I would like to modify my amplifier (Peavey 6505+ 112: https://www.thetubestore.com/lib/thetubestore/schematics/Peavey/Peavey-6505PLUS-112-Schematic.pdf), by removing some components and testing some mods (SLO-100, Treble-bleed cap, etc.).
I can solder and discharge capacitors, but I don't have the technical knowledge to understand some concepts.
For example, what should I do if I remove capacitor C5?
Do I have to solder the two pins, do I have to solder another capacitor?
Everyone talks on a theoretical level, but I'm interested in knowing what I have to do on a practical level.
\$\begingroup\$
\$\endgroup\$
8
-
2\$\begingroup\$ We can't see what capacitor C5 really does in the circuit. The amplifier may not work if you simply remove a capacitor and leave it open circuited, and it might be totally wrong to replace it with a short circuit. What is your intention to modify this circuit, what do you expect to achieve? \$\endgroup\$– JustmeCommented Jul 2, 2023 at 8:28
-
2\$\begingroup\$ What's the point of the exercise? More likely than not, components are designed in for a purpose. \$\endgroup\$– greybeardCommented Jul 2, 2023 at 8:28
-
1\$\begingroup\$ Don't worry guys, these are well tested mods on 6505+ amps. SLO-100 (on which 6505 is based) only has R2, R55 in the Input Stage. Removing C5 is to eliminate the Treble-Bleed "effect". \$\endgroup\$– Vince SkylerCommented Jul 2, 2023 at 8:33
-
1\$\begingroup\$ If these are "well tested mods" then you should also be able to find an answer to your questions in the same documentation. At least provide a link to the information you are using to motivate these changes. \$\endgroup\$– Elliot AldersonCommented Jul 2, 2023 at 14:00
-
1\$\begingroup\$ Vince, according to the full schematics, if you remove C5 you must short its pins for otherwise nor the Lead Gain, the Lead Volume and the tone controls will not work. 😉The fact that you have only put an excerpt of it has caused the closure of the question for without it is impossible to understand what happens with any change in the circuit. \$\endgroup\$– Daniele TampieriCommented Jul 4, 2023 at 8:31
|
Show 3 more comments
2 Answers
\$\begingroup\$
\$\endgroup\$
10
In general if someone writes "remove the capacitor" it means to remove the capacitor in question from the circuit and leave it open. At audio frequencies that generally means you can either completely remove the part (preferred) or just disconnect one of the two leads.
If someone writes "replace the capacitor with xxx" it means to remove the original capacitor and replace it with something like a capacitor that is of different value or has some other difference.
Here, for example, is a list of mods from a forum:
THESE SO FAR HAVE ALREADY BEEN COVERED BY MANY:
- Replace the 470pF capacitor at C5 with a .0022μF capacitor and a 470KΩ resistor in series. Makes for a rounder, looser feel.
- Replace the 1nF capacitor at C26 with a .022μF capacitor. Brings back more low end.
- Replace the 37.4KΩ resistor at R12 with a 39KΩ resistor.
In the first case you would normally remove C5 completely (though you could leave it hanging by one lead) and replace it with a 2.2nF capacitor and 470kΩ in series (the common connection between the two new parts must not be connected anywhere else).
Here (from another source) is a capacitor replaced by a series R-C:
Whether these changes work reliably or not, or whether they are stable and reproducible is another question. But if done carefully they should be reversible.
answered Jul 2, 2023 at 8:53
-
1\$\begingroup\$ Ok, you get the point, but I still don't have an answer. People talk about bypassing, jumping or shorting the capacitor. All right. But what does that mean in practice? What should I do if I want to "remove" the component from the circuit? \$\endgroup\$ Commented Jul 2, 2023 at 10:22
-
1\$\begingroup\$ Show us a photo of what the circuit looks like. It will be different for an SMT part, a through-hole PCB part, and a point-to-point circuit. In the latter case you might just cut the leads. \$\endgroup\$ Commented Jul 2, 2023 at 10:45
-
1\$\begingroup\$ It's the classic PCB circuit you have in modern guitar amps or pedals: thetubestore.com/lib/thetubestore/schematics/Peavey/…. \$\endgroup\$ Commented Jul 2, 2023 at 11:01
-
\$\begingroup\$ So you would use a desoldering tool and/or cut the leads with a pair of cutters image from Amazon.ca. Sometimes it's easier (that is, it minimizes damage to the PCB) to destroy the part by cutting it apart or severing the leads and remove the leads from the PCB one by one. \$\endgroup\$ Commented Jul 2, 2023 at 11:45
-
1\$\begingroup\$ To short a capacitor you can solder a wire to one lead of the capacitor on the bottom (non-component side) of the PCB, route it over to the other lead and solder the wire to that. Ensure any uninsulated portion of the wire does not come into contact with any other metal than intended. That's one way. \$\endgroup\$ Commented Jul 2, 2023 at 12:20
\$\begingroup\$
\$\endgroup\$
2
I'm merely directly answering the question. Make sure you stay safe: this is a mains powered amp. The risk to yourself, other musicians, and the equipment is quite real.
To "remove C5", you simply unsolder the two red pads (ideally with solder sucker), take the capacitor off and put it in the bin/spares box.
https://www.thetubestore.com/lib/thetubestore/schematics/Peavey/Peavey-6505PLUS-112-Schematic.pdf
-
\$\begingroup\$ That's it? I don't break the circuit by doing this? \$\endgroup\$ Commented Jul 2, 2023 at 12:01
-
\$\begingroup\$ My (very limited) understanding of the purpose of C5 is to send a certain amount of higher frequences in towards "Lead Gain". If it is absent then they won't. Lower frequencies still go up towards "Rhythm Gain". You'll have to rely on your other sources about whether it is a good idea: but for certain "remove C5" means exacty what I've said. Solder it back in if you don't like what it sounds like. \$\endgroup\$ Commented Jul 2, 2023 at 12:07