Marshall Valvestate 8080 modding

[Guga Ramone]

Hello.

I have an old Marshall Valvestate 8080 and the reverb on it isn't working. The springs came lose on the metal box and it is beyond repair. The cost of a new reverb pan here is a bit outside my price range, and since I don't use reverb that much, I thought if there is anything that I can mod on the circuit to make this "footswitchable reverb section" on it usable again. I was thinking if I could turn it into a level boost section. Is this possible? Any ideas on how to acomplish this?

Thanks!!

Schematic: https://music-electronics-forum.com/...6&d=1240638819

[Marshtech]

This suggestion is highly un-technical for the most part, but try this - completely disconnect the entire reverb tank and run a jumper from R103 to R108 and see what it sounds like. Keep the Reverb control turned down at first. No predicting how much or how little gain there will be when bypassing the reverb tank like this. If this seems to work ok, you may have to change out some of the capacitors in the circuit because the reverb circuit design won't have much bottom end to it and you're thinking about level boost. Trial and error. Having said all of that, I would still search out a reverb tank (used) since budget is important.

[g1]

The tank is just an 8DB2C1D. The Mod brand version is quite cheap. I assume the problem with pricing is due to getting it to Brazil?

https://www.amplifiedparts.com/produ...decay-3-spring

[vintagekiki]

If you want the 8080 (without reverb) still work as in mint condition, forget any extra boost (mode).
8080 already has two boost (crunch and overdrive) and any boost on boost will amplifier lead to unstable operation.

[Guga Ramone]

Hi!

Marshtech, the reverb circuit seems to have a very steep High Pass Filter. Just putting a jumper in place of the reverb pan may not work as I need it.

g1, I found the reverb pan on a brazilian online marketplace, but still a little expensive, especially when I don't use reverb at all. Great to know the reverb specs, though!

vintagekiki, the two boost modes you are talking are the distortion channel and the gain/distortion that it provides is enough for me. What I'm trying to get is more of a solo boost, just a few dB's more, after the distortion, just to get some parts of a song a little louder.

I simulated the reverb portion of the circuit using a website. Here it is (with no reverb pan connected, but it is usefull to see the frequency response): Stock reverb

And here is with the mod: Modded reverb circuit
I removed C44, C57, C58, R91, R92, R93 and R108, changed C38, C46 and C50 to 1uF, and added a 1k resistor in parallel with C51.
It seems to provide up to 11 dB of almost flat boost, with not too invasive modifications. Looking good on the simulation, now I just need to know if it will work on real life! heheheh

Is there any thing that I might be concerned about this? What do you guys think?

Thank you for all input! Cheers!!

[Helmholtz]

Your links don't work.

[Guga Ramone]

Helmholtz, I editted the post and they should be working now.