PR-40 Necklace reverb not working

**eticket** · 08-24-2010, 08:57 PM

I recently picked up a PR-40 that works perfectly except for, not surprisingly, the necklace reverb.

I've swapped out the appropriate tubes and also tested the drive/return circuits on a digital reverb (which worked fine except for an overabundance of high frequencies that I assume the spring reverb filters out).. so I'm fairly confident both the reverb driver and return circuits are in good working order on the amp. I can also tap on the springs and hear 'thunder' in both reverb channels so the return appears to be working on the reverb itself.

Do these spring reverbs just wear out (i.e. the pickup loses it's magnetism) or is more likely a mechanical issue? Any thoughts? Thanks!

Randy

**tojpeters** · 08-24-2010, 09:07 PM

are your springs locked in traveling position ?

**eticket** · 08-24-2010, 09:09 PM

nope, unlocked and unobstructed

**Orgrinder010** · 08-24-2010, 09:15 PM

By chance is this plugged into an organ with a leslie tremolo switch? Try flipping it and seeing what happens.

**eticket** · 08-24-2010, 09:19 PM

no, the only connection for these purposes is between my stock B3 and this PR-40.. a standard 5-to-6 pin cable, nothing extra.

**Orgrinder010** · 08-24-2010, 09:32 PM

My PR-40 had this issue as well; like yours I could tap on the springs and hear the thunder but no effect from the organ. Turns out the RCA end to the amp and a short between the leads. I made a fresh connection and it worked fine.

**geoelectro** · 08-24-2010, 11:39 PM

The coaxial cable with the RCA plug should be replaced. They all short out when they get brittle.

Geo

**eticket** · 08-25-2010, 01:13 AM

Geo, a previous owner already did that.. the RCA cable is modern (looks to be a cheap Radio Shack cable, but quite intact).

Guess I'll check all the connections for possible shorts.

**geoelectro** · 08-25-2010, 03:41 AM

Well that seems to narrow it down to either the drive circuit or the spring. I say that because subbing a digital reverb is not a good test for the drive circuit. Any effects processor can amplify signals that could be too weak to drive the spring unit. If you look at the schematic you will see they inserted a test signal of 2.4Vac at the input. This can easily be recreated with the organ by playing a key and adjusting the expression pedal until measuring 2.4Vac at the GG terminals. Then, you should be able to measure 4Vac between the spring drive terminal and ground. If it's there, bad spring. If it's not, check the V9 circuit. (voltages)

Geo

**eticket** · 08-25-2010, 03:31 PM

Thanks, I'll test the voltage. I'm thinking I can also do a quick and dirty test with the spring reverb from my mid 70's Fender Vibrolux Reverb guitar amp. I'm not sure if the input/output values are compatible but it probably can't hurt.