100 % wet spring reverb mod ( marshall amp )

[Mikaellanden]

I got an old Marshall Master Reverb 30 for free because it only worked when hitting it hard. Took it home and cleaned the pcb where I found something that probably used to be a beer. However. It has a really nice reverb and I want to use it on mixes. Therefore it would be awesome to be able to get the 100% wet signal from somewhere and I have no idea how to do this. Would be very happy with any tips/tricks from you pros!
To get reverb pot to act as dry and wet maybe could work also?

Here's the schematic :
https://drtube.com/schematics/marshall/5203.gif

Only weird thing is that my version uses only ca1458 op amps and no tl071. It's the exact same model so don't know the reason for this.
Any ideas?

[Phoenix]

Removing R27 or C17 will eliminate the dry signal and leave you with only wet. A switch could be fitted to allow this to be turned on or off.

Are you sure about all op amps being CA1458? Only one is noted as being TL071 on the schematic (IC3). CA1458 are dual op amps, TL071 is single. With all CA1458 there would either be one spare or one too few op amps, though an unused stage is not uncommon, and is often the more economical choice for production reasons.

[Mikaellanden]

Thanks a million!!

I put a switch on c17 and it worked, however. When engaging the 100% mode the noise increases. hum noise. Maybe impedance issue?. it is usable though and sounds great!

[Mikaellanden]

As for the op-amps I still have no idea. I think my op amp nr 3 has either leg 2,3 or 6,7 soldered together ( This upside down workflow is confuses me haha )

[Phoenix]

Glad to help.
Better to not leave R27 floating, especially if there are long leads to the switch. Grounding the junction of C17 and R27 should minimize noise.

Connecting pins 1 and 2 and grounding pin 3, or 6 and 7 and grounding pin 5 of the spare op amp would configure it as a voltage follower which is the proper way to terminate an unused op amp, so that would make sense.

[Mikaellanden]

https://www.instagram.com/p/CAk-c-2pFQx/

Here's the results!:)
Last video on post is a soundclip