Hi DC Dan: M is right; you can smack your T-bird wherever you want; might or might not work depending on what ails it. I have a schematic for your amp; PM or email if you or your tech want it. Amps are a little like cars in that each of us can do as much or little as we have the skills or time for. The problem with your reverb section may or may not be something you can fix or it could be something that you're not interested in messing with yourself anyway.
Shown below are both the schematic of the reverb section of the amp and a pic of your amp:
The green arrow ties together the reverb transformer on your schematic and in your amp. The yellow box and arrows represent both the schematic and real reverb 'pan' or 'tray'. The red lines and circles are the connections in and out of the reverb tray. The reverb tray has small transducers - enclosed in the red circles - that convert the inbound electrical signal to mechanical vibrations and then back to an electrical signal on exit from the tray. The transducers cannot be repaired; if they are damaged, the tray will have to be replaced.
The pic below is the signal path of the reverb section; also shown are some items you can address if you choose:
As an aside, this amp represents a departure by Guild from speaker-driven reverb. Several predecessor models fed the reverb can from the primary speaker; notably the first generation Thunder 1 RVTs and the Thunderbird (V1). In your amp, the signal is taken from the line section and fed to the first stage of the 6GW8 (V4A on the schematic). The signal is amplified and then sent to the reverb transformer whose function is impedance-matching. Tubes including the 6GW8 have high internal impedance; the tray has low internal impedance - the transformer allows the two to be connected; in the same manner as speakers to output tubes.
The signal is converted, and then back again, by the transducers from an electrical, to a mechanical, and back to an electrical signal. At the output of the reverb tray is a ground leg with a switch in it (blue circle on left); this is the reverb button switch in your footswitch. The switch opens and closes a path to ground. Your amp always produces a reverb signal but if the switch is in the off/closed position, the reverb tray output is grounded. You ought to consider opening the footswitch box and bathing both switch bodies in contact cleaner and operating both buttons several times. If the contacts are dirty, even if everything including the 6GW8 is working correctly, the crud on the switch can shunt your signal to ground .... no boingy boingy boingy even though everything is ok.
The signal is recovered and amplified by the other 1/2 of the 6GW8 (V4B). From there it travels to a pot which is something, if you choose, you can work with; this pot and every other one on the control panel will benefit from spraying them with lubricating-type contact cleaner. You can have a perfectly good reverb section but if the pot is dirty, you won't get a signal. Spray liberally into the opening among the three little legs; if you're worried about getting zapped with high voltage which is present in certain areas of the amp, put your other hand in your pocket. Spin the pots back and forth a few times; when turned slowly, you should feel a slight vibration and a little drag. Finally, gently wiggle and tug the 6GW8 out of its socket; if there's any resistance at all, spray some contact cleaner on it and try again ... gently. If/when it comes free, spray some more cleaner in the socket and insert/remove several times allowing the friction between the pins and sockets to scrape the corrosion off.
It's also possible that the electrical supply to the 6GW8 is off or other purely electronic problems - wth, it could be anything - but if the reverb was working when the amp was last shut off, then the chances are the problem isn't the 6GW8. Everybody has a different threshold for how much of this stuff they are willing to mess with but the control pots, the footswitch, and the pin/socket of the 6GW8 are as strong, or stronger, reasons than the 6GW8 for no reverb output.
Even if you do these items and the reverb doesn't improve, your amp will perform better and you will have ruled out common maintenance as the source of the problem. If it does improve, then you will have saved humping the amp to and from a tech including an open-ended exposure on bench fees ... including paying him to spray cleaner around the amp. Good luck with your amp! John
