is about the cap value to change the timing of the footswitch. I have a requested a schematic from Peavey and they have yet to get back to me. Plus I wouldn't know how to find it on the schematic. How do I locate this capacitor?

I repeat an earlier answer:

I've been listening to your switching mute delay.
It's not 1 second long , more like 1/4 of a second, but definitely heard.
Its duration is controlled by the "time constant" provided by a 1M resistor and a .1uF to .22uF capacitor, which is discharged by a MAC97 Triac everytime you switch any footswitch on or off.
I don't refer to specific part numbers because it depends on your particular model, I've checked a Rockmaster preamp and an Ultra 60, the basic idea is the same.
I'd suggest you replace that capacitor with another half the capacity, that means .1->.047uF or .22 to .1uF.
This should cut your mute time in half.
Maximum mod suggested: 1/4 the original value.
Don't overdo it or you will start to hear the clicks.

But since an image is worth 1000 words, here go 2000 word equivalent:
1) The part of the circuit you have to mod:

2) the MAC97 itself, so you recognize it :

This refers to a Rockmaster preamp, the idea is the same, schematic part identifiers will *not* match.
Soooooooooooooooo:
1) good light, good glasses, look carefully around the board until you find a little black, D shaped, 3 legged "transistor" labelled MAC97. *Maybe* Peavey uses some in-house number, you'll confirm it's the one because, through tracks, :
2)one of its pins is grounded, close to it there is a capacitor with also a pin grounded
3) the other pin of such capacitor, which might be labelled .1 something, is connected to other pin of the suspect MAC97, and to a 1M resistor.
4) Said suspect's third pin will be connected to a second .1 capacitor and a 47 ohm resistor.
5) once you identify the first capacitor mentioned, the one connected to 2 pins of Mac97, read its value and replace it by another approximately half value, so:
.1 becomes .047
.047 becomes .022
etc.
You will not find *exact* half values, there is a series of preferred standard values, choose the closest one.
Good luck.

[Trick]

wow, thanks for that info... I believe I found it since it is the only one on the board labeled Mac 97 and there is a cap that is connected to it. I have attached a picture. The number on the cap reads 224E. So I'm assuming half this would be to use a .1 microfarad cap. Also, does it matter what type of cap, like a ceramic, orange drop, etc.

Also, wondering what type of residue that is poured over the large caps. I always find this over components and wondering what it is and what it does?

thanks again for the help

[Enzo]

The "residue" is hot melt glue, or in some cases silicone sealer. It helps prevent the larger parts from shaking as much, and so prevents them from breaking off their wire leads.

[J M Fahey]

Hi Trick.
Well, you found it
Even though the little bugger was (still is) well hidden behind al that wire
You assume correctly: 224 means .22uF; "half" it will be .1, which may be marked 104.
Forget Orange Drops, Beeswax caps and the like, the original one seems to be a regular generic good quality Polyester , Polycarbonate or MKP type, get something similar.
A 100V one is more than enough, it never sees more than a few volts.
Even a Ceramic x50V will do, but let's keep the excellent part quality traditional in Peavey.
The cost is nil.
It should cut your mute time in half, I get that should do.
If you still find it annoying you might even lower it to .047/473/47nF but you risk it not being enough to do its work.
Good luck.
PS: that "goo", as Enzo said, is to avoid mechanical vibration on some parts.

[Trick]

Glad to know I located it. Once I get some different value caps I will be giving this a go. Thanks for all the help here. I will let you know my results. I am just a little nervous getting the iron on there again, I'm using a 25 watt, just don't want to take any solder pads off again.

[J M Fahey]

Use the best solder pump you can, not the "fat pencil" type but the ones that look like a compact bicycle pump.
Some solder wick to get the last remains is an extra precaution.
What you don't want is wiggling the part off, that pulls pads.
Clean it before, so that the part practically falls off all by itself.
Remember: no wiggling or twisting.
Good luck.

[Trick]

wow...it worked, thanks so much

Well, I changed the caps out. I first tried a .022uF and I know that is too small, but I couldn't wait and you were correct, the pops were there. But I couldn't believe it actually worked and switched seamlessly. So then I went out and found, from Radio Shack, so hope they are decent caps. A .047 and .1 polyester film. I tried the .1 and there was still a slight audible drop out. Then tried the .047 and It's AWESOME! I switched constantly and I slightly may have heard a pop here and there. There is no drop out, I'm excited. I measured it and it is about 10 ms. So it went from 58 to 10ms. I never modded anything like this and could not have done it without the help here. Mr. Fahey thanks for your time and walking me through this.

There is a slight buzz that I'm getting around where the fuses and some large caps are located.It almost sounds like a sparkler or crackle, not a hum. Like a grounding issue possibly. It amplifies and comes through the speaker too. It's very intermittent, so I'm hoping I can catch it in time and record it to post here.

I appreciate all this help, wow!

Sincerely,
Sean Lehman

[J M Fahey]

OK , I'm happy that we got to a happy ending, and, of course, YOU actually did it.
It's a balancing act of sorts, happily you could reach a point where dropout is *almost* inaudible and pops are *almost* inaudible too.
Sometimes it does not exist such an evenly balanced point and you have to choose the lesser of two evils, ............... but not today.